Syntheses and Antioxidant Screening of Pyrazole-4-Carboxaldehyde Derivatives

Nine new derivatives of pyrazole-4-carboxaldehydes (Va-i) have been synthesized by aceticacid mediated condensation of different aromatic ketones with phenylhydrazines in ethyl alcohol toafford different phenylhydrazones. Phenylhydrazones so prepared were further allowed to react withtwo moles of DMF-POCl3 adduct (Vilsmeier Haack reagent) in the DMF at 60-70°C for 6 hours withformation of immonium perchlorate. Introduction of phenyl ring at first & third position of pyrazolemay increase the antioxidant activity. The participation of the C=C bond is important in stabilizing theantioxidant radical by resonance. Introduction of electron releasing groups on phenyl rings attached toheterocycles increase the electron donating capacity of antioxidants. Further more on alkalinehydrolyses (NaOH) they afforded different pyrazole-4-carboxaldehyde derivatives. The structures ofsynthesized compounds have been characterized on the basis of IR, 1H-NMR, ESI-MS and elementalanalysis. All the synthesized compounds were screened for antioxidant activity. In order to neutralizingthe threat of free radicals to the tissues and cells, body enzymes take participate include: glutathioneperoxidise (GSH), superoxide dismutase (SOD) and catalase Antioxidants may intervene with thesefree radicals at different levels in the oxidative process. In FRAP assay, increased absorbance of thecompounds with concentration indicates increased reducing power. Compounds with higherconcentrations showed a higher reducing power. The reducing power showed good linear relation (R2)in both standard as well as compounds. These results clearly reveal that compounds have antioxidantactivity.