Structural characterization and antioxidant activities of polysaccharides from Citrus aurantium L.

Three polysaccharide fractions were obtained from Citrus aurantium L. (CAL) by sequential extraction with cold water, hot water, and 1.0 M NaOH, respectively. The fractions were denoted CALA, CALB, and CALC. Structural characterization was conducted by physicochemical property, FTIR, and SEM analyses. Antioxidant activities in vivo and in vitro were also evaluated. CALB, which showed the highest activity, was further isolated to afford four purified polysaccharides (CALB-1-4) by various ion exchange and gel-filtration chromatography. Meanwhile, the purified polysaccharides were subjected to composition analysis and screened by antioxidant activity in vitro. Among the four purified polysaccharides, CALB-3 had the highest antioxidant activity and its structure was analyzed by FTIR, SEM and AFM microscopy. Overall, these results indicated that polysaccharides from CAL had potential therapeutic applications in the medical and food industries because of their antioxidant activities.