Beneficial effect of the unsaponifiable matter from rice bran on oxidative stress in vitro compared with α-tocopherol
✍ Scribed by Jin-Won Lee; Seog-Won Lee; Min-Kyung Kim; Chul Rhee; In-Hwan Kim; Kwang-Won Lee
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- English
- Weight
- 128 KB
- Volume
- 85
- Category
- Article
- ISSN
- 0022-5142
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✦ Synopsis
Abstract
Unsaponifiable matter (UM) was prepared from rice bran using n‐hexane extraction followed by removal of its fatty acid methyl ester with supercritical CO~2~ under heat‐stable conditions. The UM was made up of 1% of vitamin E isomers, 28% of γ‐oryzanol and 71% of uncharacterized compounds. The aim of this study was to determine the antioxidant activities of the UM, using α‐tocopherol (α‐T) as a positive control, by measuring the Fe^3+^‐reducing antioxidant power (FRAP), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH^•^) free‐radical‐scavenging property and lipid peroxidation in rat liver microsomes. In addition, the effects of the UM on the tert‐butyl hydroperoxide (t‐BOOH)‐induced cytotoxicity in cultured rat hepatocytes were also investigated. In FRAP assay and DPPH^•^ free‐radical‐scavenging assay, the results were expressed g^−1^α‐T or g^−1^ UM. The amount of UM used in lipid peroxidation assay and cytotoxicity assay was the amount required to have equal amounts of total vitamin E isomers in the sample and the control α‐T. The UM, as well as α‐T, exhibited significant antioxidant activities in FRAP, radical‐scavenging and membrane‐lipid oxidation. The FRAP value for total vitamin E isomers in the UM (TVEIUM) was 9.1 times higher than that for α‐T. In terms of their capacities to perform radical‐scavenging and lipid peroxidation, both TVEIUM and α‐T showed similar antioxidant activities. In experiments using cultured rat hepatocytes, the t‐BOOH‐induced lactate dehydrogenase release was significantly inhibited by the addition of 63.5 and 160 µg ml^−1^ of TVEIUM treatments (84 and 89%, respectively), and that of 63.5 and 160 µg ml^−1^ of α‐T treatment (88 and 93%, respectively). The antioxidant function against oxidative stress of the UM prepared from rice bran may extend its use to being a potential dietary supplement. Copyright © 2004 Society of Chemical Industry