Investigation of Antibacterial and Anti-Diarrhoeal Activities of 80% Methanol Leaf and Fruit Extract of Leonotis ocymifolia (Burm. F) Iwarsson (Lamiaceae)

BACKGROUND: Leonotis ocymifolia (Burm.F) Iwarsson (Lamiaceae) is among the medicinal plants that are claimed to have various pharmacologic activities. However the leaves and fruits of L. ocymifolia have not yet been explored scientifically for antibacterial and anti-diarrhoeal activities. This study was aimed at investigating the anti-diarrhoeal and antibacterial activities of 80% methanol leaf and fruit extract of Leonotis ocymifolia in mice and selected diarrhea causing bacterial species. METHODS: The leaves and fruits of Leonotis ocymifolia were extracted using 80% methanol through maceration technique. The anti-diarrheal activity was evaluated using a castor oil induced diarrheal model, prostaglandin induced anti-enteropooling, and castor oil induced charcoal meal test in mice of either sex. Data were analyzed using one-way analysis of variance followed by Tukey post-hoc test. The antibacterial activity was evaluated on using an agar well diffusion assay. Bacterial species used were Salmonella typhi, Salmonella paratyphi, Salmonella typhimurium, Shigella species, Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli. For anti-diarrhoeal activity, the extract was tested at 100, 200, and 400 mg/kg. Positive and negative control groups were treated with loperamide (3 mg/kg) and 2% tween 80 (10 mL/kg), respectively. RESULTS: A significant (p<0.05) reduction in frequency of wet stools and watery content of diarrhea as well as in delaying onset of diarrhea as compared to controls was observed in mice at the stated doses. The extract showed a dose-dependent inhibition in all used models. L. ocymifolia leaf and fruit extract also showed antimicrobial activity against all tested organisms. CONCLUSION: Results from this study collectively indicated that 80% methanol leaf and fruit extracts of L. ocymifolia possessed significant anti-diarrhoeal activity and antibacterial activities, hence provides the scientific base for its traditional use as a diarrhea treatment.