Structural Characterization and In Vitro Hypoglycemic Activity of a Polysaccharides Obtained from Fructus arctii

In recent years, the number of diabetes patients worldwide has been increasing daily, and more than 700 million people are in a prediabetic state. Fructus arctii exhibits notable anti-diabetic activity, but its active components remain unclear. In this study, a polysaccharide (FAP-W) was extracted and characterized using UV, FTIR, HPLC, NMR, AFM, the Congo red test, and SEM. FAP-W has a molecular weight of 1.99 × 104 Da and mainly consists of α-d-glucopyranosyl-(1→2)-[β-d-fructofuranosyl-(1→2)]10-β-d-furanofructosyl units. Monosaccharide analysis revealed mannose, glucose, galactose, and arabinose in a 3.4:23.59:21.27:47.7 ratio. In insulin-resistant HepG2 cells, FAP-W significantly increased glucose consumption, enhanced glycogen content, and elevated HK and PK activities. It also decreased TG, MDA, and ROS levels while improving SOD activity. These results suggest that FAP-W ameliorates insulin resistance, regulates glucose–lipid metabolism, and alleviates oxidative stress, indicating its potential as a functional food or therapeutic candidate for diabetes.