Structural properties, antioxidant and hypoglycemic activities of polysaccharides purified from pepper leaves by high-speed counter-current chromatography

Abstract

In the present study, polysaccharides with antioxidant and hypoglycemic activities were isolated from the crude extract of pepper leaves by high-speed countercurrent chromatography in one step for the first time. An aqueous polymer two-phase system comprising PEG1000-K2HPO4-KH2PO4-H2O (0.8:1.25:1.25:6.5, w/w) was used for separation. During each separation, 2.0 g of the crude sample yielded two homogeneous components of polysaccharides PLP1 (226 mg) and PLP2 (273 mg). The molecular weights of PLP1 and PLP2 were 123 kDa and 243 kDa, respectively. PLP1 primarily consisted of mannose and glucose at a molar ratio of 1:2.4, whereas PLP2 was mainly composed of galactose, glucose, and rhamnose at a molar ratio of 2.6:1:2.2 with 10.3% (w/w) sulphates. Biological activity showed that sulfated PLP2 exhibited stronger antioxidant activity in vitro and hypoglycemic activity in diabetic mice than PLP1. The results demonstrated that sulfated PLP2 possessed potential as natural hypoglycemic agents or antioxidants in food or pharmaceuticals.

Keywords

• Pepper leaves
• Polysaccharides
• High-speed countercurrent chromatography
• Aqueous polymer two-phase system
• Hypoglycemic activities