Antimicrobial activity of the extracts of Albizia masikororum R.Vig., a Fabaceae from Madagascar

This study is aimed at the assessment of antimicrobial potential of Albizia masikororum, a Malagasy Fabaceae. Hexanic and methanolic extracts from fruit pods, stem bark, leaves and seeds were tested by disc diffusion and microdilution methods on 10 pathogenic microorganisms including four Gram positive bacteria, five Gram negative bacteria and one yeast. Only the leaf and seed methanolic extracts, LME and SME respectively, were active on some bacteria. LME and SME had a broad-spectrum activity, with SME more effective. The minimum inhibitory concentration (MIC) values of both extracts were <1000 µg/ml of which 30% <100 µg/ml, 20% between 100 and 500 µg/ml and 50% between 500 and 1000 µg/ml. SME MICs ranked from 6.10 µg/ml (Streptococcus pneumoniae) to 781.25 µg/ml (Yersinia enterocolitica) and those of LME from 97.65 µg/ml (Streptococcus pneumoniae) to 781.25 µg/ml (Bacillus cereus, Streptococcus pneumoniae and Yersinia enterocolitica). LME was bactericidal on all sensitive bacteria whereas SME was bactericidal on some and bacteriostatic on others. Both extracts contained different chemical groups known for their antimicrobial properties, saponins in SME and phenolic compounds in LME. Key words: Albizia masikororum, antimicrobial activity, disc diffusion method, microdilution method, minimum inhibitory concentration, minimum bactericidal concentration.