Antimicrobial activity screening of isolated flavonoids from azadirachta indica leaves

The antimicrobial activities of two flavonoids, namely genistein 7-O- -glucoside (1) and (-)-epi-catechin (2), isolated from Azadirachta indica A. Juss (neem) leaves, were evaluated against five fungal species, viz: Alternaria alternata (Fr.) Keissler, Aspergillus fumigatus Fresenius, Aspergillus niger van Tieghem, Macrophomina phaseolina (Tassi) Goid. and Penicillium citrii, and four bacterial species, viz. Lactobacillus sp., Escherichia coli, Azospirillium l- ipoferum and Bacillus sp. Six concentrations, viz. 100, 300, 500, 700, 900 and 1000 ppm of each of the two flavonoids were employed using malt extract agar medium. All the concentrations of both the test compounds significantly sup- pressed fungal as well as bacterial growth. The highest concentration (1000 ppm) of both fractions 1 and 2 reduced the growth of the different test fungal species by 83-99 % and 82-95 %, respectively. Compound 1 was highly effective against Lactobacillus sp., against which its various concentrations reduced the bacterial growth by 52-99.8 %. Compound 2 was highly effective against A. li- poferum and Bacillus sp., resulting in 94-100 % and 73-99% reduction in bac- terial growth, respectively.