Isolation, identification and antimicrobial activity of ombuoside from Stevia triflora

Abstract

From aerial parts of Stevia triflora DC the flavonal glycoside ombuoside (7,4'-di-O-methylquercetin-3-O-β-rutinoside) has been isolated and identified on the basis of spectral data. Ombuoside and the synthetic derivatives octa-acetylombuoside, ombuine and retusine were tested for antimicrobial activity against several strains of Gram-positive and Gram- negative bacteria and the yeast Candida albicans, using the agar diffusion method. The flavonol glycoside ombuoside and the respective aglycone ombuine, both exhibited moderated activity against Corynebacterium diphteriae, Staphylococcus aureus, Escherichia coli and Candida albicans. To a lesser degree, octa-acetylombuoside and retusine showed activity against the Gram- positive bacteria C. diphteriae and S. aureus, but proved to be inactive against Gram-negative bacteria and Candida albicans. These results indicate that the presence of free hydroxyl groups, either alcoholic or phenolic, is an important chemical feature for the expression of flavonol antimicrobial activity. It is worth hating that this is the first study reported on the antibacterial and antifungal activity of these substances.