Micropreparative isolation of Cu(II) complexes of isoniazid and ethambutol and determination of their structures

We report the chromatographic behavior of the antitubercular drugs isoniazid (INH), pyrazinamide (PYR), ethambutol (ETB), and p -aminosalicylic acid (PAS) in reversed-phase TLC with organic aqueous mobile phases modified with Cu(II) chloride. The spectra of the free ligands and complexes formed during chromatography were measured densitometrically by use of a scanner equipped with a diode-array detector and compared in the range 200–700 nm. The complexes of Cu(II) with isoniazid and ethambutol were isolated on a micropreparative scale. The structures of the INH-Cu and EMB-Cu complexes were analyzed by electron paramagnetic resonance (EPR) spectroscopy and illustrated graphically by molecular modeling using GaussView software.