Antioxidant and hepatoprotective activities of five eggplant varieties

Eggplant is consumed throughout the world and varies in fruit color, shape, and size. In this study, five varieties of eggplant (purple colored moderate size, white-green colored moderate size, long green, green striped moderate size and pale-green colored small size, respectively, called SM1–SM5) were evaluated for total phenolic and flavonoid content, antioxidant activity and hepatoprotection against cytotoxicity of tert-butyl hydroperoxide (t-BuOOH) in human hepatoma cell lines, HepG2. Total phenolic content found in methanol extracts of SM1–SM5 ranged from 739.36 ± 1.59 to 1116.13 ± 7.30 gallic acid equivalents mg/100 g extract and total flavonoid content from 1991.29 ± 6.32 to 3954.20 ± 6.06 catechin equivalents mg/100 g extract. SM1 and SM2 which contained high total phenolic and flavonoid had better antioxidant activities than the other varieties. Pretreatment of HepG2 cells with 50 and 100 μg/mL of SM1–SM5 significantly increased the viability (p < 0.05) of t-BuOOH-exposed HepG2 cells by 14.49 ± 1.14% to 44.95 ± 2.72%. The antioxidant activities of the eggplant were correlated with the total amounts of phenolic and flavonoid (r = 0.5310−0.7961). Significant correlation was found between hepatoprotective activities and total phenolic/flavonoid content (r = 0.6371–0.8842) and antioxidant activities (r = 0.5846–0.9588), indicating the contribution of the phenolic antioxidant present in eggplant to its hepatoprotective effect on t-BuOOH-induced toxicity.