Modulation of aflatoxin B1 activated protein kinase C by phenolic compounds.

Several natural phenolic compounds were tested in vitro for their effect on the activity of protein kinase C isolated from liver cytosol, particulate and nuclear fractions of normal and aflatoxin B1 treated rats. Quercetin and kaempferol inhibited the enzyme activity of all these fractions at very low dose levels. These phenolics were particularly effective in inhibiting the elevated enzyme activity following aflatoxin B1 administration. Ellagic acid and curcumin were found to be inhibitory only towards particulate enzymes obtained after carcinogen treatment, while curcumin and rutin were moderately active against nuclear enzymes. Constitutive activation of protein kinase C can drive the cell to a proliferative state, thereby initiating the process of carcinogenesis, however, suppression of this activation by phenolic compounds may be an effective way to control carcinogenesis.