Polysaccharide of nectarine gum exudate: Comparison with that of peach gum

The gum exudate polysaccharide from the trunk of nectarine (PPNEC) was compared with that of peach, being composed of Ara, Xyl, Man, Gal, and uronic acids in 37:13:2:42:6 molar ratio and had M-w 3.93 x 10(6) g mol(-1), compared with 5.61 x 10(6) g mol(-1) for peach gum polysaccharide. Methylation analysis of PPNEC indicated a highly branched structure with relatively high amounts of di- (16%) and tri-O-substituted (9%) Galp units and nonreducing end-units of Araf (26%) and Xylp (17%). Combination with C-13 NMR data, showed the presence Of alpha-L-Araf (nonreducing end, 3-O-, 5-O-, and 2,5-di-O-subst.), beta-L-Arap (4-O- and 2,4-di-O-subst.), beta-D-Galp (3-O-, 2,3-di-O-, 3,6-di-O-, and 3,4,6-tri-O-subst.), and alpha- and/ or beta-D-Xylp nonreducing end-units. A signal appeared from 4-O-Me-alpha-D-GlcpA units. PPNEC had structures similar to those of polysaccharide from peach tree gum, although in different proportions and with a lower M-w. (C) 2008 Elsevier Ltd. All rights reserved.