Disulfated Ophiuroid Type Steroids from the Far Eastern Starfish Pteraster marsippus and Their Cytotoxic Activity on the Models of 2D and 3D Cultures.

New steroidal 3β,21-disulfates ( 2 - 4 ), steroidal 3β,22-disulfate ( 5 ), and the previously known related steroidal 3β,21-disulfate ( 1 ) were isolated from the ethanolic extract of the Far Eastern starfish Pteraster marsippus , collected off Urup Island in the Sea of Okhotsk. The structures of these compounds were determined by intensive NMR and HRESIMS techniques as well as by chemical transformations. Steroids 2 and 3 have an oxo-group in the tetracyclic nucleus at position C-7 and differ from each other by the presence of the 5(6)-double bond. The Δ 24 -22-sulfoxycholestane side chain of the steroid 5 has not been found previously in the starfish or ophiuroid steroids. The cytotoxic activities of 1 , 4 , 5 , and the mixture of 2 and 3 were determined on the models of 2D and 3D cultures of human epithelial kidney cells (HEK293), melanoma cells (SK-MEL-28), small intestine carcinoma cells (HuTu80), and breast carcinoma cells (ZR-75-1). The mixture of 2 and 3 revealed a significant inhibitory effect on the cell viability of human breast carcinoma ZR-75-1 cells, but other tested compounds were less effective.