Friday, July 13, 2018

Antioxidant in green tea

Green tea is made from leaves of camellia sinensis that have undergone minimal oxidation during processing. The chemical composition of green tea varies with genetic strain, climatic conditions, soil properties, plucking season, position of the leaf, processing and storage.

The chemical composition of tea leaves has been well documented. The main constituents of tea leaves are polyphenols. Polyphenols constitute the most interesting group of green tea leaf components and in consequence green tea can be considered as an important dietary source of polyphenols, particularly flavanoids. Especially, catechins, the main component of polyphenols, are well known for their antioxidant properties, which have led to their evaluation in many diseases associated with free radicals, including cancer, cardiovascular and neurodegenerative diseases.

Generally, the major catechins of tea leaves are (+)-catechin (C), (−)-epicatechin (EC), (+)-gallocatechin (GC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECg), (−)-epigallocatechin gallate (EGCg), and (+)-gallocatechin gallate (GCg).

The antioxidant activity of green tea polyphenols is primarily attributed to the combination of aromatic rings and hydroxyl groups that assemble their chemical structure and consequently binding and neutralization of lipid free radicals by these hydroxyl groups. Catechins also exhibit antioxidant activity via chelating redox active transition-metal ions. Polyphenolic compounds, possess hydroxyl and carboxyl groups, are able to bind particularly iron and copper.

A wide variety of other components exists, including, flavones, phenolic acids and depsides, carbohydrates, alkaloids, minerals, vitamins and enzymes. Green tea also contains carotenoids, tocopherols, ascorbic acid (vitamin C), minerals such as Cr, Mn, Se or Zn, and certain phytochemical compounds.
Antioxidant in green tea
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