Cytotoxic chromenes from Myriactis humilis.

Two new chromenes, myriachromene and 2,2-dimethyl-6,7-methylenedioxy-2H-chromene, together with ten known compounds including alpha-tocopherylquinone, alpha-tocopherol acetate, diphenyl sulfone, beta-carotene, chondrillasterol, beta-sitosterol, beta-sitostenone, vanillin, and vanillic acid were isolated from the whole plant of Myriactis humilis. The structures of these new compounds were determined through spectral analyses. Among the isolates, four compounds exhibited cytotoxicity (ED50 values < 4 microg/mL) against P-388 or HT-29 cell lines in vitro.