Wild gorillas eat the same tree bark used by traditional healers that can inhibit the growth of E. coli in petri dishes, according to a new study. Scientists have found that wild gorillas in Gabon eat some of the same plants used by traditional healers in the region, and these plants show antibacterial properties in the lab.
In a new study, compounds in the bark of different trees have shown efficacy against antibiotic-resistant strains of Escherichia coli, which can cause difficult-to-treat infections in humans, including pneumonia and bloodstream infections. The researchers behind the work believe that these plants from the gorillas’ diet could lead to promising drugs for humans, but much more work is needed to develop such drugs.
In a study published Sept. 11 in the journal PLOS One, the researchers monitored western lowland gorillas (Gorilla gorilla gorilla) in Gabon’s Mukalaba-Dudou National Park, recording what plants they ate. They also interviewed people in the nearby village of Doussala, including healers and herbalists, about the plants they used in their traditional medicine.
The team’s previous research has found drug-resistant E. coli among the park’s gorillas; these microbes have the potential to cause illness in humans, but the apes can often carry the germs without symptoms. The researchers wanted to understand how the gorillas carry pathogenic E. coli without becoming seriously ill, and hypothesized that it might be related to plants that the gorillas eat but aren’t critical to their diet — like tree bark.
A team of scientists identified four native plant species that gorillas eat and use in traditional medicine: Ceiba pentandra, giant yellow mulberry (Myrianthus arboreus), African teak (Milicia excelsa) and fig (Ficus).
Traditional healers use the plants in infusions, extracts and ointments intended to treat a range of ailments, including coughs, stomach ulcers, diarrhea and fatigue. Tree bark is not a staple food for gorillas, who primarily eat fruit, but primatologists consider the bark a fallback food for the apes when their preferred foods are less available.
The researchers created bark extracts from powders of each tree, then tested the effects of the bark extracts on bacteria by placing them in petri dishes containing drug-resistant E. coli. These strains had previously been taken from gorillas, and the researchers observed whether the extracts inhibited bacterial growth and how well they inhibited it.
The bark of all four trees had antibacterial properties, with each showing some activity against at least one of the 10 E. coli strains tested. Fromager bark showed the best results in inhibiting E. coli growth and was effective against all 10 strains. However, the researchers did not determine which chemicals in the extract were responsible for this effect.
All plants also contained various phenols, alkaloids, flavonoids and proanthocyanidins – compounds with anti-inflammatory, anesthetic and antiviral properties.
The four plants may show promise for treating multidrug-resistant bacterial infections in humans, Yinda said. Their antibacterial and antioxidant properties may also explain their use in traditional medicine, he added.
Scientists have not directly studied how consuming these plants might affect gorillas’ health, or whether different doses of the plants might have different effects. However, other great apes are known to use plants with medicinal properties: chimpanzees periodically eat leaves that can clear their intestines of parasites, and orangutans apply leaves to their wounds. Traditional medicine in the regions where these primates live often uses the same plants to treat people with various ailments.
If we assume that tree bark is good for monkeys, it might be tempting to follow the example of primates, but it is unknown how the human body would react to the same substances.
“We were unable to conduct toxicological and cytotoxicological studies to confirm the absence of adverse effects,” Yinda said. “The fact that these plants have been used in traditional medicine since ancient times and that gorillas consume them was one of the factors that led us to consider them relatively safe and effective for humans.”
Studying the medicinal properties of plants in gorillas can also help us understand which plants we need to protect.