Structural characterisation and antioxidant activities in vitro and in vivo of a novel polysaccharide from Salvia miltiorrhiza

Polysaccharides have received extensive attention due to their multiple physiological functions, especially their remarkable antioxidant capacity. In this study, a novel acidic polysaccharide (PSMP-2) with a molecular weight (Mw) of 1.28 x 10(6) Da from Salvia miltiorrhiza Bunge was extracted and purified via DEAE-52 cellulose column and Sephadex G-100 column chromatography. The structure of PSMP-2 was characterised by high-performance gel permeation chromatography (HPGPC), high-performance liquid chromatography (HPLC), Fourier transforms infrared spectroscopy (FT-IR) and methylation analysis. The results showed that PSMP-2 was an acidic heteropolysaccharide composed of rhamnose (Rha) (6.15%), galacturonic acid (GalA) (55.98%), and galactose (Gal) (21.27%) and arabinose (Ara) (16.69%). PSMP-2 contained five major glycosidic linkages, (1 ->)-linked-Ara, (1 -> 2, 4)-linked-Rha, (1 -> 4)-linked-Gal, (1 -> 6)-linked-Gal, (1 -> 3, 6)-linked-Gal, in a molar ratio of 5.98: 1.45: 72.23: 16.40: 3.94. The IC50 of PSMP-2 on 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl free radical scavenging ability were 0.991 mg/mL and 4.007 mg/mL, respectively. It could regulate the activity of antioxidant enzymes in vivo and had good antioxidant activity. To sum up, a novel acidic polysaccharide (Mw of 1.28 x 10(6) Da) with antioxidant activity was isolated from S. miltiorrhiza, and its application prospect in the field of medicine and food was preliminarily revealed.