There are four primary polyphenols in green tea and they are often collectively referred to as catechins. 

Powerful antioxidants, catechins have been shown in recent studies to fight viruses, slow aging, and have a beneficial effect on health. Clinical tests have shown that catechins destroy free radicals and have far-reaching positive effects on the entire body....

Free radicals are highly reactive molecules and fragments of molecules that can damage the body at the cellular level leaving the body susceptible to cancer, heart disease, and many other degenerative diseases.

Green tea antioxidants have been shown to lower cholesterol. 

For information on green tea and its effect on weight loss please click here- weight loss benefits of green tea .

EGCG is a potent antioxidant.

Epigallocatechin gallate (EGCG), an antioxidant found in green tea, is at least 100 more times more effective than vitamin C and 25 times more effective than vitamin E at protecting cells and DNA from damage believed to be linked to cancer, heart disease and other serious illnesses. This antioxidant has twice the benefits of resveratrol, found in red wine.