b ) Istituto di Chimica Biomolecolare-CNR, Two new polyhydroxylated steroids, (2b,3b,4a,5a,8b,11b)-4-methylergost-24(28)-ene-2,3,8,11-tetrol-(1) and (3b,5a,6b)-ergosta-22,24(28)-diene-3,5,6,19-tetrol (3), together with the six known related steroids 2 and 4 -8, were isolated from the Hainan soft coral Sinularia sp. Their structures were elucidated on the basis of spectroscopic analysis and by comparison with previously reported data. The structure of the known compound 9 (hyrtiosterol) was revised as 2 by extensive analysis of the ROESY data and by the NOE difference experiment.
Introduction. -Soft corals are Coelenterates (class Anthozoa, subclass Octocorallia, order Alcyonacea, family Alcyoniidae), of which some are symbiotic associations of coral animals (polyps) with their algal partners (Zooxanthellae) [1]. They are rich sources of terpenoids, notably cembranoid diterpenes, and steroids, of which many were reported to have various biological activities ranging from antitumor, antiallergy, to anti-inflammatory [2]. The genus Sinularia, which is very speciose in the South China Sea, is reputed for its versatile chemical constituents and their biological activity. Terpenoids [3 -6] and steroids [7 -9] compose the main secondary metabolites isolated from the genus. In particular, many biological activities were reported for these metabolites, including cytotoxicity [10], enhancement of glucose transport in rat adipocytes [11], and histamine-release inhibition [12].
In our previous study [13], we have reported the isolation and structural elucidation of two new 19-acetylated steroids from an undetermined species of Sinularia (01HN-75). However, strangely enough, we did not find the presence of diterpenoids from the mentioned collection. Recently, in the course of our continuous efforts aiming at searching for new bioactive molecules from South China Sea invertebrates [14 -17], we made another collection of the soft coral Sinularia sp. (02HN-75), which showed the same appearance as the sample 01HN-75 and was identified by Prof. R.-L. Zhou of the South China Sea Institute of Oceanology-CAS to be the same species as the first collection from the same place but different location. Chemical investigation of the Et 2 A C H T U N G T R E N N U N G O-soluble fraction of this animal resulted in the isolation of two new polyhydroxylated steroids, named (2b,3b,4a,5a,8b,11b)-4-methylergost-24(28)-ene-2,3,8,11tetrol-(1), (3b,5a,6b)-ergosta-22,24(28)-diene-3,5,6,19-tetrol (3), along with the six known related steroids 2 and 4 -8 (Fig. 1). Once again, we did not discover diterpene constituents from this collection. In the present paper, we report the isolation and structure elucidation of the new compounds.