title: Identification of hydrogen peroxide as a major cytotoxic component in Maillard reaction mixtures and coffee.
abstract: The cytotoxic activity of Maillard reaction products and coffee was studied using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay and the neutral red uptake (NRU) assay. Equimolar mixtures of sugars and lysine were heated at 120 degrees C and used to stimulate bovine aorta endothelial cells for 24 h. The cytotoxic activity increased with increase in educt concentration and heating time. Mixtures containing ribose were most active, followed by lactose and glucose. Hydrogen peroxide, which was present in the Maillard mixtures in concentrations between 7 and 87 microM, was identified as one of their major cytotoxic components. H2O2-concentrations increased further up to 130 microM under cell culture conditions. Filter coffee, espresso, and green coffee extract reduced cell viability significantly to 10, 19, and 83% of PBS-treated control. The effect was largely attenuated by the addition of catalase. Nil, 33, and 41 microM H2O2 was measured in green coffee extract, filter coffee, and espresso, respectively, increasing to 13, 369, and 333 microM during cell culture conditions. No additional H2O2 formation was detected when coffee was incubated for up to 5 h without further treatment. In conclusion, hydrogen peroxide is a major product in Maillard mixtures and coffee inducing cell death in vitro.
authors.affiliation: Department of Chemistry and Pharmacy, Food Chemistry, Friedrich-Alexander University Erlangen, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Hegele
authors.forename: Gerald
authors.initials: G
authors.lastname: Münch
authors.forename: Monika
authors.initials: M
authors.lastname: Pischetsrieder
mesh_terms: D000818:Animals; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003069:Coffee / Q000737:chemistry; D005562:Formazans / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D015416:Maillard Reaction; D009499:Neutral Red / Q000493:pharmacokinetics; D013778:Tetrazolium Salts / Q000378:metabolism
chemical_list: D003069:Coffee; D005562:Formazans; D013778:Tetrazolium Salts; C079782:MTT formazan; D009499:Neutral Red; D006861:Hydrogen Peroxide