Antimicrobial activity of the crude extract, fractions and compounds from stem bark of Ficus ovata (Moraceae)

Abstract

Aim of the study This study was designed to investigate the antimicrobial activities of the methanol extracts from the stem bark of Ficus ovata (FOB), fractions (FOB1–6) and compounds isolated following bio-guided fractionation [3-friedelanone ( 1), taraxeryl acetate ( 2), betulinic acid ( 3), oleanoïc acid ( 4), 2-hydroxyisoprunetin ( 5), 6,7-(2-isopropenyl furo)-5,2,4-trihydroxyisoflavone ( 6), Cajanin ( 7) and protocatechuic acid ( 8)]. Materials and Methods The micro-dilution method was used for the determination of the minimal inhibition concentration (MIC) and the minimal microbicidal concentration (MMC) against fungi (two species), Gram-positive (three species) and Gram-negative bacteria (five species). Results The results of the MIC determinations indicated that the crude extract (FOB), fractions FOB2 and FOB4 as well as compound 5 were active on the entire studied organisms. Other samples showed selective activity, fractions FOB1, FOB3 and FOB5 being active against 50% of the tested microbial species while FOB6 was active on 40%. Compounds 8, 6, 2 and 7 prevented the growth of 80%, 70%, 50% and 20% of the organisms respectively. The lowest MIC value (156g/ml) observed with the crude extract was recorded on Streptococcus faecalis, Candida albicans and Microsporum audouinii. The corresponding value for fractions (39 μg/ml) was noted with FOB4 against Staphylococcus aureus, while that of the tested compounds (10 μg/ml) was observed with compound 8 on Microsporum audouinii. The results of the MMC determination suggested that the cidal effect of most of the tested samples on the studied microorganisms could be expected. Conclusions The overall results provided evidence that the studied plant extract, as well as some of the isolated compounds might be potential sources of new antimicrobial drug.