title: 1,3-diene probes for detection of triplet carbonyls in biological systems.
abstract: Electronically excited triplet carbonyls are formed during the oxidative degradation of polyunsaturated fatty acids, amino acids, and beta-dicarbonyl metabolites. Due to their long lifetime and high alkoxyl radical-like reactivity, triplet carbonyls may initiate deleterious reactions in biological systems. Here we study the quenching properties of conjugated dienes, specifically 2,4-hexadienoate (sorbate) and its alkyl ester, on triplet acetone generated chemically (thermolysis of tetramethyl-1,2-dioxetane) or enzymatically (horseradish peroxidase-catalyzed aerobic oxidation of isobutanal). Triplet acetone quenching rates were near diffusion control ( k q = 10 (8)-10 (9) M (-1) s (-1)) and accompanied by diene cis-trans isomerization. None of the dienes displays antioxidant activity in classical systems known to generate reactive oxygen species: superoxide anion radical, hydroxyl radical, alkoxyl and alkylperoxyl radicals, or singlet oxygen. Experiments with model systems used widely to study lipid peroxidation showed that sorbate can inhibit mitochondrial swelling induced by enzymically formed triplet benzophenone and quench the chemiluminescence of microsome preparations challenged with iron and ascorbate. Altogether, our data indicate that conjugated dienes can be used as specific quenchers of triplet carbonyls formed in biological systems during oxidative stress. Moreover, they suggest that the well-known food preservative properties of sorbate may be due to its triplet carbonyl quenching activity.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Adriana C
authors.initials: AC
authors.lastname: Velosa
authors.forename: Wilhelm J
authors.initials: WJ
authors.lastname: Baader
authors.forename: Cassius V
authors.initials: CV
authors.lastname: Stevani
authors.forename: Camila M
authors.initials: CM
authors.lastname: Mano
authors.forename: Etelvino J H
authors.initials: EJ
authors.lastname: Bechara
mesh_terms: D000096:Acetone / Q000737:chemistry / Q000378:metabolism; D000447:Aldehydes / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*; D000466:Alkadienes / Q000737:chemistry / Q000378:metabolism / Q000633:toxicity*; D000818:Animals; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D004952:Esters / Q000737:chemistry / Q000378:metabolism; D005520:Food Preservatives / Q000494:pharmacology / Q000633:toxicity*; D006735:Horseradish Peroxidase / Q000378:metabolism; D007700:Kinetics; D008163:Luminescent Measurements; D013058:Mass Spectrometry; D008933:Mitochondrial Swelling / Q000187:drug effects* / Q000502:physiology; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000737:chemistry / Q000378:metabolism; D013011:Sorbic Acid / Q000494:pharmacology / Q000633:toxicity*; D013696:Temperature
chemical_list: D000447:Aldehydes; D000466:Alkadienes; D004952:Esters; D005520:Food Preservatives; D017382:Reactive Oxygen Species; D000096:Acetone; C017439:isobutyraldehyde; D006735:Horseradish Peroxidase; C502503:2,4-heptadienal; D013011:Sorbic Acid