Pregnane steroids from the Vietnamese octocoral Carijoa riisei.

Six pregnane steroids including one new compound namely 15β-hydroxypregna-4,20-dien-3-one (1), were isolated and structurally elucidated from the octocoral Carijoa riisei. The cytotoxic activity against a panel of eight human cancer cell lines of isolated compounds was also evaluated by SRB method. As the results, 18-acetoxypregna-1,4,20-trien-3-one (5) showed significant cytotoxicity against all the tested cell lines with the IC ₅₀ values from 22.29 ± 1.47 to 48.73 ± 3.93 μM, whereas 15β-acetoxypregna-1,4,20-trien-3-one (3) and 20R-acetoxypregna-1,4-dien-3-one (6) only exhibited weak effect on KB cell line with IC ₅₀ values of 93.62 ± 7.32 and 71.38 ± 5.45 μM, respectively.