Antioxidant activity of different bamboo species.
Bamboos are described as one of the most important renewable, easily obtained, and valuable of all forest resources. These plants belong to the grasses’ family (Poaceae), which covers about a quarter of the world’s plant population, within the subfamily Bambusoideae. The estimated diversity of bamboos in the world is approximately 1400 species, distributed in 116 genera. Bamboo species have been used in Southeast Asia, as a base material to produce paper, furniture, boats, bicycles, textiles, musical instruments, and food, and their leaves have also been used as a wrapping material to prevent food deterioration since ancient times. These species accumulate biologically active components such as polyphenols and other secondary plant metabolites that might explain the use of bamboo leaves in Asian traditional medicine for the treatment of hypertension, arteriosclerosis, cardiovascular disease, and certain forms of cancer. Besides the usual secondary metabolites, bamboo extracts may contain biologically active peptides and polysaccharides that still need to be further studied for their activity and their synergistic with other metabolites. Most of the studies found in the literature are from Asian bamboo species, and the potential of the Southern American species is yet to be explored.
- traditional medicine
Bamboos are described as one of the most important renewable, easily obtained, and valuable of all forest resources. Bamboo species have been known and used by human kind since the beginning of civilization; its use as building materials can be traced back to the pre-ceramic period 9500 years ago, while relics from bamboo mats and baskets were dated at 3300-2800 BC . In Asian countries, their leaves are used as a food wrapping material to prevent food deterioration since ancient times, besides using the culms as a construction material. In this region, bamboo leaves are described in the traditional medicine for treating hypertension, arteriosclerosis, cardiovascular disease, and certain forms of cancer. These therapeutic properties are most likely mediated by their antioxidant capacity.
These plants form a large subfamily of the grasses (
Bamboos have a large ecological amplitude in response to canopy disturbances and can become super dominant species after opening in natural or anthropic origin. In addition, they have a very rapid growth from the stem base to the top of the plant . Currently, bamboo species are considered as one of the most available forest resources. In tropical and subtropical areas, bamboos represent approximately 20–25% of the total biomass, which contributes to their status as one of the most important renewable resources . Considered a rapid atmospheric carbon sink, bamboo has also physical and mechanical properties that make it suitable to be used in the development of products normally produced with native wood or from reforestation, such as construction components, furniture industry, cables for agricultural tools, panels, and plates, among others.
Bamboo species share some common characteristics of their phenolic composition with other grasses. They contain several glycosylated flavones whose aglycones are represented by apigenin, luteolin, and tricin [9, 10, 11]. This is also the case in, for example, durum wheat (
2. Biological activities of bamboo species
2.1 Antioxidant potential of bamboos
The production of reactive oxygen species (ROS) is a result of normal cell metabolism; however, once the oxidative processes start to be predominant over the antioxidant, the imbalance called “oxidative stress” can be harmful to human body . Oxygen’s reactivity, which is under normal conditions, permits the high-energy electron transfer allowing the formation of big quantities of adenosine-5-triphosphate (ATP) by the oxidative phosphorylation and jeopardizes the cells of living organisms by attacking molecules such as proteins, lipids, or DNA . Free radicals created in this process cause various genetic changes causing cancer, cardiovascular and neurological diseases, nephropathy, rheumatoid arthritis, and other disorders . Plants provide an abundant source of the substances with biological activity. In case of antioxidant protection, flavonoids stand for one of the most efficient molecules combating the oxidative stress.
There are two terms describing the antioxidant efficacy: “antioxidant activity” and “antioxidant capacity,” and they have different meanings. The prior expresses the kinetics of a reaction between an antioxidant and the prooxidant or radical scavenging activity, and the latter one measures the thermodynamic conversion efficiency of the reaction. The analytical methods to evaluate antioxidant activity may be divided into electron transfer (ET)-based and hydrogen atom transfer (HAT)-based methods. ET-based methods utilize the process of the reduction in the oxidative component by the antioxidant, which leads to the change in color that can be observed . Within this group, we can specify: DPPH (2,2-di(4-
The majority researchers working with bamboo-derived products use DPPH, ABTS, and FRAP methods or the combination of those to evaluate the antioxidant effect of their samples, when ORAC is less common. Values are expressed in the percentage of the radical inhibition, IC50, which is an inhibitory concentration (concentration needed to deactivate 50% of the radical formation) or Trolox equivalents. Table 1 demonstrates the results grouped by the method and unit used by the authors, and Table 2 shows IC50 against DPPH of the compounds isolated from the bamboo species.
|Leaf ethyl acetate||117.68||19.66||51.88||2.73|
|Culm ethyl acetate||244.85||33.25||51.22||3.47|
|Inner culm at 1 m height ethanol||373.80|
|Inner culm at 5 m height ethanol||88.50|
|Inner culm at 1 m height water||231.90|
|Inner culm at 5 m height water||198.30|
|Shoot ethyl acetate||800.00|
|Shoot ethyl acetate||400.00|
|Bamboo species||Part of the plant||Isolated compound||DPPH (IC50)||Reference|
|Leaves||3-O-(3′-methylcaffeoyl) quinic acid||16.00|||
The most popular method (also as per the number of results included in Table 1) is the certainty DPPH radical scavenging test. IC50 is a unit that is easy to compare because it gives an idea of the concentration, which is necessary to decrease the radical formation by 50%. The values obtained for different species of bamboo varied between 51 μg/mL for
Two from the chosen authors [10, 26] described the results for two Asian bamboo species:
The results expressed in IC50 for the DPPH and other methods such as ABTS, FRAP, and ORAC varied due to different mechanisms of action between prooxidant and antioxidant molecules. An ethyl acetate fraction from a Brazilian bamboo,
Trolox equivalents received by two methods: DPPH and FRAP were also compared, and it was found that in case of
In general, bamboos were classified as good antioxidants, which can be related to their high flavonoid and phenol contents . The scavenging activity against superoxide anion and hydroxyl radical of some methanol and hot water extracts from a bamboo powder, used in Japan for different purposes, was higher than the ones received for the control—α-tocoferol and ascorbic acid . A polysaccharide-rich extract from
Few studies of the functional antioxidant activity with correlated health effect were described in the literature as well. The lignophenol derivatives obtained from a wood mixture containing bamboo
2.2 Antimicrobial properties
Quality and safety of various products can be affected by the presence of microorganisms; therefore, antimicrobial substances are widely used in cosmetic, food, and pharmaceutical industries. In cosmetics, preservatives protect the formulation during the production and the use by the consumers . In the food industry, these additives can improve organoleptic characteristics of food, such as color, smell, and taste, in addition to the protection of food during production, storage, and consumption . The growing microbial resistance to existing drugs has generated the need for the pharmaceutical industry to search for new molecules that can be used as preservatives, antibiotics, and disinfectants . This factor associated with the toxicity of certain additives  and the consumer appeals for the reduction in synthetic substances , encourage the search for alternative solutions. The complexity and molecular diversity of natural products make them an interesting source of new molecules .
The antimicrobial capacity of bamboo species was evaluated through several methodologies, resulting in different units for the presentation of the results. In Table 3, results are shown as minimal inhibitory concentration (MIC), which is the lowest concentration that is able to completely inhibit microbial growth.
|Bamboo species||Product||Microorganism||MIC (μg/mL)||Ref.|
|Chloroform/methanol extract (bark)||10,000|||
|Chloroform/methanol extract (bark)||50,000|||
|Ethanol extract (outer culm)||400|||
|Hot water extract (leaf)||1200|||
|Hot water extract (branch)||1400|
|Hot water extract (inner culm)||>16,000|
The lower the MIC values, the more potent the substance is. To be considered as promising antimicrobial agents, natural products must have MICs below 100 μg/mL . Therefore, the essential oils of
In Table 4, the species were evaluated using the disk diffusion method. Three different extracts of each species were compared. All of them presented similar inhibition zones, around 7 mm. The wider inhibition zones were presented by the ethanolic extract of
|Bamboo species||Product||Inhibition zone (mm)||Ref.|
|Hot water extract||7.4||7.4|
|Hot water extract||7.3||7.3|
|Hot water extract||7.2||10.7|
|+++||>20||Very good activity|
The search for bioactive compounds is not limited only to the compounds produced by a plant species. Microorganisms hosted in plant tissues and organs have become a new source of useful metabolites for the pharmaceutical, agricultural, and food industries [45, 46]. Found in various parts of plants (roots, stems, leaves, and barks), endophytic fungi colonize various species , and the relationship between the endophytic fungi and the host plant may be advantageous since many of them improve the growth and protect the plant against pathogens .
Using the agar diffusion method, some authors evaluated the antimicrobial activity of fungal strains isolated from bamboos. The antimicrobial potential of the strains was evaluated against human pathogens, and in Table 6, it is possible to find the main results. Isolate 130 from
|Bamboo species||Isolate no.||Ref.|
One of the studies also evaluated the activity of fermentation products of fungal strains of
|Isolate no.||Inhibition zone (mm)||Ref.|
Despite the search for new substances with the ability to inhibit microbial growth, the presence of microorganisms is not always harmful. In some cases, certain microorganisms may contribute to human health, such as the human intestinal microbiota. It is composed of more than 400 bacterial species, and bifidobacteria and lactobacilli are the main ones . They help in the digestion and synthesize bioactive compounds, besides preventing diseases, avoiding the growth of pathogenic microorganisms . Through the consumption of probiotics and prebiotics, it is possible to maintain the balance of these intestinal bacteria. Probiotics are supplements containing the microorganisms of interest. Nondigestible carbohydrates that undergo fermentation by intestinal microbes are called prebiotics [48, 49].
Prebiotic activity was evaluated in bamboo shoots, since they are a rich source of polysaccharides and oligosaccharides . The polysaccharides isolated from the shoots of
2.3 Miscellaneous activities
Chinese traditional medicine has described the use of different parts of bamboos, such as leaves and rhizomes, to treat many diseases. Nowadays, scientific studies have demonstrated that bamboo extracts have excellent biological efficacy regarding their antioxidant activity. Theoretically, this activity might also be related for the treatment of diverse pathologies, such as resistance to free-radical, cardiovascular protection against neurodegenerative diseases, anticancer, and many others.
Bamboo shavings are a sort of Chinese traditional medicine that can be obtained from different bamboo species by scraping off the coating from bamboo stems, cutting the stems into slices, and binding them together by drying in shadowy places. A triterpenoid-rich extract of bamboo shavings was obtained from
Bamboo extracts used as dietary supplement demonstrated a protective effect on the development of induced breast cancer by 7,12-dimethylbenz[a]anthracene (DMBA). A crude hydroethanolic extract from
Bamboo vinegar, a natural liquid derived from the condensation produced during bamboo charcoal production, a pyrolyzate product, has been used in agriculture and used as a food additive. This liquid is composed mainly by water and acetic acid, but it also contains a variety of phenolic compounds. A vinegar preparation produced from
Besides the usual secondary metabolites, aqueous bamboo extracts contain many amino acids and polysaccharides that have not been investigated for their biological activities. Hypertension is associated with cardiovascular diseases such as arteriosclerosis, stroke, and myocardial infarction. Angiotensin converting enzyme (ACE, EC 22.214.171.124) is a dipeptidyl carboxypeptidase involved in different blood pressure regulating mechanisms. A peptide enriched
Most of the bamboo applications are related to the paper, textile, and construction industries, due to its high fiber contents. For this reason, scientists have been isolating and characterizing bamboo hemicelluloses since the 1970s. Hemicelluloses are polysaccharides found in plant cell walls that are characterized by being neither cellulose nor pectin and by having β-(1 → 4)-linked backbones with an equatorial configuration. Some of these polysaccharides are known to have an immunomodulatory activity. Hemicelluloses isolated from
Although bamboo has been used for centuries by the Traditional Chinese Medicine, this is still a group of plant under investigated regarding its medicinal properties. In Asian countries, such as China, Korea, and Japan, among others, the most used species have already been studied regarding their biological properties and chemical composition. On the other hand, in Southern American countries, where a huge bamboo diversity is available, very little has been done to access its medicinal properties.
Several species have shown an important antioxidant potential demonstrating that they can be applied in the treatment of different diseases such as anti-inflammatory, antitumor, and several other ailments involving oxidative processes. Additionally, besides the usual secondary metabolites, bamboo extracts may contain biologically active peptides and polysaccharides. The combined effect of these macromolecules with polyphenols and other metabolites may lead to multiple biological effects, such as antifree radical, antiaging, antifatigue, antibacteria, antivirus, and as a functional dietary supplement, cosmetic ingredient, and food additive.
The authors wish to thank CAPES and CNPq for the scholarships granted.
Conflict of interest
The authors declare that there is no conflict of interest.