Inhibition of eukaryotic DNA polymerase alpha by persimmon (Diospyros kaki) extract and related polyphenols

The effects of persimmon extract (Diospyros kaki) and related polyphenols o n eukaryotic DNA polymerase alpha were examined. It was found that persimmo n extract, epigallocatechin gallate, and epicatechin gallate strongly inhib ited the activity of DNA polymerase alpha purified from calf thymus. Among these polyphenols, persimmon extract had the most potent effect on DNA poly merase alpha activity and the concentration of persimmon extract producing 50 % inhibition of the activity was 0.191 mu M. Persimmon extract showed a weaker effect on DNA polymerase beta and slightly inhibited primase and DNA polymerase I. The inhibition of DNA polymerase alpha by persimmon extract was competitive with the template-primer and noncompetitive with dTTP subst rate. The K-i value of DNA polymerase a for persimmon extract was estimated to be 70 nM. Moreover, persimmon extract inhibited [H-3]thymidine incorpor ation of human peripheral lymphocyte cells stimulated by PHA.