Yellow lupin (Lupinus luteus L.) polysaccharides : antioxidant, immunomodulatory and prebiotic activities and their structural characterisation

Yellow lupin polysaccharides (YLP-1, YLP-2 and YLP-3) were isolated from the whole seeds of Lupinus luteus L. Their antioxidant activities were evaluated by ABTS +[rad] and hydroxyl radical scavenging, and Fe 2+ chelating assays. Immunostimulatory activities were measured by their ability to activate macrophages to produce TNF-α and NO. Four strains of probiotic bacteria were used to measure their prebiotic activities. YLP-2 with largest galactose content displayed the best activity amongst the three isolated polysaccharides. NMR and FT-IR spectroscopic methods have revealed that YLPs contain galactans and galactomannans which are linked with β-(1,4) glycosidic bond in the main chain. The side chain Galp unit of galactomannan is connected to the main chain Manp by α-(1,6) linkage. The results presented in this paper strongly suggest that YLPs display significant antioxidant, immunostimulatory and prebiotic activities and hence hold great potential as nutraceutical and functional agents.