Effect of structure modification of chondroitin sulfate C on its enantioselectivity to basic drugs in capillary electrophoresis

Spectral study of fluorone dyes adsorption on chitosan-based polyelectrolyte complexes

Polyelectrolyte complexes of the chitosan-chondroitin sulfate and chitosan-hyaluronate polycation-polyanion pairs were synthesized and characterized as potential dye adsorbents at different pH levels. Equilibrium isotherm analysis was applied to investigate the efficiency and the mechanism of the adsorption of fluorone dyes (fluorescein, eosin Y, erythrosin B) on the synthesized complexes. The inefficiency of the fluorescein adsorption was proved by two different quantitative spectroscopic methods. The adsorption isotherm for both eosin Y and erythrosin B was adequately described in terms of the Langmuir-Freundlich model. The observed room-temperature phosphorescence of the adsorbed erythrosin B was attributed to the surface inhomogeneity of the synthesized complexes. The revealed variation in the adsorption properties of fluorone dyes was related to the differences in their ionic forms as well as in their polarity and hydrophobicity.

Differentiation of enantiomers by capillary electrophoresis

Capillary electrophoresis (CE) has matured to one of the major liquid phase enantiodifferentiation techniques since the first report in 1985. This can be primarily attributed to the flexibility as well as the various modes available including electrokinetic chromatography (EKC), micellar electrokinetic chromatography (MEKC), and microemulsion electrokinetic chromatography (MEEKC). In contrast to chromatographic techniques, the chiral selector is mobile in the background electrolyte. Furthermore, a large variety of chiral selectors are available that can be easily combined in the same separation system. In addition, the migration order of the enantiomers can be adjusted by a number of approaches. In CE enantiodifferentiations the separation principle is comparable to chromatography while the principle of the movement of the analytes in the capillary is based on electrophoretic phenomena. The present chapter will focus on mechanistic aspects of CE enantioseparations including enantiomer migration order and the current understanding of selector-selectand structures. Selected examples of the basic enantioseparation modes EKC, MEKC, and MEEKC will be discussed.

Study on the Interaction between the chiral drug of propranolol and α1-acid glycoprotein by fluorescence spectrophotometry

The interaction between the chiral drug of propranolol (PPL) and alpha1-acid glycoprotein (AGP, orosomucoid) has been first studied by fluorescence spectrophotometry. The fluorescence intensity of PPL increased due to the addition of AGP into PPL. The equation of Scatchard was employed to calculate the association constant and binding site number of the two enantiomers with AGP. The association constant is 2.62 x 10(5)M-1 for R-PPL and 8.57 x 10(5)M-1 for S-PPL and the binding site number is 0.41 for R-PPL and 1.17 for S-PPL at 17 degrees C respectively. The method of thermodynamics was applied to determine the binding type of S-PPL with AGP. The results suggested that the binding type is mainly van der waals force or hydrogen bond. At last the effect of three metal cations on the association constant and the binding site number of S-PPL with AGP was examined.

Capillary electrophoretic separation of drug enantiomers in human serum

Enantiomers of various solutes including several basic drugs and alpha-amino acids were analyzed by capillary electrophoresis in diluted human serum, and chloroquine and tryptophan were found to be well enantioseparated. In order to specify the protein responsible for enantioseparation, these drug enantiomers were analyzed in the presence of various serum protein fractions. The results indicated that albumin fraction caused enantioseparation but the alpha and beta -globulin mixed fraction, the gamma-globulin fraction and the alpha(1)-acid glycoprotein fraction did not exhibit any enantioseparation. The association constants between these drugs and albumin were roughly estimated based on our method. Approximate values were 1.50 x 10(3) and 1.85 x 10(3) M(-1) for chloroquine enantiomers, and 1.51 x 10(4) and 2.45 x 10(4) M(-1) for tryptophan enantiomers. The difference of the association constant values between the enantiomers was found to be 19% for chloroquine and 38% for tryptophan, when calculated based on the slower moving enantiomers.

Colominic acid: a novel chiral selector for capillary electrophoresis of basic drugs

We introduced colominic acid as a new chiral selector for capillary electrophoresis of basic drugs. Use of a low concentration phosphate buffer containing this polysaccharide and a Polybrene/colominic acid double coated capillary allowed excellent separation of the enantiomers of primaquine, chloroquine and tryptophan. Other drugs giving partial enantioseparation include laudanosine and salbutamol. Capillary coating with Polybrene followed by colominic acid eliminated the problems of peak tailing and low reproducibility of migration time in uncoated capillaries. The optimum pH was in the acidic region but varied among drugs. A low capillary temperature of 16 degrees C and a colominic acid concentration of 9 w/v% are recommended for practical analysis of these drugs. Colominic acid preparations having higher molecular masses gave better enantioseparation, and N-acetylneuraminic acid, the component monosaccharide, did not give any enantioseparation.