Synthetic 4,4′-{(Arylmethylene)}bis(1H-pyrazol-5-ols): Efficient Radical Scavenger

Functionalized 4,4'-{(arylmethylene)}bis(1H-pyrazol-5-ols) 1-22 were screened for their antioxidant activity. Antioxidant activity was performed by measuring their radical scavenging activity. These compounds demonstrated diverse in vitro DPPH radical scavenging activities with IC(50 )values ranging between 55.2 +/- 1.2-149.6 +/- 1.7 mu M, as compared to standard BHT (butylated hydroxytoluene) (IC50 = 128.8 +/- 2.1 mu M). Compounds 4,4'-((4-bromo-2,6-dimethoxyphenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol 18) IC50 = 5 5. 2 +/- 1.2 mu M, 4,4'-(naphthalen-1-ylmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol 20) (IC50 = 58.3 +/- 0.9 mu M), 4,4'-((3-bromo-4-methoxyphenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol 19) (IC50 = 59.6 +/- 0.1 mu M), 4, 4'-((4-methoxyphenyl)methylene)bis(3-methyl-1-phenyl-1H-pyraz ol-5-ol 6) (IC50 = 60 .0 1 +/- 0.7 mu M), 4,4'-((4-(methylthio)phenyOmethylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol 10) (IC50 = 6 1. 5 +/- 0.6 mu M), 4, 4'-((2,4-dimethylphenyOm ethylene)bis(3-methyl-1-phenyl- 1H-pyraz ol-5-ol) (1) (IC50 = 68.3 +/- 0.2 mu M), 4,4'-((2-ethoxyphenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (8) (IC50 = 80.5 +/- 1.5 mu M), 4,4'-((3-nitrophenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (12) (IC50 = 70.8 +/- 1.4 mu M), 4, 4'-((3 -bromophenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (17) (IC50 = 77.9 +/- 2.06 mu M), and 4,4'--((2-fluorophenyl)methylene)bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) (22) (IC50 80.0 +/- 2.3 mu M) showed better antioxidant activity than the standard BHT. Varying substituents at aryl part (aldehydic part) have been responsible for diversified activity.