Antioxidant ability of polyphenols from black rice, buckwheat and oats: In vitro and in vivo

Grains (black rice, buckwheat and oats) contain polyphenols and have stronger antioxidant capacity than staple foods. Their polyphenols were identified and investigated for their antioxidant capacity. The black rice and buckwheat polyphenols were mainly flavonoids; those in oats were phenolic acids. In vitro, their radical-scavenging capacities were determined as black rice > buckwheat > oats. Similarly, in vivo, the increase in total antioxidant capacities and decline in malondialdehyde indicated the enhancement of radical-scavenging and repair abilities of all polyphenol extracts. Differences in superoxide dismutase, catalase activities, glutathione peroxidase activities and oxidase activities suggested that polyphenols from black rice and buckwheat have higher antioxidant activities, indicating that their antioxidant ability is related to polyphenol composition which depends on a polyphenol source. Thus, a combination of diets will make a complementary mixture of polyphenols that can enhance absorption in the intestinal tract and defence ability against oxidative stress.