A galacturonan from Dioscorea opposita Thunb. regulates fecal and impairs IL-1 and IL-6 expression in diarrhea mice.

Antibiotic-associated diarrhea (AAD) is a common side-effect of antibiotic treatment resulting from an imbalance in the colonic bacteria. The hypothesis of this study is to ask whether polysaccharide from the rhizome of Dioscorea opposita which is recorded as conventional herbs and food for diarrhea treatment in Southeast Asia, may be an active compound against diarrhea induced by antibiotics. To address, firstly, a homogenous polysaccharide, DOP0.2-S-3 was characterized as a homogalacturonan containing linear repeating units of → 4)-α-D-GalAp(1 → 4)-α-D-GalAp(1 → with the average molecular weight of 14 kDa. DOP0.2-S-3 significantly reduced the water content and defecation times caused by AAD in mice, while it also remarkably attenuated the cytokines of IL-1ß and IL-6 expression in mice colon tissues. DOP0.2-S-3 decreased potential pathogen and increased Bacteroidetes in the mice gut. These results suggested DOP0.2-S-3 might be a new leading compound for the functional foods or drug candidate development against AAD partially through regulating gut flora.

Structural characterization of a galactan from Dioscorea opposita Thunb. and its bioactivity on selected Bacteroides strains from human gut microbiota.

Dioscorea opposita Thunb. is widely used as functional foods and traditional Chinese medicine in China for its activity of regulating function of spleen and stomach. Polysaccharides may contribute to the function of regulation. To investigate structure features and bioactivities of polysaccharides from D. opposita, the rhizome of D. opposita was extracted with boiling water, yielding crude polysaccharides DOP. A novel polysaccharide named DOP0.1-S-1 was isolated from DOP by further purification. The average molecular weight of DOP0.1-S-1 was 10,000 Da and the range was around 12,000 -1,200 Da. The carbohydrate content of DOP0.1-S-1 was 100% and no protein was detected. The monosaccharide analysis showed that DOP0.1-S-1 was mostly composed of galactose. Methylation and NMR spectra analysis indicated that DOP0.1-S-1 was a 1,4-ß-galactan. Bioactivity test showed that DOP0.1-S-1 could promote the growth of B. thetaiotaomicron and B. ovatus and produce the short-chain fatty acids during the utilization of the polysaccharide.