ABSTRACT
Tea drinking has been a tradition for centuries and remains the most widely consumed beverage today, next only to water (Mukhtar et al., 1992). e history of tea drinking dates back more than 4000 years and has been documented in China as early as 1911 in Kissa Yojoki (Book of Tea) by Aisai, a Zen priest. Tea is derived from the leaves of the Camellia sinensis plant, which is grown in the
5.1 Introduction 83 5.2 Cancer: Risk Factors and Field Effects 84 5.3 Modification of Oxidative Stress by Green Tea Polyphenols 86 5.4 Epigenetic Regulation by Green Tea Polyphenols 88 5.5 Alteration of Growth Signals by Green Tea Polyphenols 93 5.6 Regulation of Cell Cycle and Apoptosis by Green Tea Polyphenols 98 5.7 Inhibition of Invasion, Metastasis, and Angiogenesis by Green
Tea Polyphenols 101 5.8 Modulation of Other Signaling Pathways by Green Tea
Polyphenols 103 5.9 Potential Limitation of the Work 106 5.10 Conclusion and Future Directions 108 References 108
eastern part of the world, predominantly in China, India, Japan, Sri Lanka, and ailand. Based on the technology of manufacturing, tea is classified as green, black, or oolong tea. e different methods used for its production alter the chemical composition of the dried tea leaves. Green tea, which accounts for 20% of the world tea consumption, is prepared by steaming the tea leaves. is process preserves the characteristic of tea catechins, which constitute 10 to 15% of the weight of the dried leaves by inactivating polyphenol oxidase enzyme. e major catechins present in green tea are (–)-epigallocatechin3-gallate (EGCG), (–)-epigallocatechin (EGC), (–)-epicatechin-3-gallate (ECG), and (–)-epicatechin (EC). EGCG contributes more than two-fifths of the total phenols present in green tea and has been widely reported for its health benefits (Zaveri, 2006). A typical cup of green tea, brewed with 2.5 g of tea leaves in 250 ml hot water, contains 620 to 880 mg of water-extractable solids, of which about one-third are catechins. e presumed beneficial effects of tea in the prevention of cancer, as well as cardiovascular, neurodegenerative, obesity, and other diseases, have been extensively studied.
