Optimization of technology, structural characterization, derivatization, antioxidant and immunomodulatory activities of Salvia miltiorrhiza polysaccharides

The polysaccharides of Salvia miltiorrhiza (SMP) were prepared through water-extraction and alcohol-precipitation method optimized by employing the response surface methodology. Furthermore, the structural characteristics and activities of SMP as well as its three derivatives (SMP-S, SMP-Fe and SMP-Se) were analyzed. SMP was composed of galacturonic acid, glucose, galactose and arabinose and the molecular weights were 3.79 × 10 6  Da, 3.17 × 10 4  Da and 693.68 Da. The sulfur content of SMP-S was 13.53%, the iron content of SMP-Fe was 26.12% and the content of selenium in SMP-Se was 0.984 mg/g. Their surface morphology, meso-structure and thermal stability were determined by scanning electron microscope, transmission electron microscope and thermogravimetric analyzer, respectively. Further, the antioxidant and immunomodulatory activities of SMPs were studied. The study found that three modified polysaccharides not only exhibited higher antioxidant activity, but also higher immunomodulatory activity compared to SMP. This lays a theoretical foundation for the development of Salvia miltiorrhiza polysaccharide-related foods.