Antioxidant activity/ IC50 Inhibition values of doum part by different methods.
The doum palm (Hyphaene thebaica) is a type palm tree which has a wood texture and has edible oval fruits and the origin native to upper Egypt. The trunk of this small palm is dichotomous. It is one of the most important useful plants in the world. All parts of doum palm have a useful role such as fiber and leaflets which used to weave baskets and doum nuts which have antioxidants and secondary metabolites such as tannins, phenols, saponin, steroids, glycosides, flavonoid, terpenes and terpinoids. Also, roots, stems and leaves are used in medicine, ropes and baskets. Studies on anti-inflammatory, antioxidant, antimicrobial, anticancer and pharmacological potential of Hyphaene thebaica extracts and its major phytoconstituents like the phenolic, essential oil and flavonoid compounds are extensively discussed in this review.
- phenolic compounds
2. Botanical description
The doum palm is a dioecious palm and grows up to 17 m (56 ft) high. The trunk, which can have a girth of up to 90 cm (35 in), the trunk divided into two branches, each branch divided again into two branches, and the ends of the branches contain tufts of large leaves. The bark is smooth, dark gray and contains the scars of fallen leaves. The petioles are about 1 m long, sheathing the branch at the base and contain curved claws. The leaves are fan-shaped and measure about 120 by 180 cm (47 by 71 in) (Figure 1). Male and female flowers are produced on separate trees. The inflorescences are similar in general appearance, up to about 1.2 m (3 ft. 11 in) long, irregular in the branching and have two or three spikes in each branch. Male flowers have a short-stalk, solitary in pits of the spadix, spathe-bracts encircling the spadix, pointed. Branches of female spadices become thicker in the fruiting stage. Woody fruits are produced in the female palm that continues on the tree for a long time. They are 6–10 × 6–8 cm, smooth, rectangular to cubical with rounded edges, shiny brown when ripe. Its fresh weight is about 120 g and dry weight is about 60 g and each one containing a single seed. The size of seeds about 2–3.5 × 3 cm, the color is ivory, truncate at the base and the apex is obtuse .
3. Traditional uses
Also, aqueous doum palm extracts increased the viability and activity of some certain dairy starter cultures which used in the manufacture of some dairy products especially probiotics .
4. Chemical composition of doum fruit
Doum fruit has a high-quality protein varied between 2.86 and 5.01%, high proportion of lysine and cysteine of crude protein varied between 4.09–4.16% and 0.2–1.62%, respectively, the limited amino acid threonine, crude fat varied between 1.2 and 8.4%, crude fiber varied between 52.26 and 66.5%, the most important carbohydrates component was mannose varied between 13 and 75.9%, also the presence of calcium, magnesium, potassium, iron sodium and negligible amount of nickel, cobalt and molybdenum. Phytochemical compounds of doum fruit such as tannins, saponin, steroids, glycosides, flavonoid, terpenes and terpinoids were found at low and moderate concentrations .
5. Pharmacological activities of doum
Various extracts of
Also, triglycerides were independently related to coronary heart disease and most of the antihypercholesterolemic drugs did not decrease triglycerides levels, but the aqueous extracts of doum fruits lower it significantly . This effect may be related to the increase in endothelium bound lipoprotein lipase which hydrolyzes the triglycerides into fatty acids. Previously, the authors reported that the hypolipidemic properties of the aqueous pulp suspension of doum could be partly due to the presence of glycosides . Saponins have been reported to form complexes with cholesterol and bile in the intestine thereby indirectly reducing the cholesterol level in the blood . In addition, administration of 200, 400 and 800 mg/kg body weight of aqueous extracts of both stem and bark of
6. Bioactive compounds of doum palm
6.1. The chemical structure of volatile components
Doum fruit yielded a yellowish color volatile oil with a fragrant aromatic odor at a yield of 0.5% (fresh wt). Physical constants measured include: specific gravity (0.168) and refractive index (1.383). The result of analysis of essential oil of doum by GC and GC–MS techniques revealed the presence of a total 57 compounds (Figure 2). Monoterpenes represented 15.97% including compounds such as sabinene (0.82%), ß-pinene (1.97%), limonene (2.42%), terpinen 4-ol (1.77%), α-terpineol (0.95%), sesquiterpenes (3.2%), diterpenes represent 40.49%, of which incensole (19.81%) and incensole acetate (17.52%) were found to be the main components, non-terpenoidal components amount to 15.21% of which octylacetate (9.38%) was found to be the major and fatty acid (8.55%) with the main component palmitic acid (5.90%). Oxygenated compounds constituted 66.78% of the total compounds identified which indicated the economic value of this oil. Fruit of doum oil was found to contain volatile diterpenes especially cembrene A which showed cytotoxic activity, and this revealed the medical importance of the volatile oil of doum which could be utilized medicinally .
6.2. Chemical structure of doum fruit phenolic compounds
6.2.1. Total soluble phenols content and compounds
Different total soluble phenols values in doum were published in different studies; it ranged from 45.08 to 64.90 mg GAE/g DW . While it recorded the highest values in pitted doum fruit extracts varied from 116.26 to 139.48 mg GAE/g DW . The bioactive potential of fruits and vegetables attributed to their high content of polyphenols .
The most abundant phenolic compounds recorded in doum were metoxicinnamic acid, sinapic acids (hydroxycinnamic acids), chlorogenic acid, catechin, p-hydroxybenzoic acid, vanillic acids, 3,4 di hydroxycinnamic acid, caffeic acid, 2-hydroxycinnamic acid, Epicatechinand cinnamic acid, respectively (Figure 3) . Doum pulps exhibited higher caffeic acid contents in comparison to the domestic fruits . The highest four concentrations of phenolic compounds in doum fruit aqueous extracts were found to be 3-OH tyrosol, E-vanillic acid, catechin and chlorogenic acid, while the lowest were of alpha-coumaric acid, cinnamic acid, p-coumaric acid and coumarin .
6.2.2. Total flavonoids content and compounds
The total flavonoids content in different extracts of doum fruit extracts varied widely ranging from 24.04 to 47.17 mg rutin/g DW . Similar results found that the content of flavonoids (mg/g) of fruits of
6.2.3. Chemical structure of doum palm leaves phenolic compounds
Doum leaves were extracted in 80% ethanol and filtrate. The aqueous ethanolic extract used to scavenge reactive oxygen species (ROS). The phenolic content of doum was determined by using HPLC and recorded the presence of four major compounds correspond to Gallic acid, Quercetin glucoside, Kaempferol rhamnoglucoside, Dimethyoxy quercetin rhamnoglucoside, respectively. An in-depth phytochemical investigation showed the presence of 14 compounds (Figure 5): 8
7. Biological activities of doum fruit extracts
7.1. Antioxidant activity of doum fruit extracts
Doum is one of the commonly consumed traditional beverages in Egypt and is rich in polyphenolic compounds. Several studies have recorded that doum fruit extracts contain high amount of flavonoids, phenols and used as antioxidant and antibacterial activities (Table 1), which can alleviate the adverse effects of oxidative stress and prevent diseases caused by pathogenic bacteria . It is well-known that plant phenolic compounds are highly effective free radical scavengers (Figure 6). Phenolic compounds antioxidant activity is associated with the presence of functional groups in the ring and the annular structure of the molecule, conjugated double bonds . The antioxidant activity increased with the increase in concentration and the consumption of doum plant which would exert several beneficial effects by the value of its antioxidant and antimicrobial activities .
|Doum part||Method used||Extract type||Antioxidant activity/ IC50 Inhibition values||References|
|Fruit||DPPH||Dichloromethane||343.4 μ moles trolox /g||Salih and Yahia |
|Fruit||DPPH||Hexane||42.67 μ moles trolox /g||Salih and Yahia |
|Fruit||DPPH||Ethanol||IC50 = 172.7 μg/ml||Aboshora et al. |
|Fruit||DPPH||Methanol||IC50 = 107.6 μg/ml||Aboshora et al. |
|Fruit||DPPH||Water 12 h||40.77%||Aamer |
|Fruit||DPPH||Methanol||64.55%||Mohamed et al. |
|Bark||DPPH||Methanol||90.7%||Fayad et al. |
|Fruit||FRAP||Methanol||28.93%||Sani et al. |
|Fruit||FRAP||Distilled water||31.91%||Sani et al. |
|Fruit||FRAP||Methanol||24.3%||Mohamed et al. |
|Fruit||FRAP||Dichloromethane||13.57 μmoles trolox /g||Salih and Yahia |
|Fruit||FRAP||Hexane||7.69 μmoles trolox /g||Salih and Yahia |
|Leaves||Superoxide anion radical||Ethanol||IC50 = 1602 μg/ml||Eldahshan et al. |
2,2-Diphenyl-1-Picrylhydrazyl (DPPH) is a free radical that received an electron or hydrogen radical and become a stable diamagnetic molecule . DPPH was determined by the decrease in its absorbance at 517 nm, which was induced by antioxidants. The ability of hydrogen donating in the polyphenolic compounds in the doum fruit extracts helps in the scavenging ability of DPPH. The antioxidant activity measured from doum extracts was 343.4 μ moles trolox equivalents/g DW in hydrophilic extract and 42.67 μ moles trolox equivalents/g DW in lipophilic extract when using DPPH . In addition, the IC50 values of doum extracts varied from 107.6 to 172.7 μg/ml . These results are lower than the results reported by Abou–Elalla  who found that the aqueous doum extract exhibited 50% antioxidant activity (IC50) at the concentration of 1000 μg/ml, also 1500 μg/ml extract exhibited 80% antioxidant activity. Also, the aqueous ethanolic extract of doum leaves appeared to be a potent scavenger of reactive oxygen species . Strong correlation between total phenolics content and total antioxidant activity reported in many studies concluded the significant role that total phenols can play in antioxidant activity .
Iron is known as an essential transition metal element in the human body for the activity of many enzymes and for some important proteins participated in cellular respiration, O2 transport, and redox reactions. However, because its transition metal, it contains one or more unpaired electrons that enable them to share in one-electron transfer reactions. Hence, its potent catalysts of autoxidation reactions, such as involvement in the production of OH− from H2O2 in the Fenton reaction and in the decay of alkyl peroxides to alkoxyl and hydroxyl radicals . Because of this property, transition metal chelation to shape low redox potential complexes is significant antioxidant property and measuring chelation of iron (II) is one method for estimating this property . The reaction is based on the relationship of an antioxidant toward iron (II) in relation to ferrozine, the assay is affected by both concentration of antioxidant and binding constant and thus only powerful iron antioxidant chelator is detected. With this assay, many plant phenolic compounds have been described as antioxidants due to their chelating ability to iron ions.
It displayed the Fe2+ chelating effect in a concentration-dependent manner. The antioxidant activity measured from doum extract was 13.57 μmoles trolox equivalents/g DW in hydrophilic extract and 7.69 μmoles trolox equivalents/g DW in lipophilic extract when using FRAP assay . These results are in agreement with previous study, who found that doum fruit contained contain iron (II) chelating activity .
Superoxide radical is harmful to the body because it is a portent of the hydroxyl radical in the Fenton reaction and is the part of lipid peroxidation as an allylic hydrogen abstractor. Phenazine methosulphate/ß-NADH/nitro blue tetrazolium (PMS/NADH/NTB) system is used to determine superoxide radical . Again, an antioxidant activity can come about by antioxidant donation of hydrogen or electron to superoxide or by direct reaction with it. Using this assay, doum fruit was found a very poor activity toward superoxide; it contains 0.02 mmol gallic acid equivalents/g extract. In addition, the significant inhibition percentage of superoxide generation was shown at 300 μg/ml concentration of
7.2. Anticancer activity of doum fruit extracts
Free radicals can react with biomolecules, causing extensive damage to DNA, protein, and lipid, which are considered to be related to aging, degenerative diseases of aging, cancer [48, 49]. Antioxidants play an important role in the later stages of cancer development. The oxidative stress is defined as the imbalance between oxidants and antioxidants in favor of the oxidants potentially leading to damage in human cells. Physiologically, antioxidants play a major role in preventing the formation of free radicals, which are responsible for many harmful oxidative processes . Antioxidants may be synthetic or of natural source . Antioxidants play an important role in the later stages of cancer development. The methanol extract of
The logic behind this is that the antioxidant will reduce, if not prevent, the DNA mutations and adducts caused by cytosolic free radicals and consequently prevent the initiation of cancer through induction of mutations. The anticancer activity will be useful in early eliminating any newly formed neoplastic cells that are not clinically detectable. However, these cancer cytotoxic agents should be with minor or no side effects as they are planned to be used for prolonged time preventing cancer formation .
7.3. Anti-inflammatory activity of doum fruit extracts
Ulcerative colitis (UC) and Crohn’s disease (CD) are two major categories of inflammatory bowel diseases (IBDs). Familiar drugs that are administrated for the management of IBD include glucocorticoids and sulfasalazine. Antibiotics, monoclonal antibodies (Infliximab) and immunosuppressants are also sometimes used for difficult disease conditions . These medicinal agents have side effects, and they could not suitably cure IBD patients . In many studies, it has been reported that antioxidants show useful effects in experimental colitis . The effect of various herbal drugs on experimental models of inflammatory bowel diseases (IBD) has been reported earlier with the antioxidant potential as the main mechanism of action against IBD . As the plant
Doum extracts treatments inhibited the activity of cyclooxygenase (COX-1), an enzyme known to be involved in inflammation .
7.4. Antimicrobial activity of doum fruit extracts
Methanol and aqueous extracts of doum fruit showed higherantibacterial activity against Gram-positive bacteria and Gram-positive bacteria except for
The authors would like to show appreciation to Faculty of Agriculture, Cairo University, Department of Biochemistry and Faculty of Education, Ain Shams University, Department of Biological and Geological Sciences for continuing cooperation to support research that provided facilities necessary to accomplish the most wanted objectives of research.