ARS | Publication request: Polyphenols and antioxidant capacity: Rice versus other common cereal grains

Submitted to: Agricultural Experiment Station Publication
Publication Type: Experiment Station
Publication Acceptance Date: June 2, 2011
Publication Date: July 14, 2011
Citation: Chen, M. 2011. Polyphenols and antioxidant capacity: Rice versus other common cereal grains. Texas Rice Special Section, Highlighting Research in 2011. p. VII-VIII.

Technical Abstract: The consumption of whole cereal grains has been strongly recommended by many governmental and non-profit health organizations based on epidemiological studies associating whole-grain consumption with reduced incidences of chronic diseases. Bioactive phytochemicals, such as polyphenolic compounds, rich in the whole grains are hypothesized to contribute part of the protective effects against these chronic diseases. The objective of this study was to compare polyphenols and antioxidant capacity in the extractable and cell-wall-bound fractions of whole-grain rice differing in bran color (light-brown, brown, red, and purple color classes) with those of other cereal grains: corn, oat, red wheat, white wheat, and barley. In the extractable fraction, darker bran (red and purple) whole-grain rice contained significantly higher total phenolic (4- to 7-fold) and flavonoid (5- to 14-fold) concentrations and antioxidant capacity (2- to 4.5- fold) than most cereal grains except barley. The purple bran rice had 50 and 40% higher total flavonoids and antioxidant capacity, respectively, than barley, while the red color bran rice had 70% higher total phenolics than barley. The higher polyphenol concentration (total phenolics and flavonoids) and antioxidant capacity of darker bran rice and barley were primarily attributed to anthocyanins in purple rice and proanthocyanidins (condensed tannins) in red bran rice and barley. The consumption of anthocyanins in the United States was estimated to be 12.5 mg per day per person. In comparison, the purple rice variety IAC600 contained 140 mg anthocyanins/100 g. Proanthocyanidins in red bran rice were 127 mg/100 g, and their composition was 6.5, 33.5, 30.6 and 29.4% as 1-3, 4-6, 7-10 mers (or units), and polymer (>10 mers), respectively. Specific health-benefits suggested for anthocyanins or anthocyanin- and proanthocyanin-rich fractions include prevention of oxidative damage, the provision of anti-inflammation and anticarcinogenic activities, and the prevention of obesity in vitro and in animal studies. Darker color bran whole-grain rices have potential to positively impact human health.