Noritoshi Koyama

Evaluation of phase transition temperature of liposomes by using the tautomerism of α-Benzoylacetoanilide

Abstract The phase transition temperatures for liposomes of dipalmitoyl- and distearoylphosphatidylcholines (abbreviated here as DPPC and DSPC) and for the other liposomes containing small amounts of soybean oil in the bilayer were determined from the changes of absorbance ratios ( R E K ) of enolic form to ketonic form in UV spectra for the tautomer of α-benzoylacetoanilide (BAA) incorporated into the liposomes. R E K values changed with increasing temperature and showed a maximum at a certain temperature. The DPPC liposome showed maximum at the temperature of 41°C corresponding to the phase transition temperature (Tc) of these lipids. The DSPC liposome showed the maximum at 54°C. The Tc values for other liposomes containing soybean oil could be determined in the same way. This method using the tautomerism of BAA was found to be very useful for the determination of the Tc.

Effect of water-Insoluble Powder Addition on Physical Properties of Gelatin Gel

AbstractWater-insoluble powder is often dispersed in shells of commercial soft capsules for various reasons, but little reports have been published about the effect of powder addition on the physical properties of the gelatin gel. Glass powder, titanium oxide, calcium carbonate and γ-orizanol were used as model of powder. Changes of Young modulus obtained from the tensile test showed that any powder addition to the gelatin sheet made the gelatin sheet hard not by the surface effect of powder but by the volumetric effect of it. In this test, any powders had no effect on the tensile strength of the gelatin sheet because there was little interaction between each powder and the gelatin gel in the break point. The limiting strain was decreased a little up to the specific amount of each powder and then beyond the specific amount that decreased steeply in the case of glass powder and γ-orizanol. There might be a suitable range of the amount of powder for the gelatin sheet to keep the plastic flow similar to the ...

Rectal Absorption of E-2078 (Dynorphin Analogue Peptide) in Rats

Abstract— The plasma levels in rats of a dynorphin analogue peptide (E‐2078) after rectal administration have been studied. The bioavailabilities of E‐2078 after rectal administration, subcutaneous injection, intramuscular injection, and oral administration were 21·6, 67·8, 67·1, 0·7%, respectively. The effect of dose, pH, osmolarity and viscosity on the rectal absorption of E‐2078 were studied. A sigmoid relationship between the dose and the AUC was observed on rectal administration, while there was a linear relationship on intramuscular administration. The AUC was increased in acidic solution and highly viscous solution. The osmolarity did not affect the absorption of E‐2078. In microscopic studies, E‐2078 caused little or no damage to the rectal mucosa in rats.