Free and bound phenolic extracts from three varieties of black, indica, and Japonica rice bran were evaluated for their compositions, antioxidant activity and inhibitory effects on ɑ-amylase and ɑ-glucosidase activities. The free and bound phenolics displayed numerous antioxidant activities of ABTS , DPPH and T-AOC. HPLC results revealed that p -coumaric and ferulic acid mainly existed in bound forms, whereas anthocyanins contents were mainly in free phenolics of black rice bran. The bound phenolics in three varieties of rice bran exhibited higher inhibitory rate towards ɑ-amylase than their corresponding free phenolics did. The ɑ-glucosidase inhibitory rate of the bound phenolics in indica, and Japonica rice bran was higher than that of free forms, which showed the similar trend with that on ɑ-amylase. However, lower ɑ-glucosidase inhibition was observed in the bound phenolics from black rice bran, and the IC 50 values of free and bound phenolics on ɑ-glucosidase were 8.59 and 15.26 μg/mL, respectively. This may be attributed to the differences of phenolic composition and content in free and bound forms from varieties of bran. These findings may encourage the consumption of rice in forms of rice bran or whole brown rice for promoting health.
Ammonium toxicity affecting plant metabolism and development is a worldwide problem impeding crop production. Remarkably, rice ( Oryza sativa L.) favours ammonium as its major nitrogen source in paddy fields. We set up a forward-genetic screen to decipher the molecular mechanisms conferring rice ammonium tolerance and identified rohan showing root hypersensitivity to ammonium due to a missense mutation in an argininosuccinate lyase (ASL)-encoding gene. ASL localizes to plastids and its expression is induced by ammonium. ASL alleviates ammonium-inhibited root elongation by converting the excessive glutamine to arginine. Consequently, arginine leads to auxin accumulation in the root meristem, thereby stimulating root elongation under high ammonium. Furthermore, we identified natural variation in the ASL allele between japonica and indica subspecies explaining their different root sensitivity towards ammonium. Finally, we show that ASL expression positively correlates with root ammonium tolerance and that nitrogen use efficiency and yield can be improved through a gain-of-function approach.
危险品化学品经营许可证（带存储）