EFFECTS OF TEA, DECAFFEINATED TEA, AND CAFFEINE ON UVB LIGHT-INDUCED COMPLETE CARCINOGENESIS IN SKH-1 MICE - DEMONSTRATION OF CAFFEINE AS ABIOLOGICALLY IMPORTANT CONSTITUENT OF TEA

Oral administration of green or black tea inhibited UVB light-induced complete carcinogenesis in the skin of SKH-1 mice. Green tea was a mor e effective inhibitor than black tea. Oral administration of decaffein ated green or black tea resulted in substantially less inhibitory acti vity than did administration of the regular teas, and in one experimen t, administration of a high-dose level of the decaffeinated teas enhan ced the tumorigenic effect of UVB. Oral administration of caffeine alo ne had a substantial inhibitory effect on UVB-induced carcinogenesis, and adding caffeine to the decaffeinated teas restored the inhibitory effects of these teas on UVB-induced carcinogenesis. In additional stu dies, topical application of a green tea polyphenol fraction after eac h UVB application inhibited UVB-induced tumorigenesis. The results ind icate that caffeine contributes in an important way to the inhibitory effects of green and black tea on UVB-induced complete carcinogenesis.