Biomedical subjects

Tetsuo Hayase

Publications and source records attributed to Tetsuo Hayase.

3 recordsLinked to original sources

PubMed2006

Solid-state 13C NMR study of indomethacin polymorphism.

The purpose of this study was to analyze the difference in the molecular conformation packed in the crystal lattice between the meta-stable alpha-form and stable gamma-form of indomethacin on the basis of solid-state (13)C NMR spectral patterns. The chemical shifts of each resonance of the alpha-form were distinctly different from the gamma-form. Each carbon nucleus of the gamma-form showed a single signal with no splitting. In contrast, carbon nuclei of the alpha-form showed a complicated set of resonances for each carbon. For some carbons of the alpha-form, four signals assigned to one carbon were observed at 203 K. Two of these four signals were merged between the temperature range from 203 to 343 K without a transformation in the crystal structure. It was found that solid-state (13)C NMR can be a powerful tool to estimate the number of molecular conformations as well as configurational differences in the packing of molecules in a unit cell.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2005

Comparison of molecular mobility in the glassy state between amorphous indomethacin and salicin based on spin-lattice relaxation times.

PURPOSE: The purpose of the current study was to evaluate the molecular mobility of amorphous indomethacin and salicin in the relaxed glassy state based on spin-lattice relaxation times (T(1c)) and to clarify the effects of molecular mobility on their physical stability. METHODS: Pulverized glassy amorphous indomethacin and salicin samples were completely relaxed, and the T(1c) values were investigated using solid-state (13)C-nuclear magnetic resonance (NMR) at temperatures below the glass transition temperature (T(g)). All NMR spectra were obtained using the T(1c) measurement method combined with variable-amplitude cross-polarization, the Torchia method, and total sideband suppression method. RESULTS: The T(1c) value of amorphous indomethacin indicated that 73% of carbons were in a state of monodispersive relaxation, suggesting that the amorphous state was relatively homogeneous and restricted, particularly in backbone carbons. On the other hand, 92% of carbons of amorphous salicin exhibited both fast and slow biphasic relaxation. Individual structures of the salicin molecules behaved heterogeneously, and thus the entire molecule showed relatively fast local as well as slow mobility. CONCLUSIONS: At temperatures below T(g), amorphous salicin had relatively greater molecular mobility than amorphous indomethacin. This difference in the molecular mobility of the two compounds is correlated with their crystallization behavior. Solid-state (13)C NMR provides valuable information on the physical stability of amorphous pharmaceuticals.

Benzyl Alcohols↗

PubMed2002

Sensitive determination method of estradiol in plasma using high-performance liquid chromatography with electrochemical detection.

The improvement in the sensitive determination method of estradiol using HPLC with electrochemical detection is described. The improvement was due to the optimization of the potential applied to the electrode of the analytical cell and employment of a guard cell. The detection conditions were optimized from the electrochemical properties of estradiol in acidic and alkaline eluents. The employment of the guard cell drastically decreased the background noise without any reduction in the response of estradiol, and contributed to improvement in the sensitivity. The optimized method combined with pretreatment by liquid-liquid extraction was applied to the determination of estradiol in rat plasma. The detection limit of 8 pg for the standard solution and 24 pg for the plasma sample, which was about 6-8-fold more sensitive compared to the previous reports, was attained.

Animals↗