Comparison on characterization and biological activities of Mentha haplocalyx polysaccharides at different solvent extractions.

This study aimed to compare the effects of four solvent extractions on the physicochemical properties, antioxidant and hypoglycemic activities of polysaccharides from Mentha haplocalyx (MHPs). The solvent extractions included hot water, citric acid (pH 3.0), 5% NaOH/0.05% NaBH and 0.9% NaCl. Four corresponding MHPs named as MHP-W, MHP-C, MHP-A and MHP-S were obtained, respectively. The experimental results showed that the extraction yields, basic chemical components, monosaccharide contents, molecular weights, antioxidant and hypoglycemic activities of four MHPs were significantly different. However, their thermal stabilities, preliminary structural characteristics and monosaccharide types were similar. MHP-A possessed the highest extraction yield of 9.37 ± 0.24% and the smallest molecular weight. MHP-W had the highest uronic acid content and the largest molecular weight. More specifically, MHP-C exhibited the highest sugar content, the most remarkable antioxidant abilities of DPPH radical scavenging activity and ferric reducing power, and the strongest inhibitory activities on α-glucosidase and α-amylase. The above results indicated that MHP-C extracted with citric acid could be served as a promising bioactive substance for applications in the functional food and medicine industries.