After neutralising a lipid peroxyl radical, alpha-tocopherol itself becomes the tocopheroxyl radical. Which water-soluble antioxidant regenerates active vitamin E from this radical at the membrane interface?
- A Ascorbic acid (vitamin C) ✓
- B Ubiquinone (coenzyme Q)
- C Beta-carotene
- D Alpha-lipoic acid bound to pyruvate dehydrogenase
Correct answer: A. Ascorbic acid (vitamin C)
Explanation
Ascorbate donates an electron to the tocopheroxyl radical, regenerating alpha-tocopherol while becoming the semidehydroascorbate radical, which is then recycled by dehydroascorbate reductase using glutathione. This ascorbate-tocopherol coupling links aqueous and lipid antioxidant networks. Beta-carotene is itself a lipid-phase singlet oxygen quencher and cannot regenerate tocopherol, which makes it the strongest distractor.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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