| Summary: | 博士 === 國立中興大學 === 食品暨應用生物科技學系 === 96 === In the present study, the water extracts prepared from the Amomum villosum seed, Zizyphus jujuba fruit, Salvia plebeia, and Vitis thunbergii were used to investigate their composition, in vitro physiological effects, and cholesterol-lowering and intestinal health-promoting abilities using an animal model. The proximate composition analyses revealed that the A. villosum seed, S. plebeia, and V. thunbergiiextracts were rich in water-soluble polysaccharides (60.5-63.0 g/100 g dried extract, DW), while Z. jujuba fruit extract contained a considerable amount of water-soluble carbohydrates (~77.1 g/100 g dried extract, DW) including polysaccharide (20.1 g/100 g dry extract, DW), fructose (29.6 g/100 g dry extract, DW), and glucose (27.4 g/100 g dry extract, DW). The chemical analyses on the monomeric sugar in the polysaccharides, it was suggested that water-soluble polysaccharides of the A. villosum seed, Z. jujuba fruit, S. plebeia, and V. thunbergii were pectic polysaccharides, followed by hemicellulose. In vitro study showed that the four plant extracts and their polysaccharides (except the polysaccharide from the S. plebeia extract) significantly (P < 0.05) exhibited an inhibitory effect on theα
-amylase activity. The four extracts and their polysaccharides could effectively increase the activities of proteases (e.g. pepsin and trypsin/chymotrypsin). Moreover, lipase activities were significantly (P < 0.05) decreased with increasing concentrations of the four extracts and their polysaccharides (20 to 120 mg/mL). Furthermore, an elevation in the concentrations of the four extracts and their polysaccharides lead to a significant (P < 0.05) decrease of the stability and solubility of cholesterol-micelle and also a significant (P < 0.05) increase in the bile acids binding ability.
In order to investigate the cholesterol-lowering effects of the four extracts, a hypercholesterolemic diet (with cholesterol at 0.2 g/100 g) and a hamster model were used. The experimental diets were supplemented with cholestyramine (0.5 g/100 g) and the four extracts at three different levels including low, medium, and high doses (0.17, 0.5, and 1.5 g/100 g, respectively). After 30 days of feeding, the results showed that the addition of cholestyramine and the four extracts at different levels (0.17-1.5 g/100 g diet) significantly (P < 0.05) reduced the serum triglyceride and total cholesterol levels. The LDL cholesterol levels of the hamsters taking the cholestyramine and extracts at 0.5 g/100 g diet or above were significantly (P < 0.05) lower than those of the control group. A significant (P < 0.05) elevation in the HDL:total cholesterol ratio was observed with a supplementation of the Z. jujuba fruit, S. plebeia, and V. thunbergii extracts (medium and high doses). The feeding of A. villosum seed extract at all three doses significantly (P < 0.05) increased the HDL:total cholesterol ratio. The consumption of cholestyramine and the four extracts (at 0.5 g/100 g diet or higher) significantly (P < 0.05) reduced the LDL:total cholesterol ratio. As compared to the control group, the cholestyramine- and extract-supplemeted groups (medium and high doses) resulted in a significant (P < 0.05) reduction in the liver total lipids and cholesterol levels. The fecal excretion of cholesterol and bile acids were significantly (P < 0.05) reduced by an increased consumption of the four extracts in a dose-dependent response. An apparent increase in the fecal excretion of total lipids was observed with increasing the doses of the S. plebeia and V. thunbergii extracts to 1.5 g/100 g diet. The significant (P < 0.05) increases in the levels of fecal total lipids were observed by only feeding the A. villosum seed and Z. jujuba fruit extracts at the medium dose. These results implied that the hypocholesterolemic actions of these extracts were attributed to the elevated fecal excretion of cholesterol and bile acids. With respect to the hypocholesterolemic effects of the four extracts, there were negative correlations between the serum total cholesterol and the fecal cholesterol, the liver total lipids and the fecal total lipids, the liver cholesterol and the fecal bile acids, and the serum total cholesterol and the fecal bile acids.
After feeding the hamsters with the four extracts at different doses (0.17-1.5 g/100 g diet) for 30 days, the results revealed that the consumption of the four extracts effectively (P < 0.05) increased the fecal moisture contents, shortened hamsters gastrointestinal transit time, reduced the pH values, and decreased the cecal and fecal ammonia contents with the increasing concentrations of extracts. Respecting to the activities of intestinal enzymes, it was suggested that the feeding of the four extracts resulted in significant (P < 0.05) reductions in the maltase and sucrase activities. As compared to the control diet, the four extracts-containing diets resulted in significant (P < 0.05) decreases in the activities of the fecal bacterial enzymes such asβ-D-glucosidase, β-D-glucuronidase, mucinase, and urease. Chemical analyses on the cecal contents and feces showed that the addition of the four extracts into the control diet significantly (P < 0.05) increased the total SCFA concentrations in the cecal contents and feces as well as the total SCFA pools in the cecum and feces.
These results suggested that the consumption of the four extracts (at lest 0.5 g/100 g or 40 mg/day) might exert effects on cholesterol-lowering as well as maintaining or improving the intestinal health. It was speculated that these activities were partly associated with the water-soluble polysaccharides and/or carbohydrates in the extracts. The highest increase in the excretion of bile acids and cholesterol was observed with an adequate consumption of A. villosum seed and Z. jujuba fruit extract (0.5 g/100 g) among the four plant extracts. The increased fecal output of bile acids and cholesterol therefore led to a significant reduction of serum total cholesterol concentration. Among the four plant extracts, the consumption of Z. jujuba fruit extract had a better effect on the SCFA production while the lowest fecal bacterial activity was observed with an intake of A. villosum seed. Our findings also provided a clue to substantiate their traditional therapeutic uses and dosage for the hypocholesterolemic and intestinal health-improving effects. Therefore, the hypocholesterolemic activities of the extracts might be attributable to a reduction in cholesterol absorption and an increase in the fecal excretion of cholesterol and bile acids. Moreover, the four extracts might affect the metabolic activities of intestinal microflora and thereby reduce the exposure of intestine to the damage of detrimental toxicity.
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