Fifteen steroids, including two new compounds, leptosteroid (1) and 5,6β-epoxygorgosterol (2), were isolated and structurally elucidated from the Vietnamese soft coral Sinularia leptoclados. Their cytotoxic effect against a panel of eight human cancer cell lines was evaluated using sulforhodamine B (SRB) method. Key words Sinularia leptoclados; Alcyoniidae; soft coral; steroid; cytotoxic activityThe phylum Cnidaria includes about 10000 species which are traditionally divided into three classes: Anthozoa, Hydrozoa, and Scyphozoa. The best-known representatives of the class Anthozoa are the gorgonians and soft corals among the subclass Octocorallia and the sea anemones and stony corals among the subclass Hexacorallia. Soft corals attracted considerable attention because of the wide range of their bioactive secondary metabolites. In these marine invertebrates, genus Sinularia (phylum Cnidaria, class Anthozoa, subclass Octocorallia, order Alcyonacea) is one of the most widely distributed soft corals and constitutes a dominant portion of the biomass in the tropical reef environment.1,2) Sinularia soft corals are a rich source of steroids and terpenoids.
2-5)As a part of our ongoing investigations on cytotoxic steroids from Vietnamese Sinularia soft corals, [6][7][8] this paper addressed the isolation, structure elucidation, and cytotoxic evaluation of fifteen steroids, including two new compounds, leptosteroid (1) and 5,6β-epoxygorgosterol (2), from the soft coral S. leptoclados.
Results and DiscussionUsing various chromatographic separations, fifteen steroids (Fig. 1) were isolated from a methanol extract of the soft coral S. leptoclados. The known compounds, 7-oxogorgosterol (3), 6) crassumsterol (4), 9) 7β-hydroxygorgosterol (5), 10) sarcophytosterol (6), 11) 3β-hydroxyergosta-5-ene-7-one (7), 12) ergost-5-en-3β,7β-diol (8), 13) ergost-5-en-3β,7α-diol (9), 14,15) ergosta-5,24(28)-diene-3β-ol (10), 16) 3β-hydroxyergost a-5,24(28)-diene-7-one (11), 17,18) ergosta-5,22,24(28)-trien-3β-ol (12), 19) 3β,7β-dihydroxyergosta-5,24(28)-diene (13), 20) 3β,7α-di hydroxyergosta-5,24(28)-diene (14), 20) and 3β,4α-dihydroxyergosta-5,24(28)-diene (15), 7) were identified by detailed analysis of their one and two dimensional (1-and 2D)-NMR and MS data as well as comparison of them with those reported in the literatures.Leptosteroid (1) was isolated as a white powder with molecular formula of C 29 H 48 O 3 , determined by high-resolution electrospray ionization (HR-ESI)-MS at m/z 445.36819 [M+H]