Ultrasonic-assisted extraction and the antioxidative mechanism of eggplant root polysaccharide

Abstract

Polysaccharides from eggplant roots were extracted by ultrasonic-assisted water extraction, and purified polysaccharides were obtained by sevage deproteinization, dialysis and freeze drying. To study its in vitro antioxidant effect on RAW264.7 cells, in vivo antioxidant activity in mice model and protective effect of H₂O₂-induced oxidative stress damage in RAW264.7 cells, and to reveal its mechanism. The result showed that eggplant root polysaccharide was an acid heteropolysaccharide composed of Fuc (fucose), Rha (rhamnoose), Ara (arabinose), Galg (alactose), Glc (glucose), Xyl (xylose), Man (mannose), Gal-UA (galacturonic acid), and Gle-UA (glucuronic acid). The results of in vitro experiment showed that eggplant root polysaccharide had no obvious cytotoxic activity in the concentration range of 40–640 μg/mL. At the concentration of 320 μg/mL, it could significantly increase the secretion of CAT (catalase), SOD (superoxide dismutase), and GSH-Px (glutathione peroxidase) on RAW264.7 cells, while significantly decrease the secretion of MDA (malondialdehyde). It has obvious protective effect on RAW264.7 cells damaged by H₂O₂. In vivo experiment results showed that medium and high dose (320 and 640 μg/mL) of eggplant root polysaccharide can significant increase activities of SOD and GSH-Px in the serum and liver of mice, but significant reduce content of MDA, which plays a good role in vivo antioxidant. The preliminary mechanism results showed that the addition of eggplant root polysaccharide could increase protein content of Nrf2 (nuclear factor-related factor 2), HO-1 (heme oxygenase 1), and NQO1 (NADPH quinone oxidoreductase 1). It was preliminarily speculated that the antioxidant effect of eggplant root polysaccharide in vivo may be the result of Nrf2, HO-1, NQO1 protein or gene interaction.