Synthesis of hydroxylated azomethine compounds and the antioxidant activity

Azomethine compounds are one group of compounds that play a biologically important role as antioxidants. Azomethine compounds have a group (>C=N-) from the condensation reaction between the carbonyl group of the aldehyde or ketone and the nucleophilic primary amine through an addition-elimination reaction. The presence of a substituent such as a hydroxyl group (-OH) attached to an azomethine is reported to affect antioxidant activity. The purposes of this study were to synthesize hydroxylated azomethine derivative compounds including N,N’-Bis(2-hydroxy benzylidene) ethylenediamine from salicylaldehyde and ethylenediamine and N,N’-Bis(4-hydroxy-3-methoxy benzylidene) ethylenediamine from vanillin and ethylenediamine, and synthesize azomethine compound N,N’- Bis(benzylidene) ethylenediamine as a comparison. The antioxidant activity of three azomethine derivatives was tested using DPPH method. The results were hydroxylated azomethine derivative compounds. N,N’-Bis(2-hydroxy benzylidene) ethylenediamine was obtained as a yellow solid with a yield of 87.04% and a melting point of 125.6-127.5 °C. N,N’-Bis(4-hydroxy-3-methoxybenzylidene)ethylenediamine was obtained as a light brown solid with a yield of 70.045% and a melting point of 220.2-222.1 °C. N,N’-Bis(benzylidene)ethylenediamine was obtained as an orange solid with a yield of 34.83% and melting point 110.2-111.4 °C. The antioxidant activity test results show IC50 values for the three azomethine derivatives of N,N’-Bis(2-hydroxybenzylidene) ethylenediamine, N,N’-Bis (benzylidene)ethylenediamine and N,N’-Bis(4-hydroxy-3-methoxybenzylidene) ethylenediamine were 130.573 ppm, 187.66 ppm and 235.164 ppm, respectively.