New cytotoxic benzopyrans from the leaves of Mallotus apelta.

Two new benzopyrans 6-[1'-oxo-3'(R)-hydroxy-butyl]-5,7-dimethoxy-2,2-dimethyl-2H-1-benzopyran (1) and 6-[1'-oxo-3'(R)-methoxy-butyl]-5,7-dimethoxy-2,2-dimethyl-2H-1-benzopyran (2) were isolated from the leaves of Mallotus apelta Muell.-Arg., (Euphorbiaceae). Their chemical structures were elucidated by spectroscopic analyses, especially by 1 D-, 2D-NMR and MS spectra. Compound 1 was found to have strong cytotoxic effect against two human cancer cell lines as human hepatocellular carcinoma (Hep-2, IC50: 0.49 microg/mL) and rhabdosarcoma (RD, IC50: 0.54 microg/mL), while compound 2 showed moderate activity against Hep-2 cell line (IC50, 4.22 microg/mL) by in vitro assay.