Bioassay-guided fractionation of an active organic extract of Piper caninum, using a sensitive yeast assay to monitor putative double-strand DNA-damaging activity, resulted in the isolation of the 4,5-dioxoaporphine alkaloid cepharadione A (1). Compound 1 exhibited potent inhibitory activity in a yeast cytotoxicity assay with IC(50) values of 50.2 nM toward RS321NpRAD52 grown on glucose versus 293 nM toward the same yeast strain grown on galactose.
