Structural elucidation of a glucan from Crataegus pinnatifida and its bioactivity on intestinal bacteria strains

Crataegus pinnatifida is widely used as functional food and traditional medicine in China for various applications. Polysaccharides may contribute to health benefits, such as modulating human gut microbiota (HGM). To investigate structure features of polysaccharides from this plant, fruits of C. pinnatifida were extracted with boiling water, yielding crude polysaccharides HAW. A novel polysaccharide, named HAW1-1, was pooled by DEAE Sepharose™ Fast Flow column and further purified by Sephacryl S-100 HR column. The molecular weight of HAW1-1 was 42.35 kDa. The carbohydrate content of HAW1-1 was 99.42% and no protein was detected. The monosaccharide analysis showed this polysaccharide was only composed of glucose. According to the partial acid hydrolysis, methylation analysis and NMR spectra, the backbone of HAW1-1 was consisted of 1,4-linked α-D-glucan and 1,4,6-linked α-D-glucan. The side chains were composed of 1,6-linked α-D-glucan and terminal-linked α-D-glucan. The bioactivity tests showed that HAW1-1 could promote the growth of three species of intestinal Bacteroides and produce short-chain fatty acids (SCFAs). The results suggested that HAW1-1 might be a potential prebiotic candidate to maintain intestinal homeostasis and improve human gut health.