Abies nephrolepis leaf phenolics prevent the inhibition of gap junction intercellular communication by hydrogen peroxide in rat liver epithelial cells

Recent reports suggest that carcinogenicity of hydrogen peroxide (H2O2) is implicated in inhibition of gap junction intercellular communication (GJIC), which is a cellular event associated with the tumor promotion. The present study investigated the effect of phenolics (KF) from leaves of Abies nephrolepis (Khingan fir) on inhibition of GJlC by H2O2 in WB-F344 rat liver epithelia] cells. The phenolics were extracted from fresh leaves by using 80% aqueous methanol, and were analyzed mainly as catechin derivatives including epigallocatechin gallate (EGCG) and catechin itself. KF and EGCG protected the inhibition of GJlC by H2O2, whereas butylated hydroxytoluene, a commercial antioxidant, had no effect. Our results indicate that KF exhibits potential chemopreventive effects against carcinogenesis, which may be attributable to phenolics such as EGCG.