A quantitative approach to the free radical interaction between alpha-tocopherol or ascorbate and flavonoids

Area of Science:

• Biochemistry
• Free Radical Chemistry
• Antioxidant Research

Background:

• The precise mechanisms of free radical interactions between alpha-tocopherol (VE), ascorbate, and flavonoids as coantioxidants are not fully understood.
• Investigating these interactions is crucial for understanding their roles in biological systems and potential applications.

Purpose of the Study:

• To investigate the synergistic antioxidant effects of VE and L-ascorbyl 2,6-dibutyrate (ASDB) with various flavonoids (MG, EC, EGC, ECG, EGCG).
• To elucidate the free radical interaction mechanisms and regeneration processes involved in these coantioxidant systems.

Main Methods:

• Utilized the induction period method to study the polymerization of methyl methacrylate (MMA) initiated by alkyl radicals (R *).
• Examined the effects of VE and ASDB in combination with different flavonoids under nearly anaerobic conditions.

Main Results:

• VE exhibited synergy with MG, EC, EGC, and ECG, but not EGCG. ASDB showed synergy with EGC and ECG, but not EGCG or MG.
• Synergistic effects, including VE regeneration, were observed even when coantioxidant BDEs were higher than VE.
• EGCG in combination with VE or ASDB decreased antioxidant effects, potentially enhancing prooxidant activity and cytotoxicity.

Conclusions:

• The regeneration of VE by flavonoids (MG, EC, EGC, ECG) is driven by the removal of flavonoid semiquinone radicals.
• ASDB can scavenge flavonoid radicals and potentially regenerate flavonoids, similar to the VE/ascorbate system.
• EGCG's interaction with VE or ASDB leads to decreased antioxidant capacity and increased prooxidation, suggesting potential cytotoxic effects.