E Vitamer Fraction in Rice Bran Inhibits Autooxidation of Cholesterol and Linoleic Acid in Emulsified System during Incubation

Abstract

: The antioxidant activities of E vitamer fraction extracted from rice bran were investigated and compared with α-tocopherol at 2 concentration levels (16 ppm and 160 ppm) in the emulsified cholesterol and linoleic acid systems. 7-Ketocholesterol, 7α-hydroxycholesterol (7α-OH), 7β-hydroxycholesterol (7β-OH), 25-hydroxycholesterol (25-OH), and 5,6-epoxycholesterol (5,6-EP) were found at different incubation times (0, 6, 12, 24, and 48 h) in the emulsified cholesterol system accelerated by using 2, 2′-azobis (2-methylpropionamidine) dihydrochloride (AAPH) at 80°C and pH 5.5. Samples treated with 160 ppm of E vitamer fraction exhibited a significant antioxidant activity by inhibiting the formation of cholesterol oxidation products (COPs). Addition of E vitamer fraction to the emulsified linoleic acid model at 37°C significantly inhibited the hydroperoxide formation and decomposition more than that of α-tocopherol. The former was more effective in inhibiting the primary and secondary oxidations of the polyunsaturated fatty acid (PUFA). No significant differences (P < 0.05) were found in inhibition of the linoleic acid autoxidation between the E vitamer fraction and the α-tocopherol at 16 and 160 ppm, respectively. E Vitamer fraction was most effective in inhibiting both emulsified cholesterol and linoleic acid. These results suggested that compounds inhibiting cholesterol autoxidation and PUFA autoxidation in both food and biological systems were present in the rice bran extract. Thus, the addition of E vitamer fraction to animal- derived muscle food may be a more compelling way to replace the synthetic antioxidants currently used in the food industry because the former is both natural and effective in inhibiting both cholesterol and PUFA autoxidation.