Investigations of antimicrobial activity of some Cameroonian medicinal plant extracts against bacteria and yeast with gastrointestinal relevance

Ethnopharmacological relevance: Resistance against antibiotics of many bacteria is accumulating. Therefore, searches for new substances with antimicrobial activity have become an urgent necessity. Medicinal plants are frequently used in popular medicine as remedies for many infectious diseases (intestinal infection, malaria, tuberculosis, etc.). Aim of the study: This study aimed to determine the in vitro antimicrobial activity of hexane, ethyl acetate and methanol extracts from different parts (leaves, stem bark, entire plant) of five different plant species against bacteria and yeast of gastrointestinal relevance. Material and methods: Twenty-one extracts from all the following plants (Albizia gummifera (leaf), Ficus exasperata (leaf and stem bark), Nauclea latifolia (leaf and stem bark), Ricinodendron heudelotii (stem bark), Senna hirsuta (entire plant) have been screened for their antimicrobial activity against eight bacteria species including Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus), Gram-negative bacteria (Escherichia coli, Shigella dysenteriae, Shigella flexneri, Salmonella typhi, Pseudomonas aeruginosa, and Klebsiella pneumoniae) and one yeast species (Candida albicans) using agar disc-diffusion, and microbroth dilution assays. Results: Results demonstrated that F. exasperata and N. latifolia were active against the whole set of tested microorganisms. The methanol extract of N. latifolia (leaf and stem bark) was the most active against against C albicans, E. coli, S. aureus, P. aeruginosa with a minimum inhibitory concentration (MIC) of 2, 32, 64 and 64 mu g/ml, respectively. The methanol extract of leaf of F. exasperata was also most active with significant inhibitory activity against E. coli, S. dysenteriae, S. Typhi and P. aeruginosa with MIC values of 128 mu g/ml. Only the extract of N. latifolia (stem bark and leaf) showed anticandidal property. Conclusion: The results show that these plant extracts exhibit antimicrobial activity and N. latifolia proved to be most effective as an antibacterial and antifungal. (C) 2012 Elsevier Ireland Ltd. All rights reserved.