Analysis of the water-soluble polysaccharides from Camellia japonica pollen and their inhibitory effects on galectin-3 function

Pollen has been defined as dietary supplement used to supplement the diet in many countries, but the primary structure and activity of Camellia japonica pollen polysaccharide remain unclear. In this study, the water-soluble polysaccharide extracted from Camellia japonica pollen (WCPP) was fractionated into one neutral fraction (WCPP-N) and two acidic fractions (WCPP-A1 and WCPP-A2) by DEAE-cellulose column, and WCPP-A2 was further fractionated into two homogeneous sub-fractions (WCPP-A2a and WCPP-A2b) by Sepharose CL-6B column. Monosaccharide composition results showed that WCPP-N might mainly contain starch-like glucan as well as some arabinogalactan, while WCPP-A1, WCPP-A2 and its sub-fractions might mainly composed of rhamnogalacturonan I (RG-I) pectic polysaccharide domain backbone with some different types of side chains, including arabinan, galactan, and/or arabinogalactan. The primary structure analysis of WCPP-A2a by NMR spectra analysis suggested that WCPP-A2a was an RG-I-like pectic polysaccharide, branched at the O-4 of Rha residues in the backbone, with α-(1 → 3,5)-L-arabinan as well as type-II arabinogalactan side chain to which were attached. The results of galectin-3-mediated hemagglutination assay indicated that WCPP-A2a exhibited the strongest inhibitory effect on galectin-3 with MIC value around 0.27 μg/mL. These results suggested the potential use of Camellia japonica pollen polysaccharide as a galectin3 inhibitor in functional foods.