| Summary: | 碩士 === 輔仁大學 === 食品營養學系 === 88 === Dietary soy protein has been shown its specific hypochesterolemic effect. Genistein, an isoflavones of soybean has the highest antioxidant capacity. The purpose of this study was to investigate the effect of various contents of defatted soy on antioxidant enzyme systems and tissue genistein in rats. Five weeks old Wistar rats were randomly divided into five groups and fed diets containing various levels of soy protein (5, 10, 15 or 20%, respectively) of defatted soy and casein as control group for 6 weeks. Analyzing the antioxidant enzymes, genistein contents, TBARS value, fatty acid compositions, and cholesterol levels in serum, liver and RBC were undertaken. Intake of the defatted soy significantly lowered the serum cholesterol but didn’t affect glutathione contents of RBC and liver. Feeding of 20% soy protein significantly increased serum glutathione. There were no difference of the glutathione peroxidase (GPx) activity in RBC and serum among groups. The GPx activity in liver reduced significantly by feeding of the soy protein more than 10%. There were no difference of the glutathione reductase (GR) activity both in RBC and serum among 5 groups. There were no difference of the linoleic acid (18:2) either in serum or liver in each group. Serum and liver arachidonic acid (20:4) increased with the increase of the dietary protein. Serum thiobarbituric acid reactive substances (TBARS) decreased in parallel with the increase of the dietary soy protein; but hepatic TBARS didn’t correlate with the contents of soy protein intake. Genistein levels were increased after feeding of the soy protein. There was a negative correlation between GPx activity and the contents of genistein in liver. A significant inverse correlation was observed between the contents of genistein and cholesterol in serum. However, there was a positive correlation between the levels of cholesterol and TBARS in serum. Taken together, these results suggested that higher soy protein in diet might affect isoflavones contents and antioxidative enzyme activity in vivo.
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