[Experimental studies on the cancer chemoprevention of tea pigments].

A batch of short-term tests were used to examine the effects of tea pigments on three stages of carcinogenesis, i.e. initiation, promotion and progression. Forward gene mutation test and micronuclei test were used to study the initiation stage of carcinogenesis; metabolic cooperation test and mice ear test to study the promotion stage. Viability and growth ability of Hela cells in soft agar and S180 solid tumor test in mice were used to examine the effect of tea pigments on the third stage of carcinogenesis. The results showed that both tea pigments and tea polyphenols had significantly protective effects on initiation, promotion and progression stages in carcinogenesis. In vitro study showed that tea pigments and tea polyphenols could induce QR and GST activity in Hep G2 cells. Oral administration of 0.1% tea polyphenols and 0.1% tea pigments could increase GST activity in rat liver by 25% and 18% respectively, and this increase was accompanied by the significant increase of GST 1-1, 1-2 and 3-3 protein expression level in rat liver. Our results suggested that the anticancer effect of tea pigments was the same as that of tea polyphenols, and the anticancer properties of tea pigments might be mediated by activating the enzymes such as QR and GST, which play important roles in the detoxification and exclusion of carcinogen.