Keishiro Miyake

Determination of partition coefficients of very hydrophobic compounds by high-performance liquid chromatography on glyceryl-coated controlled-pore glass

Abstract Reversed-phase high-performance liquid chromatography of more than 80 compounds with glyceryl-coated controlled-pore glass as the stationary phase and a mixture of methanol and water as the mobile phase showed that the capacity factor ( k ′) correlates well with the partition coefficient between octanol and water ( P oct ). This method is very efficient for the determination of P oct for compounds with log P oct > 5. A general method for the determination of P oct by high-performance liquid chromatography in this way is proposed.

Phosphatidylcholine-coated silica as a useful stationary phase for high-performance liquid chromatographic determination of partition coefficients between octanol and water

Phospholipid-coated silica gel is a useful stationary phase to determine the partition coefficient between octanol and water, Poct, by high-performance liquid chromatography (HPLC). A column of silica gel coated with dipalmitoyl phosphatidylcholine is easy to prepare, and is stable over a long period. With this column and an aqueous mobile phase containing acetonitrile, a good single correlation was observed between the log of the capacity factor, k′, and log Poct, for a wide variety of compounds. Thus, this chromatographic system, which overcomes the limitations of the standard shake-flask method and the HPLC method on an octadecyl silica column, is very useful for determining log Poct.

Effect of hydrogen bonding on the high-performance liquid chromatographic behaviour of organic compounds: relationship between capacity factors and partition coefficients

Abstract Capacity factors ( k ′) of various compounds were determined by high-performance liquid chromatography on ODS (octadecylsilica) and gly-CPG (glyceryl-coated controlled-pore glass) with a mobile phase consisting of various proportions of methanol and water, and the correlation of the k ′ values with the P oct values (partition coefficients between octanol and water) of these compounds was examined. On both columns, log k ′ increased with increase in log P oct . However, introduction of a hydrogen bonding term was necessary to obtain a single correlation between log k ′ and log P oct for a wide variety of compounds. On both columns, the effect of hydrogen bonding on k ′ became smaller with a decrease in the proportion of methanol in the mobile phase, but in different manners on the two columns: among compounds with the same log P oct values, those with the ability to form hydrogen bonds had less affinity than those with no ability to form hydrogen bonds on ODS, and vice versa on gly-CPG.

Enantioselective pharmacokinetics of homochlorcyclizine II: disposition and metabolism of (+)-, (−)- and racemic homochlorcyclizine after oral administration to man

SummaryThe pharmacokinetics of a single oral dose of 20 mg (+)-, (-)- and racemic homochlorcyclizine (HCZ) have been studied in humans. The formation of the quarternary ammonium-linked glucuronide was an important metabolic pathway, and the metabolic process was enantioselective as a result of differing urinary excretion rates of (+)-, (-)- and racemic glucuronide.There were significant differences between (+)-, (-) and racemic HCZ in AUC (0-14 h) and plasma protein binding, but all HCZ enantiomers were slowly absorbed and eliminated (elimination half-lives about 11 h).The results shows help to establish a more efficient dosage regimen for HCZ therapy.

Preparation and Characterization of Branched β-Cyclodextrins Having Manno-Oligosaccharide Side Chains Derived from Yeast Mannan and Study of Their Functions

Branched β-cyclodextrins (β-CDs) having manno-oligosaccharide side chains were investigated. Three kinds of monobranched β-CDs and five kinds of dibranched β-CDs were chemically synthesized using the trichloroacetimidate method. Their structures were analyzed by HPLC, MS, and NMR spectroscopies. The specific interaction between those compounds and mannose-binding lectins (Concanavalin A and Pisum sativum agglutinin) was investigated by inhibition tests of hemagglutinating activity and by using an optical biosensor of the IAsys apparatus with a resonant mirror detector. The results showed that all branched β-CDs interactedwith lectins. The binding affinity was 61,64-(Man3)2- ≫ 61,64-(Man2)2- > 61,64-(Man4)2-β-CD when the derivatives were compared on the basis of side chain length and 61,63- ≫ 61,64- > 61,62-(Man2)2-β-CD when compared on the basis of side chain position.

Enantioselective pharmacokinetics of homochlorcyclizine. III. Simultaneous determination of (+)- and (-)- homochlorcyclizine in human urine by high-performance liquid chromatography.

A method is described for the simultaneous determination of (+)- and (-)-homochlorcyclizine (HCZ) in human urine by high-performance liquid chromatography on a chiral stationary phase of ovomucoid-bonded silica. The pH of the buffer and organic modifier in the mobile phase markedly affected the chromatographic separation. A mobile phase of methanol-0.02 M acetate buffer (pH 4.7) (25:75,v/v) at a flow-rate of 1.0 ml/min was used for the urine assays. The ultraviolet absorption was monitored at 240 nm, and diphenhydramine was employed as the internal standard for the quantitation. (+)-HCZ, (-)-HCZ and the internal standard were eluted at retention times of 15, 25 and 8 min, respectively. The limit of determination for HCZ enantiomers was ca. 50 ng/ml of urine. One of the metabolites in human urine, which was a quaternary ammonium-linked glucuronide, could also be determined in a manner similar to unchanged HCZ after beta-glucuronidase hydrolysis. A pharmacokinetic study was conducted with three healthy volunteers, who each received a single oral dose of racemic HCZ (20 mg). Distinct differences were found between the two enantiomers, particularly in the metabolic process, that is, the urinary excretion as (-)-HCZ-glucuronide within 48 h was ca. four times higher than that of the (+)-isomer. This method should be very useful for enantioselective pharmacokinetic studies of HCZ.

Enantioselective Pharmacokinetics of Homochlorcyclizine: Disposition of (+)- and (–)-Homochlorcyclizine after Intravenous and Oral Administration of Racemic Homochlorcyclizine to Rats

Abstract— Concentrations of homochlorcyclizine enantiomers in blood, urine, and tissues of the liver, lung, kidney, brain, heart, spleen, intestine and stomach of rats after drug administration were determined by high‐performance liquid chromatography on a chiral stationary phase. After intravenous administration (10 mg kg−1), homochlorcyclizine was rapidly distributed in many tissues, with the highest concentration in lung. No differences were found between enantiomers in blood concentrations. After oral administration (50 mg kg−1), the concentrations of the (+)‐isomer in nearly all tissues were higher than those of the (–)‐isomer. The AUC0‐x values of the (+)‐ and (–)‐isomers differed significantly. The absorption of racemic homochlorcyclizine from rat small intestine was not enantioselective. These results suggested that the different concentrations between enantiomers after oral administration were not caused by enantioselective absorption or distribution but rather by preferential first‐pass metabolism of the (–)‐isomer in the liver. The enantioselectivity of metabolism was also demonstrated by in‐vitro experiments.