Antioxidant compounds and antioxidant activities of fermented black rice and its fractions

Abstract

The aim of this study was to determine the total phenol, total flavonoids, and proanthocyanidin contents of fermented black rice and its fractions, as well as to assess the antioxidant activities. Antioxidative activities were assessed in various in vitro models using 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), reducing power, ferric ion reducing antioxidant power (FRAP), and nitrite scavenging activity (Griess reagent assay). Our results show that the antioxidant activity was significantly higher in the low-molecular fraction of fermented black rice than in the other samples (p<0.05). Among the fermented black rice and its fractions, the low-molecular fraction had the highest total phenol (109.2±2.9 mg GAE, gallic acid equivalent/g), total flavonoids (39.4±0.8 mg RE, rutin equivalent/g), and proanthocyanidin (32.9±1.4 mg CE, catechin equivalent/g) contents, which correlated strongly with its antioxidative activity. Considering the high consumer demand due to the beneficial health effects, fermented black rice and its fractions can be utilized to develop functional food, as well as health-promoting and pharmaceutical agents.