Subergorgiaols A–L, 9,10-secosteroids from the South China Sea gorgonian Subergorgia rubra

•Twelve new 9,10-secosteroids were isolated from the gorgonian Subergorgia rubra.•The configuration of 1 was established by an ICD and the Mosher’s method.•Compounds 1–12 represent the first series of 9,10-secosteroids with an 8-OH.•Compound 4 exhibited promising cytotoxicity against the CaSki cell line.

Twelve new 9,10-secosteroids designated as subergorgiaols A–L (1–12), along with four known analogues (13–16), were isolated from the gorgonian Subergorgia rubra collected from the South China Sea. Their planar structures and the relative configurations were elucidated by comprehensive spectroscopic methods including NOESY spectra. The absolute configuration of 1 was established by a dimolybdenum tetraacetate [Mo2(AcO)4] induced circular dichroism (ICD) procedure and the modified Mosher’s method. Compounds 1–12 represent the first series of 9,10-secosteroids characterized with a hydroxy group at C-8, which are 8-OH derivatives of astrogorgiadiols/calicoferols. Compound 4 exhibited cytotoxicity against the cervical carcinoma cell line (CaSki) with an IC50 value of 2.4 μM, and 6 showed toxicity toward brine shrimp Artemia salina with an LC50 value of 2.0 μM.

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