Antioxidant Compounds and Antioxidant Activities of the Methanolic Extracts from Milling Fractions of Black Rice

흑미의 도정분획 메탄올 추출물의 항산화 성분 및 항산화 효과

The colored 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 antioxidant activities as well as health-beneficial properties. The purposes of this study were to evaluate the antioxidant compounds and antioxidant activities of the methanolic extracts from milling fractions and whole grain of two black rice cultivars. Whole black rice of the two 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 polyphenolics, 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 and 2.7, 15.5, and 1.1% for Heugkwangbyeo, respectively. The methanolic extracts from rice bran showed generally higher antioxidant activities than the extracts from whole grain and endosperm. In addition, antioxidant compounds distributed much higher contents in rice bran extract than in the 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 notable antioxidant activity in black rice bran are considered to have significant health benefits.

본 연구에서는 흑미 두 품종(흑진주벼와 흑광벼)의 도정 분획별 메탄올 추출물의 항산화 성분과 항산화 활성을 비교 분석하고자 하였다. 흑미의 항산화 성분으로 polyphenolic, flavonoid, anthocyanin과 ${\gamma}$-oryzanol, tocopherol 및 tocotrienol 함량을 측정하였으며 항산화 활성은 DPPH와 ABTS radical 제거능을 측정하였다. 각 도정 분획별 메탄올 추출물에서 rice bran 층에서 약 $15.3{\sim}15.5%$의 가장 높은 수율을 보였으며 endosperm 메탄올 추출물에서 약 $0.9{\sim}1.1%$의 가장 낮은 수율을 보였다. 실험결과 rice bran의 추출물에서 endosperm, whole grain의 추출물보다 높은 함량의 항산화 성분이 분포함을 확인할 수 있었다. 또한 이러한 항산화 성분이 다량 분포하는 rice bran 추출물의 우수한 항산화력을 측정할 수 있었다. 품종 간에는 흑진주벼의 rice bran층의 항산화 성분이 흑광벼보다 높은 함량을 나타내었다. 본 연구결과 흑미의 rice bran은 기능성식품의 성분으로 활용가능성이 높을 것으로 예상된다.