Flavonoids increase the intracellular glutathione level by transactivation of the gamma-glutamylcysteine synthetase catalytical subunit promoter

Free Radic Biol Med. 2002 Mar 1;32(5):386-93. doi: 10.1016/s0891-5849(01)00812-7.


Fruits and vegetables protect against cancer by so far not well-characterized mechanisms. One likely explanation for this effect is that dietary plants contain substances able to control basic cellular processes such as the endogenous defense against oxidative stress. Oxidative stress is pivotal in many pathological processes and reduced oxidative stress is implicated in prevention of disease. Our results demonstrate that extract from onion and various flavonoids induce the cellular antioxidant system. Onion extract and quercetin were able to increase the intracellular concentration of glutathione by approximately 50%. Using a reporter construct where reporter expression is driven by the gamma-glutamylcysteine synthetase (GCS) heavy subunit (GCS(h)) promoter we show that onion extract, quercetin, kaempferol, and apigenin increased reporter gene activity, while a fourth flavonoid, myricetin and sugar conjugates of quercetin were unable to increase reporter expression. Quercetin was also able to induce a distal part of the GCS(h) promoter containing only two antioxidant-response/electrophile-response elements (ARE/EpRE). Our data strongly suggest that flavonoids are important in the regulation of the intracellular glutathione levels. This effect may be exerted in part through GCS gene regulation, and may also contribute to the disease-preventing effect of fruits and vegetables.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antineoplastic Agents / pharmacology*
  • Apigenin
  • COS Cells
  • Chlorocebus aethiops
  • DNA Primers / chemistry
  • Diet
  • Flavonoids / pharmacology*
  • Gene Expression Regulation, Enzymologic
  • Glutamate-Cysteine Ligase / genetics*
  • Glutamate-Cysteine Ligase / metabolism
  • Glutathione / metabolism*
  • Kaempferols*
  • Luciferases / metabolism
  • Onions / metabolism
  • Plasmids
  • Polymerase Chain Reaction
  • Promoter Regions, Genetic / drug effects*
  • Protein Subunits
  • Quercetin / pharmacology*
  • RNA, Messenger / drug effects
  • RNA, Messenger / metabolism
  • Regulatory Sequences, Nucleic Acid
  • Sequence Deletion
  • Transcription, Genetic
  • Transcriptional Activation
  • Transfection


  • Antineoplastic Agents
  • DNA Primers
  • Flavonoids
  • Kaempferols
  • Protein Subunits
  • RNA, Messenger
  • kaempferol
  • myricetin
  • Apigenin
  • Quercetin
  • Luciferases
  • Glutamate-Cysteine Ligase
  • Glutathione