Charge-Transfer Reaction of Chloranilic Acid with Crizotinib: Spectrophotometric Study, Computational Modeling and Use in Development of Microwell Assay for Crizotinib

The reaction of chloranilic acid (CA) with crizotinib (CZT); a novel drug used for treatment of non-small cell lung cancer) was investigated in different solvents of varying dielectric constants and polarity indices. The reaction resulted in the formation of a violet-colored product. Spectrophotometric investigations confirmed that the reaction proceeded through CT complex formation. The molar absorptivity of the CT complex produced was found to be linearly correlated with the dielectric constant and polarity index of the solvent. The association constant of the CA–CZT CT complex and the stoichiometric ratio of CA:CZT were determined. Computational molecular modeling for the CT complex between CA and CZT was conducted, the sites of interaction on CZT molecule were determined, and the mechanism of the reaction was postulated. The reaction was employed as a basis for the development of a novel 96-microwell assay for CZT. In this assay, the absorbances of the CA–CZT CT complex solutions were measured by a microwell-plate absorbance reader. The CZT limits of detection and quantitation are 8.8 and 26.4 μg·mL−1, respectively. The assay was successfully applied to the analysis of CZT in its bulk form and capsules with good accuracy and precision. The assay described herein has great practical value as it has high throughput and consumes minimum volume of organic solvent, thus it reduces the exposures of the analysts to the toxic effects of organic solvents, and significantly reduces the analysis cost.