背景唐古特大黄被用作治疗胃肠道疾病的众所周知的中药之一。最近,唐古汀多糖(RP)由于其多种药理活性而受到越来越多的关注。通常,多糖的药理活性与其从胃到肠的代谢特性密切相关。然而,RP的消化行为和粪便发酵特性未知,这需要充分调查。
方法:在本研究中,建立了体外模拟胃肠道模型,研究了RP的消化行为和粪便发酵特性。RP物理化学性质的可能变化,如分子量,单糖组成,减少释放的糖,化学成分,pH值,和短链脂肪酸,在体外模拟消化和人粪便发酵过程中测定,并评估了其对肠道微生物组成调节的影响。
结果:结果表明,根据其理化性质的稳定性,RP在体外模拟消化条件下是不可消化的。相反,在体外发酵后,人粪便中的结肠微生物可显著利用难消化RP(RPI),尤其是,在初始发酵阶段(0-6小时)。揭示了RPI的粪便发酵特性。结果表明,发酵初期还原糖含量从0.177mg/mL明显增加到0.778mg/mL,在发酵结束时,其分子量从2.588×105Da明显下降到0.828×105Da。值得注意的是,结肠细菌对RPI中阿拉伯糖和半乳糖的利用快于半乳糖醛酸。此外,RPI可以通过促进几种有益菌的相对丰度明显调节肠道微生物组成,例如拟杆菌属,双歧杆菌,和Megamonas,促进了几种短链脂肪酸的生产,比如醋酸,丙酸,和丁酸。
结论:这项研究的结果表明,RP在体外人体上消化道是不可消化的,但是在发酵的初始阶段,人类粪便中的结肠微生物群很容易利用。RP可作为改善肠道健康的潜在益生元。
BACKGROUND: Rheum tanguticum is utilized as one of the well known traditional Chinese medicine for the treatment of gastrointestinal diseases. Recently, R. tanguticum polysaccharides (RP) have received increasing attention due to their diversely pharmacological activities. Usually, the pharmacological activities of polysaccharides are closely correlated to their metabolic properties from the stomach to the intestine. However, the digestive behavior and fecal fermentation characteristics of RP are unknown, which need to be fully investigated.
METHODS: In this study, an in vitro simulated gastrointestinal model was carried out for the investigation of the digestive behavior and fecal fermentation characteristics of RP. The possible changes in physicochemical properties of RP, such as molecular weight, monosaccharide composition, reducing sugar released, chemical composition, pH value, and short chain fatty acids, were determined during in vitro simulated digestion and human fecal fermentation, and its effect on the modulation of gut microbial composition was also evaluated.
RESULTS: The results revealed that RP was indigestible under the in vitro simulated digestion conditions according to its stabilities in physicochemical properties. Conversely, the indigestible RP (RPI) could be notably utilized by colonic microbiota in human feces after the in vitro fermentation, especially, at the initial fermentation stage (0-6 h). The fecal fermentation characteristics of RPI were revealed. Results showed that the content of reducing sugars obviously increased from 0.177 to 0.778 mg/mL at the initial stage of fermentation, and its molecular weight notably declined from 2.588 × 105 to 0.828 × 105 Da at the end stage of fermentation. Notably, the utilization of arabinose and galactose in RPI by colonic bacteria was faster than that of galacturonic acid. Besides, RPI could obviously modulate gut microbial composition via promoting the relative abundances of several beneficial bacteria, such as genera Bacteroides, Bifidobacterium, and Megamonas, resulting in the promoted production of several short-chain fatty acids, such as acetic, propionic, and butyric acids.
CONCLUSIONS: Results from this study showed that RP was indigestible in the human upper gastrointestinal tract in vitro, but could be easily utilized by colonic microbiota in human feces at the initial stage of fermentation. RP could be used as potential prebiotics for the improvement of intestinal health.