Antimicrobial Activity of 23 Endemic Plants in Madagascar

Purpose: To screen the crude methanol extracts obtained from 23 endemic plants in Madagascar for antimicrobial activity. Methods: In order to assess the antimicrobial properties of the extracts, their minimum inhibitory concentrations (MICs) were obtained using the broth microdilution method. The six test pathogenic species used were Bacillus subtilis , Staphylococcus aureus , Escherichia coli , Salmonella typhi , Pseudomonas aeruginosa and Candida albicans . Bioautography agar overlay test and phytochemical screening were also performed on the most active extracts. Results: From the 23 plants tested, 16 of which are used in traditional medicine, Poivrea phaneropetala (Combretaceae), Koehneria madagascariensis (Lythraceae) and Rhopalopilia perrieri (Opiliaceae) exhibited the broad spectrum of activity, being active against all the test organisms, while Monoporus clusiifolius (Myrsinaceae) showed the strongest antifungal activity against Candida albicans with a minimal inhibitory concentration of 0.250 mg/ml. Bioautography and phytochemical analysis of the five active extracts against bacterial strains and of one active extract against C. albicans indicate that the active compounds responsible for antimicrobial activity may be mainly flavonoids and/or terpenes. Conclusion: These preliminary results are the first antimicrobial studies on these plants and lend support for the use of some of them in traditional medicine.