Ultrasonic‐Assisted Extraction, Structural Characteristics, and Activity of Polysaccharides From <i>Gymnocladus chinensis</i> Baill

In this study, the response surface method (RSM) was used to determine the optimal parameters of ultrasonic-assisted extraction of Gymnocladus chinensis Baill. polysaccharides (GCBPs). The optimal extraction conditions were as follows: a liquid-solid ratio of 50.4 mL/g, an extraction temperature of 60°C, an extraction time of 43 min, and an extraction power of 240 W. Under these conditions, the extraction rate of GCBP reached 50.1%. Three fractions of GCBP-40, GCBP-60, and GCBP-80 with sugar contents of 64.33%, 59.16%, and 59.46% were obtained by different concentrations of ethanol purification. All the three fractions consisted of six monosaccharides with different ratios, namely, Man, Rha, Gal, Glu, Ara, and Xyl. From Congo red test, it is confirmed that all three fractions could have a triple helix structure. In addition, the antioxidant and hypoglycemic experiments showed that all three components had excellent antioxidant activity (2,2-diphenyl-1-picrylhydrazyl [DPPH] free-radical scavenging activity, 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) [ABTS] free-radical scavenging activity, and OH^- free-radical scavenging activity) and hypoglycemic activity (α-glucosidase inhibitory activity).