Synergistic effect of green tea polyphenols with trolox on free radical-induced oxidative DNA damage

The antioxidant effect of the principal polyphenolic components extracted from green tea leaves, namely (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG) and (−)-epigallocatechin gallate (EGCG), and their synergistic antioxidant effects with trolox against oxidative DNA damage were studied. The oxidative DNA damage was initiated by a water-soluble azo initiator, 2,2′-azobis (2-amidinopropane hydrochloride) (AAPH) and the ability of green tea polyphenols and/or trolox (a water-soluble analogue of α-tocopherol) to inhibit the oxidative damage of DNA was assessed, in vitro, by measuring the conversion of supercoiled pBR322 plasmid DNA to the open circular and linear forms. It was found that these green tea polyphenols could significantly inhibit the oxidative damage of DNA synergistically with trolox, with an activity sequence of EC = ECG > EGCG > EGC.