Pectic type II arabinogalactans from starfruit (Averrhoa carambola L.)

A structural characterization of polysaccharides from edible tropical fruit named starfruit (Averrhoa carambola L.) was carried out. After the purification steps, two homogeneous fractions were obtained. Fraction 50R was composed of rhamnose, arabinose, galactose and uronic acid in 4.3:56.2:37.4:2 M ratio, respectively and fraction 10R was composed of rhamnose, arabinose, galactose and uronic acid in 2.8:65.8:28.5:3 M ratio, respectively. Methylation and NMR spectroscopy analyses showed that these fractions are formed by pectic arabinogalactans, which contain (1 → 3), (1 → 6) and (1 → 3,6)-linked Galp units. The side chains have 3-O-, 5-O- and 3,5-di-O-linked α-Araf and nonreducing end-units of α-Araf, Arap, β-Galp and α-GlcpA. These arabinogalactans were linked to type I rhamnogalacturonans.