Polysaccharides from peach pulp: Structure and effects on mouse peritoneal macrophages

Pulp from peaches contained polygalacturonic acid and arabinogalactan as main polysaccharides, which were isolated and characterised. The polygalacturonic acid (AE-CWI) contained 95% GalA and its 13C NMR spectrum showed signals at δ 98.9, 78.0, 71.4, 69.1, 68.4, and 175.1 from C-1, C-4, C-5, C-3, C-2, and C-6 respectively, from (1 → 4)-linked α-GalpA units. Methylation-MS analysis of carboxy-reduced material (AE-CWI-CR) gave 90% of 2,3,6-Me3-galactitol acetate. The arabinogalactan (AE-AG) was composed mainly of Ara (41%) and Gal (50%) and was characterised (methylation analysis and 13C NMR) as a type II-arabinogalactan. It induced peritoneal macrophage activation in mice, ∼70% of cells treated with this fraction (1–50 μg/mL) having morphology of activated cells. However, NO production in macrophages treated with AE-AG was not affected. This suggests a new biological activity for peach polysaccharides.