Microwave assisted extraction, characterization of a polysaccharide from Salvia miltiorrhiza Bunge and its antioxidant effects via ferroptosis-mediated activation of the Nrf2/HO-1 pathway

A microwave-assisted extraction procedure for the crude Salvia miltiorrhiza polysaccharides (SMPs) obtained from Salvia miltiorrhiza Bunge was optimized. Four independent variables were studied: microwave power, extraction time, solvent-to-solid ratio, and concentration of ethanol, with optimal settings of 1200 W, 12 min, 38, and 86 %, respectively. The SMPs were successively purified by DEAE Sepharose Fast Flow and Sephadex G-100 chromatography to produce a novel polysaccharide termed SMP1. The SMP1 was composed of glucose, galactose, and fructose in a molar ratio of 1:1.67:1.12 with an average molecular weight of 6087 Da. Pharmacological studies showed that SMP1 protected from OGD/R-induced ferroptosis and lipid peroxidation by activating Nrf2/HO-1 pathway in PC12 cells. Our research systematically indicated that polysaccharide could inhibit ferroptosis to alleviate oxidative stress injury, which laid the foundation for the future clinical application of Salvia miltiorrhiza polysaccharide.