Methanolysis of ethyl esters of N-acetyl amino acids catalyzed by cyclosophoraoses isolated from Rhizobium meliloti.

Methanolysis of four ethyl esters, N-acetyl-L-phenylalanine ethyl ester, N-acetyl-l-tyrosine ethyl ester, N-acetyl-l-tryptophan ethyl ester, and ethyl phenylacetate was catalyzed by a mixture of microbial cyclooligosaccharides termed cyclosophoraoses isolated from Rhizobium meliloti. Cyclosophoraoses [cyclic-(1-->2)-beta-d-glucans, collectively 'Cys'] are a mixture of large-ring molecules consisting of various numbers of glucose residues (17-27) linked by beta-(1-->2)-glycosidic bonds. Cys as a catalytic carbohydrate enhanced the methanolysis about 233-fold for N-acetyl-L-tyrosine ethyl ester in comparison with a control. The effect of dry organic solvents on the methanolysis of N-acetyl-L-tyrosine ethyl ester was investigated by high-performance liquid chromatography (HPLC), and it was found that the rate enhancement correlated closely with the hydrophobicity of the solvent.

Enantioseparation of some chiral flavanones using microbial cyclic beta-(1-->3),(1-->6)-glucans as novel chiral additives in capillary electrophoresis.

Cyclic beta-(1-->3),(1-->6)-glucans, microbial cyclooligosaccharides produced by Bradyrhizobium japonicum USDA 110, were used as novel chiral additives for the enantiomeric separation of some flavanones such as eriodictyol, homoeriodictyol, hesperetin, naringenin, and isosakuranetin in capillary electrophoresis (CE). Among the flavanones, eriodictyol was separated with the highest resolution (R(s) 5.66) and selectivity factor (alpha 1.18) when 20mM cyclic beta-(1-->3),(1-->6)-glucans were added to the background electrolyte (BGE) at pH 8.3.

Separation of some chiral flavonoids by microbial cyclosophoraoses and their sulfated derivatives in micellar electrokinetic chromatography.

Neutral cyclosophoraoses (Cys) and highly sulfated cyclosophoraoses (HS-Cys) were successfully applied as chiral selectors with SDS for the separation of some chiral flavonoids in MEKC. HS-Cys were synthesized by the chemical modification of a family of neutral Cys isolated from a soil microorganism, Rhizobium meliloti 2011. Chiral catechin was separated with a resolution (R(s)) of 0.754 by neutral Cys and SDS. In the case of isosakuranetin and neohesperidin, resolution (R(s)) values of 1.483 and 1.306 were obtained with HS-Cys and SDS, respectively.

Structural analyses of novel glycerophosphorylated alpha-cyclosophorohexadecaoses isolated from X. campestris pv. campestris.

Novel periplasmic anionic cyclic glucans produced by Xanthomonas campestris pv. campestris were isolated by trichloroacetic acid treatment and various chromatographic techniques. No report has been made on the presence of substituted cyclic glucans of the Xanthomonas species. We show, for the first time, that X. campestris pv. campestris produces the anionic cyclic glucans with phosphoglycerol residues, the presence of which can be predicted by analyzing the sequence database with the aid of the NCBI RefSeq database. To analyze the structure of isolated anionic cyclic glucans analyses, we used NMR spectroscopy, matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOFMS) and electrospray-ionization mass spectrometry (ESIMS). The results suggest that the novel anionic forms of the cyclic glucans of X. campestris pv. campestris are glycerophosphorylated alpha-cyclosophorohexadecaose with one or two phosphoglycerol substituents at the C-6 positions of the glucose residues.

Enantioseparation using sulfated cyclosophoraoses as a novel chiral additive in capillary electrophoresis.

Highly sulfated cyclosophoraoses (HS-Cys) were synthesized by the chemical modification of a family of neutral cyclosophoraoses isolated from Rhizobium leguminosarum bv. trifolii. The HS-Cys were then analytically characterized using Fourier transform-infrared spectroscopy and elemental analysis. These HS-Cys were successfully used as a novel chiral additive, in low-pH aqueous background electrolytes, for capillary electrophoretic separation of five basic chiral drugs such as arterenol, atenolol, isoproterenol, propranolol, and metoprolol.

Synthesis and characterization of carboxymethylated cyclosophoraose, and its inclusion complexation behavior.

Carboxymethylated cyclosophoraoses (CM-Cys) were synthesized by chemical modification of a family of neutral cyclosophoraoses isolated from Rhizobium leguminosarum biovar trifolii. Structural analyses of the CM-Cys were carried out using NMR and FTIR spectroscopies, and the molecular weight distributions were confirmed with MALDI-TOF mass spectrometry. Based on structural characterization, native cyclosophoraoses were successfully substituted with carboxymethyl groups at the OH-4 and OH-6 of the glucose residues with degrees of substitution (DS) ranging from 0.012 to 0.290. CM-Cys was also used as a host for the inclusion complexation with hydrobenzoin (HB) and N-acetyltryptophan (N-AcTrp) as guest molecules. NMR spectroscopic analyses of the complexes showed that the CM-Cys induced chemical shifts of some protons of the guest molecules upon the complexation. Phase solubility studies of the guest molecules by CM-Cys were performed using HPLC, and the results were compared with those of native cyclosophoraoses. The solubility of HB and N-AcTrp was enhanced by the CM-Cys about 5.1- and 299-fold, respectively.

Solubility enhancement of a hydrophobic flavonoid, luteolin by the complexation with cyclosophoraoses isolated from Rhizobium meliloti.

A plant flavone, luteolin is a well-known inducer of nod genes in the Rhizobium meliloti. Its poor aqueous solubility was greatly enhanced by the complexation with a family of cyclosophoraoses synthesized in R.meliloti. Nuclear magnetic resonance (NMR) spectroscopic analysis showed that the chemical shifts of the aromatic ring moieties of the luteolin were changed greatly by the complexation with cyclosophoraoses. Fourier transform infrared (FTIR) spectroscopic analysis also showed a restricted vibrational pattern in carbonyl stretching region of the luteolin due to the complexation. This effective complex formation of cyclosophoraoses with a plant flavone, luteolin, suggests that rhizobial cyclosophoraoses play an important role as a solubility enhancer of the hydrophobic legume-derived flavonoids.