Dramatic solvent effect on the synergy between α-tocopherol and BHT antioxidants.

During the DPPH scavenging assay carried out in non polar and non protic solvents, such as toluene, BHT regenerates α-tocopherol from tocopheryl radical, whereas in polar and protic solvents, like methanol, no regeneration is observed due to a fast electron transfer reaction from the tocopheryl radical to the reactive DPPH radical. Surprisingly, in the presence of a small amount of alcohol, the synergy is exalted and BHT regenerates twice as much α-tocopherol due to a nucleophilic addition of short alcohols on the BHT oxidation product, giving a new phenolic co-antioxidant.