List of reviewed Ethiopian medicinal plants used for various traditional disease treatments with their parts and ecology/habitat.
\r\n\tThe discovery of Nylon by Wallace Hume Carothers, a Harvard-educated world-renowned organic chemist born in Burlington, IA in 1896, successfully crowned the attempts developed by E.I du Pont de Nemours & Company to investigate the structure of high molecular weight polymers and to synthesize the first synthetic polymeric fibre.
\r\n\tWhen it hit the market, it was in the form of stockings and all the women in the US wanted to get their hands on a pair. Despite the successful launch of Nylon on the synthetic fibre market and the high expectations created by its extraordinary features, the unexpected war events in 1941 diverted the production of the new synthetic fibre almost exclusively on military applications. Parachutes, ropes, bootlaces, fuel tanks, mosquito nets and hammocks absorbed the production of Nylon, which helped to determine the WWII events. When the war ended and production returned to pre-war levels, consumers rushed to the department stores in search of stockings, accessories and high-fashion garments.
\r\n\tEven if the world of high fashion now seems to more appreciate the use of natural fibres, Nylon is one of the most widely used polymers for the production of technical fibres and fabrics, automotive and micromechanical components. The global nylon 6 & 66 market is expected to reach USD 41.13 billion by 2025, by the following growth at 6.1% CAGR owing to the Increasing focus on fuel-efficient and less polluting vehicles.
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\r\n\tThe amazing success story of Nylon still continues. While its wide availability inspired the development of innovative applications, such as the additive manufacturing, on the other hand, proper disposal after use of high amounts of Nylon resin energised the development of efficient recycling methodology, including chemical recycling. Moreover, the production of Nylon precursors from biomass has become desirable due to the depletion of fossil hydrocarbons and to reduce greenhouse gas (GHG) emissions. This unique combination of technical and socio-economic driving forces is one that aims to further promote the development of Nylon as one of the most suitable ""best polymers"" with a low ecological footprint.
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\r\n\tThe aim of this publication is to unveil the relationships between the chemical structure and the outstanding properties of the broad family of polyamides and to describe the most recent use of Nylon in fostering new applications and promoting a culture aware of environmental sustainability.
Osteosarcoma is the most common primary malignancy that arises from bone. While relatively rare, with an annual incidence of 1–3 cases per million [1], it is fatal if left untreated. Osteosarcoma has a bimodal distribution affecting patients in the 2nd and 3rd decade of life and those after the 6th decade of life [2]. It is the sixth most common paediatric cancer and is the second-highest cause of cancer-related death in this age group [3, 4].
\nCurrent treatment protocols for osteosarcoma combine neoadjuvant chemotherapy, surgery and adjuvant chemotherapy. The five-year survival rate for patients diagnosed with osteosarcoma remains at 60–75% [5]. The medical and surgical treatments of osteosarcoma can cause significant morbidity for the patient. Chemotherapy agents are systemically toxic and surgery, in the form of amputation or limb salvage, require a prolonged period of rehabilitation. Despite the advent of multi-agent chemotherapeutic regimens, the prognosis for osteosarcoma has not significantly improved; hence, there is a real need to optimize current strategies and to develop novel approaches for treatment.
\nOur understanding of osteosarcoma has traditionally been based upon anatomical and histological principles. Primary osteosarcoma arises in the metaphysis of long bones, most commonly, within the medullary cavity. The most common sites for osteosarcoma are the distal femur, proximal tibia and proximal humerus. The occurrence of osteosarcoma in sites other than long bones increases with age. The tumour typically breaks through the cortex of the bone into surrounding soft tissues, around which a pseudocapsule forms [6].
\nHistologically, osteosarcoma is a malignant mesenchymal cell tumour, characterized by pleomorphic spindle-shaped cells, capable of producing an osteoid matrix. Tumour cells metastasize primarily via the haematogenous route. There are various subtypes of osteosarcoma, including the intramedullary ‘classic’ osteosarcoma already described, periosteal osteosarcoma, parosteal osteosarcoma, small cell osteosarcoma and telangiectatic osteosarcoma.
\nCurrent standards for staging and surgical resection of osteosarcoma rely on this anatomical knowledge [1]. However, recent advances in molecular biology have provided insight into the molecular pathogenesis of the disease. Through the identification of specific mediators of osteosarcoma progression and tumour pathways, novel approaches for targeting osteosarcoma are being developed.
\nThis chapter will outline our current understanding of the molecular pathogenesis of osteosarcoma with some reference to the development of novel treatment agents. The environmental, genetic and molecular alterations that underlie osteosarcomagenesis will be discussed with further emphasis on the role of mesenchymal stem cells (MSCs). MSCs have been identified as playing a role in not only sarcomagenesis but also the progression of disease. This role of MSCs in osteosarcoma contrasts with their ability to differentiate into the various cell types of connective tissue for tissue repair. This chapter discusses MSC origin, differentiation and transformation in sarcomagenesis. The interactions between MSCs and osteosarcoma cells are outlined. A number of research models that utilize MSCs in order to replicate the human condition will be discussed along with the potential use of MSCs in biologic reconstruction.
The pathogenesis of osteosarcoma is a complex process, which is not completely understood and involves tumorigenesis from mesenchymal cells, alterations in cellular apoptosis, adhesion, migration and invasion, as well as tumour-induced osteolysis and angiogenesis. Various genetic and molecular alterations underlie these processes. It is hoped that by targeting the deranged molecular signalling of these pathways that novel treatment agents could be developed that enhance the efficacy of conventional chemotherapeutics and possibly reduce patient morbidity.
\nPhysical, biological and chemical agents have been implicated in osteosarcoma pathogenesis. There is a well-documented risk of osteosarcoma following exposure to ultraviolet and ionizing radiation, which occurs in 2-3% of cases. The first identified case of radiation exposure association with osteosarcoma was found in female watch-makers working with radium [7]. Nevertheless, only 2% of osteosarcoma cases are associated with radiation exposure [8] and it is not thought to contribute significantly to paediatric disease. Samartiz et al., have identified that radiation-related-sarcoma formation can even occur in those with low-level radiation exposure. Of children who received radiotherapy for treatment of a solid tumour, 5.4% develop a secondary neoplasm and only 25% of these are sarcomas [9]. A latent period of 10–20 years between radiation exposure and osteosarcoma formation has been observed [10]. Methylcholanthrene and chromium salts [11], beryllium oxide [12], zinc beryllium silicate [13], asbestos and aniline dyes [14] are among the chemical agents associated with osteosarcoma formation.
Amplifications of chromosomes 6p21, 8q24 and 12q14, and loss of heterozygosity of 10q21.1, are among the most common genomic alterations in osteosarcoma [15]. Numerical chromosomal abnormalities associated with osteosarcoma include loss of chromosomes 9, 10, 13 and 17, as well as gain of chromosome 1 [4]. Osteosarcoma has been reported in patients with Werner syndrome, Rothmund-Thompson syndrome, Bloom syndrome, Li-Fraumeni syndrome, and hereditary retinoblastoma [14]. In particular, Werner, Rothmund-Thompson and Bloom [16] syndromes are characterized by genetic defects in the RecQ helicase family. DNA-helicases separate double stranded DNA prior to replication [17, 18].
\nPagetic osteosarcoma occurs in approximately 1% of patients with Paget’s disease [19]. These tumours are characteristically high grade pleiomorphic intramedullary tumours. Loss of heterozygosity of chromosome 18q is a recognized genetic anomaly contributing to tumorigenesis: the specific region located between loci D18S60 and D18S42 contains the tumour suppressor locus [20]. This region also encodes for receptor activator of nuclear factor kappa B (RANK), a peptide which is a mediator of osteoclastic activity [21].
The p53 mutation is the most common genetic aberrancy in malignancy, and is a causative factor in the transformation and proliferation of osteosarcoma cells [22]. Here, it is found to be mutated in 22% of cases [4]. The presence of p53 mutation in osteosarcoma was initially identified in the autosomal dominant Li-Fraumeni syndrome, which is a syndrome characterised by a predisposition to forming multiple malignancies, such as osteosarcoma, rhabdomyosarcoma and breast cancer.
\nNormally, p53 is a vital protein in cell cycle arrest, cellular senescence and DNA damage response and repair [23]. It is regulated by mouse double minute 2 homolog (MDM2), a protein that inhibits p53 activation via multiple methods including the ubiquitin degradation pathway and competitively binding to the amino terminus of p53 (instead of transcriptional co-activators) [24]. Transcriptional activation of p21 (cyclin-dependent kinase inhibitor) mediates p53 activity, where its expression results in cellular arrest in either the G1 or G2 phase. This can be either temporary, until the source of the cellular stress has been removed or subsided, or can be irreversible, which is known as cellular senescence. Cellular senescence is stimulated by the presence of oncogene activation or presence of DNA damage. Its ability to arrest the cell cycle in the G1/G2 phase is dependent on its response to stressful stimuli [25].
\nMutation in the retinoblastoma gene (Rb1) is the most common mutation found in osteosarcomas whereby greater than 70% of cases are associated with an alteration in Rb gene. The association between hereditary retinoblastoma and osteosarcoma has been localised to this mutation, where it acts as a dysfunctional tumour suppressor. Normally, Rb1 is found on chromosome 13, which encodes for a nuclear protein allowing sequestration of transcription factors and acts as a tumour suppressor. This protein is vital in regulation of cell cycle progression from the G1 to S phase of the cell cycle. Hypophosphorylation of Rb protein allows it to bind to E2F transcription factor which inhibits cellular progression from G1 into the S phase. Once pRb is phosphorylated, it releases E2F, allowing continuation of the cell cycle. Additional biological characteristics include regulating DNA replication, apoptosis, cellular differentiation, as well as DNA damage response and repair [26–28].
Osteosarcoma cells produce a number of transcription and growth factors that contribute towards continued tumour cell growth and proliferation. During transcription single-stranded messenger RNA (mRNA) is formed from double-stranded DNA. Transcription factors bind to promoter sequences for specific genes to initiate the process. Transcription is usually a tightly regulated process and deregulation can lead tumour formation. Growth factors may act via both autocrine and paracrine mechanisms and overexpression or constitutive activation may lead to accelerated osteosarcoma cell proliferation.
\nThe activator protein 1 complex (AP-1) is a regulator of transcription that controls cell proliferation, differentiation and bone metabolism. AP-1 is comprised of Fos and Jun proteins, products of the c-fos and c-jun proto-oncogenes, respectively. Upregulation of Fos and Jun is seen in high-grade osteosarcomas [29, 30] and is also associated with a propensity to develop metastatic lesions [31].
\nMyc is a transcription factor that acts in the nucleus to stimulate cell growth and division. Myc amplification has been implicated in osteosarcoma pathogenesis and resistance to chemotherapeutics. Overexpression of Myc in bone marrow stromal cells leads to osteosarcoma development and loss of adipogenesis [32]. This factor is amplified in U2OS osteosarcoma cell line variants with the highest resistance to doxorubicin and gain of Myc was found in SaOS-2 methotrexate-resistant variants [33].
\nIn addition to Myc, transforming growth factor beta 1 (TGF-β1) has been shown to be overexpressed in high grade osteosarcomas [34]. Smad activation was implicated downstream of TGF-β with an inability to phosphorylate the Rb protein.
\nInsulin-like growth factor (IGF)-I and IGF-II are overexpressed by osteosarcomas. Activation of the IGF-1R receptor leads to the activation of phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways. This leads to accelerated cell proliferation and inhibition of apoptosis [35].
\nConnective tissue growth factor (CTGF) is a potent stimulator for the proliferation of osteosarcoma cells, leading to increased expression of type I collagen, alkaline phosphatase, osteopontin and osteocalcin, markers for bone cell differentiation and maturation [36]. CCN3, a related protein, is overexpressed in osteosarcoma and is associated with a worse prognosis [37].
\nThe wingless-type (Wnt) canonical pathway, is a specific cascade that occurs within the Wnt family of glycoproteins and has been identified in the molecular basis of osteosarcoma formation. The Wnt family is essential in cellular differentiation and cell fate determination, and in the context of osteosarcomas, directing mesenchymal stem cells down the osteogenic lineage. Through this pathway, bone morphogenic protein 2 (BMP-2) is the key factor in osteogenesis. Another factor has been identified to inhibit the Wnt cascade, and histologically has been identified at the peripheries of osteosarcomas, Dickkopf 1 (DKK1). A secreted antagonist of Wnt pathway is low density lipoprotein receptor related protein 5 (LRP-5) which has been correlated with metastatic disease in osteosarcoma, independent of the histological type. When LRP-5 is expressed, the Wnt pathway is activated resulting in the up-regulation of a number of genetic factors including matrix metalloproteinases (MMP) which have been known to be involved in metastatic activity of cancers. Hoang et al. have analysed osteosarcoma patients expressing LRP-5, who were metastases free at time of diagnosis to have a lower probability of an event-free survival [38].
\nStromal cell derived factor-1 (SDF-1), also known as C-X-C motif chemokine 12 (CXCL-12), [39] is a ligand for CXCR-4 and a part of the cxc chemokine family, where CXCR-4 has been implicated in various cancer types. SDF-1/CXCL-12 is a chemokine that has a paracrine effect within the interstitial space stimulation migration of pluripotent cells as well as tumour cells. The interaction between CXCR-4 and SDF-1/CXCL-12 has an important role in cancer progression as it promotes osteosarcoma cell migration and angiogenesis [40]. Within osteosarcoma the level of CXCR-4 mRNA is low however the SDF-1/CXCL-12/CXCR4 combination is required in osteosarcoma cell proliferation. Tumour promotion occurs by SDF-1/CXCL-12 in a paracrine manner, stimulating cellular growth and survival. Besides tumour promotion CXCR-4 is involved in metastatic spread of tumour cells into areas where SDF-1/CXCL-12 is expressed. This factor is important in angiogenesis as it promotes endothelial cells into the tumour microenvironment [39].
Degradation of the extracellular matrix by osteosarcoma cells allows for invasion of surrounding tissues by the primary tumour mass. Matrix metalloproteinases (MMPs) and the urokinase plasminogen activator (uPA) system are the effectors of this matrix breakdown.
\nThe MMPs include collagenases, gelatinases and stromelysins. Collagenases break down collagen types I, II and III. Gelatinases break down collagen type IV, while stromelysins break down collagen types III, IV and V as well proteoglycans [41].
\nThe urokinase plasminogen activator (uPA) system has been studied extensively with relation to osteosarcoma invasion. When uPA binds to its receptor uPAR it becomes active. Activated uPA then cleaves plasminogen to form plasmin. Plasmin is both responsible for direct breakdown of the extracellular matrix but also for further activation of pro-MMPs [42, 43].
\nuPA levels possess prognostic significance in osteosarcoma. An inverse relationship exists between survival time and uPA levels in osteosarcoma [44]. The downregulation of uPAR in a clinically relevant murine model of osteosarcoma resulted in limited primary tumour growth and inhibited metastatic spread [45].
Substantial osteolysis may result from osteosarcoma growth. This osteolysis at the tumour site is the result of interactions between osteosarcoma cells, osteoclasts, osteoblasts and the bone matrix. Growth factors such as transforming growth factor beta (TGF-β) are released from degraded bone matrix and stimulate the release of tumoral cytokines that induce osteoclastic resorption of bone. Among the osteoclast-stimulating cytokines are parathyroid hormone-related protein (PTHrP), interleukin-6 (IL-6) and interleukin-11 (IL-11) [46, 47]. Further growth factors are then released from the bone matrix, leading to a cycle of osteolysis, osteoclast activation and osteosarcoma invasion.
\nThe critical involvement of osteoblasts in the osteolytic process is a surprising finding. Among the other factors that osteosarcoma cells release are the osteoblast-stimulating factors endothelin-1 (ET-1), vascular endothelial growth factor (VEGF), and platelet-derived growth factor (PDGF) [48, 49]. Osteoblast stimulation by these factors leads to increased expression of receptor activator of nuclear factor κB ligand (RANKL). RANKL is a key regulator of osteoclast differentiation and activity. Osteosarcoma cells have been noted to produce RANKL independently also [50].
Tumour neovascularization is required for continued osteosarcoma growth and progression. Osteosarcoma cells obtain the necessary oxygen and nutrients for cellular proliferation from the neovasculature and gain access to these vessels in order to metastasize.
\nThe process of angiogenesis is regulated by a balance between pro-angiogenic and anti-angiogenic regulators. Loss of tumour suppressor gene function and oncogene activation pushes this balance toward neoangiogenesis. The hypoxic and acidotic environment that surrounds the primary tumour also promotes vascular proliferation. Such conditions lead to de-ubiquitination of the von Hippel Lindau protein. Von Hippel Lindau protein releases hypoxia-inducible factor-1α (HIF-1α). HIF-1α upregulates vascular endothelial growth factor (VEGF) [51]. VEGF is pro-angiogenic through stimulation of the processes of endothelial cell proliferation, migration and maturation. An immature, irregular and leaky vasculature is thus formed in and around the tumour.
\nAnti-angiogenic factors are downregulated in osteosarcoma. These include thrombospondin 2, transforming growth factor beta (TGF-β) [52], troponin I, reversion-inducing cysteine rich protein with Kazal motifs (RECK) [53] and pigment epithelial derived factor (PEDF) [54]. Downregulation of such molecules may lead to increased invasion through predominately avascular zones, such as the growth plate [55, 56].
\nOsteosarcoma is a particularly vascular tumour. However, the true significance of vascular density is yet to be fully elucidated. While vascular tumours may be more likely to lead to increased rated of metastasis, increased osteosarcoma microvascular density may offer a survival advantage attributed to improved tumour penetration by intravenously delivered chemotherapeutics [57].
The defining features that characterise stem cells as a group are the ability to self-renew and the ability to differentiate into distinctive cell line types. Stem cells, broadly speaking, may fall into one of four main categories:\n
Embryonic stem cells
Pluripotent stem cells
Cancer stem cells
Tissue specific stem cells
Various tissue specific stem cells have been identified and mesenchymal stem cells (MSCs) are but one of these. Other tissue specific stem cells include cord blood stem cells, neural stem cells, gut stem cells, amniotic fluid stem cells and others. MSCs are multipotent cells that are able to differentiate into bone, cartilage, fat and muscle. Due to this ability they represent a promising source for tissue repair and regeneration. Research has focused on the cellular and molecular pathways that direct differentiation towards a particular cell type and aberrant differentiation of MSCs may contribute to sarcomagenesis. Prior to understanding the interactions between MSCs and osteosarcoma cells, an understanding of the biological factors that characterize MSCs is essential.
\nThe initial work of identifying and characterising MSCs can be largely credited to the work of Friedenstein, Cohnheim and Caplan [58–61]. Cohnheim hypothesised that certain fibroblastic cells originating from bone marrow were a key factor in wound healing. In the 1970s and 1980s, Friedenstein isolated a population of plastic adherent stromal cells from bone marrow, which had the capacity to differentiate into certain colony forming units (CFU). These CFUs possessed the capacity to give rise to osteoblasts, chondrocytes, adipocytes, muscle and haematopoietic tissue. Beyond this, Kopen et al. [62] have demonstrated that not only are MSCs able to differentiate into mesoderm-derived cells but they are also able to undergo transdifferentiation, forming endoderm-derived cells.
\nSince these early studies, MSCs have been identified and isolated from tissues other than bone marrow, including adipose tissue, muscle, peripheral blood, placenta, umbilical cord and amniotic fluid. Irrespective of the tissue of origin of MSCs are able to adhere to plastic and differentiate along mesenchymal cell lines. The expression of specific surface antigens has also been used to identify MSCs. The International Society for Cellular Therapy use the following characteristics to identify and standardize isolated human MSCs [63]:\n
Plastic adherence – in vitro under standard culture conditions (1–5 days);
Tri-lineage differentiation into cells of mesodermal lineage (osteoblasts, chondroblasts and adipocytes);
Surface antigens:
Expression of CD105, CD73, CD 90
Absence of CD45, CD 34, CD 14, CD 11b, CD79b, CD 19, HLA-DR (haematopoietic markers)
Most relevant in the setting of translational research, however, is that significant variation exists in the expression at surface antigens across species. MSCs of murine origin may be identified by the expression of CD106 and Sca-1, and the absence of CD31, CD45 and CD11b. Studies have demonstrated significant variability in surface antigen expression which changes once MSCs undergo expansion and ex-plantation [64].
\nMSCs are found in nearly all tissues, including adult bone marrow, peripheral blood and adipose tissues. MSCs are derived from pericytes (cells surrounding blood vessels) and exist in a perivascular niche. This explains the presence of adult MSCs in a number of different tissue types [65], including:\n
Bone marrow
Synovium and synovial fluid
Periosteum
Peripheral blood
Adipocytes
Liver
Brain
Kidney
Lung
Spleen
Blood vessels
While MSCs may be obtained from a variety of different tissue types, the concentration of MSCs in these tissues varies widely. Pittenger et al. [66] isolated MSCs from bone marrow, adipocyte and peripheral blood. 0.001-0.01% of bone marrow cells were MSCs in comparison to ~5000 cells of 1g of adipose were MSCs. Furthermore, in addition to the variable concentration of the stem cells sourced from different tissues, it has been demonstrated that there is altered capacity to form osteocytes in vivo dependent on the tissue of origin of MSCs. Cosimo De Bari showed that periosteal derived MSCs have a greater potential to form osteocytes than those derived from synovium [67].
\nMesenchymal stem cells can also be obtained from birth associated tissues [65], including:\n
Placenta
Human amnion membrane
Umbilical cord
Cord blood
Chorionic villi and chorion membrane
Wharton’s jelly
The major advantages of MSCs derived from birth associated tissue, over those obtained from bone marrow, are the availability of the tissue, as well as the greater proliferative and differentiation capacity of these cells. The rate of expansion varies between adult and birth associated tissue derived MSCs. The mean doubling time for umbilical cord MSCs is approximately 24 hours whilst it is 40 hours for bone marrow MSCs. Additionally, umbilical cord MSCs proliferate with multi-layering, while bone marrow MSCs demonstrate contact inhibition. Bone marrow MSCs are multipotent, while birth associated tissue MSCs are pluripotent and are able to differentiate into all three germinal layers.
Friedenstiein et al. initially demonstrated that bone marrow derived MSCs differentiated exclusively into cells of mesodermal lineage, namely osteocytes, adipocytes and chondrocytes [59]. More recently, however, MSCs have been shown to also possess the ability to differentiate along endodermal and neuroectodermal lines. In vitro studies have shown formation of neural tissue from bone marrow derived MSCs. This has propagated multiple studies determining the factors that stimulate MSCs to differentiate into cell lineages.
\nPittenger et al. [66] highlighted that in vitro mesenchymal stem cells can maintain a stable and undifferentiated state, however when exposed to certain cues or cultured in certain media they are able to differentiate into diverse cell types. MSCs that have undergone 20 cumulative population doublings maintain this multipotent ability.
\nThe osteogenic potential of MSCs has been observed in vitro, however this ability in vivo is still incompletely defined. Osteoblasts may stimulate the expansion of MSCs and regulate differentiation down the osteogenic pathway, however this may be secondary to the role of osteocytes in stimulating differentiation toward osteogenesis.
\nHuang et al. demonstrated the process of osteogenic differentiation in vitro, through multiple stages [68, 69]:\n
Day 1–4
Peak number of cells
Day 5–14
Early cell differentiation
Deposition of type 1 collagen early in this phase
Expression of alkaline phosphatase (ALP), however the level of ALP decreases at the end of the second phase
Day 14–28
Expression of fibroblast growth factor 2 (FGF-2) and bone morphogenetic protein 2 (BMP-2)
Expression of osteocalcin and osteopontin
Calcium and phosphate deposition
The early response growth factors were distinguished from the growth factors present in late cycle. The early response factors include transforming growth factor beta, insulin-like growth factor and vascular endothelial growth factor. The later phase growth factors include platelet derived growth factor, bone morphogenetic protein 2 (BMP-2) and fibroblast growth factor 2 (FGF-2)
\nTransforming growth factor beta (TGF-beta) administration stimulates osteoblast activity as well as cell proliferation, alkaline phosphatase activity and calcium deposition. BMP-2 is a notable cytokine which is osteoinductive, and has been shown to commit cells into either a chondrogenic or osteogenic lineage depending on its culture medium. When these two factors co-exist in an environment, there is approximately five-fold greater osteogenic potential.
\nOther groups of factors are important for adipogenic and chondrogenic differentiation. Factors favouring adipogenic differentiation include 1-methyl-3-isobutylxanthine, dexamethasone, insulin and indomethacin, whereby the adipocytes expressed lipoprotein lipase, fatty acid-binding protein (Ap2) and peroxisome proliferation-activated receptor gamma 2 (PPAR-2) [66, 68]. Factors for chondrogenic potential include glutamine, linoleic acid, dexamethasone, ascorbic acid, proline and sodium pyruvate. Dexamethasone is required as it promotes TGF-beta1 upregulation of type II collagen. The potent factors which were found to be important in chondrocyte formation are BMP-2 and BMP-7, with TGF-beta being a weaker factor. The effect of BMP-2 is dose-dependent, whereby it stimulates the production of mRNA for type II collagen and aggrecan [70, 71].
\nThere are two main pathways important in differentiation. One discussed previously is through TGF-beta, involved in the formation of chondrocytes. This occurs through multiple intra-cellular cascades (mitogen activated protein, JNK, p38). The other pathway is the Wnt canonical pathway, where soluble glycoproteins stimulate and regulate cellular differentiation and expansion. Like the TGF-beta pathway, the binding of Wnt to receptors on cells trigger an intracellular cascade, however, this pathway has an osteogenic potential.
Transformation is the sequential accumulation of genetic changes in a cell that may lead to altered behaviour and function of the subsequent cell lineage. Transformation causes cells to both acquire new and lose certain characteristics of the original cell type. This may be reflected as changes in the morphology of the cells, altered expression of surface antigens, changes in the growth characteristics, as well as increased tumorigenicity. Differentiation of MSCs at a variety of stages may underlie sarcomagenesis. Sarcomas may arise from cells already committed to a particular differentiation pathway, or alternatively, from multipotent cells that are pushed towards a particular sarcoma subtype. Alterations in oncogenes, tumour suppressor genes, growth factors and transcription factors may underlie the transformation of MSCs.
\nStudies that have utilised MSCs of both murine and human origins have supported the concept of transformation of MSCs for tumorigenesis. The findings of human studies have been conflicting, however, and warrant further evaluation. Transformed murine MSCs demonstrate altered morphology and growth characteristics. Transformed murine MSCs exhibit a compact morphology, demonstrate anchorage-independent growth, lack contact inhibition and form multiple layers in culture. This is in contrast to the spindle-shaped single layer growth characteristics of MSCs [72–75]. The proliferation rates of transformed murine MSCs have been shown to be increased and genetic and molecular signalling alterations underlie these changes [72, 76, 77]. Increased chromosome number beyond the usual 40 acrocentric chromosomes have been demonstrated in transformed murine MSCs by multiple authors [72, 73, 78]. Additionally, Matushansky et al. [79] showed that inactivation of the Wnt pathway in transformed MSCs gave rise to a cell population with a similar appearance to that of malignant fibrous histiocytoma.
\nHuman models require MSCs that are able to undergo ex vivo expansion prior to its clinical application and through this process some cells undergo spontaneous transformation. This is particularly concerning when considering the potential therapeutic use of MSCs for tissue repair and regeneration. There are also pharmacological agents that mobilise MSCs into the bloodstream. However, there has been some variability in studies using human MSCs. Some studies have shown spontaneous transformation of human MSCs in culture [80, 81] while other research groups have demonstrated that human MSCs are not able to spontaneously transform into malignant cells and with prolonged in vitro culturing become senescent [82–85]. These conflicting studies have been further confounded by Torsvik et al. [86] and de la Fuente et al. [87] that demonstrated previously considered transformed MSCs were tainted by contamination. Pan et al. [88] have subsequently shown MSCs to undergo transformation and have eliminated the possibility of contamination. In this study, 46 cultures of MSCs were studied and 4 of these cultures showed characteristics of transformation, including morphological changes and increased proliferation rates. Increased tumorigenicity was demonstrated when these cells were introduced into immunodeficient mice.
\nIn addition to the cellular, molecular and genetic changes underlying osteosarcoma pathogenesis, the transformation of MSCs have also been implicated in the tumorigenesis of osteosarcoma. Wang et al. [89] were among the first to hypothesise that a subpopulation of cancer stem cells existed in human osteosarcoma. In order to demonstrate such a subpopulation of tumorigenic cells, Wang et al. characterised cells with high aldehyde dehydrogenase (ALDH) in 4 human osteosarcoma cell lines. Of these, the OS99-1 cell line, which was derived from an aggressive primary human osteosarcoma, had significantly higher ALDH activity. When OS99-1 cells were introduced into a murine xenograft model, 3% of tumour cells demonstrated high ALDH activity and these cells demonstrated the characteristics of MSCs, namely self-renewal, tri-lineage differentiation and the expression of typical cell surface antigens.
\nSince then, Adhikari et al. [90] have further characterised a subpopulation of cancer stem cells in osteosarcoma using cell surface antigens. This study took the concept of tumour-initiating cells further by identifying a possible role of cancer stem cells in highly metastatic and resistant osteosarcoma. Mouse and human osteosarcoma stem cells were identified using the MSC markers CD117 and Stro-1. Expression of these markers were largely in spheres and doxorubicin-resistant cells. Cells that were positive for both CD117 and Stro-1 were serially transplantable and gave rise to more aggressive metastatic disease when applied to an orthotopic murine model. CD117 and Stro-1 positive tumours in the model were highly invasive and demonstrated drug resistance.
\nAlterations in oncogenes, tumour suppressor genes, growth factors and transcription factors may underlie the transformation of MSCs for osteosarcoma tumorigenesis. In one study, Mohseny et al. [74] examined the pre-malignant stages of osteosarcoma using murine mesenchymal cells. A functional and phenotypical analysis of MSCs, transformed MSCs and osteosarcoma cells was performed in parallel using. Aneuploidization, translocations, homozygous loss of the cyclin-dependent kinase inhibitor (cdkn2) region, and alterations in sarcoma amplified sequence (SAS), retinoblastoma 1 (Rb1), mouse double minute 2 homolog (Mdm2), c-myc, p53 and p16 have all been implicated in the transformation of MSCs for osteosarcoma formation [74, 91].
\nTao et al. [92] identified the transformation of immature osteoblasts as a potential source for osteosarcoma transformation. Using a murine model of osteosarcoma with conditional overexpression of intracellular domain of Notch1 (NICD), expression of NICD in osteoblast stem cells caused the formation of bone tumours including osteosarcoma. These tumours demonstrated histopathological, metastatic and genetic features of human osteosarcoma. Additionally, when overexpression of NICD and loss of p53 were combined in the murine model, osteosarcoma development and progression was accelerated.
The interaction between MSCs and tumour cells is an evolving area of current research. MSCs have been shown to be capable of migrating to not only sites of inflammation and injury but also to tumours and sites of metastasis. Once at these tumour sites, cellular interactions may cause progression of both primary and metastatic lesions. While these interactions between MSCs and osteosarcoma cells in the tumour microenvironment have been demonstrated, some studies show that MSCs may cause increased proliferation of tumour cells while others show reduced proliferation and pro-differentiation. Khakoo et al. [93] showed that systemically injected MSCs inhibit the growth of Kaposi sarcoma using a xenotransplant model.
\nYu et al. [40] characterised the interaction between MSCs and osteosarcoma cells in vitro and showed that bone marrow derived MSCs had the potential to promote osteosarcoma cell proliferation and invasion. In this study bone marrow MSCs were cultured with osteosarcoma cells. Osteosarcoma cells were also cultured with conditioned media from MSCs. Cellular proliferation was measured by cell counting kit 8 (CCK-8) assay and a matrigel assay was used to evaluate tumour cell invasion. Tumour cell proliferation and invasion were promoted under these conditions with the implication of stromal derived factor-1 (SDF-1). SDF-1 is a cytokine that controls tumour neoangiogenesis, apoptosis, migration and invasion through binding to the CXCR4 receptor.
\nTsukamoto et al. [94] showed that MSCs may provide a favourable environment for osteosarcoma growth and metastasis in a rat osteosarcoma model. In this study, rat COS1NR osteosarcoma cells were injected along with rat bone marrow derived MSCs. Injections were performed subcutaneously and intravenously. Osteosarcoma tumour formation and growth was increased significantly prior to 5 weeks using the subcutaneous injection model. When injected intravenously there was increased pulmonary lesion formation in the group that received co-injections of COS1NR and MSCs. The expression of genes by MSCs involved in cellular adhesion and extra-cellular matrix receptors were suggested as possible explanations for this tumour behaviour.
MSCs are being portrayed in the literature as the key to biological reconstruction, however, studies are few and results are varied. There are significant challenges to be overcome if we are to utilise MSCs in biological reconstruction after tumour resection. Much of the concern relates to the yet to be fully characterised ability of MSCs to transform into sarcomas and the interactions between MSCs and tumours that cause increased tumorigenesis and disease progression. In order to apply MSCs to clinical reconstruction the cells require prior in vitro expansion. As has been discussed above, there are concerns of chromosomal instability and malignant transformation during this process of expansion.
\nA number of attempts at utilizing MSCs in the reconstruction process after tumour resection have been made. Perrot et al. [95] raised concern of osteosarcoma recurrence after autologous fat grafting, reporting a case of late recurrent osteosarcoma 13 years after the use of a lipofilling procedure. Following this they utilised a pre-clinical murine model of osteosarcoma to show that injection of fat grafts and MSCs promoted tumour growth.
\nSince then, Centeno et al. [96, 97] has published two papers with results for 339 patients that were treated following orthopaedic procedures with in vitro expanded, autologous bone marrow derived MSC implantation. Follow up by general observation and MRI tracking beyond 3 years post-operatively did not demonstrate tumour formation at the sites of injection. 2 patients were diagnosed with cancer during the follow up period, however these cases were assessed not to be related to the MSC therapy and the rate of neoplasm development was comparable to that of the general population. While the results presented by Centano et al. [96, 97] appear reassuring with regards to the safety of MSCs for reconstruction, further studies, particularly in the setting of reconstruction after treatment for malignancy are required. There are hundreds of clinical trials currently underway evaluating the therapeutic safety and efficacy of MSC based treatments.
While the advent of multi-agent chemotherapeutic regimes dramatically improved the prognosis for patients with osteosarcoma, novel treatment agents are required in order to reduce morbidity and improve function following surgical reconstruction. The pathogenesis of osteosarcoma is complex and current research is focusing on defining the deranged cell behaviours and molecular signalling pathways that underpin tumorigenesis and disease progression. Mesenchymal stem cells have attracted great interest over recent years due to their ability to expand into mesodermal tissues including bone, cartilage, fat and muscle; however, pre-clinical studies have highlighted possible roles in the processes of sarcomogenesis through transformation and interactions with the tumour cells themselves. Further studies defining the role of MSCs in osteosarcoma pathogenesis are required prior to studies of therapeutic safety and efficacy.
Medicinal plants are very vital in their uses for medication, besides providing ecological, economic, and cultural services. The world primary means of treating diseases and fighting infections have been based on the use of medicinal plants. From ancient times, plants have been rich sources of effective and safe medicines [1]. Globally, about 64% of the total world population is reliant on traditional medicine for their healthcare needs [2]. According to the World Health Organization (WHO), nearly 3.5 billion people in developing countries including Ethiopia believe in the efficiency of plant remedies and use them regularly [3].
Ethiopia is located in the Horn of Africa between 3 and 15° northing, latitude, and 33 and 48° easting, longitude, and is also comprised of nine national regional states and two administrative states with varied agroecological zones. Since the country is characterized by a wide range of ecological, edaphic, and climatic condition, Ethiopia is also very diverse in its flora composition [4]. The flora of Ethiopia is estimated to contain close to 6500–7000 species including medicinal plants; of those, 12–19% are endemic to the country [5]. The medicinal plants have been used for various types of human and animal treatments in the country. According to [6, 7], in Ethiopia, about 80% of human population and 90% of livestock rely on traditional medicine. As also stated by many authors (e.g. [6, 7]), the medicinal plants have shown very effective medicinal values for some diseases of humans and livestock.
Even due to the trust of communities on medicinal values of traditional medicines, culturally associated traditions, and their relatively low cost, medicinal plants are highly demanded in Ethiopia [7]. Inadequate health centers and shortage of medicines and personnel in clinics might be the other reasons for driving the people of Ethiopia, in general, and the low-income community and the rural people, in particular, to the traditional health centers, whereby increasing the demand of medicinal plants.
However, these plants have got little attention regarding the documentation of scientific names, uses, ecology, and conservation in Ethiopia, in particular and world-wise, in general. Moreover, in Ethiopia, traditional medicine is faced with a problem of sustainability and continuity mainly due to the loss of taxa of medicinal plants [8, 9] besides having lack of quality control for herbal medicines. The main causes for the loss and decline of diversity of plants in Ethiopia are human-made factors [10, 11, 12]. Habitat destruction and deforestation for commercial timber and forest encroachment for urbanization, investment, agriculture, and other land uses are the major causes of the loss of many thousand hectares of forest that harbor medicinal plants yearly for the past several decades. In addition to these, the medicinal plant materials and associated traditional knowledge are being lost due to the lack of systematic conservation, research, proper utilization, and documentation [13]. The knowledge on identifying and managing the medicinal plants with their parts, use, and ecology is mostly associated with local and elder people, who transmitted their knowledge verbally. Such verbal transmissions of knowledge on medicinal plants have thus resulted in eroding and loss of knowledge and the plant materials as well. The quantity and quality of the safety and efficacy data on traditional medicine are also far from sufficient to meet the criteria needed to support its use worldwide [14]. Therefore, assessing and documenting the medicinal plants along with their useful medicinal parts, use, and ecology in Ethiopia, as well as revising the quality control for herbal materials and medicine, are very crucial for giving priority to their conservation and sustainable utilization.
The materials for this review were published documents. However, regarding the screening of medicinal plants, some medicinal plants not yet identified or available in more than one article being revised during this revision time, and published before 2000 with their uses, were not listed and included for this review analysis so as to increase the quality of the present review, provide the current information to the readers, and restrict the revised papers. Based on this, of the total (32) revised documents, 15 articles, which are assessing the different medicinal plants with their uses and parts, were revised for documenting the medicinal plants for this review. Additionally, the habitats (ecology) of each medicinal plant were assessed from the Flora Volumes of Ethiopia and Eritrea and [15], besides the articles revised for listing the medicinal plants for this review. The data were analyzed and described quantitatively using frequency, percentage, tables, and figures via applying Microsoft Excel Spreadsheet 2010 and SPSS with version 20, as well as qualitatively using content analysis, narrating via drawing sub-contents.
Traditional healers in Ethiopia utilize the herbal resources available in nature for various disease treatments. As reported before, approximately 800 species of the medicinal plants grown in Ethiopia are used for treating about 300 medical conditions [16]. However, based on the present review, the number of medicinal plants and the treatments/medications identified and listed are limited as presented here under section by section.
As reported by many authors [6, 7, 12, 13, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27], there are different types of medicinal plant species with their parts, habitats, and disease types being treated and described here in Table 1. Accordingly, as depicted in Table 1, there were 80 medicinal plant species with 63 genera, used by the local communities for various human treatments. Among other revised, the common medicinal plants used for treating and curing various diseases are Aloe species, Eucalyptus globulus, Hagenia abyssinica, Cupressus macrocarpa, Buddleja polystachya, Acmella caulirhiza, Acacia species, Citrus species, Clematis species, Coffee Arabica, Croton macrostachyus, Euphorbia species, Ficus sycomorus, and Moringa stenopetala (Table 1).
Scientific names | Local name | Ha. | Habitat | Parts used | Uses [references cited] |
---|---|---|---|---|---|
Acacia abyssinica Hochst ex. Benth | Qontir | S | Deciduous bushland | Leaves | Used for treating goiter [18, 22] |
Acacia nilotica (L.) Del. | Girar | T | Dry bushland | Fruits Leaflets | For treating diarrhea, diabetes, sore gum, hemorrhage, and loose teeth For curing sickness of stomach [19, 21, 27] |
Acacia albida Del. | Grar | T | Dry bushland | Latex | Latex from the stem pounded is taken with honey for curing amebiasis; for treating fire wound [13, 27] |
Acmella caulirhiza Del. | Yemdir berbere | H | Wetlands, forest floors, stream banks | Leaves Flowers | Used for curing tonsillitis via chewing the flowers and spitted on tonsillitis [18, 22] |
Aerva javanica (Burm.f.) Schultes | Nech shinkur | S | Dry sandy plains, dried river course | Root | For treating cancer [20, 24] |
Allium sativum L. | H | Irrigable cultivated land, home garden | bulb | For preventing and treating malaria [7, 13, 18, 22, 23, 25] | |
Amaranthus caudatus L. | Chigogot | H | Roadsides, riverbanks, floodplain | Leaves | Used for curing diarrhea via pounded and boiled leaves [18, 22] |
Aloe monticola Reynolds | Eret | H | Steep bare mountain slopes | Root | For also curing anthrax by pounding the root and mixing it with cold water and local alcohol [12, 22] |
Aloe macrocarpa Reynolds | H | Rocky slopes | Leaves | For preventing wart by powdering leaf and then mix it with honey [12, 22, 26] | |
Artemisia abyssinica Sch. Bip. ex. Rich | Chigugn | H | Juniper forest, open grassland, fallow fields | Fresh root | For preventing evil spirit by smelling and drinking after crushing the root and normalizing it in water [7, 22, 25] |
Asparagus africanus L. | Yeset qest | H | Acacia woodland Forest margins | Roots | For curing uterine and breast cancer [17, 20, 24] |
Barleria eranthemoides R. Br. ex C. B. Cl | Yeset af | S | Acacia woodland Scrublands | Roots | For curing hear burn [12] |
Bersama abyssinica Fresen. | Azamir | T | Riverine forest, rainforest | Leaves-stem | For treating wound by squeezing the leaves and creaming on the wound [22, 24] |
Bridelia scleroneura Mul. Arg. | T | Open woodland Dry riverine forest | Seeds | For curing skin diseases by crushing and applying on wound parts [12, 18, 19] | |
Brucea anti dysenterica Fresen. | Abalo | S/T | Montane, evergreen forest margins | Leaves | For treating cancer, skin problem, leprosy, and external parasites [6, 25] |
Buddleja polystachya Fresen. | Anfar | T | Degraded woodland in cultivated fields, around houses | Leaves | For treating the cattle eye diseases by chewing and spitting on the affected area [18, 22] |
Calpurnia aurea (Ait.) Benth. | Digita | S | Forest margins, bushland/grassland, favored by over grazing | Leaves Roots Seeds | For preventing poisonous snake bite by boiling the leaves and drinking with honey [12, 24] For curing amebiasis by crushing and boiling with leaf of coffee for drink. The seeds can be used as a fish-poison or as a cure for dysentery [12] |
Capparis tomentosa Lam | S | Riverine forest, grassland with scattered trees | Bark | For curing sore, anthrax, and evil eye using the powder of the bark with hot water [18, 20] | |
Carica papaya L. | papaya | T | Home gardens, small and large plantations | Seeds | Used for treating diarrhea and ascariasis by drinking the ground and boiled seeds with honey [12, 19, 27] |
Carissa edulis (Forsk.) | Agam | S | Open Acacia bushland | Root | Used for shorten the labor period just before delivery of women [19, 21] |
Carissa spinarum L. | Agam | S | Disturbed areas, along edges of roads, riverine vegetation | Roots | Used for preventing evil eye by inhaling the smoke of pounded roots. It is also used for treating wounds via applying the powder of the roots [12, 17, 19, 27] |
Clausena anisata (Wild.) Benth. | Limich | S | Montane forest margins, moist forest, secondary bushland | Leaves | For treating skin irritation by pounding together the leaf of C. anisata, Solanecio gigas, and Justicia schimperiana [6, 18, 20, 22] |
Citrus aurantifolia Swingle | Bahre-Lomi | T | In lowlands, evergreen forest | Fruit | For treating dermatophyte [6, 12, 19] |
Citrus sinensis (L.) Engl. | Birtukan | S | Cultivated in irrigable areas | Fruit Bark | Used for treating stomach infection and wound [12, 18] |
Clematis hirsuta Per. | Nech Azo hareg | Cl | Edges and remnants of montane forest, roadsides, paths | Leaves/stems Barks | Used for treating tumor/cancer on the neck [19, 24] |
Clematis simensis Fresen. | Hareg | Cl | >> | Leaves Root | Used for curing wound and stomachache [12, 18] |
Clerodendrum myricoides (Hochst.) | Misrich | S | Not specified yet | Root | Used for treating earache and headache [12, 20] |
Coffee arabica L. | Buna | S | In shaded coffee plantations | Seeds | For curing diarrhea by pounding and mixing with honey [6, 12, 18] |
Cordia africana Lam. | Wanza | T | Moist evergreen forest, riverine vegetation, woodland, grassland | Roots | For curing itching via applying the powder of the root on the area [6, 12, 13, 18, 19] |
Crinum abyssinicum | Yejb shinkurt | H | Waterlogged valley grasslands, swampy or along stream banks, fallow fields | Leaves | Used as treatment of tumor in general [13, 20, 24, 25] |
Croton macrostachyus Hochst. ex Del. | Bisana | T | Forest margin, edges of roads, disturbed areas, woodland | Bark | For curing splenomegaly and gonorrhea [12, 17, 18, 20, 22, 25] |
Croton zambesicus | Bisana | T | Stony streambeds, within broad-leaved deciduous woodland | Bark | Used for treating mental disturbance [21, 27] |
Cucurbita pepo L. | Duba/Yebarqil | H | Cultivated in home garden, farmland | Leaves | Used as a means of treating gastritis [12, 22] |
Datura stramonium L. | Atse-faris | H | Disturbed places, waste ground, near water holes, roadsides | Seed | Used for treating depression [22, 25] |
Dodonaea angustifolia (L.fil.) J.G.West | S | Not defined | Root | For curing toothache and wound [6, 7, 12, 18, 23] | |
Dorstenia barnimiana Schwienf. | Worq-bemeda | H | Woodland bushland, upland grassland, evergreen bushland | Roots/tubers | For treatment of tumor visible in body surface [20, 24] |
Echinops kebericho, Mesfin | Kebericho | H/S | Montane Acacia woodland, disturbed bushland | Root | For treating toothache, vomiting, and headache [22, 27] |
Ehretia cymosa Thonn. | Oulaga | H/S | Montane and riverine forest, evergreen bushland, hedgerows around compounds | Leaves | Used for curing bleeding, fibril illness [12, 18] |
Eucalyptus globules Labill. | Nech-bahirzaf | T | A wide variety sites (plantations) | Leaves | Used for treating influenza and allergic [7, 13, 18, 22, 23, 26] |
Euclea racemosa L. | Dedeho | S | Open montane and bushland; in clearings and along margins | Roots | For treating evil spirit, evil eye, and heartburn [12, 17] |
Euphorbia tirucalli L. | Qinchib | S | Live fence of home garden | Roots Latex | Used as treatment of tumor/cancer [7, 12, 23] |
Euphorbia abyssinica J. F. Gmel. | Qulkual | T | Steep rocky hillsides, around churches; live fence at higher altitudes | Latex | For treating skin cancer [20, 22] |
Rhus natalensis Beru ex Krauss. | H | Acacia-Commiphora woodland, wooded grassland, near rivers on various soil types | Leaves | Used for treating skin wound and boils [12, 21] | |
Ficus sycomorus L. | Banba | T | River and lake margins, woodland, forest edges and clearings, wooded grassland | Bark | For curing hepatitis [18, 19, 22] |
Gladiolus schweinfurthii (Baker) Goldblatt and M.P. de Vos | Milas golgul | H | Open grassland; Acacia woodland; rocky limestone slope | Root | Used for treating headache [12, 22, 24] |
Glinus lotoides L. | Meterie/Amkin | H | Disturbed sites | Leafy stem | For treating tapeworm |
Guizotia scabra (Vis.) Chiov. | Mechi | H | Open wasteland, grassland, weed of cultivation, roadside ditches, riverbanks | Leaves | Used as wound treatment [6, 22] |
Justicia schimperiana Hochst. ex A. (Nees) T. Anders | Sensel | S | Open woodland, riverine vegetation, live fence of house | Leaves | For preventing bat urine [6, 7, 12, 18, 20, 26] |
Harrisonia abyssinica | Ddugot | S | Montane forest and grassland | Barks | For giving human physical strength [21] |
Hagenia abyssinica (Bruccie)T.F.Gmel | Kosso | T | Montane forest and grassland Moist evergreen forest | Fruits | Tapeworm [7, 23, 25, 26] |
Laggera crispata (Vahl.) | Gemie | S | Cultivation and waste places, grassland, riverbanks | Leaves | For preventing dizziness [12, 20] |
Maesa lanceolata Forssk | T/S | Gallery forest, margin of evergreen forest, along river banks and streams, open woodland and valleys | Bark | For curing elephantiasis [6, 18, 26] | |
Malva verticillata L. | Lut | H | Paths and clearings in upland forest, upland grassland, cultivated areas near houses | Root | For curing cancer/tumor [6, 18, 24, 25] |
Mimusops kummel A. DC. | Safa/kummel | T/S | In gullies, in riverine forest, in riparian woodland, in woody vegetation on lake shores | Root | Used for preventing lung cancer [12, 18] |
Moringa stenopetala (E.G. Baker) Cufod. | Shiferaw | T | Cultivated in terraced fields, gardens, small towns, in riverine and woodland | Root | Used for asthma relief [7, 12, 21] |
Musa sapientum L. | Koba | H | Cultivated on large irrigated farms and in house gardens | Bulb | It is taken as an abortion medicine [19, 21] |
Nicotiana tabacum L. | Timbaho | H | Cultivated in villages, home gardens, tobacco farms | Leaves | For treating snakebite [6, 12, 18] |
Nigella sativa L. | Tikur azmud | H | Cultivated in homesteads, in fields; growing in wild | Seed | Used as treatment of headache [18, 22] |
Ocimum lamiifolium Hochst. ex. Benth. | Damakesie | S | Acacia-Commiphora bush- and woodland, limestone slopes, home gardens | Leaves | Fibril illness [7, 12, 18, 20, 22] |
Olea europaea L. | Woira | T | Home garden, monasteries and churches, woody vegetation | Leaves/roots | For curing dysentery, wound stomachache, bone TB [6, 12, 17, 18, 20, 26] |
Opuntia ficus-indica (L.) Miller | Yebereha qulkual | S | Disturbed areas, degraded areas, live fence of houses | Leaves | For killing malaria vectors [22, 25] |
Plumbago zeylanica L. | Amira | H | Disturbed habitats by roads and paths, bushland, woodland, savannah | Root | For preventing gonorrhea and hemorrhoids as well as for toothache [12, 20, 22] |
Verbascum sinaiticum Benth. | H | Disturbed sites | Root/leaves | For treating heart disease, cancer, trypanosomiasis [6, 20, 27] | |
Premna schimperi Engl. | Chocho | S | Degraded and secondary forests, grassy meadows and along paths in forests | Root Leaves | Used for treating mastitis Used for preventing boils [12, 18] |
Solanum nigrum | Embuay | H | In cultivation and ruderal areas, on road-, hill-, river- or streamsides; in bushland areas | Leaves roots, stems | Leaf, root, and stalk are used for cancerous sores and wound treatments. Stems eaten as pot herb for virility in men and for dysmenorrhea in females, for dysentery, and sore throat [21, 24] |
Solanum incanum L. | Tikur awud | H | Cultivated and riverine gallery forest, disturbed habitats | Leaves/roots | Used for curing bleeding, menstruation, amebiasis [12, 17, 18, 19, 20] |
Stephania abyssinica (Dill. and A. Rich.) Walp. (Etse Eyesus, Nech- Hareg) | Yayit hareg | Cl | In thickets bordering forest margins, hillsides, cultivated fields, in clearings | Root | For treating external tumor/cancer and stomachache [6, 12, 8, 24, 25] |
Stereospermum kunthianum Cham. | Arziniya | S/T | Open woodland and savanna, widespread in tropical Africa | Bark | Used for treating kidney via drinking the juice crushed from bark [12, 13, 19] |
Tamarindus indica L. | Humer/Roqa | T | Grassland, woodland Combretum bushland, riparian | Fruit | Used for curing stomachache; it is also used for treating bile and intestinal worm using the fruit juice with hot water in the morning before breakfast [12, 19] |
Thunbergia ruspolii Lindau | Marte | H | Combretum-Terminalia woodland, grassland, wooded grassland, evergreen forest, seasonally waterlogged | Not reported | For curing poisonous snakebite [21] |
Thymus capitatus (L.) Link | Tosign | H | Not reported | Leaves | For curing stomach diseases, cough, and asthma [21, 25] |
Tragia cordata Michx. | Alebilabet | H | Among open rock bushlands | Root | For treating urinary tract and external parasite [12, 18, 19] |
Tribulus terrestris L. | Kurnchit | H | Open and disturbed places, often on sandy soils | Stem Fruit Seed | For curing scabrous skin diseases For congestion, headache, hepatitis, liver, vertigo, stomatitis, kidneys, liver, and vision For treating anemia, hemorrhoid coughs, fluxes, and stomatitis [21] |
Urtica pilulifera L. | Sama | H | Unknown | Leaves | For curing sore joints by mixing the plant juice with oil; provide cure for rheumatism and hemorrhage [18, 21] |
Vernonia amygdalina Del. | Girawa | S | Bush/woodland, forest habitats, home gardens | Leaves | For preventing headache and intestinal worm and for treating tumor/cancer in general [6, 7, 12, 18, 20, 22, 24, 26, 27] |
Xanthium strumarium L. | Deha nikel | H | Wet forest margins, in riverine vegetation by streamside | Leaves | Used for treating dandruff [12, 27] |
Ximenia americana L. | Enkoy | S | Acacia woodland, Acacia-Ballanites, woodland, Combretum-Terminalia, wooded grassland | Fruit Kernel Root | Oil from the fruit kernel is applied to fresh wounds to prevent infections and also used by some people, who have their ears or lips pierced Used for treating stomachache and tonsillitis [6, 12, 19, 20] |
Warburgia ugandensis Sprague | T | Transitional montane forest, adjacent woodland | Stem | Used for treating boils and cough [12, 17] | |
Withania somnifera L. Dunal | Gizawa | S | In cultivations, disturbed places in the highlands, on lake shores, along riverbanks in disturbed places in open woodland | Leaves | Used for treating malaria [12, 13, 17] |
Ziziphus spina-christi (L.) Desf | Qurqura | T | Wooded grassland, along dry riverbeds, edges of cultivations and home gardens | Fruits | Used for treatments of stomachache, tonic, for tooth aches, and tumors [21, 13] |
List of reviewed Ethiopian medicinal plants used for various traditional disease treatments with their parts and ecology/habitat.
NB: Ha, habits; T, tree; S, shrub; H, herbs; Cl, climbers; T/S, shrubs/trees; H/S, herbs/shrubs.
Based on the review, all plant growth forms were not equally used as remedies, because of the difference in distribution among the growth forms. Accordingly, the life forms of medicinal plants reviewed constituted 18 trees (22.78%), 23 shrubs (29.11), 29 herbs (36.71%), 3 climbers (3.81%), 4 trees/shrubs (5.06%), and 2 herbs/shrubs (2.53%) (Figure 1). Of all life forms, herbs were, thus, the major medicinal plants used by the community for human treatment followed by shrubs and trees.
Life forms/habits of medicinal plants reviewed with their percentage (%).
The review indicated that the plant parts used for medication preparation by the traditional healers are variables. Healers mostly used fresh specimens from commonly available plants [25] to prepare remedies for their patients; this might be mostly due to the effectiveness of fresh medicinal plant parts in treatment since the contents are not lost before use compared to the dried ones [12]. As also referred from many authors, the traditional healers have harvested leaves, roots, barks, seeds, fruits, stems, flowers, barks, seeds, or latex of medicinal plants (Figure 2) to prepare their traditional medicines for their patient treatments. As depicted in Figure 2, most remedies were prepared from the leaf (32.98%) and root (29.79%) parts of the medicinal plants to treat the diseases compared to the other parts of them. This finding of the review is in line with the findings of the majority of authors’ papers (e.g. [18, 25, 27]). The main reason that many traditional medicine practitioners used the leaf parts compared to others for remedial preparation is due to their accessibility and for preventing them from extinction [25]. In fact, harvesting the root parts of the medicinal plant for preparation of traditional medicines has negative consequences on the existence of the plants themselves in the future. That is why most of the medicinal plants are currently at risk, declining highly due to them using their root parts besides other human pressures.
Distribution of medicinal plant parts used for disease traditional treatments by healers.
Using these medicinal plants revised in Table 1, the local communities could be able to treat about 69 disease types. The disease types treated by these various medicinal plants were skin disease, gonorrhea, diarrhea, wound, tapeworm, snake bites, stomachache, headache, evil eye, heartburn, cancer/tumor, and malaria (see Table 1 for the detail). Particularly, most of the patients (who come from rural areas) with their perspective disease types have been treated by traditional healers, before coming to clinics and/or hospitals located far away by many kilometers from their residential areas. The disease types most frequently treated by traditional medications (traditional healers) provided by those medicinal plants were stomachaches, wounds, cancers/tumors, skin diseases, headaches, toothaches, and coughs and diarrhea, which took the first, second, third, fourth, fifth, sixth, and seventh ranks, respectively, although the majority of disease types were frequently treated less than four times, ranging from one to three times (Table 2). This also points out that one medicinal plant species can be used for treating more than one disease types.
No. of disease type | Frequency of treatments | Rank |
---|---|---|
1 (Stomachaches) | 12 | 1 |
1 (Wounds) | 11 | 2 |
1 (Cancer/tumor) | 10 | 3 |
1 (Skin diseases) | 7 | 4 |
1 (Headaches) | 6 | 5 |
1 (Toothaches) | 5 | 6 |
2 (Cough, diarrhea) | 4 (each) | 7 |
8 (Tonsillitis, malaria, evil eye, snakebites, dysentery, boils, throat sore, intestinal worms) | 3 (each) | 8 |
10 (Earache, amebiasis, urinary tract, heartburn, external parasites, fibril illness, kidney, liver, hemorrhoids, tapeworms) | 2 (each) | 9 |
43 (Elephantiasis, asthma, eye diseases, diabetes, anthrax, leprosy, etc.) | 1 (each) | 10 |
Disease type categories and their rank based on their frequency being treated by different medicinal plant species (as described in Table 1).
Because of this, medicinal plants are very vital in providing traditional medicines, prepared by local healers, and thereby used for treating and curing different types of diseases that affected the local communities, where they occurred. Even, following the traditional uses and effectiveness of the medicinal plants [23], the traditional healers are also popular by the local societies, providing cultural values. The study of [23] also confirmed that the traditional health practitioners are with a good knowledge of medicinal plants used to treat different diseases of their locals.
In addition to these contributions pertinent to traditional medications and cultural values, the individual medicinal plants could provide regulating, provisioning, and supporting services. For instance, they could provide regulating services via regulating soil erosion, climate change, disease, pollution, and pollination; they also provide provisioning services such as fuel wood, timber for house construction, food (fruits, honey), and fodder and shelter for wild animals [11]. Hence, almost all of the medicinal plants are multipurpose species, providing more than one benefits.
As referred from the revised documents for this review, the habitat preference of medicinal plants varied from place to place (Table 1). As referred in Table 1 and Figure 3 drawn from the review, the majority of medicinal plants were available along the edges of river/streams and wetlands, disturbed sites, grasslands, cultivated lands, woodlands, bushland, grasslands, and home gardens. Generally, the majority of medicinal plants were found in wild compared to those plants found in cultivated and home gardens together. Many of the authors of the reviewed articles (e.g. [12, 23, 25]) confirmed that the majority of medicinal plants were collected from natural habitats or wild by traditional practitioners compared from home gardens. Among medicinal plants found along stream/riverbanks (Figure 3), the majority of them are supposed to be medicinal plants having herbal life forms/habits (Figure 1). This could be due to their shallow roots, which cannot bring water from the deep parts of their habitats.
Summary of distributions of medicinal plants along their major habitat categories in Ethiopia.
Because of the anthropogenic factors such as over harvesting, fire/deforestation, agricultural expansion, overgrazing, and urbanization [25, 28], most of the medicinal plants have also been lost. This implies that the availability and accessibility of most medicinal plants in Ethiopia are also very difficult [25]. Hence, most of the medicinal plants were restricted to areas (such as cliffs, hills/mountains, gorges, disturbed areas, riverbanks, and valleys of wild) which are not easily accessible to use/harvest them. Not only is this, but also the knowledge of traditional practitioners pertinent to identification of medicinal plants with their parts and ecology and the process of preparation of herbal medicines and medication with their quality/effectiveness are declined/lost since the knowledge is mostly transferred orally from generation to generation, not documented. Therefore, the effects of human on the natural habitat of medicinal plants are the problems for the conservation of medicinal plants and associated knowledge of traditional healers [12]. With the present ecological and socioeconomic changes, medicinal plants together with the associated ethnobotanical knowledge in Ethiopia are under serious threat and may be lost at alarming rate.
Under such circumstances, the use of plants for medicinal purposes will also decline, and consequently the once effective traditional healthcare system will also be lost [19]. Hence, documenting medicinal plants with their uses and ecology as well as the knowledge of traditional practitioners is so vital. Moreover, it is very essential to give conservation priority for those medicinal plants through protecting them where they are found, propagating them in cultivated areas and home gardens, and creating awareness to the locals. Hence, following community and research-based approach is advised to save medicinal plants from their loss and extinction.
Plant materials are used throughout developed and developing countries as home remedies, as over-the-counter drug products, and as raw materials for the pharmaceutical industry, which represent a substantial proportion of the global drug market [29]. Thus, the traditional herbal medicines and their preparations have been widely used for thousands of years in many countries. Therefore, it is so essential to overview here some modern control histological techniques or tests, suitable standards, and practical experiences used for assessing the quality of medicinal materials and their products. Quality control of herbal medicine using histological techniques and pharmaceutical practices is also very vital for avoiding the risks happened on patients and the beliefs in services provided by traditional healers. According to [30], quality control is a phrase that refers to processes involved in maintaining the quality or validity of the manufactured products. However, the quality control of herbal medicine is beyond this, meaning it is the management of medicinal plants and their products during cultivation, identification process of the plant species with their parts and localities (their being free from polluted environment causing diseases), and medicine preparation including its components, medication processes, storage standards, and dosage; all should be taken into account. This means, without proper all-round quality control, there is no assurance that the contents of the herbs contained in the package are the same as what are stated outside the package [30]. Climatic factors (prevailing temperature, rainfall, humidity, altitude of the growing region, light), nutritional factors (nutrients, pH, cation exchange capacity), harvesting factors (age, season, collection time, plant organ), and post-harvesting factors (storage hygiene, drying process) are the major factors affecting the contents and composition of medicinal plant raw materials and their products [29, 30]. For these, some of the most important laboratory test methods (histological techniques), common sense, and good pharmaceutical practices are used [29]. Techniques such as thin-layer chromatography and microscopic and electrophoretic techniques are widely used to evaluate the quality of herbal drugs [14, 29, 31] and the content and quality of meats [32] as well. These techniques and good pharmaceutical practices are also used to support the development of national standards based on local market conditions, with due regard to existing national legislation and national and regional norms [29]. Therefore, improved and currently available pharmaceutical analytical methods led to improvements in harvesting schedules, cultivation techniques, storage, product purity, and activity and stability of active compounds [30].
Among others, thin-layer chromatography, macroscopic and microscopic examinations, gas chromatography and volatile components, and electrophoretic techniques [14, 29] are the most important quality control methods for medicinal plant materials and their products, described briefly here below.
Herbal materials are categorized based on sensory, macroscopic, and microscopic characteristics, which are the first steps toward establishing the identity and the degree of purity of such materials, and should be carried out before any further tests undertaken, according to [29]. Therefore, to establish identity, purity, and quality, visual inspection (macroscopic examination) provides the simplest and quickest means. Herbal materials should be entirely free from visible signs of contamination such as insects, molds (fungi), and other animal contamination, including animal excreta; any soil, stones, sand, dust, and other foreign inorganic matter must also be removed before herbal materials are cut or ground for testing [29]. Moreover, plant parts used for medication with abnormal odor, discoloration, slime, or signs of deterioration should be detected to exclude them from being used for medication products.
Moreover, during storage, products should be kept in a clean and hygienic place for avoiding contamination occurring; special care should also be taken to avoid formation of molds, since they may produce aflatoxins [29]. For determination of foreign matter and storage conditions, macroscopic examination can properly be employed for determining the presence of foreign matter in whole or cut plant materials. For these, common sense and good pharmaceutical practices are used. Such common senses and good pharmaceutical practices can, even, be used after laboratory tests since the test procedures cannot take account of all possible impurities in deciding whether an unusual substance not detectable by the prescribed tests can be tolerated [29]. For instance, if a sample is found to be significantly different from the specifications in terms of color, consistency, odor, or taste, it is considered as not fulfilling the requirements. However, such examination may need further microscopic examination for either rejecting or accepting their requirements.
This technique is simple, can be employed for multiple sample analysis, and so has manyfold possibilities of detection in analyzing herbal medicines [14]. The report of [29] also confirmed that TLC is used for evaluating herbal materials and their preparations; particularly, it is valuable for the qualitative determination of small amounts of impurities.
Many pharmacologically active components in herbal medicines are volatile chemical compounds; thereby, the analysis of volatile compounds by gas chromatography is very important in the analysis of herbal medicines [14]. GC is a useful analytical tool in the research field of herbal medicines via analyzing their volatile oils, which have a number of advantages: (1) the GC of the volatile oil gives a reasonable “fingerprint” which can be used to identify the plant and to detect the presence of impurities in the volatile oil, and (2) the extraction of the volatile oil is relatively straightforward and can be standardized, and the components can be readily identified using GC analysis [14].
It is a good tool for producing the chemical fingerprints of the herbal medicines and has similar technical characteristics of liquid chromatography [14]. Electrophoretic method, especially capillary electrophoresis (CE), used in the analysis of herbal medicines, is a versatile and powerful separation tool with a high-separation efficiency and selectivity when analyzing mixtures of low-molecular-mass components [14].
There are various forms of medicinal plants including trees, shrubs, climbers, and herbs; of those herbal medicinal plants are dominantly used for different human and animal treatments in Ethiopia. These plants are collected mainly from riverbanks, cultivated areas, bushlands, forest, woodlands, and grasslands, among others. They are used for treatments of stomachaches, dysentery, diarrhea, asthma, cancer, evil eyes, earaches, sores of throat and gum, cough, and so on. For such treatments, these medicinal plants have specific parts used for treatment; most of them are leaves and roots. Hence, traditional medicine plays a significant role in the healthcare of the majority of the people in developing countries, including Ethiopia, and medicinal plants provide valuable contribution to this practice. However, the vegetative resources that are unique to the country, particularly used for medication, are dwindling due to continuous exploitation and pressure on the limited resources. Hence, conservation priority should be given to such medicinal plants and their habitats besides the knowledge of traditional practice of medication via designing appropriate strategies, particularly in the rural areas of the country, where there are less accessibility to clinics and hospitals with their medicines and health experts (doctors). Community- and research-based conservation mechanisms could be an appropriate approach for mitigating the problems pertinent to the loss of medicinal plants and their habitats and for documenting medicinal plants and the knowledge of traditional healers on how to prepare and provide the traditional medication to their patients. Medicinal plants should be multiplied through medicinal gardens, proper handling practices, and scientific development. Moreover, for controlling the quality of medicinal plant materials and their products, chromatography, electrophoretic, macroscopic/microscopic techniques, and pharmaceutical practices are the most important tools.
The authors would like to thank Debre Birhan University of Ethiopia for its library facilitation while writing this manuscript. We also extend our thanks to Hirut Fisiha for assisting us during editing and revising of this manuscript.
The authors declare that there is no any conflict of interest between authors and other organizations as well.
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