Shigeya Takeuchi

Effects of green tea tannin on cisplatin-induced nephropathy in LLC-PK1 cells and rats

A study was conducted to clarify whether green tea tannin ameliorated cisplatin‐induced renal injury in terms of lactate dehydrogenase and malondialdehyde leakage from a renal epithelial cell line, swine‐derived LLC‐PK1 cells in culture. Green tea tannin was shown to suppress the cytotoxicity of cisplatin, the suppressive effect increasing with the dose of green tea tannin. The effect of cisplatin was then investigated in rats given green tea tannin for 40 days before cisplatin administration and in control rats given no green tea tannin.

Effect of acetonitrile/water mobile-phase composition on adsorption characteristics of reversed-phase liquid chromatography.

The influence of volumetric composition of acetonitrile in a mobile phase on adsorption characteristics of reversed-phase liquid chromatography using octadecylsilyl (ODS)-modified silica gel was studied by the pulse response method and the moment analysis. The results were compared with those obtained for the reversed-phase system consisting of ODS-silica gel and methanol/water mixtures. In both systems, surface diffusion was dominant for intraparticle diffusion in ODS-silica gel particles. The contributions of three mass transfer steps in a column to peak broadening were of about the same order of magnitude. The activation energy of surface diffusion, E(s), was found to be larger than the isosteric heat of adsorption, Q(st). Because similar tendencies were observed for these adsorption characteristics, adsorption mechanisms may be analogous in both chromatographic systems. However, absolute values of the adsorption equilibrium constant, K, the decreasing ratio of hydrophobic surface area, ΔA/A, Q(st), and E(s) for acetonitrile/water systems were smaller than the corresponding values for methanol/water systems. Oppositely, greater values of D(s) were obtained for acetonitrile/water systems. It was concluded that the interaction between ODS ligands and adsorbate molecules was weaker compared with that in methanol/water mobile-phase systems when acetonitrile was used as an organic modifier in a mobile phase of reversed-phase liquid chromatography.

Adsorption Characteristics in Reversed-Phase Liquid Chromatography Using Ethanol/Water Mixed Solvent

Adsorption characteristics were studied in a reversed-phase liquid chromatography consisting of an octadecylsilyl (ODS)-silica gel and ethanol/water mixture (70/30, v/v), and were compared with corresponding results obtained by using methanol/water and acetonitrile/water mixtures (70/30, v/v) as mobile phase. Similar tendencies were observed for some adsorption characteristics in the three chromatographic systems. However, the magnitude of the characteristics was not entirely identical in the three systems. Surface diffusion was dominant for intraparticle diffusion in the ODS-silica gel particles irrespective of the type of the organic modifiers in mobile phases. A few correlations were confirmed with regard to surface diffusion, i.e., an enthalpy-entropy compensation and a linear free-energy relation. The analogous correlations on surface diffusion phenomena suggest the similarity in the mechanism of surface diffusion in the three chromatographic systems.

Pyrolysis and mass spectra of trimethylsilyl derivatives of monosaccharides

The pyrolysis of trimethylsilyl derivatives of saccharides (1) was investigated by DTA-TG, MS, GC/MS and TG-GC/MS. The DTA-TG/DTG curves showed that the pyrolysis of 1 occurred in one stage. The exothermic peaks were due to sublimation or thermal decomposition by vaporization. The cleavage mechanism by electron impact of 1 was classified into four categories: 1) stepwise elimination of the side-chain, 2) cleavage of the side-chain, 3) cleavage of the pyranose ring, and 4) cleavage of the pyranose ring and side-chain at the same time. The mass-spectrum for 1 revealed the main common four fragment ions, such asm/z 73, 191, 204 and 217, with cleavage of the pyranose ring. These fragment ions were detected with a similar retention time in the gas cromatogram by GC/MS or TG-GC/MS. The retention time for 1 increased in the sequence aldopentose<ketohexose<aldohexose. This result indicates that the trimethylsilyl derivatives are thermally stable. Subsequently, the pyrolysis regime for 1 obeyed apparent 1/2-order kinetics and their apparent activation energy was estimated as 75–100 kJ/mole.ZusammenfassungMittels DTA-TG, MS, GC/MS und TG-GC/MS wurde die Pyrolyse von Trimethylsilylderivaten von Sacchariden (1) untersucht. Die DTA-TG/DTG-Kurven zeigten, daß die Pyrolyse von (1) in einem Schritt stattfindet. Die exothermen Peaks sind der Sublimation oder der thermischen Zersetzung durch Verdampfen zuzuschreiben. Der Abspaltungsmechanismus durch Elektronenstoß von 1 kann in vier kategorien unterteilt werden: 1) schrittweise Eliminierung der Seitenkette, 2) Abspaltung der Seitenkette, 3) Abspaltung des Pyranoseringes und 4) gleichzeitige Abspaltung von Pyranosering und Seitenkette. Das Massenspektrum von 1 zeigt die vier häufigsten Fragmentionen mitm/z 73, 191, 204 und 217 bei Abspaltung des Pyranoseringes. Diese Fragmentionen werden für 1 mit einer ähnlichen Retentionszeit detektiert, ansteigend in der Reihenfolge Aldopentose Ketohexose Aldohexose. Dieses Ergebnis zeigt die thermische Stabilität der Trimethylsilylderivate. Anschließend unterliegt das Pyrolsysesystem einer scheinbaren Reaktionsordnung von 1/2 und die scheinbare Aktivierungsenergie wurde mit 75–100 kJ·mol−1 geschätzt.