Metabolites from the Paracel Islands Soft Coral Sinularia cf. molesta .

Five new oxygenated sesquiterpenes, molestins A⁻D ( 1 , 3 ⁻ 5 ) and epi -gibberodione ( 2 ), three new cyclopentenone derivatives, ent -sinulolides C, D, and F ((+)- 9 ⁻(+)- 11 ), one new butenolide derivative, ent -sinulolide H ((+)- 13 ), and one new cembranolide, molestin E ( 14 ), together with 14 known related metabolites ( 6 ⁻ 8 , (⁻)- 9 ⁻(⁻)- 11 , (±)- 12 , (⁻)- 13 , 15 ⁻ 19 ) were isolated from the Paracel Islands soft coral Sinularia cf. molesta . The structures and absolute configurations were elucidated based on comprehensive spectroscopic analyses, quantum chemical calculations, and comparison with the literature data. Compound 5 is the first example of a norsesquiterpene with a de-isopropyl guaiane skeleton isolated from the genus Sinularia . Molestin E ( 14 ) exhibited cytotoxicities against HeLa and HCT-116 cell lines with IC ₅₀ values of 5.26 and 8.37 μM, respectively. Compounds 4 , 5 , and 8 showed significant inhibitory activities against protein tyrosine phosphatase 1B (PTP1B) with IC ₅₀ values of 218, 344, and 1.24 μM, respectively.