Ascorbate and several phenolic compounds readily oxidise in cell culture media to generate hydrogen peroxide. However, addition of cc-ketoglutarate, which is known to be released by several cell types, decreased the levels of H2O2, and the alpha-ketoglutarate was depleted and converted to succinate. These observations could account for previous reports of the protective effects of alpha-ketoglutarate in promoting the growth of cells in culture, and may contribute to explaining some of the variability in the literature in reported rates of H2O2 production from autoxidisable compounds in cell culture systems. (C) 2011 Elsevier Inc. All rights reserved.