Structural properties and bioactivities of pectic polysaccharides isolated from soybean hulls

The purpose of this study was to investigate the structural characteristic and its antioxidant of a pectic polysaccharide (ASP-3A) extracted and purified from soybean hulls. Results of structural and morphological characterization according to high-performance gel-permeation chromatography, methylation analysis and nuclear magnetic resonance spectroscopy etc. showed that ASP-3A was composed of rhamnose, galactose, galacturonic acid, arabinose, xylose, glucuronic acid, glucose, mannose, and glucosamine hydrochloride with molar ratios of 1.000 : 0.745: 0.570 : 0.189: 0.135 : 0.098: 0.036 : 0.036: 0.008. ASP-3A was mainly consisted of 4)-α-D-GalAp-(1→ and β-D-Glap-(1 → 4)-α-L-Rha-(1→, with branch consisting principally of α-L-Araf-(1 → 5)-α-L-Araf-(1→, which suggested that ASP-3A was a pectin polysaccharide including homogalacturonan (HG) and rhamnogalacturonan I (RG-I) domain. ASP-3A exhibited dose-dependent antioxidant activities in superoxide anion radical, hydroxy radical, ABTS•+ and DPPH• scavenging assays with SC50 values of 1.083 ± 0.060, 2.507 ± 0.387, 1.677 ± 0.027 and 1.325 ± 0.002 mg/mL, respectively. ASP-3A alleviated oxidative stress induced by CCl4 through enhancing antioxidant capacity of hepatocytes via NRF2/ARE pathway. This study provides information useful for screening natural polysaccharide-based antioxidants in soybean hulls.