Interaction and Dissolution Characteristics of Ajmaline-PVP Coprecipitate

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The ajmaline-PVP coprecipitates were prepared for the purpose of increasing the solubility of ajmaline. The dissolution rate of 1 : 5 w/w coprecipitate was approximately 130-fold enhanced compared with ajmaline. In nuclear magnetic resonance (NMR) spectrum of ajmaline, the signal of C (21)-proton was shifted to lower magnetic field by polyvinylpyrrolidone (PVP), and 2-pyrrolidone showed the same effect on ajmaline, while NMR spectrum of 17,21-diacetylajmaline was not affected by PVP. On addition of PVP, the λ_<max> of ajmaline shifted to shorter wavelength in chloroform, but ultraviolet (UV) spectra of diacetylajmaline were not affected. By 2-piperidine, the shift of C (21)-proton signal of ajmaline in NMR spectra could not be detected. From these results, C (21)-hydroxyl groups of ajmaline were considered to form weak hydrogen bond to carbonyl groups of pyrrolidone rings of PVP. The coprecipitate and the physical mixture of PVP and diacetylajmaline, in which the interaction could not be detected as far as spectroscopic investigation was concerned, were also prepared. The dissolution rate of diacetylajmaline was enhanced in the coprecipitate and slightly in the physical mixture compared with that of diacetylajmaline alone. From the solubility study and the equilibrium dialysis study, it was suggested that one PVP molecule interacts with two or three molecules of ajmaline or diacetylajmaline in aqueous solution. The dissolution characteristics of ajmaline-PVP coprecipitate were discussed in comparison with diacetylajmaline-PVP coprecipitate.
公益社団法人日本薬学会の論文
1977-10-25

Interaction and Dissolution Characteristics of Ajmaline-PVP Coprecipitate

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