Assessment of total antioxidant capacity in human plasma.

INTRODUCTION: Human serum contains many different antioxidants that may be important in the maintenance of antioxidant screen. Aging decreases the level of enzymatic and non-enzymatic antioxidant in plasma. In this study we investigated total antioxidant capacity in plasma obtained from healthy young and old volunteers. MATERIAL AND METHODS: The ferric reducing antioxidant capacity was used to measure the total antioxidant capacity of plasma. In in vitro experiments, the effects of exogenous compounds (ascorbic acid, uric acid, Trolox) on total ferric reducing activity of plasma obtained from young females were tested. Total antioxidant capacity of plasma was expressed as micromol Trolox equivalent/1 (a water-soluble analog of vitamin E). RESULTS: We demonstrated that total antioxidant capacity of plasma obtained from healthy young females and males did not differ significantly between each other (22.9 +/- 1.1 and 24.4 +/- 1.1 micromol Trolox equivalent/1, respectively) and was significantly higher than plasma antioxidant capacity of elderly volunteers (15.8 +/- 1.0 and 16.4 +/- 0.98 micromol Trolox equivalent/1, respectively). In vitro addition of ascorbic acid, uric acid, or Trolox to plasma samples significantly increased their total antioxidant capacity, but it did not act additively. CONCLUSIONS: Our results confirmed that plasma antioxidant capacity declines with the volunteers' age and supplementation of antioxidants could be useful for enhancement of antioxidant screen in plasma.