Polyhydroxylated steroids from the South China Sea soft coral Sarcophyton sp. and their cytotoxic and antiviral activities.

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.