Phenolic content, anthocyanins and antiradical capacity of diverse purple bran rice genotypes as compared to other bran colors

Authors: Chen, Ming Hsuan; McClung, Anna; BERGMAN, CHRISTINE - University Of Nevada Las Vegas, Las Vegas, Nv

Submitted to: Journal of Cereal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2017
Publication Date: 7/20/2017
Citation: Chen, M., Mcclung, A.M., Bergman, C.J. 2017. Phenolic content, anthocyanins and antiradical capacity of diverse purple bran rice genotypes as compared to other bran colors. Journal of Cereal Science. 77:110-119.

Interpretive Summary: Anthocyanins are a class of naturally occurring compounds found in plants that have health benefit in reducing the risk of developing chronic diseases in animal and human clinical trials. Fruits, such as berries and grapes are known to contain anthocyanins. In an effort to develop phytonutrient-rich whole grain rice, we evaluated the genetic variation for anthocyanin concentration found in rice having purple (or black) bran. More than a 25-fold variation in total anthocyanin concentration was found among 25 global rice varieties having purple brans. Using a non-destructive colorimeter to measure the purple color of the whole grain rice, the color parameter b*, measuring yellowness, negatively correlated with the concentration of total anthocyanins suggesting that this color parameter would be an efficient screening tool for selecting anthocyanins in whole grain rice. In conclusion, rice varieties with high concentration of anthocyanins were identified that can be used for breeding to enhance phytonutrients in rice.

Technical Abstract: Phenolic compounds reportedly may reduce the risk of developing chronic disease and their risk factors. Anthocyanins are flavonoids, a subgroup of phenolic compounds in purple colored whole grain rice that have shown these health benefits in animal studies and human clinical trials. We studied the genotypic diversity of purple bran rice in terms of total phenolic, total flavonoid and anthocyanin contents, as well as oxygen radical absorbance capacity. More than 13-, 12-, 25- ,and 8-fold variations were found for these respective traits. Cyanidin-3-glucoside and peonidin-3-glucoside were the major anthocyanins identified in the genotypes studied accounting for 82.3% and 14.6% of the anthocyanin content. The color parameter b* of whole grain rice was correlated with anthocyanins and can be used as a non-destructive quick screening tool. Purple bran genotypes that accumulated both anthocyanins and proanthocyanidins had the highest total phenolics, total flavonoids, and oxygen radical absorbance capacity among all color (i.e., white, light brown, brown, red and purple) brans. Purple brans had the widest genotypic diversity of these chemical traits, followed by red, brown, light brown, and white. In terms of antioxidant properties of total flavonoid compounds in the sample extracts, purple and red brans had similar reducing capacity per unit of total flavonoids; while purple bran had higher oxygen radical absorbance capacity per unit of total flavonoids. The genetic variation found in this study suggests that new rice cultivars with colored bran having specific amounts and types of phenolic compounds can be developed using traditional breeding.