RESUMO
Objective: To extract and isolate polysaccharide from Cyclocarya paliurus leaves, characterize its structural features and study its α-glucosidase inhibitory effect. Methods: C. paliurus polysaccharide (CP50) was isolated and purified by water extraction and ethanol precipitation, deproteinization with 732 cation exchange resin and 50% ethanol precipitation. Molecular weight of CP50 was determined by high performance gel permeation chromatography-multiple angle laser light scattering (HPGPC-MALLS), and monosaccharide composition was analyzed by HPLC with PMP (1-phenyl-3-methyl-5-pyrazolone) pre-column derivatization. The structure of CP50 was characterized by methylation, Fourier transform infrared spectroscopy (FT-IR), and proton nuclear magnetic resonance spectrum (1H-NMR), respectively. The α-glucosidase inhibitory effect of CP50 was investigated by PNPG method. Results: The molecular weight of CP50 was 59 000. It contained eight kinds of monosaccharides including galacturonic acid, glucose, galactose, arabinose, mannose, xylose, rhamnose, and glucuronic acid with molar ratio of 29.1:25.6:16.5:9.3:6.7:6.1:4.1:2.6. CP50 was mainly composed of →4) GalA (1→, →4) Glc (1→ and →4) Gal (1→ with branches at C-6 position of galactose. Furthermore, our results showed that CP50 exhibited a potent inhibitory effect on α-glucosidase, and the value of IC50 was determined to be 3.3 μg/mL which was much lower than the anti-type 2 diabetes drug acarbose (193.6 μg/mL). The inhibitory mode belongs to the mixed noncompetitive inhibition. Conclusion: CP50 is a pectin-like acidic polysaccharide with complex structure. Moreover, CP50 possesses better α-glucosidase inhibitory effect and potential value for the drug development and utilization.