Chiral separation and discrimination of catechin by sinorhizobial octasaccharides in capillary electrophoresis and 13C NMR spectroscopy

Abstract

Succinoglycan, a sinorhizobial exopolysaccharide produced by Sinorhizobium meliloti, is composed of an octasaccharide subunit. S. meliloti produces both high-molecular-weight and low-molecular-weight ( M r < 10,000) succinoglycans which consist of monomers, dimers, or trimers. Succinoglycan monomers were isolated and further purified in the monomer series (M1, M2, and M3) by the degree of succinylation. We used sinorhizobial octasaccharides (M1, M2, and M3) as chiral additives in capillary electrophoresis (CE) for chiral separation of catechin and also as chiral shift reagents with 13C NMR spectroscopy for chiral discrimination of catechin. Chiral separation of catechin took place when sinorhizobial octasaccharides (M2 and M3) were added to the background electrolyte (BGE) in CE. NMR signal splittings were also observed in the interactions of sinorhizobial octasaccharides with the enantiomers of catechin. Both chiral separation and discrimination of catechin depend on the presence of succinate substituents of the linear monomeric octasaccharide in CE and NMR spectroscopy, suggesting that succinylation of sinorhizobial octasaccharide is decisive for the effective chiral separation and discrimination of catechin.