In a survey of the active components of crude plant extracts for their ability to cleave DNA, a crude extract prepared from Piper caninum was found to induce the relaxation of supercoiled pBR322 plasmid DNA in the presence of Cu(2+). Bioassay-guided fractionation was carried out on this extract, guided by an in vitro DNA strand scission assay. Three active principles were isolated and identified as N-cis-feruloyl tyramine (1),N-trans-feruloyl tyramine (2), and 1-cinnamoylpyrrolidine (3). Compounds 1-3 represent a structurally new type of DNA strand scission agent.