Which laboratory measurement is considered the most reliable noninvasive index of whole-body lipid peroxidation in vivo, because these compounds arise exclusively from free-radical attack on arachidonic acid in phospholipids and are excreted unchanged in urine?

• A Urinary F2-isoprostanes ✓
• B Plasma malondialdehyde by thiobarbituric acid assay
• C Serum conjugated dienes
• D Plasma 8-hydroxydeoxyguanosine

Explanation

F2-isoprostanes are prostaglandin-like compounds formed solely by nonenzymatic free-radical peroxidation of arachidonyl-containing phospholipids, independent of cyclooxygenase. They are chemically stable, specific to lipid peroxidation, and excreted in urine, making urinary F2-isoprostane measurement the accepted gold-standard in vivo index of oxidative stress. Thiobarbituric acid-reactive substances lack specificity because the assay also detects sugars and other aldehydes, and 8-hydroxydeoxyguanosine reflects oxidative DNA damage rather than lipid peroxidation.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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