Evaluation of the cellular antioxidant activity of 25 commonly consumed fruit species in China based on Caco-2 cells

Introduction. Determination of antioxidant activity using a biological method is important in predicting antioxidant capacity in vivo. The Caco-2 cell-based antioxidant activity (CAA) assay quantifies antioxidant activity in Caco-2 cells and has proved to possess good biological relevance. The aim of this study was to determine the CAA of 25 fruits commonly consumed in China, along with total phenolic content, total flavonoid content and oxygen radical absorbance capacity (ORAC). Materials and methods. The CAA was determined in Caco-2 cells by utilizing 2',7'-dichlorofluorescin diacetate (DCFH-DA) as a probe and 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH) as the generator of peroxyl radicals. The ORAC values were measured using fluorescein and AAPH. The total phenolic content was determined by the Folin-Ciocalteu method and total flavonoid content by aluminum chloride-sodium nitrite method. Results and discussion. There was a large variation in CAA values among different fruit species with the highest value in pomegranate (96.3 +/- 5.6 mu mol quercetin equivalents (QE) 100 g(-1)) and the lowest value in papaya (0.453 +/- 0.031 mu mol QE 100 g(-1)). For melons (white muskmelon, hami melon and watermelon), pineapple, pitaya, nectarine and loquat, the CAA was too low to be measured. Data analysis showed that CAA values were significantly correlated to total phenolic content (R-2 = 0.159, P < 0.05), and not correlated with total flavonoid content (R = 0.003, P> 0.05) or ORAC values (R-2 = 0.123, P > 0.05). Conclusion. Increasing the consumption of fruits, especially pomegranate, is an effective strategy to increase antioxidant intake, thus helpful for consumers to protect against the oxidative stressors.