Abstract: Shenlingbaizhu powder is a classical prescription with the function of tonifying spleen.Modern researches have found that its clinical efficacy is closely related to the regulation of intestinal flora;however,it is not clear which ingredient works and which bacteria are regulated.Since polysaccharide is a main ingredient of traditional Chinese medicine,and Bacteroides is the most abundant bacterial group which occupied the advantages in the utilization of polysaccharides,we propsoed that Shenlingbaizhu powder polysaccharide may play roles in regulating the intestinal flora (Bacteroides as the most significant target) as bacterial competitive carbon source.In this study,we explored the in vitro growth of two typical Bacteroides under the influence of Shenlingbaizhu powder polysaccharide as “carbon source”.Two typical Bacteroides strains were cultured under different carbon sources (1-40% concentration of traditional Chinese medicine polysaccharides,glucose,BHI)，with two Firmicutes as control.The in vitro growth rates on different carbon sources were determined by continuous samplings.The results showed that the in vitro growths of Bacteroides were influenced by Shenlingbaizhu powder polysaccharide under different concentrations (the optimal concentration of polysaccharide is 20%).As for the in vitro growth of Bacteroides thetaiotaomicron ATCC29148 under different carbon sources on,the result as below:BHI group> the optimal concentration of polysaccharide group>Glucose group,while that of Bacteroides fragile ATCC25285 is:the optimal concentration of polysaccharide >BHI group>Glucose group.As for the in vitro growth of different bacteria under influences of Shenlingbaizhu powder polysaccharide,the result is:Bacteroides>Firmicutes.In conclusion,the traditional Chinese medicine polysaccharide can be used regulate the balance of intestinal flora as carbon prebiotics for Bacteriodetes,which may be one of the micro ecological mechanisms related to the clinical effect of Shenlingbaizhu powder.

Key words: Shenlingbaizhu powder, polysaccharide, Bacteroides, Firmicutes, carbon source