Isolation, structure and activity of a novel water-soluble polysaccharide from Dioscorea opposita Thunb

• Published in: International journal of biological macromolecules Vol. 133; pp. 1201 - 1209
• Main Authors: Zhi, Fei, Yang, Tian-Le, Wang, Qiang, Jiang, Bin, Wang, Zhong-Ping, Zhang, Jing, Chen, Yun-Zhong
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 15.07.2019
• Subjects: Antioxidant activity; Dioscorea opposita Thunb; Isolation; Monosaccharide composition; Polysaccharide; Structural characterization; Dioscorea opposita Thunb; Isolation; Polysaccharide; Monosaccharide composition; Structural characterization; Antioxidant activity
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2019.04.087

A previously unknown, water-soluble polysaccharide, named DOTP-B, was isolated from the roots of the plant Dioscorea opposita Thunb, a well-known edible and medicinal plant in China. DOTP-B was found to be neutral in charge, with an average molecular weight of 5623 Da. Monosaccharide composition analysis by GC–MS revealed that DOTP-B was a hetero-polysaccharide consisting of glucose and galactose at a molar ratio of 14.6:1.0. Structural features of DOTP-B were investigated with a combination of chemical and instrumental methods, including complete acid hydrolysis, periodate oxidation, methylation, GC–MS, FTIR and several NMR spectra. Highly correlated results demonstrated that the main chain of DOTP-B consisted of →4)-α-d-glc(1 → residues, with about 6% internal →6)-β-d-gal(1 → residues. The antioxidant activity of DOTP-B was also evaluated as the EC50 values against DPPH and PTIO radicals were 2.1 ± 0.1 mg/mL and 1.6 ± 0.1 mg/mL, respectively. Therefore, the polysaccharide DOTP-B could be possibly developed as a promising natural antioxidant for application in medical and food industries.