Tea made from Camellia Sinensis: An Up-To-Date Review of Chemistry and Health Benefits

Since the ancient period, various plants have been used for dietary consumption for their tastes as well as beneficial effects on health. Among them, the tea plant (<i>Camellia sinensis</i>) is a notable one. Brewed tea is amongst the top most consumed beverages around the globe. Tea leaves undergo different processes and fermentations to produce tea powder from which brew is prepared. Depending upon its processing, it is divided into various varieties like green, oolong, white, and black tea. Fermentation processes also affect the phytochemical contents in each variety which further determines its dietary significance. Among various phytochemicals present in tea leaves, polyphenolic catechins are the most abundant ones among which epigallocatechin-3-gallate is the dominant catechin. At the time of fermentation, most contents of catechins are found in green tea as oxidation of catechins takes place. Black tea undergoes the most extensive fermentation process and hence catechins get reduced. Most of the catechins in black tea bind with each other and form polymeric structures (e.g. theaflavins and thearubigin) which also exhibit prominent health benefits. Theaflavins, one of the categories of polymeric catechin compounds, are antioxidants and also have various medicinal properties. Apart from the entire polyphenolic compound present in tea, various other non-polyphenolic compounds like enzymes, and non-protein amino acids like L-theanine, pigments, etc. can also be found that exhibit beneficial properties. A detailed study of polyphenolic green tea catechins mainly EGCG, polyphenolic black tea compound theaflavins, and non-protein Ltheanine are described in this chapter containing physical properties, chemical, and biosynthesis process, isolation process, pharmacokinetic study, analytical process, toxicity study, and health beneficial studies.