Dolabrane-type diterpenes from the mangrove plant Ceriops tagal with antitumor activities

Chemical examination of the barks of mangrove plant Ceriops tagal resulted in the isolation of six new dolabrane-type diterpenes with the trivial names of tagalenes A-F (1-6), together with 10 known analogues. The structures of new compounds were elucidated by extensive spectroscopic data analyses. Tagalenes A-C (1-3) are characterized by 18-nordolabrane scaffold, while tagalene F (6) featured by a 2,3-seco dolabrane derivative. Antitumor assay revealed that seven compounds exhibited potent inhibitory effects against a panel of tumor cell lines with IC50<10 μM, while tagalsin C (8) exerted the most potent activities in comparison with the IC50 values of the rest compounds. The primary structure-activity relationship is discussed. Tagalsin C also exerted the potent effects against a panel of drug-resistant human tumor cell lines, indicating it to be a promising molecule for further evaluation as an antitumor lead compound.