Effects of edible whole citrus fruits on endogenous antioxidant enzymes of HepG2 cells

The effects of eating fresh citrus fruits including two varieties of mandarins, one of sweet oranges, one of grapefruit, two of pomelo, and one of kumquat cultivated in China on endogenous antioxidant enzymes were investigated by in vitro digestion and HepG2 cells. The correlations between enzyme activity and cell uptake of phytochemicals and cellular antioxidant capacities were analyzed. The results showed that most fresh citrus fruits increased the endogenous antioxidant activity. Bairoumiyou, Hongroumiyou, Ponkan, and Jinju after digestion significantly increased the activity of catalase (P<0.05). Hongroumiyou, Bairoumiyou, Ponkan navel orange, and Jinju after digestion significantly increased glutathione peroxidases (GPxs) activity (P<0.05), while Huyou and satsuma could not increase the activity of GPxs after digestion. Thioredoxin oxidoreductase activity was improved significantly by most of the digested whole citrus fruits except Ponkan (P<0.05) and thioredoxin oxidoreductase added whole citrus fruits had a higher increase than added citrus fruits extracts. The results indicated that edible whole citrus fruits had similar effects as extracts on enzymes.