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Generation of singlet oxygen by the aerobic oxidation of formylhydrazine, a mushroom toxin

Grant number: 11/20791-7
Support type:Scholarships in Brazil - Scientific Initiation
Effective date (Start): January 01, 2012
Effective date (End): December 31, 2012
Field of knowledge:Biological Sciences - Biochemistry - Metabolism and Bioenergetics
Principal Investigator:Etelvino José Henriques Bechara
Grantee:Camila Usan Elvino
Home Institution: Instituto de Ciências Ambientais, Químicas e Farmacêuticas (ICAQF). Universidade Federal de São Paulo (UNIFESP). Campus Diadema. Diadema , SP, Brazil

Abstract

Molecular oxygen excited to the excited singlet state (O2 1Dg) is a highly reactive oxygen species (EROS), known to be involved in cellular damage and possibly implicated in signal transduction. Hence is the interest in revealing cellular sources, molecular targets and biological responses of singlet oxygen. We aim to investigate possible production of singlet oxygen by the aerobic oxidation of formylhydrazine and its ±N-methylated derivative, both being natural toxicants found in poisonous mushrooms, notably Gyromitra sp. Endogenous oxidants such as superoxide anion radical, provided by either KO2, xanthine/xanthine, H2O2/peroxidase, or NADPH/rat liver microsomes and, for comparison, inorganic oxidants (e.g., ferricyanide and permanganate salts), will be added to hydrazine-containing aerated phosphate buffer, pH 7.4. Similar to the glyoxal/peroxynitrite system (Massari et al., Submitted), the reaction is expected to initially yield an unstable formyldiazene, whose subsequent one-electron oxidation would cleave to N2 and formyl radical. Combination of formyl radical with dissolved oxygen has been shown to yield formylperoxyl radical, which can undergo Russell disproportionation to O2 (1Dg), CO2 and formate. The kinetics of reaction of hydrazine oxidation will be monitored by UV-Vis spectrophotometry, the formyl radical production by EPR spin trapping with MNP, the formate generation via capillary electrophoresis, and the characteristic O2 (1Dg) momolecular emission at 1270 nm detected in a photocounter and tested with well-known physical (azide, H2O/D2O) and chemical quenchers (L-His, anthracene derivatives). This work will probably contribute for the elucidation of the molecular basis of mushrooms toxicity, whose intake has been associated with vomiting, diarrhea, jaundice, convulsions and coma, as well as hepatitis, cancer and neurological disorders.