Antibacterial lignans and triterpenoids from Rostellularia procumbens

One new lignan, rostellulin A ( 1), four known lignans, justin B ( 2), justicidin C ( 3), cilinaphthalide A ( 4), and justicidin A ( 5), and four known triterpenoids, ursolic acid ( 6), euscaphic acid ( 7), 2 alpha-hydroxyursolic acid ( 8), and tormentic acid ( 9), have been isolated from the whole plants of Rostellularia procumbens. Their structures were established on the basis of spectral data, including extensive NMR experiments. To our knowledge, compounds 6 - 9 are known compounds but not previously isolated from R. procumbens, 4 was previously reported from other Rostellularia species. Antibacterial activities of 1 - 9 were evaluated against eight bacterial strains with the agar dilution method, and they were found to possess antimicrobial activity with MIC values in the range of 1.56 - 100 microg/mL. None of the lignans exhibited cytotoxic activity against HCT-8 and Bel-7402 cells at concentrations up to 5 microg/mL.