Isoniazid is a first-line drug for the treatment of tuberculosis, a bacterial disease caused by Mycobacterium tuberculosis. Its terminal amino group is highly reactive, leading to significant metabolic deactivation, drug interactions and hepatotoxicity. It is speculated that the activity of isoniazid derivatives is, in part, related to the cleavage of the protecting group. Therefore, this study aimed to evaluate the cleavage characteristics of previously developed isoniazid derivatives through kinetic studies by high-performance liquid chromatography with ultraviolet-diode array detectio to establish a comparison between the rates of the process and the respective activities against M. tuberculosis. Chromatographic separations were performed on an XDB C18 column coupled to an XDB C18 precolumn. The mobile phase consisted of ultrapure water and acetonitrile in gradient mode. The flow rate was 1.0 mL/min, the injection volume was 20 μL, and the detection wavelengths were 230 nm (derivatives and isatins) and 270 nm (isoniazid). Incubation of derivatives was carried out for 5 days in 10 mmol/L phosphate buffer solution (pH 3.0, 7.4, 8.0) or in fetal bovine serum at 37 °C. The incubation reduced the concentration of the derivatives and led to the formation of isoniazid in a first-order kinetic reaction. Isoniazid formation was logarithmically correlated with the minimum inhibitory concentration of the derivatives. The results showed that higher cleavage rates are associated with greater activities against M. tuberculosis, providing important information for the development of future generations of isoniazid derivatives and for screening drug candidates for the treatment of tuberculosis.
Keywords: Cleavage; Isatin; Isoniazid; Kinetics; Liquid Chromatography; Tuberculosis.
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