Chimpanzees seek out tree bark and ferns with medicinal benefits, researchers discover

By Pooja Toshniwal Paharia Reviewed by Danielle Ellis, B.Sc. Jun 25 2024

In a recent study published in PLoS ONE, researchers investigated the behavioral and pharmacological effects of self-medicative plants in the diets of Budongo chimpanzees. Study: Pharmacological and behavioral investigation of putative self-medicative plants in Budongo chimpanzee diets. Image Credit: Martin Pelanek/ Background

Wild chimpanzees eat plants for nutrition and health, some containing bioactive poisons. Health professionals use these plants occasionally to treat illnesses. Chimpanzees have displayed therapeutic self-medication by eating leaves and chewing bitter pith, decreasing nematode infection.

In vivo investigations have demonstrated that pith extracts permanently paralyze mature Schistosome parasites. Chimpanzees and other primates may also engage in medical activities like bark feeding and dead wood chewing. About the study

In the present study, researchers explored the medicinal properties of plants consumed by wild chimpanzees and their potential health benefits.

The researchers monitored two habituated chimp communities in Uganda's Budongo Forest to sample 17 botanical plants they consumed that had potential self-medication properties (such as dead wood consumption, pith-stripping, and bark feeding) or occurrences (e.g., high parasite loads, injury, or abnormal urinalysis).

They selected components from 13 plant species, including four herb varieties and nine trees, to extract three samples using solvents such as ethyl acetate, methanol/water, and n-hexane to examine them for anti-inflammatory and antibacterial properties.

They assessed the plants' growth inhibition properties against multidrug-resistant bacterial isolates, including ESKAPE biological strains. They also evaluated cyclooxygenase-2 (COX-2) inhibitory activities.

The researchers tested the bark of eight species consumed by Budongo chimps for antibacterial and anti-inflammatory compounds to improve their understanding of the function of bark-eating activities and their potential significance in chimp health maintenance. They tried a combination of bark and congealed resin on K. anthotheca, which Budongo chimpanzees preferred.

The researchers also examined the pharmacology of two kinds of dead wood (A. boonei and Cleistopholis patens) ingested by the Sonso chimp colony to investigate whether this habit served multiple purposes or provided health advantages. They assessed the bioactivity of 51 plant extracts derived from 17 part-specific samples (13 species) for bacterial growth inhibition and anti-inflammatory COX-2 inhibitory activity.

During a four-month field season (June to October for 2021 and 2022), the researchers collected behavioral and health data from two nearby chimpanzee populations. Following three months of data collection, they chose plants for pharmacological testing. They selected ten samples from nine species based on firsthand observations made over this period and five species based on their historical presence in Sonso chimpanzees' bark-eating repertoire. They tested plan samples for antibacterial susceptibility, growth inhibition, and dose-response. Related StoriesKey transport systems fuel rapid E. coli growth in UTIsResearch explores firefighters' awareness of cancer risk and dietary practicesUnveiling the role of SOS genes in E. coli survival during antibiotic treatment

The researchers recorded ad libitum feeding events to capture unique feeding habits, including bark ingestion, dead wood consumption, pith peeling, and geophagy. They collected individual health data from both populations, including opportunistic macroscopic and microscopic fecal examination, parasite burden, and urinalysis tests. Results

Wild chimpanzees in the Budongo Forest consumed 13 plant species associated with putative self-medication behaviors. Pharmacological tests on these plant extracts showed antibacterial and anti-inflammatory properties, with 45 of 53 plant extracts (88%) showing≥40% growth inhibition against bacteria at a 256.0 μg/mL concentration, indicating potent medicinal properties. Most (91%) active extracts demonstrated bactericidal activity at ≤256.0 μg/mL.

The S. guineense stem bark extract was the most effective against 11 bacterial types, followed by its leaves and dead wood obtained from P. patens and A. boonei. S. guineense bark extracts showed significant inhibition against P. aeruginosa and E. cloacae at the highest concentration. E. coli strains showed the highest susceptibility, with one or more plant extracts retarding their development. E. coli strains with high antibiotic resistance showed inhibited growth in most (80%) of the examined extracts.

K. anthotheca resin and bark extracts robustly inhibited E. faecium growth and n-hexane extracts of A. boonei were the most effective against S. aureus. Both extracts showed low half maximal inhibitory concentration (IC50) concentrations of 16.0 μg/mL, indicating robust inhibition of their strains. S. guineense exhibited the highest inhibitory effects on S. maltophilia, with IC50 values of ≤256 μg/mL against the bacterium.

All plants adversely negatively impacted E. coli growth, with 33% of 51 extracts showing ≥50% COX-2 enzyme inhibition at 5.0 μg/mL concentrations. Overall, the K. anthotheca resin and bark menthol-water extract and the Christella parasitica fern extract were the most potent. Conclusion

The findings contribute to the field of zoo pharmacology by providing insight into the self-medicative sources in wild chimpanzee dietary components and emphasizing the distinction between preventive and curative self-medication. Budongo chimpanzee diets include potent bioactive secondary plant compounds for probable diseases. Prioritizing the conservation of natural forest pharmacy and primate relatives is critical.

Future studies could assess ecological factors related to climatic data to improve understanding of the effects of climate change on plant bioactivity.Journal reference:

Freymann E, Carvalho S, Garbe LA, Dwi Ghazhelia D, Hobaiter C, Huffman MA, et al. (2024) Pharmacological and behavioral investigation of putative self-medicative plants in Budongo chimpanzee diets. PLoS ONE 19(6): e0305219. 
DOI: 10.1371/journal.pone.0305219