Isolation, structural characterization and antioxidant activity of a neutral polysaccharide from Sisal waste

A new water-soluble polysaccharide (PSP) was isolated from the waste of a Sisal (Agave sisalana) plant after the plantʹs fibers were extracted. The monosaccharide composition analysis showed that PSP consists of galactose, glucose, mannose, rhamnose, arabinose, and galacturonic acid in a molar ratio of 3.0:2.4:1.4:1.0:0.2:0.2. The structure analysis indicated that the PSP backbone chain comprises 1,4-linked β-D-Galp; 1,3-linked β-D-Glcp; 1,3-linked α-D-Manp; and 1,2-linked α-L-Rhap in a ratio of 3:1:1:1. Some of the Glcp, Manp, and Rhap residues in the backbone chain were branched. The in vitro antioxidant activity assay showed that PSP moderately scavenges hydroxyl and DPPH radicals in a dose-dependent manner.