Polyphenols in whole rice grain: Genetic diversity and health benefits

• The extractants and the contents of the polyphenols in rice and rice products are summarized.
• Polyphenols mainly exist in rice bran, followed by embryo and endosperm.
• CAP system and phenylpropanoid pathway are the genetic basis of polyphenols.
• Wide applications and health benefit of whole rice grain are summarised.
• Some challenges that need to be addressed in future are presented.

Polyphenols, such as phenolic acid, anthocyanin and proanthocyanidins, have both nutraceutical properties and functional significance for human health. Identification of polyphenolic compounds and investigation of their genetic basis among diverse rice genotypes provides the basis for the improvement of the nutraceutical properties of whole rice grain. This review focuses on current information on the identification, genetic diversity, formation and distribution patterns of the phenolic acid, anthocyanin, and proanthocyanidins in whole rice grain. The genetic analysis of polyphenol content and antioxidant capacity allows the identification of several candidate genes or quantitative trait loci (QTL) responsible for polyphenol variation, which may be useful in improvement of these phytochemicals by breeding. Future challenges such as how to mitigate the effects of climate change while improving nutraceutical properties in whole grain, and how to use new technology to develop new rice high in nutraceutical properties are also presented.