To optimize the extraction process of walnut flower polysaccharides and explore its potential regulatory effect on intestinal flora.

Walnut flower polysaccharides was extracted by enzyme-assisted deep eutectic solvent method. Based on single-factor experiments, response surface methodology was employed to optimize the extraction parameters with moisture content, enzyme concentration, extraction temperature and liquid-to-solid ratio as independent variables. Fourier transform infrared spectroscopy and ultraviolet spectrophotometry were employed for the preliminary structural characterization of walnut flower polysaccharides.Furthermore, in vitro fermentation experiments were conducted to analyze the effects of walnut flower polysaccharides on the diversity, structure and short-chain fatty acids (SCFAs) production of hyperlipidemia-related intestinal microbiota. The correlation between microbiota and SCFAs was elucidated using a correlation heatmap.

The optimal extraction conditions were determined as follows: moisture content of 30%, enzyme concentration of 2%, extraction temperature of 50 ℃, and liquid-to-solid ratio of 21:1 (mL:g). Under these conditions, the extraction yield of walnut flower polysaccharides reached (5.91±0.42)% and the established model exhibited reliable predictive ability. The polysaccharide content of the extracted walnut flower polysaccharides was determined to be 88.03%. Structural characterization indicated that WFP contained uronic acid groups and pyranose ring structures, as well as both α- and β-glycosidic bonds. In vitro fermentation results showed that walnut flower polysaccharides significantly improved the diversity and structural composition of the intestinal microbiota, promoted the proliferation of beneficial bacteria, inhibited the growth of pathogenic bacteria and increased the production of SCFAs including acetate, propionate and butyrate. Correlation analysis indicated that the aforementioned beneficial genera were strongly positively correlated with core SCFAs, which could serve as biomarkers for the recovery of intestinal beneficial metabolic functions.

The extraction process of walnut flower polysaccharides is feasible and walnut flower polysaccharides exhibits regulatory effects on the intestinal microbiota. This study provides a theoretical basis for the development of functional foods in the field of intestinal health.