Ascorbate reacts with singlet oxygen to produce hydrogen peroxide

Photochem Photobiol. Nov-Dec 2006;82(6):1634-7. doi: 10.1562/2006-01-12-RN-774.


Singlet oxygen is a highly reactive electrophilic species that reacts rapidly with electron-rich moieties, such as the double bonds of lipids, thiols, and ascorbate (AscH-). The reaction of ascorbate with singlet oxygen is rapid (k = 3 x 10(8) M(-1) s(-1)). Here we have investigated the stoichiometry of this reaction. Using electrodes to make simultaneous, real-time measurements of oxygen and hydrogen peroxide concentrations, we have investigated the products of this reaction. We have demonstrated that hydrogen peroxide is a product of this reaction. The stoichiometry for the reactants of the reaction (1 1O2 + 1AscH--->1H2O2 + 1dehydroascorbic) is 1:1. The formation of H2O2 results in a very different oxidant that has a longer lifetime and much greater diffusion distance. Thus, locally produced singlet oxygen with a half-life of 1 ns to 1 micros in a biological setting is changed to an oxidant that has a much longer lifetime and thus can diffuse to distant targets to initiate biological oxidations.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Ascorbic Acid / chemistry*
  • Dihematoporphyrin Ether / chemistry
  • Hydrogen Peroxide / chemistry*
  • Kinetics
  • Oxidants
  • Singlet Oxygen / chemistry*


  • Oxidants
  • Singlet Oxygen
  • Dihematoporphyrin Ether
  • Hydrogen Peroxide
  • Ascorbic Acid