Green tea exerts antioxidant action in vitro and its consumption increases total serum antioxidant potential in normal and dyslipidemic subjects

Antioxidant defenses can be characterized as agents (enzymes and low-molecular-mass antioxidants) in biological systems that prevent the noxious action of free radicals or other reactive species. The present study examined whether the use of green tea may exert antioxidant action in vitro and improve antioxidant defenses and serum lipids in normal and dyslipidemic subjects. Forty-one hypercholesterolemic individuals, 18 women and 23 men (age [mean +/- SD], 44.81 +/- 14.41), were evaluated before and after the daily intake of 6 g of green tea in 500 mL of water for 1 month. Likewise, 27 normolipidemic individuals, 12 women and 15 men (age, 37.07 +/- 16.08), were also evaluated. Serum lipids were measured by an automated clinical chemistry system. The total serum antioxidant potential (TRAP) and serum levels of lipid hydroperoxides were quantified using the chemiluminescence method. Total polyphenols present in green tea ingested by the patients were verified by using Folin-Ciocalteau reagent. The in vitro evaluation of green tea antioxidant activity was performed using microsomes obtained from rat liver, which was oxidized by tert-butyl hydroperoxide. From this system, thiobarbituric acid reactive substances were measured. In the in vitro test, green tea polyphenols proved to be efficient at protecting microsomes from the oxidant activity of tert-butyl hydroperoxide. There were no significant alterations in the lipid profiles of the normolipidemic or hypercholesterolemic subject groups. Although there was no decrease in lipid hydroperoxides, both groups showed increased antioxidant defenses, which was evidenced by TRAP. In conclusion, the results obtained indicate that besides achieving antioxidant action in vitro, the consumption of green tea increased the TRAP of normal and dyslipidemic subjects. (c) 2006 Elsevier Inc. All rights reserved.