Pentacyclic triterpenoids from Freziera sp. that inhibit DNA polymerase β

Abstract In a survey of crude plant extracts for DNA polymerase β inhibitors, a methyl ethyl ketone extract prepared from Freziera sp. exhibited potent inhibition of DNA polymerase β. Bioassay-guided fractionation of the extract, guided by an assay to detect DNA polymerase β inhibition, resulted in the isolation of six active pentacyclic triterpenoids ( 1 – 6 ). These triterpenoids had IC 50 values ranging from 7.5 to 16 μM in the presence of bovine serum albumin (BSA) and 2.6–5.8 μM in the absence of BSA, consistent with the possibility that these inhibitors may be of use in vivo.