Characterization of an immunologically active pectin from the fruits of Lycium ruthenicum

An immunologically active pectin, named LRGP5, was firstly isolated from the fruits of Lycium ruthenicum Murr. It contained rhamnose, arabinose, xylose, galactose and galacturonic acid in the molar ratio of 1.0:2.2:0.5:1.2:4.7. Its molecular weight was estimated to be approximately 1.37 × 105 Da by high performance gel permeation chromatography. The structure was elucidated using methylation analysis, partial acid hydrolysis, NMR and ESI-MS analysis. Results showed that LRGP5 consisted of a (1 → 4)-linked galacturonic acid backbone occasionally interrupted by (1 → 2)-linked rhamnose. The side chains were attached to position 4 of the rhamnosyl units, including (1 → 3)-linked arabinose, (1 → 3)-linked galactose, (1 → 3,6)-linked galactose, (1 → 4)-linked galacturonic acid, (1 → 2)-linked rhamnose and (1 → 2,4)-linked rhamnose, and the termini were arabinose and rhamnose. Immunological assay results demonstrated that LRGP5 could significantly promote macrophage proliferation and enhance the secretion of nitrogen monoxide in vitro.