A novel chiral stationary phase LC-MS/MS method to evaluate oxidation mechanisms of edible oils

Abstract

The elucidation of lipid oxidation mechanisms of food is vital. In certain lipids, characteristic lipid hydroperoxide isomers are formed by different oxidation mechanisms (i.e., photo-oxidation or auto-oxidation). For example, linoleic acid is photo-oxidized to 13-9Z, 11E-hydroperoxyoctadecadienoic acid (HPODE), 12-9Z,13E-HPODE, 10-8E,12Z-HPODE and 9-10E,12Z-HPODE, whereas 13-9Z, 11E-HPODE, 13-9E,11E-HPODE, 9-10E,12Z-HPODE and 9-10E,12E-HPODE are formed by auto-oxidation. Therefore, we considered that oxidation mechanisms could be evaluated by analyzing these characteristic positional and cis/trans lipid hydroperoxide isomers. In this study, we developed a novel chiral stationary phase LC-MS/MS (CSP-LC-MS/MS) method to analyze the positional and cis/trans isomers of HPODE, with the use of a chiral column and sodium ion. Also, as an application of the method, either light-exposed or heated edible oils were treated with lipase to hydrolyze triacylglycerols. The resultant fatty acids including HPODE isomers were analyzed with the developed method. As a result, HPODE isomers characteristic to photo-oxidation were certainly detected in light-exposed edible oils. On the other hand, in heated edible oils, the HPODE isomers characteristic to auto-oxidation were largely increased. Thus, the combination of the developed CSP-LC-MS/MS method with lipase proves to be a powerful tool to evaluate the involvement and mechanisms of lipid oxidation in the process of food deterioration.

Kinetic Study of the Scavenging Reaction of the Aroxyl Radical by Eight Kinds of Vegetable Oils in Solution

“…values observed for vegetable oils 1–8 with the k s ( f ) (Calcd.) values calculated using the rate constants () and the concentrations ([AOH‐ i ]) of each AOH included in vegetable oils 1–8, measurements of the concentrations (in mg 100 g −1 ) of four Tocs and four Toc‐3s were performed (Ito et al, ; Mukai et al, ). The results obtained are listed in Table .…”

“…Concentrations of α‐, β‐, γ‐, and δ‐Tocs and ‐Toc‐3s in vegetable oils 1–8 were determined using HPLC–MS/MS, as reported in a previous study (Ito et al, ). Briefly, 100 mg of edible oil was weighed and dissolved in 2 mL of n ‐hexane.…”

“…Second, the rate constants ( k s ( f ) and k s ( t 1/2 )) for seven vitamin E homologs (α‐, β‐, γ‐, and δ‐Tocs and α‐, γ‐, and δ‐Toc‐3s) were also measured in the mixed solvent (see Table ). Third, the concentrations (in mg 100 g −1 ) of α‐, β‐, γ‐, and δ‐Tocs and ‐Toc‐3s included in vegetable oils 1–8 were determined using high performance liquid chromatography‐mass spectrometry/mass spectrometry (HPLC‐MS/MS) (Ito et al, ). Furthermore, comparison of the k s ( f ) values observed for the above vegetable oils 1–8 with the sum of the product of the values obtained for each AOH‐ i (i.e., four Tocs and three Toc‐3s) and the concentration ([AOH‐ i ]/10 5 ) of AOH‐ i included in the vegetable oils was performed, to ascertain the validity of the ARAC assay method developed (Mukai et al, ; Nagaoka et al, ).…”

Kinetic Study of Singlet-Oxygen Quenching and Aroxyl-Radical Scavenging Activities of Vitamin E Homologs and Fatty Acids Present in Vegetable Oils

“…In the present study, first, concentrations of nine fatty acids 1 -9 i.e., Acid-i i 1 -9 contained in vegetable oils 1 -8 were determined, via gas chromatography GC 34,35 . Second, measurements of the rate constants k Q LH S and k Q LH t 1/2 were performed for five fatty acid esters LH I -V Fig.…”

Evaluation of squalene oxidation mechanisms in human skin surface lipids and shark liver oil supplements

“…We previously reported the analysis of SQOOH isomers in human SSLs by using LC−MS/MS with atmospheric pressure chemical ionization (APCI), but due to the nature of APCI fragmentation, fragment ions with similar patterns were produced, making it difficult to selectively analyze SQOOH isomers . Thus, we recently developed an improved method that can selectively and sensitively analyze SQOOH isomers on the basis of evidence that the analysis of sodium adducts during LC−MS/MS analysis enables the selective analysis of other lipid hydroperoxide isomers . With the use of this method, we investigated the oxidation mechanisms of squalene and identified that singlet oxygen oxidation of squalene forms six SQOOH isomers in nearly equal amounts, whereas free radical oxidation mainly forms 2‐ and 3‐OOH‐SQ .…”