In Vitro Study of the Effect of 2,6-Substituents at the New 4-Ethoxy-Phenols as Antioxidants

The antioxidant effect of the different groups in the 2,6-positions of the new 4-ethoxy-phenols were evaluated. To address our research, 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and reducing power capacity, were employed to analyze the antioxidant activity. The results of the antioxidant test indicated that most of the new molecules 6a-l presented high antioxidant activity. Compound 6f had the highest activity (1.47 +/- 0.39 mu g/mL) when it was compared with 2,6 di-tert-butyl hydroxytoluene (BHT, 6.72 +/- 0.47 mu g/mL) and trolox (2.81 +/- 0.31 mu g/mL) as standards using DPPH assay. ABTS method confirmed that 6f was the most active antioxidant molecule. Theoretical analysis showed that phenyl group in 6f has a similar effect in the O-H energy that t-butyl in BHA, but the steric hindrance is different. In the three tests, compound 6i turned out to be the one with the least antioxidant effect; it demonstrated the main role of hydroxyl group on the topology of the species to achieve the desired antioxidant effect, which was completely lost when this group was absent.