Enrichment, purification and in vitro antioxidant activities of polysaccharides from Umbilicaria esculenta macrolichen

Umbilicaria esculenta as an edible macrolichen possesses nutritional properties, such as antioxidant, immune-boosting, and lipid peroxidation inhibitory properties. A new enrichment and separation technology for the polysaccharides from Umbilicaria esculenta (UEP) with AB-8 resin was established, and its adsorption data were well fitted to the pseudo-second-order kinetic model and the Langmuir isotherm, with a process of monolayer coverage of UEP onto it. After purification by DEAE (diethylaminoethyl) Cellulose-52 chromatography, two polysaccharide fractions (UEP-1, UEP-2) were obtained and characterized. UEP-1 was composed of mannose, rhamnose, glucose and galactose in a molar ratio of 0.59:3.12:93.09:3.20 with a molecular weight of 124.7 kD, while UEP-2 comprised mannose and glucose in a molar ratio of 20.66:79.34 with a molecular weight of 249.4 kD. With DPPH (2, 2-diphenyl-1-picrylhydrazyl), ABTS (2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate), superoxide anion, and hydroxyl scavenging capacities as indices, their antioxidative assays in vitro indicated that the polysaccharides exhibited the very strong scavenging activities in a concentration-dependent manner. It was worth expecting that UEP could be developed as a novel potential functional component in food industries.