Purification, characterization and bioactivity determination of a novel polysaccharide from pumpkin (Cucurbita moschata) seeds

Abstract

The crude polysaccharides from pumpkin seeds were obtained with hot water extraction and ethanol precipitation. After purification by Q-Sepharose FF column and Sephadex G-100 gelfiltration, a protein-bound polysaccharide (PSP-I) was obtained and characterized. PSP-I was composed of mannose, glucose and galactose in a molar ratio of 1.0:12.9:5.3 with molecular weight of 21,100 g/mol. 1H NMR and 13C NMR spectra revealed that the backbone of PSP-I consisted of (1 → 4)-linked β-d-glucopyranosyl, (1 → 2)-linked α-d-galactose and (1 → 6)-linked α-d-mannopyranosyl. PSP-I contained 17 general amino acids and was rich in glutamic acid, alanine and glycine. The alkali sensitive O-glycoprotein was identified by β-elimination reaction. The antioxidative assays in vitro indicated that PSP-I showed the moderate scavenging activities on DPPH radical and hydroxyl radical. Moreover, PSP-I displayed the obvious inhibitory activity against α-amylase and strong antibacterial activity.