Vitamin E neutralises lipid peroxyl radicals in membranes and becomes oxidised to the tocopherol radical in the process. Which water-soluble antioxidant regenerates active vitamin E from the tocopherol radical?

• A Retinol
• B Alpha-lipoic acid
• C Ubiquinone (coenzyme Q)
• D Ascorbic acid ✓

Explanation

Ascorbate reduces the tocopherol radical back to alpha-tocopherol at the membrane-water interface, coupling lipid-phase and aqueous-phase antioxidant defence; the resulting semidehydroascorbate is then recycled by dehydroascorbate reductase using GSH. Retinol has no known redox recycling role for tocopherol, and ubiquinone functions within the mitochondrial electron transport chain rather than regenerating vitamin E.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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