Evaluation of In vivo Toxicity and In vitro Antimicrobial Activities of Crude Ethanolic Stem Bark Extract of Anonidium mannii

Aims: This study aims to evaluate the in vivo acute and sub-acute toxicity; and the antimicrobial activity of Anonidium mannii stem bark ethanolic extract.

Study Design: This is an experimental study.

Location and Duration of the Study: The work was conducted from 15 November 2020 to 31 May 2021 at several laboratories (the Faculty of Medicine and Pharmaceutical Sciences Laboratory of the University of Douala, the Animal Physiology Laboratory of the Faculty of Medicine and Biomedical Sciences at the University of Yaoundé 1 and in the Hematology and Bacteriology Laboratories of the District Hospital of the Cité des Palmiers, Douala, Cameroon).

Methodology: The in vivo acute and subacute toxicities studies were conducted following the guidelines of the OECD on Wistar rats, while the in vitro antimicrobial activity was evaluated using the microdilution method on bacterial (Neisseria gonorrheae, Escherichia coli, Salmonela spp) and fungal (Candida albicans) strains.

Results: Phytochemical screening revealed the presence of alkaloids, anthraquinones, coumarins, flavonoids, phenols, reducing sugars, tannins, triterpenes. An oral administration of the extract did not induce an abnormal variation of the physiological parameters in rats, at doses of 2000 and 5000 mg/kg body weight for 14 days. After twenty-eight days of observation during the study of subacute toxicity, the extract showed good safety in terms of subacute toxicity. No deaths were recorded at the different doses; and clinical and physiological parameters analyses revealed a non-significant statistical difference. All bacterial strains in the presence of the extract were inhibited, as well as C. albicans. The extract exhibited strong antibacterial activity against N. gonorheae (MIC 15.6 μg/mL), E. coli (MIC 62.5 μg/mL) and Salmonella spp (MIC 15.6 μg/mL).

Conclusion: These results could justify the use of A. mannii stem bark in the traditional pharmacopoeia for the treatment of gonococcal disease, diarrhea, abscesses and food poisoning.