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-α-L
arabinofuranan linked to themain chain of 1→4-β-D-galactopyranan through 1→3 linkages. The carboxylreduced
fraction II had 1→4-α-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.