Inhibitory effect of Coptidis Rhizoma and Scutellariae Radix on azoxymethane-induced aberrant crypt foci formation in rat colon.

This study was conducted to obtain effective cancer chemopreventive agents with low toxicity from medicinal herbs. The effect of aqueous extracts from 9 medicinal herbs with antiinflammatory effect were examined on the formation of azoxymethane (AOM)-induced aberrant crypt foci (ACF), putative preneoplastic lesions of the colon. Male F344 rats were treated with 15 mg/kg body weight of AOM once a week for two weeks. Herbal extract consisting of 2% of the diet was administered from 1 d prior to the first carcinogen treatment. The number of AOM-induced ACF per colon was counted at 4 week. Extracts of Coptidis Rhizoma and Scutellariae Radix significantly inhibited AOM-induced ACF formation. The number of ACF was decreased to 54% and 78% of that of the control by 2% Coptidis Rhizoma and Scutellariae Radix extract in the diet, respectively. Berberine and Baicalin, major ingredients of Coptidis Rhizoma and Scutellariae Radix, inhibited ACF formation at a dose equivalent to the amount in each herbal extract. Therefore, to investigate the mechanisms of action of berberine and baicalein which is the active substances of orally administered baicalin, their effects on cyclooxygenase 1 and 2 activities were studied. Berberine was found to inhibit cyclooxygenase 2 activity without inhibition of cyclooxygenase 1 activity, and baicalein inhibited cyclooxygenase 1 activity. Thus, Coptidis Rhizoma and Scutellariae Radix suppressed experimental colon carcinogenesis, and their chemopreventive effects were explained from the inhibition of berberine on cyclooxygenase 2 activity and baicalein on cyclooxygenase 1 activity.