The Peroxidation of Leukocytes Index Ratio Reveals the Prooxidant Effect of Green Tea Extract

Abstract

Despite tea increased plasma nonenzymatic antioxidant capacity, the European Food Safety Administration (EFSA) denied claims related to tea and its protection from oxidative damage. Furthermore, the Supplement Information Expert Committee (DSI EC) expressed some doubts on the safety of green tea extract (GTE). We performed a pilot study in order to evaluate the effect of a single dose of two capsules of a GTE supplement (200 mg × 2) on the peroxidation of leukocytes index ratio (PLIR) in relation to uric acid (UA) and ferric reducing antioxidant potential (FRAP), as well as the sample size to reach statistical significance. GTE induced a prooxidant effect on leukocytes, whereas FRAP did not change, in agreement with the EFSA and the DSI EC conclusions. Besides, our results confirm the primary role of UA in the antioxidant defences. The ratio based calculation of the PLIR reduced the sample size to reach statistical significance, compared to the resistance to an exogenous oxidative stress and to the functional capacity of oxidative burst. Therefore, PLIR could be a sensitive marker of redox status.

Phytochemical Composition and Antioxidant Capacity of 30 Chinese Teas

“…Tea polyphenols may exert antioxidant capacities through the following mechanisms: (1) straightly reducing oxidants; (2) chelating metal ions; (3) transferring hydrogen; (4) scavenging free radicals; (5) improving activities of antioxidant enzymes; (6) increasing contents of endogenous antioxidants; and (7) regulating antioxidant-related genes [4,44,45,46,47,48,49,50,51]. All of these actions lead to the health functions of tea, such as anticancer, cardiovascular protective, neuroprotective, hepatoprotective, and renoprotective effects [6,52,53,54,55,56].…”

Health Functions and Related Molecular Mechanisms of Tea Components: An Update Review

“…In the literature, some studies have reported the antioxidant activity of tea brewing, extract and its components, which may have the potential for management of oxidative stress-induced diseases [80][81][82].…”

“…The antioxidant activity of tea brewing, extract and its components has been evaluated by several in vitro biological assay methods using cellular antioxidant activity (CAA), erythrocyte hemolysis, and plasma oxidation assays [80][81][82]. Zeng et al assessed the CAA of 27 tea cultivars, and the CAA values were 37.7-134.3 µmol quercetin equivalent (QE)/g dry weight (DW) (11.4-40.6 mg QE/g DW) without phosphate buffer washing, and 25.3-75.4 µmol QE/g DW (7.6-22.8 mg QE/g DW) with phosphate buffer washing [80].…”