82846-48-8Relevant academic research and scientific papers
Preparation of fatty acid cholesterol ester hydroperoxides by photosensitized oxidation
El Hafidi,Michel,Bascoul,Crastes De Paulet
, p. 127 - 138 (2007/10/03)
Preparation of fatty acid cholesterol ester hydroperoxides was undertaken with the purpose of evaluating their biological effects on cell growth. Cholesterol stearate, oleate, linoleate and α-linolenate were oxidized using methylene blue as a photosensitizer. The structures of all compounds were established by mass spectrometry and by nuclear magnetic resonance. The photosensitized oxidation of cholesterol oleate gave two hydroperoxide isomers: 9-hydroperoxy-trans-10-octadecenoate, and 10-hydroperoxy-trans-8-octadecenoate. In the case of the cholesterol linoleate, hydroperoxide isomers formed were: 9-hydroperoxy-trans-10, cis-12-octadecadienoate; 10-hydroperoxy-trans-8, cis-12-octadecadienoate; 12-hydroperoxy-cis-9, trans-13-octadecadienoate; 13-hydroperoxy-cis-9, trans-11-octadecadienoate. The oxidation of the cholesterol α-linolenate gave a mixture of six hydroperoxide isomers, at positions 9, 10, 12, 13, 15 and 16 of the fatty acid chain. The photosensitized oxidation of cholesterol stearate produced a formation of hydroperoxide at position 5α of cholesterol. The same hydroperoxide isomers on the fatty acid chain were obtained as described in the literature for the fatty acid methyl esters. Copyright (C) 1999 Elsevier Science Ireland Ltd.
Homolytic and Heterolytic Scission of Organic Hydroperoxides by (meso-Tetraphenylporphinato)iron(III) and Its Relation to Olefin Epoxidation
Labeque, Regine,Marnett, Lawrence J.
, p. 6621 - 6627 (2007/10/02)
Reaction of 10-hydroperoxyoctadeca-8,12-dienoic acid (10-OOH-18:2) with chloro(meso-tetraphenylporphinato)iron(III) (Fe(3+)-TPP) in CH2Cl2 produces two products identified as 10-oxodec-8-enoic acid (10-oxo-10:1) and 10-oxooctadeca-8,12-dienoic acid (10-oxo-18:2).These compounds are derived from an alkoxyl radical intermediate generated by homolytic cleavage of 10-OOH-18:2.Only a trace of the heterolytic cleavage product 10-hydroxyoctadeca-8,12-dienoic acid (10-OH-18:2) is observed.Inclusion of imidazole alters the product profile so that 10-OH-18:2 is the majorproduct (62percent).Reaction of 10-OOH-18:2 or t-BuOOH (0.05 M) with Fe(3+)-TPP (0.001 M) and cis-stilbene (5 M) produces trans-stilbene oxide as the only oxidation product (55percent based on hydroperoxide).Oxidation in the presence of imidazole (0.3 M) produces approximately equal amounts of cis-stilbene oxide (22percent) and trans-stilbene oxide (23percent).Butylated hydroxytoluene inhibits formation of both epoxides from cis-stilbene whereas p-methoxyanisole selectively inhibits formation of cis-stilbene oxide.The data indicate that two separate oxidizing agents are produced in the reaction of hydroperoxides with Fe(3+)-TPP.In the absence of imidazole, Fe(3+)-TPP cleaves 10-OOH-18:2 and t-BuOOH homolytically to alkoxyl radicals and Fe(4+)=O.TPP.Both species oxidize the hydroperoxide to peroxyl radicals that epoxidize cis-stilbene nonstereospecifically.In the presence of imidazole, Fe(3+)-TPP also cleaves the hydroperoxides heterolytically to alcohol and Fe(4+)=O.TPP.+, which epoxidizes cis-stilbene stereospecifically.The results reconcile apparently conflicting observations in the literature and suggest that the pathway of hydroperoxidecleavage by heme complexes and heme proteins is a sensitive function of the environment of the heme.
