**4.5 Tea phytochemicals in cancers**

Tea nutraceutical acts as powerful antioxidants are very much promising in prevention of cancers. Experimental studies have demonstrated the use of tea bioactive compounds in prevention of cancers in different organs [51]. The tea catechins has been found to act as anticarcinogenic and chemopreventive agents. Several animal model studies in mice showed the inhibiting of chemical induced 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) tumorigenesis, tumor cell proliferation, progression of adenoma to carcinoma, as well as lung carcinogenesis. [52]. It has been conferred from several experimental evidences that tea can be effectively used in inhibition of carcinogenesis in different parts of our body such as skin, lung, stomach, esophagus, liver, small intestine, pancreas, colon, bladder, etc. [53]. In these experimental studies it was found that polyphenols in green tea acted on cell apoptosis, cell proliferation, cell cycle in tumour growth and migration. All these activities resulted in reduced the risk of certain types cancers such as skin, colorectal, prostate, breast etc. through their activity in cell apoptosis, cell proliferation, cell cycle in tumour growth and cell migration. Among four major catechins in green tea, EGCG has been extensively studied and found to be most effective polyphenols [54]. Theaflavins in black tea inhibit the DNA damage which is a major cause of induction of cancer [55] The anti-carcinogenic activity of tea polyphenols is associated with their capacity to bind with carcinogens and thereby enabled the metabolism**.** Cancer preventive activity of black tea is known from the report of induction of apoptosis in human leukemia cells by black tea and its polyphenols [56]. Black tea is also effective in protecting immunocytes from tumor-induced apoptosis [57].
