Structural characterization of raw and wine-steamed Polygonatum cyrtonema Hua oligosaccharides and their bioactivity on immune regulation via modifying the gut microbiota.

Polygonatum cyrtonema Hua (PC) is a traditional Chinese medicine with a long history of use as pharmaceuticals or functional foods. Wine steaming is the main processing method of PC, which changes the structure of polysaccharides and oligosaccharides in PC and enhances biological activities. This study investigated the structural characterization of raw and wine-steamed PC oligosaccharides and the differences in the immunomodulatory effects using cyclophosphamide (CTX)-induced immunosuppression rat model. The oligosaccharides content and molecular weight of PC after wine steaming decreased, the proportion of oligosaccharides in total sugars and the reducing sugars content increased, and the monosaccharides composition of oligosaccharides changed. The raw Polygonatum cyrtonema Hua oligosaccharides (PCCO) and the wine-steamed Polygonatum cyrtonema Hua oligosaccharides (PCWO) exerted regulatory effects on organ index, immunoglobulin G (IgG), complement 3 (C3) spleen and colon tissue morphology, hematopoietic function of immunosuppressive rats treated by cyclophosphamide (CTX). Both PCCO and PCWO significantly regulated and improved the diversity and abundance of gut microbiota in immunosuppressed rats and increased the content of short-chain fatty acids (SCFAs) in the feces of rats, and the regulating effect of PCWO was better than PCCO. Differential microbiota analysis showed that PCWO could promote the proliferation of Bifidobacterium, Bacteroides, Oscillibacter, Roseburia, and Alistipes. In summary, the difference in the structural characteristics of PC oligosaccharides might be the reason for immune enhancement. This study could provide a theoretical basis for clarifying the scientific connotation of wine steaming to enhance the efficacy of PC, and promote the application of wine-steamed PC as an immunomodulator in pharmaceuticals or functional foods.