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The influence of cyclodextrin complexation on the stability of betamethasone-17-valerate

1984; Elsevier BV; Volume: 20; Issue: 1-2 Linguagem: Inglês

10.1016/0378-5173(84)90226-6

1873-3476

Finn M. Andersen, Henning Bundgaard,

Estrogen and related hormone effects

The influence of various cyclodextrins on the stability of betamethasone 17-valerate has been investigated in basic aqueous solution at 24° C. The 17-vale-ate ester undergoes a facile hydroxide ion-catalyzed rearrangement to the less active 21-valerate ester. Whereas α-cyclodextrin did not affect the rate of rearrangement, β-cyclodextrin caused a rate acceleration and γ-cyclodextrin and heptakis-(2,6-di-O-methyl)-β-cyclodextrin resulted in a marked rate retardation. These effects were interpreted in terms of a reaction scheme involving the formation of inclusion complexes with the cyclodextrins and apparent 1:1 complex constants were determined. The reversal in the effects observed for the cyclodextrins is discussed on the basis of microsolvent and conformational effects and it is concluded that inclusion complexation of betamethasone-17-valerate with γ-cyclodextrin or, especially, 2,6-di-O-methylated β-cyclodextrin may be a potentially useful means of increasing the stability of the steroid.