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

Area of Science:

• Antioxidant chemistry
• Free radical reactions
• Phenolic compounds

Background:

• Alpha-tocopherol (vitamin E) is a key lipid-soluble antioxidant.
• Butylated hydroxytoluene (BHT) is a synthetic antioxidant used in various applications.
• DPPH radical scavenging assay is a standard method for evaluating antioxidant activity.

Purpose of the Study:

• To investigate the solvent effects on the regeneration of alpha-tocopherol by BHT.
• To explore the synergistic effects of BHT and alcohols on antioxidant activity.
• To elucidate the reaction mechanism underlying the observed synergy.

Main Methods:

• DPPH radical scavenging assay.
• Spectrophotometric analysis of antioxidant regeneration.
• Investigation of solvent effects (non-polar, polar, and mixed solvent systems).
• Analysis of reaction products using chemical principles.

Main Results:

• BHT regenerates alpha-tocopherol in non-polar solvents (e.g., toluene) but not in polar protic solvents (e.g., methanol).
• In polar solvents, rapid electron transfer between tocopheryl and DPPH radicals inhibits regeneration.
• Addition of small amounts of alcohol to the reaction system significantly enhances alpha-tocopherol regeneration by BHT.
• A novel synergistic mechanism involving nucleophilic addition of alcohols to BHT oxidation products was identified, forming a new phenolic co-antioxidant.

Conclusions:

• Solvent polarity critically influences the antioxidant regeneration mechanism of BHT.
• A synergistic interaction between BHT and short-chain alcohols enhances antioxidant capacity through a novel reaction pathway.
• The findings reveal a new co-antioxidant formation mechanism, expanding the understanding of BHT's role in complex systems.