Analysis Of The Neutral Polysaccharides Purified From The Modified Citrus Pectin (MCP) And Their Inhibitory Activities On Galectin-3

The pH-modified citrus pectin (MCP) has been demonstrated to interreact with galectin-3, inhibiting the anti-apoptotic activity and pro-angiogenic activity of galectin-3. The components and structures features of MCP related to this inhibition remained unknown. In this paper, we fractionated MCP on DEAE-Cellulose column into a homogenous neutral fraction MCP-N (molecular weight about20kD) and a pectin mixture fraction MCP-A (wide molecular distribution on Sepharose CL-6B chromatography). Hemagglutination assay showed that both MCP-N and MCP-A inhibited galectin-3with minimum inhibition concentration (MIC)625μg/ml and0.5μg/ml, respectively.After analyzed by HPLC,13C NMR and methylation, MCP-N was identified to be a type I arabinogalactan (AG-I) with a main chain of β-1,4-galactan while Ara was located in side chain. MCP-N was digested by a-L-arabinofuranosidase to give its main chain structure fraction (M-galactan, around18kD) which was more active than the original molecule, MIC was50μg/ml. The acidic degradation of M-galactan increased the inhibitory activity, MIC was about5times lower than M-galactan, but samilar with P-galactan (10.5μg/ml). These results above showed that the functional motif of the β-1,4-galactan fragment might lie in the terminal residues rather than the internal region of the chain.This is the first report concerning the fractionation of MCP and its components on galectin-3inhibition, obtaining AG fraction and β-1,4-galactan domain. The information provided in this paper is valuable for elucidating active ingredient of MCP and screening more active galectin-3inhibitors from neutral polysaccharides.