Studies of Cyclodextrin Inclusion Complexes: I - Inclusion Complexes Between α- And β-Cyclodextrins and Chloramphenicol in Aqeuous Solutions

Abstract

Chloramphenicl was found to form inclusion complexes with α- and β-cyclodextrins (α-CyD and β-CyD) in aqeuous solution. Phase solubility diagrams were obtained with β-CyD and found to be Bs type curve. An apparent 1:1 complex formation constant (Kc) of 8077 × 10⁴ M^-1 was obtained for chloramphenicol in β-CyD.

For α-CyD the phase solubility diagrams indicate AL TYPE CURVE. The complex stochiometric ratios were found to be 1:1 and 1:2 (guest: Host). The apparent formation constant, Kc and Kc, for chloramphenicol in α-CyD were found to be 3017 × 10⁴ M^-1 and 957 × 10⁴ M^-1, for 1:1 and 1:2 stochiometric ratios respectively. Thus the apparent complex formation constant for chloramphenicol is higher in β-CyD than α-CyD relatively.

It was found that the aqueous solubility of chloramphenicol more enhanced by α- and β-CyD inclusion complexation than the non-ionic surfactant solutions used in a previous study. The higher values obtained for the complex formation constants indicate a particularly good fitness of the chloramphenicol molecule with the β- and α-CyD cavities relatively.

Microcrystalline solid inclusion complex of chloramphenicol and β-CyD, 1:1, was isolated and investigated by I. R., in comparison with a physical mixture 1:1, to characterize the interaction takes place between chloramphenicol and β-CyD within the complex. Thus chloramphenicol complexed in β-CyD in aqueous and solid phases.

The effect of certain water soluble carriers, in 5%, w/v concentration, on chloramphenicol complexation in α- and β-CyD cavities was investigated. The aim of adding such additives is to reduce the concentration of the CyDs used in formulating chloramphenicol in solution. It was found that propylene glycol and P.E.G. 4000 assist chloramphenicol complexation in β-CyD, forming higher KC values, 46221 × 10⁴ M^-1 and 39883 × 10⁴ M^-1 respectively. While glycerol deminish chloramphenicol complexation in S-CyD, In case of α-CyD, P.E.G 4000 and propylene glycol rise KC and KC for chloramphenicol respectively, and the reverse is true for glycerol.