Polysaccharides from different cultivars of wolfberry: Physicochemical characteristics and protection against oxidative stress

Polysaccharides are among the main active ingredients of wolfberry (LBPs), being responsible for the biological activity. However, the effect of different cultivars on the chemical structures of LBPs remains unclear. In this study, polysaccharides from four cultivars, namely, Ningqi No. 1 (LBPN-1), No. 5 (LBPN-5), No. 7 (LBPN-7), and No. 9 (LBPN-9), were isolated. The basic physicochemical characteristics and inhibitory effects of polysaccharides on oxidative stress in ARPE‑19 cells were investigated and compared. The results showed that they were neutral protein-bound heteropolysaccharides with wide molecular weight range of over 17.94–4221 kDa. The major components of LBPs were galactose, glucose, and arabinose. The differences in preliminary structural characteristics were presented in chemical properties, monosaccharide proportions and glycosidic bond ratios, resulted in different thermal properties. The biological test demonstrated that LBPN-7 displayed the strongest protection against ROS production and antioxidant system injury in H2O2-treated ARPE‑19 cells via up-regulation of Nrf2/ARE pathway. Four polysaccharides showed different bioactivities might be attributed to their chemical properties, monosaccharide composition, and glycosidic bonds. The results will add insights to better understand the structural characteristics and bioactivities of polysaccharides from wolfberry, which could be used as a potential natural antioxidant substance in functional foods and pharmaceuticals.