Cytotoxic constituents from the stem barks of Ceriops decandra (Griff.) W. Theob

A phytochemical survey aiming to acquire pharmacologically active substances has resulted in the isolation of five dolabrane‐ (1–5), and ent‐pimarane‐type diterpenoids (6) were isolated from the methanol extract of C. decandra (Griff.) W. Theob. stem barks, via various chromatographic separations. Their structures were elucidated to be ent‐5α,3,15‐dioxodolabr‐1,4(18)‐diene‐2,16‐diol (1), tagalene I (2), ent‐5α,2,15‐dioxodolabr‐3‐ene‐3,16‐diol (3), tagalsin S (4), notolutesin H (5), and ent‐8,15R‐epoxypimaran‐16‐ol (6) by comprehensive analysis of spectroscopic data (1D, 2D NMR, and ESI‐MS data) as well as comparison with the previous literature. All of the isolates were evaluated for their cytotoxicity against human lung cancer (SK‐LU‐1), human hepatocellular carcinoma (HepG2), and human breast cancer (MCF‐7) cell lines. Compounds 2 and 6 exerted inhibitions toward three tumor cell lines (SK‐LU‐1, HepG2, and MCF‐7) with IC50 values between 5.63 and 11.70 μg/mL, while other compounds exhibited weak to moderate or no cytotoxic activities (IC50 > 20 μg/mL).