Dinor Casearin X, a New Cytotoxic Clerodane Diterpene from Casearia sylvestris

A new clerodane-type diterpene, named dinor casearin X, and four known casearins (A, B, G and J) were isolated from leaves of Casearia sylvestris (Salicaceae). These compounds were evaluated for cytotoxic activity against five human cancer cell lines (A2058, HL-60, HCT, MCF-7 and HeLa) as well as against a murine melanoma cell line (B16F10-Nex2). Among these compounds, dinor casearin X exhibited the highest cytotoxic activity against HL-60 cells with IC 50 of 0.51 ± 0.11 µg mL -1 , whereas casearin A exhibited the highest cytotoxic activity against HCT cells (IC50 1.84 ± 0.14 µg mL -1