المستخلص: |
The interaction between cyclodextrins with etoricoxib (ETR), have been investigated in different pH aqueous mediaand we notice that spectral properties of ETR changes with pH of the solution. Absorption and fluorescence studies, show that etoricoxib (ETR) could forms ground state inclusion complexes with different cyclodextrins (Beta, Hydroxypropyl beta, gamma and alpha CD) In the ground state, ETR have pKa1 = 5.87, however, in the excited state, ETR have pKa1*= 11.44 and pKa2*= 3.71 which means that ETR becomes more basic in the excited state, Steady state experiments detect the kind of etoricoxib-CD (ETR-CD) complex, Time resolved measurements were also performed to study the type of the inclusion and calculate the association constant. This study showed that ETR can only form 1:1 complexes with α-CD, β-CD, γ-CD and HPβ-CD at pH2, pH6, and pH10, and the largest association constants were found for neutral ETR (at pH10) with β-CD and γ-CD.
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