Structure elucidation and immunoactivity studies of glycan of glycoconjugate LbGp4 isolated from the fruit of Lycium barbarum L.

Glycan was isolated on Sephadex G-100 column after glycoconguate LbGp4, was released by beta -elimination, then desalted on Sephadex G-25 and named Lb Gp4-OL. The linkage between the glycan and the core protein backbone was O- linkage. The molecular weight of LbGp4-OL was 180 800. The result of its el emental analysis was C 39.1%, H 5.72%, N 0%. Component analysis showed that it was composed of Rha, Ara and Gal in a molar ratio of 0.05:1.33:1. The s tructure of repeat unit of LbGp4-OL was deduced by methylation analysis, pa rtial acid hydrolysis and H-1, C-13 NMR spectroscopy of the original glycan and products of its partial hydrolysis. Methylation analysis of LbGp4-OL i ndicated that highly branching unit in LbGp4-OL was -->3,4)Gal(1 -->, the m ajor non-reducing end was Ara(1 -->. LbGp4-OL ' was obtained by partial aci d hydrolysis. Comparing the results of methylation analysis of LbGp4 with t hat of LbGp4-OL ', we can deduced that the main chain of LbGp4-OL was compo sed of -->4)Gal(1 -->. H-1 and C-13 NMR spectra of LbGp4-OL and LbGp4-OL ' indicated that Ara(1 --> was alpha -furanose, -->3)Ara(1 --> and -->5)Ara(1 --> were beta -furanose, all the Gal were beta -pyranose, Rha(1 --> was al pha -pyranose, -->3)Ara(p)(1 --> was alpha -pyranose. Immunoactivity studie s of LbGp4 and its glycan showed that LbGp4 and LbGp4-OL not only enhanced the splenocyte proliferation in normal mouse, but also improved the reducin g immune function in the senescense-accelerated mouse. It demonstrated that LbGp4 and LbGp4-OL possess a direct effect of splenocytl proliferation. In addition, the direct elevating action of LbGp4-OL on splencyte prolifexrat ion was stronger than that of LbGp4. So it pointed out that the glycan play an important role in the immunopharmcological activity of glycoconjugate.