Phytochemical profiles of rice and their cellular antioxidant activity against ABAP induced oxidative stress in human hepatocellular carcinoma HepG2 cells

The phytochemical contents, peroxyl radical scavenging capacities (PSCs) and cellular antioxidant activities (CAAs) of free and bound fractions of rice were reported. Black rice had the highest total phenolic content and total flavonoid content in free and bound fractions, followed by red rice, brown rice, and polished rice. Black rice contained much more free phenolic compounds than other rice samples, such as cyanidin-3-O-glucoside, protocatechuic acid, and vanillic acid. Tocopherols and tocotrienols contents were highest in red rice, then in black rice, brown rice, and polished rice. PSCs and CAAs of free and bound fractions were in the order: black rice > red rice > brown rice > polished rice, except that bound CAA of red rice was higher than that of black rice. The cellular uptake rate of free phenolics was highest in red rice, while cellular uptake rates of bound phenolics were highest in brown rice and polished rice.