Polysaccharides from the Styrian oil-pumpkin with antioxidant and complement-fixing activity

Pectic polysaccharides have attracted great attention due to their health-promoting potential. From the Styrian oil-pumpkin biomass representing an alternative pectin source, two series of acidic polysaccharide fractions were isolated using in succession hot water, EDTA and dilute HCl. Chemical and spectroscopic (FTIR, NMR) analyses of the fractions revealed the predominance of partially methylesterified and acetylated pectins containing homogalacturonan and ramified rhamnogalacturonan elements, and a minority of phenolic compounds, protein and hemicelluloses. The pectins exhibited moderate antioxidant activities tested by colorimetric DPPH and FRAP assays and EPR method. The activities correlated with the total phenolic content. In the complement-fixing test, most of the pectin fractions exhibited potent effects comparable to the positive control – a pectin from Plantago major. The oil-pumpkin pectins represent potential antioxidant and immunoenhancing additives applicable in food and nutraceuticals.

► Sequential extraction of oil-pumpkin seeded fruit yielded pectic polysaccharides. ► Partially methylesterified and acetylated pectins with minor rhamnogalacturonan. ► Protein, phenolic compounds and co-extracted hemicelluloses are minor components. ► Pectins showed moderate radical scavenging capacity in various antioxidant tests. ► The complement-fixing test revealed remarkable immunomodulating activity.