Characterization and antioxidant activity determination of polysaccharide from yam peel residue

Abstract

Objective: This study aimed to fully develop the utilization value of yam bark. Methods: The extraction of polysaccharides from yam bark and the residue of polyphenols and flavonoids extracted by ethanol was carried out by water extraction and alcohol precipitation method. The polysaccharides of yam peel (P1) and yam peel residue (P2) were obtained. The structural characteristics and antioxidant activities of P1 and P2 were analyzed. Results: The yield of P1 and P2 were similar, but the polysaccharide content of P2 (33.5%) was about twice that of P1 (17.8%). Both P1 and P2 have loose and porous structures, and P2 has dense pores on its surface. Mannose, glucose, and galactose were the main monosaccharides in P1, while mannose was the main monosaccharide in P2. P1 and P2 not only have microcrystalline structures but also have polycrystalline system with crystal and amorphous structures. The two polysaccharide samples had the same functional groups and no protein was found in both the samples. Both P1 and P2 have three-helix helix structures, and their average molecular weight is 37 153.52 and 3 467.37, respectively. P2 is not as stable as P1. In the range of 0.2～1.0 mg/mL, and the antioxidant activities of P1 and P2 increased with their concentrations. P2 had better antioxidant activity than P1. The IC50 values of the DPPH radical scavenging rate of P1 and P2 were 0.964 and 0.586 mg/mL, respectively, and the IC50 values of hydroxyl radical scavenging ability were 0.962 and 0.711 mg/mL, respectively. Conclusion: After ethanol extraction of polyphenols and flavonoids, the residue of yam peel still contains rich polysaccharides. Moreover, P2 has better structural characteristics and antioxidant activity than P1.

Keywords

• yam
• residue
• polysaccharides
• structural characteristics
• oxidation resistance