Use of COMPARE analysis to discover functional analogues of bleomycin

Bleomycin was used as the reference compound in a COMPARE analysis to identify extracts in the National Cancer Institute's Natural Products Repository exhibiting cytotoxicity profiles similar to this antitumor agent. One of the extracts so identified was a CH2Cl2-methanol extract prepared from Gymnosporia trigyna, which effected relaxation of supercoiled pSP64 DNA in the presence of Cu2+. Bioassay-guided fractionation using DNA strand-scission activity as an end point resulted in the isolation of four active principles. These were identified as syringaldehyde (1), (-)-syringaresinol (2), (+)-catechin (3), and (+)-epicatechin (4). Compounds 1 and 2 represent a new type of DNA strand-scission agent.