Antioxidant compounds and antioxidant activities of the methanolic extracts from milling fractions of black rice.

摘要

Coloured rice, particularly black rice, has been well characterized to possess antioxidant properties. Rice bran, a by-product of the rice milling process, contains high levels of several phytochemicals which have antioxidative activity as well as properties beneficial to health. The purposes of this study were to evaluate the antioxidant compounds and antioxidative activities of methanolic extracts from milling fractions and whole grain of 2 black rice cultivars. Whole black rice of the 2 cultivars were milled into rice bran and endosperm using the gradual milling system. These were evaluated for antioxidative activities by DPPH and ABTS radical scavenging activities. To determine the antioxidant compounds in the methanolic extract from the milling fractions, the content of polyphenols, flavonoids, anthocycanins and gamma-oryzanol were measured by spectrophotometric methods and vitamin E analysis was carried out by HPLC. The yield of whole black rice, rice bran and endosperm were 3.1, 15.3, and 0.9% for Heugjinjubyeo cv. and 2.7, 15.5, and 1.1% for Heugkwangbyeo cv. The methanolic extracts from rice bran showed generally higher antioxidant activities than the extracts from whole grain and endosperm. In addition, contents of antioxidant compounds were much higher in rice bran extract than in extracts from whole grain and endosperm. A significant correlation was also noted between free radical scavenging activity and polyphenolic compounds. The results of this study show that black rice bran has significant antioxidative activity.