Cytotoxic 9,11-secosteroids from the South China Sea gorgonian Subergorgia suberosa

•Ten new 9,11-secosteroids were isolated from the gorgonian Subergorgia suberosa.•Their structures were elucidated by analysis of MS, 1D and 2D NMR data.•All the isolates possess the same 3β,6α,11-trihydroxy-7-en-9-one-5α-9,11- secosteroidal nucleus.•Compounds 9 and 10 showed significant cytotoxic activities.. Ten new 9,11-secosteroids, subergorgols A–J (1–10), including two pairs of epimers (3/4, and 6/7), along with three known analogues (11–13) were isolated from the South China Sea gorgonian Subergorgia suberosa. The structures of these compounds were elucidated on the basis of extensive spectroscopic analyses and comparison with the literature data. The cytotoxicities in vitro against three selected human tumor cell lines for all the compounds were evaluated. Compound 9 showed significant cytotoxicities toward both K562 and MDA-MB-231 cell lines with IC50 values of 5.5 and 6.2μM, respectively, and compound 10 also showed inhibitory activity against K562 cell line with an IC50 value of 6.5μM.