Extraction, purification, chemical characterization, and in vitro hypoglycemic activity of polysaccharides derived...

This study aimed to optimize the extraction process of polysaccharides from Rosa laevigata Michx. (RLMP) using an ultrasound-microwave-assisted method and investigate its in vitro hypoglycemic activity. Key factors affecting RLMP yield were identified using a Plackett-Burman design, followed by a Box-Behnken design and response-surface methodology, to determine the optimal extraction conditions. RLMP was purified using DEAE-52 cellulose, yielding two homogeneous fractions: RLMP-1 and RLMP-2. Monosaccharide composition was analyzed by gas chromatography, and structural characterization of RLMP, RLMP-1, and RLMP-2 was performed using FT-IR, SEM, and TEM. Methylation analysis and NMR were used to elucidate the sugar-chain structure of RLMP-1. In vitro hypoglycemic activity analysis showed that RLMP improved the glucose consumption and glycogen synthesis and enhanced the activities of pyruvate kinase and hexokinase in IR-HepG2 cells. Moreover, RLMP significantly increased the activities of antioxidant enzymes, such as CAT, SOD, and GSH-Px and decreased those of ROS and MDA. Western blotting analysis confirmed that RLMP enhances glucose and lipid metabolism and reduces oxidative stress by activating the PI3K/Akt/GLUT-4 signaling pathway, thereby exerting its hypoglycemic effect. These findings suggest that RLMP is a promising candidate for developing novel antioxidant agents or hypoglycemic drugs.