Two Natural Flavonoid Substituted Polysaccharides from Tamarix chinensis: Structural Characterization and Anticomplement Activities

Two novel natural flavonoid substituted polysaccharides (MBAP-1 and MBAP-2) were obtained from Tamarix chinensis Lour. and characterized by HPGPC, methylation, ultra-high-performance liquid chromatography-ion trap tandem mass spectrometry (UPLC-IT-MSn), and NMR analysis. The results showed that MBAP-1 was a homogenous heteropolysaccharide with a backbone of 4)-beta-d-Glcp-(1 -> and -> 3,4,6)-beta-d-Glcp-(1 ->. MBAP-2 was also a homogenous polysaccharide which possessed a backbone of -> 3)-alpha-d-Glcp-(1 ->, -> 4)-beta-d-Glcp-(1 -> and -> 3,4)-beta-d-Glcp-2-OMe-(1 ->. Both the two polysaccharides were substituted by quercetin and exhibited anticomplement activities in vitro. However, MBAP-1 (CH50: 0.075 +/- 0.004 mg/mL) was more potent than MBAP-2 (CH50: 0.249 +/- 0.006 mg/mL) and its reduced product, MBAP-1R (CH50: 0.207 +/- 0.008 mg/mL), indicating that multiple monosaccharides and uronic acids might contribute to the anticomplement activity of the flavonoid substituted polysaccharides of T. chinensis. Furthermore, the antioxidant activity of MBAP-1 was also more potent than that of MBAP-2. In conclusion, these two flavonoid substituted polysaccharides from T. chinensis were found to be potential oxidant and complement inhibitors.