Effects of hydroxypropyl-β-cyclodextrin on the chemical stability of a naphthoquinone in aqueous solutions

2-Hydroxy-N-(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinone-4-imine (1), an antibacterial agent, was shown to form inclusion complexes with HP-beta-CD in aqueous solution. In the present work the kinetics of 1 degradation in aqueous buffer solution was investigated as a function of pH (2.34-3.95), HP-beta-CD concentration (0%-28% (w/v)) and temperature (60-90 degreesC). A second-order derivative spectroscopic methodology was developed for the kinetic investigations. The degradation showed to follow pseudo-first-order kinetics. Also, an specific acid catalysis was found and the introduction of up to 28% (w/v) HP-beta-CD to the reaction medium did not change this kinetic behaviour. The obtained results indicated that HP-beta-CD stabilises.