Vitamins C and E: beneficial effects from a mechanistic perspective

Free Radic Biol Med. 2011 Sep 1;51(5):1000-13. doi: 10.1016/j.freeradbiomed.2011.05.017. Epub 2011 May 25.

Abstract

The mechanistic properties of two dietary antioxidants that are required by humans, vitamins C and E, are discussed relative to their biological effects. Vitamin C (ascorbic acid) is an essential cofactor for α-ketoglutarate-dependent dioxygenases. Examples are prolyl hydroxylases, which play a role in the biosynthesis of collagen and in down-regulation of hypoxia-inducible factor (HIF)-1, a transcription factor that regulates many genes responsible for tumor growth, energy metabolism, and neutrophil function and apoptosis. Vitamin C-dependent inhibition of the HIF pathway may provide alternative or additional approaches for controlling tumor progression, infections, and inflammation. Vitamin E (α-tocopherol) functions as an essential lipid-soluble antioxidant, scavenging hydroperoxyl radicals in a lipid milieu. Human symptoms of vitamin E deficiency suggest that its antioxidant properties play a major role in protecting erythrocyte membranes and nervous tissues. As an antioxidant, vitamin C provides protection against oxidative stress-induced cellular damage by scavenging of reactive oxygen species, by vitamin E-dependent neutralization of lipid hydroperoxyl radicals, and by protecting proteins from alkylation by electrophilic lipid peroxidation products. These bioactivities bear relevance to inflammatory disorders. Vitamin C also plays a role in the function of endothelial nitric oxide synthase (eNOS) by recycling the eNOS cofactor, tetrahydrobiopterin, which is relevant to arterial elasticity and blood pressure regulation. Evidence from plants supports a role for vitamin C in the formation of covalent adducts with electrophilic secondary metabolites. Mechanism-based effects of vitamin C and E supplementation on biomarkers and on clinical outcomes from randomized, placebo-controlled trials are emphasized in this review.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Review

MeSH terms

  • Animals
  • Antioxidants / metabolism*
  • Antioxidants / therapeutic use
  • Ascorbic Acid / metabolism*
  • Ascorbic Acid / therapeutic use
  • Cytoprotection / drug effects
  • Energy Metabolism / drug effects
  • Free Radicals / metabolism
  • Humans
  • Hypoxia-Inducible Factor 1 / metabolism
  • Inflammation / drug therapy*
  • Inflammation / metabolism
  • Neoplasms / drug therapy*
  • Neoplasms / metabolism
  • Randomized Controlled Trials as Topic
  • Vitamin E / metabolism*
  • Vitamin E / therapeutic use

Substances

  • Antioxidants
  • Free Radicals
  • Hypoxia-Inducible Factor 1
  • Vitamin E
  • Ascorbic Acid