Study of Antioxidant Activity of the Derivatives of Quinoline-4-carboxylic Acids by the Modification of Isatin via Pfitzinger Reaction

In this study, a quinoline-4-carboxylic acid derivative was synthesized through Pfitzinger reaction. reaction, isatin is modified via its reaction with ketone and refluxed for 24 h to obtain acid. The presence of carboxylic group identified by Fourier Transform Infrared (FTIR) spectroscopy ultraviolet–visible (UV-Vis) spectrophotometry. results showed that the absorption peaks C=O O–H stretching’s were detected in range 1724–1708 3436–3242 cm−1, respectively. UV-vis spectrum, shift peak observed toward larger wavelength, which referred as bathochromic shift. formation also characterized using mass spectrometry method. modification aims increase antioxidant activity acid, has better inhibition percentage than isatin. Antioxidant tests conducted 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. measured based on ability donate hydrogen radicals, revealed product had relatively inhibitory effect At concentration 5 mg/L, did not show DPPH By contrast, percentages 2-methylquinoline-4-carboxylic 2-(4-methylphenyl)quinoline-4-carboxylic approximately 30.25% 40.43%, Furthermore, an aromatic ring makes activity.