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-->5-alpha-L arabinofuranan linked to the main chain of 1-->4-beta-D-galactopyranan through 1-->3 linkages. The carboxyl-reduced fraction II had 1-->4alpha-D galactopyranuronic acid residues in the main chain, which were further involved in branching through rhamnose. The striking drop in their abundance and M-r. at the end of ripening, denoting depolymerization in situ, is discussed in the context of textural softening. (C) 2004 Society of Chemical Industry.