Abstract
Chemical investigation on the soft coral Sarcophyton sp. collected from the South China Sea yielded three new polyhydroxylated steroids, compounds (1–3), together with seven known ones (4–10). Their structures were established by extensive spectroscopic methods and comparison of their data with those of the related known compounds. All the isolates possessed the 3β,5α,6β-trihydroxylated steroidal nucleus. The cytotoxicities against selected HL-60, HeLa and K562 tumor cell lines and anti-H1N1 (Influenza A virus (IAV)) activities for the isolates were evaluated. Compounds 2, 3 and 5–8 exhibited potent activities against K562 cell lines with IC50 values ranging from 6.4 to 10.3 μM. Compounds 1, 6–8 potently inhibited the growth of HL-60 tumor cell lines, and 6 also showed cytotoxicity towards HeLa cell lines. In addition, preliminary structure-activity relationships for the isolates are discussed. The OAc group at C-11 is proposed to be an important pharmacophore for their cytotoxicities in the 3β,5α,6β-triol steroids. Compounds 4 and 9 exhibited significant anti-H1N1 IAV activity with IC50 values of 19.6 and 36.7 μg/mL, respectively.
Highlights
Polyhydroxylated steroids with a broad spectrum of bioactivities have been found in various phyla of marine organisms, and especially in the subclass Octocorallia, commonly called “soft corals” [1]
The frozen sample of Sarcophyton sp. (5.0 kg, wet weight) was homogenized and extracted with MeOH for three times (5 L × 3, each, 3 days) at room temperature, and the solution was evaporated in vacuum to yield a crude extract (70.0 g) which was subjected to column chromatography (CC) on silica gel using petroleum ether/acetone as eluent to obtain seven fractions (Fr. 1–Fr. 7)
In vitro cytotoxicities were determined by MTT [3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] colorimetric assay [16] against K562 and HL-60, SRB (Sulforhodamine B) assay [17] against HeLa
Summary
Polyhydroxylated steroids with a broad spectrum of bioactivities have been found in various phyla of marine organisms, and especially in the subclass Octocorallia, commonly called “soft corals” [1]. A series of structurally diverse polyhydroxysterols with antimicrobial activities were isolated from Sarcophyton sp. In our search for bioactive compounds from marine organisms, we obtained an unidentified species of Sarcophyton collected from Weizhou Island of Guangxi Province in the. South China Sea. Combined chemistry and bioassay-guided quick isolation of the sterols-rich portion of the MeOH extract of Sarcophyton sp., yielded three new polyhydroxysterols, compounds (1–3), along with seven known analogs (4–10) (Figure 1). 3β,5α,6β-trihydroxy moiety, but varied in the side chains and substituted patterns in the nucleus. These sterols could be divided into four types belonging to cholesterol, ergosterol, gorgosterol and 23,24-dimethyl cholesterol, of which compound 1 possessed a unique. We describe the isolation, structure elucidation of the new polyhydroxysterols (1–3) and preliminary structure-activity relationships for the isolates (1–10)
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