Pectic polysaccharides of mango (Mangifera indica L): structural studies

Pectic polymers of raw and ripe mango fruits revealed several distinct fractions upon diethylaminoethyl-cellulose chromatography. Fraction I, the arabinogalactan, had a relative ratio of 3:1 for galactose and arabinose, while the two rhamnogalacturonans (fractions II and III) were composed of galacturonic acid, arabinose, galactose and rhamnose in the relative ratios of 69:15:14:2 and 62:10:23:4, respectively. Specific rotation, FTIR, GC-MS and NMR data revealed fraction I to be a 1(right arrow)5-(alpha)-L arabinofuranan linked to the main chain of 1(right arrow)4-(beta)-D-galactopyranan through 1(right arrow)3 linkages. The carboxyl-reduced fraction II had 1(right arrow)4-(alpha)-D galactopyranuronic acid residues in the main chain, which were further involved in branching through rhamnose. The striking drop in their abundance and Mr at the end of ripening, denoting depolymerization in situ, is discussed in the context of textural softening.