Quantification of carbonyls produced by the decomposition of hydroperoxides

Abstract

Carbonyls produced by the decomposition of cyclohexene hydroperoxide and various hydroperoxides of linoleic and linolenic acids and their methyl esters were determined by gas chromatography of the 2,4,6‐trichlorophenylhydrazones. The effect of temperature, iron and copper ions, ethanol and several antioxidants on the rate of decomposition, the nature of the products and their yield was observed. The hydroperoxides of methyl esters decomposed more slowly than those of free fatty acids. Ethanol slowed, and metal ions accelerated the rates of decomposition. Metal ions, especially copper, increased the yield and complexity of the carbonyls formed, but ethanol decreased carbonyl yields. Antioxidants and decomposition temperatures changed the relative yields of carbonyls produced. The 9‐ and 13‐hydroperoxides of linoleic acid gave similar carbonyls, but those of linolenic acid did not. The carbonyl mixtures produced from autoxidized fatty acid methyl esters were more complex than those produced from lipoxygenase‐treated fatty acids.

Métodos para avaliação do grau de oxidação lipídica e da capacidade antioxidante

“…A título de exemplo, cita-se o Índice de Carbonilo, o qual corresponde à avaliação dos compostos carbonílicos que se formam no decurso do processo de oxidação. Tem por base a reação, em meio ácido, com a 2,4-dinitrofenilhidrazina e a formação dos respectivos derivados corados (2,4-dinitrofenilhidrazonas), seguida de determinação espectrofotométrica 10,11,24,27 .…”

“…A termólise representa uma variante do método anteriormente mencionado. Baseia-se na análise dos produtos voláteis formados por termodecomposição dos hidroperóxidos, por cromatografia gasosa direta ou após derivatização com a 2,4,6-triclorofenilhidrazina 7,27 . A avaliação do teor de ácidos voláteis é usualmente feita por condutimetria.…”

Thermal stability ofThevetia peruviana juss seed oil

“…The oil sample heated to 220°C had values that were significantly lower and of a closer range than the other two treatments. Sebedio et al (2,3) and Saidai and Hammond (8) have shown that peroxides form ketols which, at higher temperatures, react to form unsaturated ketones. Furthermore, unheated Thevetia seed oil showed no absorption in the UV spectrum, whereas each heated oil sample absorbed with varying intensities at ~max of 260 and 265 nm.…”

Degradation of 5′-Ribonucleotides Caused by the Peroxidation of Methyl Linoleate in Dehydrated Systems

“…14) Furthermore, these hydroperoxides are decomposed to form mainly pentanal, hexanal, 2-heptanal and 2,4-decadiena1. 15 ) The contribution of hydroperoxides and various aldehydes to the degradation of IMP or GMP was then examined.…”