Novel 16,17-epoxy-23-methylergostane derivative from Sinularia variabilis, a soft coral from the Persian Gulf, with apoptotic activities against breast cancer cell lines

The steroidal and terpenoidal composition of Sinularia variabilis was investigated by chromatography methods. One new (1), and four known [gorgasta-5-en-3β-ol (2), ergosta-5-en-3β-ol (3), ergosta-5, 22(Z)-dien-3β-ol (4), 5,8-epidioxy-5α, 8α-ergosta-6, 22E-dien-3β-ol (5)] steroids, in addition to one known diterpenoidal alkaloid [sinulasulfone (6)] isolated for the first time from S. variabilis. If we named the 23-methylergostane core structure as sinustane, new compound (1) was elucidated as 16α,17α-epoxysinusta-5-en-3β–ol-20β-yl sulfate based on NMR and HR Mass data. It was submitted for cytotoxic activity evaluation against MCF-7 and MDA-MB-231 cell lines using MTT assay. Apoptosis induction was checked by flow cytometry (annexin V/propidium iodide) staining. To determine the production of reactive oxygen species, and the mitochondrial transmembrane potential (ΔΨm), the DCFDA, and JC‐1 probes were used in this study.