A polysaccharide from the seed of Gleditsia japonica var. delavayi: Extraction, purification, characterization and functional properties

Gleditsia japonica var. delavayi is widely distributed in Yunnan and Guizhou, China, and the perisperm of its seeds is frequently used as a traditional banquet sweet food with transparent color, smooth-tasting, low-fat, and high-carbohydrate. Herein, a cellulase-assisted extraction method was applied using response surface methodology to optimize the extraction of polysaccharides from the seeds of G. japonica var. delavayi. The highest extraction yield (82.23 ± 0.50%) was obtained under 5% cellulase, 176 mL/g liquid-to-material ratio, and enzymolysis parameters of 55 °C for 90 min at pH 4.5. The purified seed polysaccharide (PS) primarily contained galactomannan (weight average molecular weight, 42.74 kDa), which was linked by the monosaccharide residues 1,6-α-Galp, 1,4,6-α-D-Galp, 1,2,4,6-β-D-Manp, and 1,3,6-α-D-Galp. The PS obtained has a single-crystal structure, is thermodynamically stable, and its molecules aggregate in water. Furthermore, PS possesses high cholate binding capacity and a substantial inhibitory effect on α-glucosidase and α-amylase. Taken together, the findings of this report offer a theoretical foundation for developing and utilizing G. japonica var. delavayi.