Lumichrome complexation by cyclodextrins: influence of pharmaceutical excipients.
Pharmazie
; 65(12): 871-6, 2010 Dec.
Article
en En
| MEDLINE
| ID: mdl-21284255
ABSTRACT
Complexation of the model drug lumichrome by 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD), the most widely used cyclodextrin derivative in pharmaceutical preparations, was investigated in this study. The influence of frequently used pharmaceutical excipients, i.e. alcohols (ethanol, glycerol, propylene glycol), buffers (phosphate, citrate) and tonicity modulators (NaCl, MgCl2) was evaluated by phase solubility, absorption and fluorescence emission spectra and fluorescence lifetime studies. Further, complex formation constants and fluorescence quantum yields were calculated. The formation of a 11 complex was indicated by phase solubility studies. The shape of the absorption and emission spectra for lumichrome was nearly independent of dissolution medium. The intensity of the absorption peak was slightly decreasing by the addition of HPbetaCD, which indicates formation of an inclusion complex of lumichrome in the ground state. The intensity of the fluorescence emission peak (i.e. fluorescence quantum yield) was also steadily decreasing by the increase in HPbetaCD concentration. Monoexponential fluorescence decay was obtained in the absence of cyclodextrin. In the presence of cyclodextrin, bi-exponential decays were observed in all aqueous vehicles with the exception of plain water or samples containing salts. The longest decay time corresponds to the lifetime of free (uncomplexed) lumichrome, while the shortest decay time was attributed to the excited state of the complexed alloxazine form of lumichrome. The selected excipients influence the complexation constant and the lumichrome excited state deactivation pathways to various extents.
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Colección:
01-internacional
Banco de datos:
MEDLINE
Asunto principal:
Ciclodextrinas
/
Flavinas
Idioma:
En
Revista:
Pharmazie
Asunto de la revista:
FARMACIA
Año:
2010
Tipo del documento:
Article
País de afiliación:
Noruega