| In the last 20 years, active oxygen and free radical have become the hot topics of modern life science, and appraisal and selection of natural resources with strong antioxidative activities have become the new trends of biology, medical science and food science and technology. As a good and important rice resource, black rice is an important source for the development of natural antioxidants due to rich natural anthocyanins in pericarp and seed coat of brown rice. In this paper, varieties with strongest activities were selected after comparing the differences of antioxidative actions of different black rice varieties in large quantities by monitoring their antioxidative activities, active substances were extracted from the materials selected, antioxidation and hypolipidemic effects were appraised at whole organism level and cell level, main active components were further separated and their basic structures were identified, the relation between quantity and effect and relation between structure and effect were investigated to determine their chemical structures and mechanisms. The main results were as follows:(1) Big differences in total antioxidant capacity (TAC), scavenging free radical capacity (SFRC), total flavonid and anthocyanin contents existed among 242 black rice varieties, and among indica rice, japonica rice, nonglutinous rice, glutinous rice, indica nonglutious rice, indica glutious rice, japonica nonglutinous rice and japonica glutinous rice. According to the fast clustering procedure, 242 black rice varieties could be clustered into 10 clusters, 184 indica rice varieties could be clustered into 10 clusters, and 58 japonica rice varieties could be clustered into 6 clusters. Most significant correlations existed between TAC and total flavonoid and anthocyanin contents, and between SFRC and total flavonoid and anthocyanin contents of black rice, respectively (P<0.01).(2) Significant differences in antioxidations, total flavonoid and anthocyanin contents of different parts of black rice such as pericarp and milled rice existed. The TAC, total flavonoid and anthocyanin contents of black rice pericarp accounted for over 98% of total contents in whole black rice. The processing and preservation techniques such as firing, microwave heating, extrusion, and addition of lipotropism and clastic enzymes had some effect on the preservation of black rice pericarp, of which extrusion and microwave heating could achieve most stable effects and had relatively less effect on the antioxidations, total flavonoid and anthocyanin of black rice pericarp.(3) The optimum extraction conditions determined by orthogonal test were: material: black rice pericarp; solvent: 60% ethanol; ratio of material and solvent: 1:4; extraction temperature: 60℃; and extraction time: 4h. The one time extraction rate under such condition was 71.38%. By comparing static and dynamic absorption performance, macropore adsorptive resin NKA-II that had highest performance in absorbingantioxidative extract of black rice (AEBR) and optimum absorption relieving agent 70% ethanol solution were selected. After absorption and purification by NKA-II, TAC of AEBR was increased by 3.97 times. All extracts obtained in different fractions by using different polarities of solvents such as petroleum ether, chloroform, ethyl acetate and normal butyl alcohol could display relatively strong antioxidative actions in vitro, with the order of water fraction, normal butyl alcohol fraction, ethyl acetate fraction, and chloroform fraction, with antioxidation of petroleum ether fraction equaled to that of chloroform fraction. The analysis by GC-MS and HPLC showed that the antioxidative extracts of petroleum fraction and chloroform fraction were mainly fatty acids. The compositions of ethyl acetate fraction, normal butyl alcohol fraction, and water fraction differed significantly. 4 red single compounds of P1, P2, P3, and P4 were separated from the main antioxidative extract fraction (water fraction) of AEBR by using TAC as t... |
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