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By Dr. Chinta SidharthanReviewed by Lexie CornerSep 19 2024Zoopharmacognosy examines the self-medicating behaviors of non-human animals that use plants, soil, or other natural substances as remedies. Recent research suggests that some plants used by animals for self-medication may have similar therapeutic benefits for humans.
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In a recent study published in PLOS ONE, a team of researchers from Gabon examined the antibacterial and antioxidant properties of plant species consumed for self-medication by western lowland gorillas (Gorilla gorilla gorilla) in Moukalaba-Doudou National Park, Gabon. The study also characterized the phytochemical properties of compounds extracted from these plants.
Background
Humans have used plants as natural therapeutics for centuries, and the World Health Organization estimates that nearly 80 % of the global population relies on medicinal plants. Zoopharmacognosy has been observed in various animal species, particularly great apes like gorillas and chimpanzees, who consume specific plants and plant parts, such as bark, to maintain their health. These animals are believed to use these natural remedies to combat illnesses like bacterial infections.
Many plant species possess compounds with antioxidant properties that can reduce inflammation and antimicrobial properties that can fight bacterial and fungal infections. However, overuse of antimicrobial agents can lead to the buildup of reactive oxygen species in the body, causing oxidative stress and contributing to the rise of antimicrobial resistance in pathogens, a major global health concern, especially for hospital-acquired infections.
About the study
The study focused on the antioxidant and antimicrobial properties of chemical compounds found in four plant species consumed by western lowland gorillas for self-medication: Ceiba pentandra, Ficus species, Milicia excelsa, and Myrianthus arboreus.
Researchers collected bark samples after observing gorillas consuming these barks. They also surveyed traditional herbalists and healers from nearby villages using structured questionnaires to obtain ethnopharmacological data.
The plants were identified by botanists, and voucher specimens were preserved for herbarium collections. The four species were selected based on observations of gorilla consumption and their known use in traditional medicine in the region. Bioactive compounds were extracted from the bark samples using ethanol and water, then concentrated and dried.
Phytochemical and biochemical analyses were conducted to screen for compounds such as alkaloids, flavonoids, phenolics, and tannins. The total content of proanthocyanidins, phenolics, flavonoids, and tannins was quantified using spectrophotometric methods.
The antioxidant potential of the compounds was assessed using three assays — 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) radical scavenging assay, Antioxidant Activity Index (AAI), and the β-carotene bleaching assay. The DPPH assay evaluated the ability of the compounds to neutralize free radicals, while the AAI calculated the inhibition percentage.
The β-carotene bleaching assay examined the ability of the extracts to prevent the oxidative degradation of β-carotene. A phosphomolybdenum method was also conducted to measure the total antioxidant capacity.
The study also evaluated the antimicrobial activity of the bark extracts from the four plant species against multidrug-resistant strains of Escherichia coli. Inhibition zones were measured using the Kirby-Bauer disk diffusion method, with amoxicillin and gentamicin serving as controls. Additionally, the minimum and maximum inhibitory concentrations were determined.
Major findings
The study found that the plants consumed by gorillas for potential self-medication contained various bioactive compounds, including phenolic compounds, tannins, flavonoids, and alkaloids. Most of the extracts were more soluble in water than in ethanol.
The DPPH assay showed that bark extracts from Myrianthus arboreus exhibited the highest antioxidant activity, while Ceiba pentandra showed the lowest, a result confirmed by the phosphomolybdenum method.
All four plant species demonstrated some level of antimicrobial activity. Ceiba pentandra extract had the strongest inhibitory effect against multidrug-resistant E. coli, while Milicia excelsa extract was the least effective. Overall, ethanol extracts proved more effective against multidrug-resistant E. coli than their water-soluble counterparts.
Conclusions
The study found that plants observed to be consumed by gorillas for potential self-medication have been widely used in traditional medicine. The bioactive compounds extracted from these plants showed varying antimicrobial and antioxidant activity levels. These findings suggest that plants used in zoopharmacognosy could have therapeutic applications in human medicine.
Journal reference
Even Doneilly Oyaba Yinda, L. (2024). Antibacterial and antioxidant activities of plants consumed by western lowland gorilla (Gorilla gorilla gorilla) in Gabon. PLOS ONE. DOI:10.1371/journal.pone.0306957 https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0306957
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