Synthesis and Antioxidant Activity of 1,3,5- trisubstituted pyrazole Derivatives

Abstract

Oxidation is a chain of chemical reactions generating free radicals by transferring electrons from a substrate to an oxidizing agent. Various types of free radicals formed within the body are superoxide anion (O2-), the hydroxyl radical (OH·), singlet oxygen (1O2 ), and hydrogen peroxide (H2O2). An antioxidant is a molecule capable of inhibiting the oxidation of other molecules by maintaining the balance between the processes generating and utilizing the free radicals. Extensive literature review revealed that the synthetic derivatives of natural antioxidants like curcumin and resveratrol show considerably good antioxidant activity. Also, various pyrazole derivatives have diverse pharmacological activity. Synthesis of substitued Pyrazole-1-carbothioamide and Pyrazole-1-carboxamide derivatives have been synthesized by the reaction of substituted dibenzalacetones with thiosemicarbazide and semicarbazide hydrochloride repectively. The key intermediates dibenzalacetones were synthesized by Clasein-Schmidt condensation between aromatic aldehydes and ketones in presence of sodium hydroxide and methanol. Structure of all synthesized compounds were established by IR, Mass and 1H NMR spectral data. The antioxidant activity of the synthesized compounds was investigated by Nitric oxide, Superoxide, DPPH and Hydrogen peroxide radical scavenging activitSy using ascorbic acid (10μg/mL) as the reference standard. Compounds exhibited highest activity against DPPH radical scavenging activity even at considerably low concentration of 10 μg/mL. Compounds with hydroxy substituents exhibited good activity against all four methods. Keywords: Pyrazole-1-carbothioamide, Pyrazole-1-carboxamide, Antioxidant.