Zoopharmacognosy is the study of the self-medication behaviors of non-human animals that use plant, animal or soil items as remedies. Recent studies have shown that some of the plants employed by animals may also be used for the same therapeutic purposes in humans. The aim of this study was to determine the antioxidant and antibacterial activity of Ceiba pentandra, Myrianthus arboreus, Ficus subspecies (ssp.) and Milicia excelsa bark crude extracts (BCE), plants consumed by western lowland gorillas (Gorilla gorilla gorilla) in Moukalaba-Doudou National Park (MDNP) and used in traditional medicine, and then to characterize their phytochemical compounds. DPPH (2,2-Diphenyl-1-Picrylhydrazyl), phosphomolybdenum complex and β-carotene bleaching methods were used to assess antioxidant activity. Antimicrobial susceptibility testing was performed using the diffusion method, while minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were assessed using the microdilution method. The highest level of total phenolics was found in Myrianthus arboreus aqueous extract [385.83 ± 3.99 mg [gallic acid equivalent (GAE)/g]. Total flavonoid (134.46 ± 3.39) mg quercetin equivalent (QE)/100 g of extract] were highest in Milicia excelsa, tannin [(272.44 ± 3.39) mg tannic acid equivalent (TAE)/100 g of extract] in Myrianthus arboreus and proanthocyanidin [(404.33 ± 3.39) mg apple procyanidins equivalent (APE)/100 g of extract] in Ceiba pentandra. Ficus ssp. (IC50 1.34 ±3.36 μg/mL; AAI 18.57 ± 0.203) ethanolic BCE and Milicia excelsa (IC50 2.07 ± 3.37 μg/mL; AAI 12.03 ± 0.711) showed the strongest antioxidant activity. Myrianthus arboreus ethanolic BCE (73.25 ± 5.29) and Milicia excelsa aqueous BCE (38.67 ± 0.27) showed the strongest percentage of total antioxidant capacity (TAC). Ceiba pentandra ethanolic BCE (152.06 ± 19.11 mg AAE/g) and Ficus ssp aqueous BCE (124.33 ± 39.05 mg AAE/g) showed strongest relative antioxidant activity (RAA). The plant BCE showed antimicrobial activity against multidrug resistant (MDR) E. coli (DECs) isolates, with MICs varying from 1.56 to 50 mg/mL and inhibition diameters ranging from 7.34 ± 0.57 to 13.67 ± 0.57mm. Several families of compounds were found, including total phenolic compounds, flavonoids, tannins and proanthocyanidins were found in the plant BCEs. The plant BCEs showed antioxidant activities with free radical scavenging and antimicrobial activities against 10 MDR E. coli (DECs) isolates, and could be a promising novel source for new drug discovery.

Natural medicines from plants have been used to enhance human and veterinary health since time immemorial, as revealed in ancient tales, scriptures and other historical literature . This practice is experiencing a resurgence.

The World Health Organization (WHO) estimates that approximately 80% of the world’s population uses medicinal plants (MPs) for their health and care needs .

Recent studies have focused on the potential to develop antioxidant and antimicrobial drugs from plants. These antioxidants, for example, reduce the incidence of many metabolic diseases . Antioxidants also reduce the incidence of chronic inflammation by reinforcing immunity, which would ultimately contribute to the efficacy of antimicrobial therapy.

The results of this study, which examined the antioxidant and antimicrobial activity of Ceiba pentandra, Myrianthus arboreus, Ficus ssp and Milicia excelsa BCEs, plants are consumed by western lowland gorilla living in MDNP and used in traditional medicine by Gabonese healers, revealed some important facts. Indeed, all plant BCEs studied showed antioxidant and antimicrobial activities.

The asymptomatic nature of theses gorillas with regard MDR E. coli (DECs) could be explained by their consumption of the bark of the four plants tested. The scientific results obtained during pharmacological analyses could justify the use of these plants in the traditional pharmacopoeia against various human diseases.

These results show that the BCE of these plants could be used as an effective treatment for diseases caused by free radicals and diseases caused by antimicrobial-resistant bacterial strains. Then, all this founding could comfort the self-medication hypothesis of non-human animals, including great apes. The results of our study suggest that all plant BCEs studied could potentially be candidate improved traditional medicines (ITMs) in the application of new therapeutic protocols against infectious diseases of bacterial origin.