DNA Polymerase β Inhibitors from <i>Tetracera Boiviniana</i>

Bioassay-guided fractionation of an active methyl ethyl ketone extract of <i>Tetracera boiviniana,</i> using a sensitive assay to monitor DNA polymerase β inhibition, resulted in the isolation of three known triterpenoids, betulinic acid (<b>1</b>), 3-<i>cis</i>-<i>p</i>-coumaroyl maslinic acid (<b>2</b>), and 3-<i>trans</i>-<i>p</i>-coumaroyl maslinic acid (<b>3</b>). Compounds <b>1</b>−<b>3</b> inhibited DNA polymerase β with IC<sub>50</sub> values of 14, 15, and 4.2 μM in the presence of bovine serum albumin (BSA) and 6.5, 7.5, and 2.0 μM in the absence of BSA, respectively. Further, compounds <b>1</b>−<b>3</b> potentiated the effects of bleomycin in cultured P-388D<sub>1</sub> cells.