| Dendrobium officinale, belongs to perennial adnascent herbaceous plant, Dendrobium officinale Kimura et Mi-go, Orchidaceae. Dendrobium officinale is mainly growed in over 1600 meters high mountainous area of Yunnan, Guangxi, Fujian, Zhejiang province in China. Due to the special and abundant medicinal value, Dendrobium officinale become one of the most famous medicinal herbs in China since ancient times. And it is famous as Ganoderma Lucidum Karst,Panax ginseng C. A. Mey and Cordyceps sinensis, to be regarded as top grade of traditional Chinese Medicine. Polysaccharides are one of the major effective active substances in Dendrobium officinale, as a result they have caused wide attention of scholars at home and abroad to study in recent years. According to the existing researches, Dendrobium officinale polysaccharides have shown significant ability in vitro antioxidant, enhancing body immunity, anti-tumor, and lowering blood sugar. Polysaccharides are a kind of macromolecule carbohydrates which necessarily required in the human body. Furthermore, Polysaccharides are also typical dietary fibers, and it generally comes to an agreement in the current functional food fields that dietary fibers play a positive regulatory role in intestinal function of the body. But it has been seldom reported about the effects of Dendrobium officinale polysaccharides on intestinal health. For this reason, our paper had used Dendrobium officinale produced in Yunnan as source material, technological means such as in vitro simulated conditions of human digestive tract and animal test were used in research. The characteristics of in vitro digestion and fermentation and the regulating effects of Dendrobium officinale polysaccharides on intestinal functions of mice were researched. We hope our study is in order to give a preliminary exploration of the the relationship between the Dendrobium officinale polysaccharides and human intestinal health, so as to provide a theoretical basis for the application of Dendrobium officinale polysaccharides in edible, medicinal functional food and component development of new type of drug. The main research content of this article is as follows:1.Study on in vitro digestion of Dendrobium officinale polysaccharides by simulating the gastrointestinal digestive system. Based on the simulating digestive system, imitated the digestive function saliva, gastric juice and intestinal juice on polysaccharides respectively. During the experiment, the molecular weight o f polysaccharides didn’t change after heat treatment or treated with electrolyte buffer. The spectrum characterization of polysaccharides was not influenced as well after mixing with inactive heated enzyme. O n this basis, we made a further research the digestive effects of three kinds of enzymes on polysaccharides. Saliva couldn’t change the molecular weight of polysaccharides and the content of reducing sugars. While in simulated gastric and bowel, molecular weight of the polysaccharides was decreasing, from 314.51±6.09 k Da to 244.79±2.99 k Da and 229.91±1.59 k Da respectively. At the same time, reducing sugar content in digestive juice was increasing. After detecting the dialysis of digestive juices, no signal of monosaccharides was found, indicating no monos accharides were produced during digestion. The experimental results show that the overall structure of the polysaccharides was not damaged, digestive juice in the stomach or small intestine couldn’t digest polysaccharides, in vitro fermentation of polysaccharides by simulating intestinal system is requested to give a further research on metabolic situation of polysaccharides.2.The fermentation of Dendrobium officinale polysaccharides of in vitro simulating fermentation system. The polysaccharides were mixed with human intestinal flora, pure water was used as the blank control. Detect the fermentation solution after 0, 1, 2, 6, 12, 24 and 48 h respectively. The results showed p H of the glycolytic products(5.3) was significantly lower than that of the blank group(5.9)(p < 0.05), the content of total sugar was reduced gradually along with the time growth during glycolysis, while the reducing sugar content was increased at first but then decreased. By fermenting, the content of short chain fatty acids was increase, highlighted the content for acetic acid, propionic acid and butyric acid. Concentration of acetic acid was from 22.89±1.06 mmol/L to 35.99±1.61 mmol/L, concentration of propionate was from 8.43±0.54 mmol/L to 15.26±0.84 mmol/L, and concentration of butyric acid was from 2.04±0.22 mmol/L to 8.60±0.74 mmol/L, all these promotions were significantly higher than the control group(p < 0.05). Signal of glucose could be detected in 1, 2, 6, 12 h and signal of mannose was detected in 1, 2, 6 h, implying they were generated as substrates of short cha in fatty acid. The results suggested that the Dendrobium officinale polysaccharides, glycoside bond was broken, and could be used by human intestinal microflora. This provided a further theoretical basis for the research of polysaccharides in mice.3. Effects of Dendrobium officinale polysaccharides on intestinal function in mice. After feeding mice with Dendrobium officinale polysaccharides, physiological and biochemical index, small intestine peristalsis and defecation time of mice showed a positive effect of improvement. Colon length(8.66-10.66 cm) and colon index(1.14-1.68%) of polysaccharides- group were higher than that of the control group(7.52 cm and 0.92% respectively), water content of colonic fecal(62.71%-66.98%) was higher than that of the control group(60.03%), and p H value of caecum, colon and external feces was decreased(p < 0.05). By oral gavage of polysaccharides, content of short chain fatty acid in cecum(30.54 mmol/L), colon(24.42 mmol/L) and external feces(25.47 mmol/L) were increased significantly(p < 0.05). After a month of oral gavage, ink progradation rate of polysaccharides-group mice(69.33%-77.90%) was faster than that o f the control group(66.75%), and the defecation time(157.4-195.6 min) was shorter than control group(250.4 min)(p < 0.05). The secret that Dendrobium officinale polysaccharides owed such promoting effect is due to its structure of rich acetyl groups, which could be degraded by specific enzyme. Glucopyranose and mannopyranose are carbon source for the preparation of fatty acid. To sum up, consumption adequate amount of Dendrobium officinale polysaccharides will help to promote the growth of colon, improve intestinal function and accelerate intestinal peristalsis. We hope this article would make a little contribution to the study of in vivo metabolism of Dendrobium officinale polysaccharides and the further exploitation of Dendrobium resources. |
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