Tea is the most widely used beverage worldwide. Japanese and Chinese people have been drinking
tea for centuries and in Asia, it is the most consumed beverage besides water. It is a rich source of pharmacologically active molecules which have been implicated to provide diverse health benefits. The three major forms of
tea are green, black and oolong
tea based on the degree of fermentation. The composition of
tea differs with the species, season, leaves, climate, and horticultural practices.
Polyphenols are the major active compounds present in teas. The catechins are the major polyphenolic compounds in
green tea, which include
epigallocatechin-3-gallate (EGCG),
epigallocatechin,
epicatechin-3-gallate and
epicatechin, gallocatechins and
gallocatechin gallate. EGCG is the predominant and most studied
catechin in
green tea. There are numerous evidences from cell culture and animal studies that
tea polyphenols have beneficial effects against several pathological diseases including
cancer, diabetes and
cardiovascular diseases. The polyphenolic compounds present in
black tea include theaflavins and thearubigins. In this review article, we will summarize recent studies documenting the role of
tea polyphenols in the prevention of
cancer, diabetes, cardiovascular and neurological diseases.