Structural Identification of Physalis alkekengi L. Polysaccharides

Physalis alkekengi L. fruit polysaccharides can reduce blood sugar, regulate blood lipids, and improve intestinal flora structure. However, the specific polysaccharide components exerting these effects are unclear. In this study, we extracted, separated, purified, and characterized the P. alkekengi polysaccharides Phy-1a, Phy-1b, and Phy-1c. Ion chromatography showed that Phy-1b was mainly composed of rhamnose, arabinose, galactose, glucose, and xylose at a molar ratio of 3.0:19.8:47.5:20.9:8.8, and Phy-1c was composed of rhamnose, arabinose, galactose, glucose, xylose, mannose, ribose Galactosamine hydrochloride and Glucosamine hydrochloride at a molar ratio of 10.4:7.9:22.8:30.5:4.6:4.4:19.4:3.9:5.8. Neither of these polysaccharides contained uronic acid, indicating their neutral property. Methylation analysis and nuclear magnetic resonance spectroscopy showed that Phy-1b was mainly composed of terminal sugars (1-Araf); 1,5-Araf; 1,4-Xylp; 1-Glcp; 2,4-Rhap; 1,3-Glcp; 1,4-Galp; 1,4-Glcp; 1,3-Galp; 1,6-Glcp; 1,3,6-Glcp; and 1,4,6-Galp at a molar ratio of 5.2:7.1:7.8:13.7:6.3:11.2:7.0:16.3:7.4:6.0:6.8:5.3, with the main chain being →2)-α-L-Rhap-(1→4)-β-d-Galp-(1→4)-β-d-Galp-(1→[3)-β-d-Glcp-(1]2→3)-β-d-Glcp-(1→[4)-β-d-Glcp-(1]2→ and the branched chains being β-L-Araf-(1→5)-β-L-Araf-(1→, β-d-Glcp-(1→4)-β-d-Xylp-(1→ 3)-β-d-Galp-(1→, and β-d-Glcp-(1→6)-β-d-Glcp-(1→. The three fragments, respectively, pass through the O-4 key of →2,4)-α-l-Rhap-(1→, O-6 key of →4,6)-β-d-Galp-(1→, and O-6 of →3,6)-β-d-Glcp-(1→ connected to the main chain. These results provide a reference for enhancing the utilization value of P. alkekengi resources to promote its high-value and efficient processing.