Synthesis, in vitro antioxidant activity, and physicochemical properties of novel 4,5-dihydro-1H-1,2,4-triazol-5-one derivatives

摘要

In this study, eight new 3-alkyl(aryl)-444-(4-methylbenzoxy)benzylidenamino]-4,5-dihydro-1H-1,2,4-triazol-5-one (4) compounds were synthesized by the reactions of 3-alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (3) with 4-(4-methylbenzoxy)benzaldehyde (1). The eight compounds were characterized using IR, H-1 NMR, C-13 NMR, and UV spectral data. In addition, the synthesized compounds were analyzed for their potential in vitro antioxidant activities, including reducing power, free radical scavenging and metal chelating activity. These antioxidant activities were compared to those from standard antioxidants, such as EDTA, BHA, BHT and alpha-tocopherol. Moreover, compounds 4 were titrated potentiometrically with tetrabutylammonium hydroxide in four non-aqueous solvents (isopropyl alcohol, tert-butyl alcohol, acetone and N,N-dimethylformamide). Thus, the half-neutralization potential values and the corresponding pK(a) values were determined in all cases. In addition, the lipophilicity of the synthesized compounds was investigated using HPLC. Kinetic parameters of the complexes were obtained for each stage of thermal degradation using the Coats-Redfern and Horowitz-Metzger methods. (C) 2015 Elsevier BM. All rights reserved.