Biscoumarin derivatives from Edgeworthia gardneri that inhibit the lyase activity of DNA polymerase β

Bioassay-guided fractionation of an active methyl ethyl ketone extract of Edgeworthia gardneri, using an assay to monitor DNA polymerase β lyase inhibition, resulted in the isolation of three known biscoumarin derivatives, 7-hydroxy-3,7'-dicoumaryl ether (edgeworin, 1), 7-hydroxy-6-methoxy-3,7'-dicoumaryl ether (daphnoretin, 2), and 6,7-dihydroxy-3,7'-dicoumaryl ether (edgeworthin, 3). Compounds 1-3 inhibited the lyase activity of DNA polymerase β with IC 50 values of 7.3 μg/mL (22.5 μM), 43.0 μg/ mL (122.3 μM), and 32.1 μg/mL (94.8 μM), respectively.