Synthesis, evaluation of antioxidant activity and crystal structure of 2,4-dimethylbenzoylhydrazones.

2,4-Dimethylbenzoylhydrazones 1-30 were synthesized by condensation reactions of 2,4-dimethylbenzoylhydrazide with various aromatic aldehydes and characterized. The assigned structures of compounds 10, 15 and 22 were further supported by single-crystal X-ray diffraction data. The synthesized compounds were evaluated for their in vitro DPPH radical scavenging activity. They exerted varying degree of scavenging activity toward DPPH radical with IC50 values between 25.6-190 µM. Compounds 1, 4, 2, 3, 7, and 6 have IC50 values of 25.6, 28.1, 29.3, 29.8, 30.0 and 30.1 µM respectively, showing better activity than an n-propyl gallate standard (IC50 value = 30.30 µM). For super oxide anion scavenging activity compounds 1, 2 and 3 with IC50 values of 98.3, 102.6, and 105.6, respectively, also showed better activity than the n-propyl gallate standard (IC50 value = 106.34 µM).