Structures and immunological activities of two pectic polysaccharides from the fruits of Ziziphus jujuba Mill. cv. jinsixiaozao Hort.

Two pectic polysaccharides were isolated from Ziziphus jujuba Mill. cv. jinsixiaozao Hort. and their structures were characterized by acid hydrolysis, methylation, partial acid hydrolysis and NMR spectroscopy. The purified fraction Ju-B-3 had a molecular mass of over 2000 kDa and showed [α]D20+151 (c = 1.00, H2O). Chemical and spectroscopic analyses indicated that Ju-B-3 was a polygalacturonan with 7.49% methoxylation. The purified fraction Ju-B-2 had a molecular weight of over 2000 kDa and showed [α]D20+125 (c = 1.00, H2O). Ju-B-2 was proposed as a polygalacturonan interspersed with rhamnogalacturonan in the main chain. 10.47% d-galacturonic acid existed as methoxylation and O-acetyl groups were amounted to 2.5%. The branched side chains were mainly composed of 1,5-linked arabinofuranosyl residues and 1,6-linked galactopyranose residues attached to O-4 of rhamnose residues. Ju-B-2 induced a rat spleen cells proliferation in a dose-dependent manner while Ju-B-3 could not show any proliferation activity compared with control.