Purification, structural identification, in vitro hypoglycemic activity and digestion characteristics of polysaccharides from the flesh and peel of wampee (Clausena lansium)

Abstract

In this study, two polysaccharides were isolated from the flesh and peel of wampee, termed as PWP-F and PWP-P respectively, and their structural characteristics, in vitro antioxidant and hypoglycemic activities and digestion were investigated. Results indicated the molecular weight of PWP-F was higher than that of PWP-P and they were both mainly composed of galactose and arabinose. Both polysaccharides exhibited α-type and β-type glycosidic linkages based on FTIR analysis. NMR spectroscopy revealed that PWP-F mainly consisted of α-Araf-(1→, →3,5)-α-Araf-(1→, →2,5)-α-Araf-(1→, →4) → β-Galp-(1 → and α-GalpA-(1→, while PWP-P was composed of α-Araf-(1→, →3)-α-Araf-(1→, →5)-α-Araf-(1→, →3,6) → β-Galp-(1→ and α-GalpA-(1→. Scanning electron microscopy showed that PWP-P had more porous surface structure compared to PWP-F. Moreover, PWP-P exhibited superior antioxidant activity and significant inhibition of both α-glucosidase and α-amylase compared to PWP-F. Specifically, PWP-P demonstrated mixed inhibition against α-glucosidase and α-amylase. In vitro digestion results showed the molecular weight, polysaccharide and reducing sugar content of PWP-F and PWP-P decreased after simulative gastrointestinal digestion. Overall, PWP-P has great potential as a kind of new antioxidant and hypoglycemic agent.