Biological activity of extracts and active compounds isolated from Siegesbeckia orientalis L.

Siegesbeckia orientalis L (Asteraceae) is an annual herb with a worldwide distribution and has been used in Asia as folk medicine. In this study, the antimicrobial, antioxidant and cytotoxic activities of various fractions from Siegesbeckia orientalis L. were investigated. The ethyl acetate fraction showed the strongest antimicrobial, antioxidant and cytotoxic activities. The bioassay guided isolation of the ethyl acetate fraction led to twelve compounds: 16 beta-hydro-ent- kauran-17,19-dioic acid (1), 16 alpha,17-clihydroxy-ent-kauran-19-oic acid (2), 16 beta,17,18- trihydroxy-ent-kauran-19-oic acid (3), 17,18-dihydroxy-ent-kauran-19-oic acid (4), siegesmethyletheric acid (5), 2-oxo-15,16,19-trihydroxyent-pimar-8(14)-ene(6), 3, 16-dihydroxy1-15-one-ent-pimar-8(14)-ene-3-O-beta-D-glucopyranoside (7),quercetin (8), ursolic acid (9), beta-sitosterol (10), stigmasterol (11) and uracil (12). Among all the twelve compounds, compounds 1-4 exhibited the striking antimicrobial activity against screened microorganisms, especially against methicillin-resistant Staphylococcus aureus. Compounds 1, 3 and 4 were found to possess antimicrobial activity for the first time. Compound 8 exhibited antioxidant and cytotoxic activities. Compound 9 exhibited cytotoxic activity. These results demonstrate that Siegesbeckia orientails extracts and active compounds could be potential pharmaceutical products, especially against antibiotic-resistant microorganisms. (C) 2016 Elsevier B.V. All rights reserved.