| Summary: | 博士 === 臺灣大學 === 食品科技研究所 === 98 === Atherosclerosis related diseases, such as cerebral hemorrhage, coronary heart disease and high blood pressure, are the 2nd, 3rd and 10th major causes of death in Taiwan. High blood lipids and oxidative stress, which cause the oxidation of low density lipoprotein (LDL), play important roles in atherosclerosis. Intrinsic antioxidants are known to scavenge free radicals in the body and thus lower the oxidative damage. Many in vitro and ex vivo studies have shown that dietary antioxidants could enhance the resistance of LDL toward oxidation. Recent studies suggested that the polysaccharides and triterpenes present in Ganoderma lucidum have antioxidative activities and are also capable of reducing cholesterol. Leguminous plants such as black soybean and Astragalus membranaceus contain isoflavones which are shown to inhibit lipid peroxidation and delay the oxidation of low density lipoprotein. Using black soybean and A. membranaceus as part of the fermentation medium, isoflavones might be transformed into the more bioavailable form (aglycone) by microbial enzymatic hydrolysis of the glycosidic linkage. The immunomodulatory polysaccharides might also undergo enzymatic degradation into smaller molecules with higher hydrophilicity and bioavailability.
The objectives of this study were to investigate the antioxidative effect and lipid modulating ability of the fermentation broth produced by using leguminous plants as part of the liquid fermentation medium of G. lucidum. This study was, therefore, divided into three parts: (1) in vitro antioxidative effect of the fermentation products of G. lucidum under different fermentation conditions; (2)Antioxidative and lipid-modulating effect of fermentation products with animal model：(a) animal study I：effect of black bean, A. membranaceus and G. lucidum on serum lipids of hamsters; (b) animal study II：effect of fermentation broth filtrate of G. lucidum on serum lipids of hamsters；(c) animal study III：effect of ethanolic extract of G. lucidum fermentation broth filtrate on serum lipids of hamsters；(d) animal study IV：effect of different diet and fat composition on serum lipids of hamsters. (3) To investigate the antioxidant compounds of G. lucidum broth filtrate.
Results of antioxidative effect of fermentation products of G. lucidum under different fermentation conditions showed: G. lucidum broth filtrate after removal of polysaccharide had better antioxidative effect. Comparing the effect of fermentation condition, broth filtrate from fermentation at 30℃ had better effect than 18 and 24℃. The better effects on inhibition of LDL oxidation at 18℃ and 24 C was aeration at 0.75 and 0.25 vvm, respectively. Also, 10% inoculum ratio had better antioxidative effect then 1% and 0.1% at 30℃. Overall, fermentation product with the best antioxidative effect was shown by GL-D after removal of polysaccharide and the antioxidative ability increased with fermentation time. Content of total isoflavone decreased with fermentation time. Isoflavone aglycone increased in the first three days, but then decreased and became undetectable at the 11th day. Total polyphenol contents of the fermentation broth filtrate increased with fermentation time and correlated well with the antioxidative effect, therefore polypheonl may play an important role on antioxitative ability of G. lucidum broth filtrate.
Results of animal study I showed that after feeding 10% black bean or A. membranaceus hamsters had higher serum HDL-C and hepatic cholesterol. Hamsters fed with A. membranaceus also reduced hepatic TBAR value. Hamsters fed with 10% black bean, 10% A. membranaceus and 8% G. lucidum all showed lowered levels of serum MDA than the high fat high cholesterol control group. Results of animal study II showed that hamsters fed with 10% G. lucidum broth filtrate had lower hepatic cholesterol and serum MDA, but the daily feed intake, body weight and hepatic TBAR value were higher than high fat high cholesterol group. Result of animal study III showed that after feeding hamsters 1% ethanolic extract of G. lucidum broth filtrate there were no significant differences in either blood or liver lipids with high fat high cholesterol control group.
Results of animal study IV showed that after feeding Purina 5001 rodent chow diet hamsters had higher serum cholesterol, VLDL, LDL, LDL-C/HDL-C ratio and hepatic cholesterol than feeding AIN-93M diet. Based on AIN-93M diet, hamster feed containing 6% lard resulted in lower serum cholesterol than feed containing 6% corn oil. Our data indicated that hamster fed on Purina 5001 rodent chow diet was a more suitable model for evaluating the effect of test sample on blood lipids than AIN-93M diet
To investigate antioxidant compounds, we found 2 compounds, pyrogallol and protocatechuic acid, were the main active compounds of G. lucidum broth filtrate. We also found that protocatechuic acid, polyphenol content and inhibiting Cu2＋-induced LDL oxidation depended on days of fermentation. The results indicate protocatechuic acid was the main antioxidant compound during fermentation of G. lucidum broth filtrate.
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