Pectic polysaccharides from hawthorn: Physicochemical and partial structural characterization

Abstract

The fruit of hawthorn (Crataegus pinnatifida Bge. var. major) is rich in pectic polysaccharides and has been used for centuries in China as food and herb. Hawthorn pectin (HP) recently has attracted rising attention due to the reported functional properties (e.g. gelling, emulsification) and health benefits towards the cardiovascular system. In this study, using hawthorn wine residue as raw material, a high methoxylated pectic polysaccharide HSP (degree of esterification up to 70%) was obtained by mild acid extraction (yield up to 20 wt%). Results from HPSEC coupled with triple detector revealed a widely dispersed (polydispersity index = 2) pectic polysaccharide with weight average molecular weight (Mw) of 111.7 kDa. Compared to pectin extracted from the hawthorn fruit, HSP showed a relatively lower molecular weight and higher polydispersity index (PDI), which suggested that the degradation of HP molecular chain during the wine-making processing (fermentation). Functionally, HSP demonstrated relatively high apparent viscosity but did not form gel in aqueous solution at concentrations up to 8 wt%. Structurally, HSP molecule was composed of over 70 mol% of 4-GalpA, with a small amount of glucose, galactose, xylose and arabinose. Under pectinase hydrolysis, over 95 wt% of the HSP was degraded into small fragments and monosaccharides; a small portion of relatively higher molecular weight rhamnose rich fragments were obtained from the hydrolytes. Combining both methylation analysis and 1D NMR spectroscopy, structural features of HSP were partially elucidated.