| Summary: | 博士 === 國立臺灣海洋大學 === 食品科學系 === 94 === Abstract
I-Tiao-Gung (Glycine tomentella Hayata) has been wildly cultured in Kinmen and used as a folk medicine for treatment of rheumatism, gout, arthritis, and ache of physique indicative of its anti-inflammatory activities. But its biological activities and pharmacological functions have not been studied systematically. The purpose of this study was to elucidate the long-claimed anti-inflammatory activity of I-Tiao-Gung by in vitro test and to assess its potential effects on atherosclerosis, using tilapia as an alternative animal to evaluate the in vivo effects of I-Tiao-Gung.
The 95% ethanol extract of I-Tiao-Gung (GT-E) showed antioxidant activity on hemoglobin-catalyzed oxidation of linoleic acid. The IC50 value was 4.6 μg/mL lower than that of trolox (IC50=14.2 μg/mL). GT-E had the ablility to scavenge 1,1-diphenyl-2- picrylhydrazyl radicals (DPPH). Its EC50 value was 18.4 μg/mL similar to trolox (17.1 μg/mL). GT-E inhibited tilapia thrombocyte (the nucleated platelet) 5-, 12-, 15-lipoxygenase (LOX). The IC50 values were 0.43, 0.72 and 0.42 μg/mL respectively, while those of nordihydroguaiaretic acid (NDGA) on 5-, 12-, 15-LOX were 2.3, 1.6, and 1.7 μg/mL respectively. The IC50 on cyclooxygenase-2 (COX-2) inhibition by GT-E was 42.0 μg/mL while that for indomethacin (as a positive control) was 0.61 μg/mL. GT-E showed antioxidant activity by prolonging the lag phase (△Tlag) of human LDL oxidation induced by Cu2+ in a dose-dependent manner. The △Tlag of LDL added with 3.2 μg/mL GT-E was similar to that with trolox at 2.0 μM (ca. 0.5 μg/mL ).
Hybrid tilapia (Oreochromis niloticus × O. aureaus), body mass 185.0±19.3, were fed daily with a commercial fish feed (protein 53.0%, lipid 7.4%, ash 11.4%, crude fiber 1%, carbohydrate 21.4%, total energy 3194 kcal/kg) at 1.6% body mass for 8 weeks. The plasma total triacylglycerol increased to 1218.6±79.2 mg/dL, total cholesterol increased to 740.3±276.3 mg/dL, and low density lipoprotein (LDL-C) increased to 392.1±56.3 mg/dL, respectively. Hyperlipidemia and hypercholesterolemia were found in fish. Mossambicus tilapia (Oreochromis mossambicus) (n=32), body mass 60±6.4 g, cultured with the same condition, fed daily 2% body mass for 8 weeks, and 1% body mass for 12 weeks were found hyperlipidemia and hypercholesterolemia. Matured male mossambicus tilapia (body mass 59.5±9.5, n=32) were randomly divided into two groups and fed with feed containing 1% (w/w) GT-E for 12 weeks. Total triacylglycerol of the GT-E group was lower than that of the control group by 41.9%, total cholesterol was lower by 30.4%, LDL-C was lower by 36.1%. Plasma total antioxidant status (TAS) of the GT-E group was higher than that of the control group by 79%. GT-E fed group had longer lag phase of Cu2+-induced LDL oxidation and retained significantly more α-tocopherol (13.3±3.0 α-tocopherol molecule/LDL) in LDL particles than the control group (8.8±2.5 α-tocopherol molecule/LDL). LDL from the GT-E group had more monounsaturated fatty acids and less polyunsaturated fatty acids than the control, indicating that GT-E may affect fatty acids metabolism. These evidences demonstrated that GT-E had hypolipidemic and hypocholesterolemic effects.
Using tilapia exposed to ammonium chloride to evaluate the fuction of GT-E on anti-environmental stress. Hybrid male tilapia (n=40) weighed 185 g were randomly divided into two groups and fed with feed either containing 1% (w/w) GT-E or control diet for 12 months than exposed to 100 ppm ammonium chloride for up to 24 hours. Both groups decreased in osmosis measured at 12 and 24 hours. 5-LOX activity increased when exposed for 12 hours. Thrombocyte 12- and 15-LOX increased in the control group but not in the GT-E group. Intake of GT-E seemed to retard the changes in tilapia exposed to stress as abnormal concentration of ammonium chloride.
The prevention of LDL oxidation and the dual inhibition of LOXs and COX-2 are indicative of the possible roles of GT-E on anti-atherosclerosis and anti-inflammation. Since GT-E inhibited LDL oxidation of tilapia in vitro, ex vivo and in vivo, GT-E had hypolipidemic and hypocholesterolemic effects in tilapia similar to that previously reported in hamster. Tilapia can serve as a surrogate animal model for prescreening hypocholesterol and anti-atherosclerosis effects of nutraceuticals and health foods.
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