Steroid compounds from pacific starfish Mithrodia clavigera and their toxicity to human melanoma cells

A new sulfated polyoxide steroid (20S)-3 beta,6 alpha,20-trihydroxi-5 alpha-cholest-9(11)-ene 3-sulfate (sodium salt) named mithrotriol was isolated from the Pacific starfish Mithrodia clavigera. Additionally, six previously known compounds were isolated and identified including glycosides echinasteroside B, granulatoside A, linckoside K, and forbeside L, as well as sulfates of thornasterol A and cholesterol. The structure of mithrotriol was elucidated by NMR (H-1, C-13, DEPT, COSY-45, NOESY, HSQC, and HMBC) and massspectrometry. Minimal inhibitory concentrations were determined for the isolated compounds that demonstrated cytotoxic activity in human melanoma cells SK-MEL-28, SK-MEL-5, and RPMI-7951.