Synthesis of the Hydrazones of 2‐((3,5‐Di‐tert‐butyl‐4‐hydroxybenzyl)thio) acetohydrazide and the Study of their Radical Scavenging Activity by the DPPH Assay and the Computational Method

Abstract

The synthesis of antioxidant compounds bearing pharmacologically active groups has become a research interest in the last decade. A series of hydrazones containing a butylated hydroxyl group were synthesized from 2-((3,5-di-tert-butyl-4-hydroxybenzyl)thio)acetohydrazide and various benzaldehyde derivatives, and their radical scavenging activity was explored by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and computational calculations. Based on the results, the effects of different substituents on the DPPH IC 50 values were discussed. The bond dissociation enthalpies (BDE) of O H and N H bonds and the spin density (SD) values of the compounds were calculated using the density functional theory (DFT) to determine the theoretical capability of the hydrazones as radical scavengers. Based on the results, the effects of the thioether group and the substituent groups next to the N H bond on the BDE values were also discussed.

Semicarbazide and thiosemicarbazide containing butylated hydroxytoluene moiety: new potential antioxidant additives for synthetic lubricating oil

“…However, the color turns into yellow when antioxidant was added into the DPPH solution due to the reduction of divalent nitrogen (N) of DPPH by antioxidant molecule. 22 The radical scavenging activity was expressed by the half maximal inhibitory concentration (IC 50 ), the concentration needed to inhibit 50% of DPPH solution. Thus, the compound which has a lower IC 50 value would shows better antioxidant properties.…”

“…Due to lower electronegativity of sulfur atom, thiol can easily release proton to DPPH radical in comparison of hydroxyl group (Scheme 4). 7,16,22,26 In addition, it was found that the degree of conjugation in thioamides is considerably higher than amides which made it as stronger p-electron attractor. 27 Nevertheless, thiosemicarbazides with thiolated BHT could convert into several radical by donating the proton to reduce DPPH radical.…”