Structural characteristics of three pectins isolated from white kidney bean

Three water-soluble pectic polysaccharides (WKBP-P2, P3 and P4) were isolated from white kidney bean by ion exchange combined with size-exclusion methods. The structural features were characterized by GC-MS, NMR spectroscopy and HPSEC-MALLS-RI. It was found that three pectic polysaccharides were the major waterextracted polysaccharides in white kidney bean. All the WKBP-P2, P3 and P4 were probably composed of various structural regions including homogalacturonan (HG), xylogalacturonan (XGA), rhamnogalacturonan I (RG-I) regions in backbone, and arabinan region mainly as side chain. However, these pectic polysaccharides were significantly different in molar ratios of these structural regions and molecular size. WKBP-P2 was HGpredominant pectin (partially methyl-esterified) with weight-average molecular weight (Mw) of 1.2 x 104 g/ mol, and contained minor RG-I, arabinan and probable XGA regions. WKBP-P3 (Mw of 4.0 x 104 g/mol) primarily embraced XGA, HG, arabinan regions and minor RG-I region. WKBP-4 with highest Mw (4.5 x 105 g/mol) had the most arabinan region (51.3%), which was probably the side chain linked to the backbone composed of RG-I, HG and slight XGA regions. These findings provided a structural basis for study on polysaccharides from white kidney bean, which was benefit for development of functional food.

Automated summary

Three water-soluble pectic polysaccharides (WKBP-P2, P3 and P4) were isolated from white kidney bean through ion exchange combined with size-exclusion methods. These polysaccharides were found to have different structural features and molecular sizes, providing a basis for the development of functional food.