L-Carnitine protects plasma components against oxidative alterations

Nutrition. 2011 Jun;27(6):693-9. doi: 10.1016/j.nut.2010.06.009. Epub 2010 Sep 24.


Objective: L-Carnitine as a dietary supplement has been reported to have a beneficial effect on several cardiovascular risk parameters and exercise capacity, but the biological relevance of its activity is poorly understood. Dietary supplements (including L-carnitine) are often used to foster exercise performance; however, these may affect some pathways of human body metabolism. The aim of this study in vitro was to determine antioxidative properties of L-carnitine (0.1-100 μM) added to plasma and to assess if L-carnitine might protect plasma proteins and lipids against oxidative/nitrative damage (determined by levels of protein carbonyl groups, thiols, 3-nitrotyrosine formation and thiobarbituric-acid reactive substances generation) caused by 100 μM peroxynitrite (ONOO(-)), a strong physiologic oxidative/nitrative agent.

Methods: The level of carbonyl group generation was measured by a colorimetric method. For the estimation of 3-nitrotyrosine formation, a competition enzyme-linked immunosorbent assay was performed. Plasma lipid peroxidation was measured spectrophotometrically as the production of thiobarbituric-acid reactive substances. High-performance liquid chromatography was used to analyze total free thiol groups of plasma proteins and low-molecular-weight thiols (glutathione, cysteine, and homocysteine) in plasma.

Results: The L-carnitine added to plasma inhibited in vitro ONOO(-)-induced oxidation and nitration of blood plasma proteins. Incubation of plasma with peroxynitrite resulted in the decrease of protein thiols. L-Carnitine had a protective effect on peroxynitrite-induced decreased -SH level in plasma proteins. The presence of L-carnitine also prevented the decrease of low-molecular-weight thiols (glutathione, cysteine, and homocysteine) in plasma caused by peroxynitrite and protected plasma lipids against peroxidation induced by peroxynitrite.

Conclusions: These results demonstrated that L-carnitine possesses antioxidative activity.

MeSH terms

  • Adult
  • Antioxidants / chemistry*
  • Blood Proteins / chemistry*
  • Carnitine / chemistry*
  • Cysteine / blood
  • Dietary Supplements*
  • Glutathione / blood
  • Homocysteine / blood
  • Humans
  • Lipid Peroxides / blood*
  • Lipids / blood
  • Lipids / chemistry*
  • Male
  • Osmolar Concentration
  • Oxidants / chemistry
  • Oxidation-Reduction
  • Oxidative Stress*
  • Peroxynitrous Acid / chemistry
  • Protein Carbonylation
  • Thiobarbituric Acid Reactive Substances / analysis
  • Tyrosine / analogs & derivatives
  • Tyrosine / blood
  • Young Adult


  • Antioxidants
  • Blood Proteins
  • Lipid Peroxides
  • Lipids
  • Oxidants
  • Thiobarbituric Acid Reactive Substances
  • Homocysteine
  • Peroxynitrous Acid
  • 3-nitrotyrosine
  • Tyrosine
  • Glutathione
  • Cysteine
  • Carnitine