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 plant's 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. [Display omitted] •A new polysaccharides (PSP) from Sisal waste residue was isolated and purified.•The structure of PSP was established by chemical methods and NMR spectroscopy.•PSP consists mainly of galactose, glucose, mannose and rhamnose.•PSP has a moderate scavenging activity on hydroxyl and DPPH radicals.