Structural characterization, α-glucosidase inhibitory and DPPH• scavenging activities of polysaccharides from guava

To explore the chemicals responsible for the health benefits of guava, water-soluble polysaccharides were extracted including GP90 and P90. They exhibited excellent alpha-glucosidase inhibition activity with an EC50 of 2.27 mu g/mL and 0.18 mg/mL. This suggests that their activities were 1379- and 17-fold higher than the positive control. The DPPH center dot scavenging activities of GP90 was even higher than Vc at some concentrations. Upon further isolation, a novel polysaccharide termed GB90-1B was obtained. Monosaccharide analysis, methylation analysis, and NMR were used to analyze the structural characterization of GB90-1B. Structural analysis revealed that its backbone consisted of (1 -> 5)-linked-alpha-L-arabinose, (1 -> 2,3,5)-linked-alpha-L-arabinose and (1 -> 3)-linked-alpha-L-arabinose. Branch linkages included( 1 -> 6)-linked-alpha-D-glucose, (1 ->)-linked-alpha-D-glucose and (1 ->)-linked-alpha-L-arabinose. The structure of the repeating unit of GP90-1B was predicted. (C) 2016 Elsevier Ltd. All rights reserved.