Secondary metabolites from the leaves of Meliosma rhoifolia and evaluation of their cytotoxic activity

One previously undescribed labdane diterpenoid, meliosmarhoifol (1), together with four known ones, 12R,15-dihydroxylabda-8(17),13E-dien-19-oic acid (2), 18-norlabda-8(17),14-diene-4 alpha,13 beta-diol (3), 5 alpha,6 alpha-epoxy-(22E,24R)-ergosta-8(14),22-diene-3 beta,7 alpha-diol (4), 5 alpha,6 alpha-epoxy-(22E,24R)-ergosta-8,22-diene-3 beta,7 alpha-diol (5), were isolated from the leaves of Meliosma rhoifolia. The structures of all isolates were elucidated on the basis of extensive analyses of spectroscopic data and comparison with literature data. In addition, the cytotoxicity of the isolates was evaluated on the MCF-7, NCI-H460 and SF-268 cell lines. Among them, compounds 2-5 were found to have moderate cytotoxic effects against these three cell lines in vitro. Four constituents, compounds 1, 2, 4 and 5 showed different sensitivities in inhibiting the growth of MCF-7 breast cancer cells, with IC50 values ranging from 4.21 to 25.70 mu M, while compound 3 did not show obvious effects. Amount these isolates, meliosmarhoifol (1) showed as the most actively compound against the MCF-7, NCI-H460 and SF-268 cell lines with IC50 values of 4.21, 4.76, and 8.32 mu M, respectively.