Structural Insight and in vitro Free Radical Scavenging Capacity of Arabinogalactan Polysaccharides from the Peels of Punica granatum

Abstract

The juice extracted from Punica granatum L. fruit has been used for ages as an important functional food that can endow with healthcare benefits besides fundamental nutritional food that we intake. Although demonstration of antioxidant activity has been shown here, the target molecule responsible for this phenomenon remains unidentified. In this present work, we report a structural insight and antioxidant activity of its polysaccharide (PF-1), purified from water extract (WE) by precipitation with ethanol, ethanol soluble fraction (PF-2) and acetone extracted fraction (PF-3). The purified polysaccharide (PF-1) contains mainly arabinose, galactose together with lesser amount of rhamnose and glucose residues, and the molecular mass was determined 180 kDa. This fraction consists of T-(1,5)- and (1,3,5)-linked Araf; T-(1,6)- and (1,3,6)-linked Galp alongside (1,2,4)-linked Rhap residues. The glucan is found to be β-(1→3)-linked glucopyranosyl residues with a molecular mass of 9 kDa. The in vitro antioxidant activity of the active fractions was determined by using 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), hydroxyl radical scavenging and total antioxidant activity (TAA) assays. The arabinogalactan showed the highest potential among the polysaccharides. This work involves an economically viable simple extraction method and reports promising antioxidant capacity. The studies suggest that this polysaccharide from Punica granatum L. fruit could be a natural antioxidant.