Beyond Autoxidation and Lipoxygenases: Fatty Acid Oxidation Products in Plant Oils,Journal of Agricultural and Food Chemistry

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Beyond Autoxidation and Lipoxygenases: Fatty Acid Oxidation Products in Plant Oils
Journal of Agricultural and Food Chemistry ( IF 5.7 ) Pub Date : 2023-08-25 , DOI: 10.1021/acs.jafc.3c02724
Elisabeth Koch ₁ , Ariane Löwen ₁ , Nadja Kampschulte ₁ , Kathrin Plitzko ₁ , Michelle Wiebel ₁ , Katharina M Rund ₁ , Ina Willenberg ₂ , Nils Helge Schebb ₁

Affiliation

For decades, research on oxidation of linoleic acid (LA, C18:2 n6) and α-linolenic acid (ALA, C18:3 n3) in plant oils has focused on autoxidatively formed and lipoxygenase-derived 9-hydro(pero)xy- and 13-hydro(pero)xy-LA and -ALA. Here, using a non-targeted approach, we show that other hydroxy fatty acids are more abundant in plant oils. Liquid chromatography–mass spectrometry and gas chromatography–mass spectrometry analyses unveiled highly abundant peaks in flaxseed and rapeseed oils. Using authentic reference standards, seven of the peaks were identified as 9-, 10-, 12-, 13-, and 15-HODE as well as 9- and 13-HOTrE. Additionally, six peaks were characterized based on the retention time, the exact mass of the [M–H]⁻ ion, and its fragment ions as 16-OH-C18:3, 18-OH-C18:3, three isomers of 12-OH-C18:2, and one of 15-OH-C18:2. 16-OH-C18:3 and 18-OH-C18:3 were tentatively identified as 16-OH-ALA and 18-OH-ALA, respectively, based on autoxidation and terminal hydroxylation of ALA using CYP4F2. Investigation of formation pathways suggests that fatty acid desaturase 3 is involved in the formation of the 12-OH-C18:2 isomers, 15-HODE, and its isomer. The dominantly occurring 12-OH-C18:2 isomer was identified as 12R,S-OH-9Z,15Z-octadecadienoic acid (densipolic acid) based on a synthetic standard. The characterized oxylipins occurred in cold-pressed flaxseed and rapeseed oils at concentrations of up to 0.1 g/100 g and thus about sixfold higher than the well-known 9-hydro(pero)xy- and 13-hydro(pero)xy-LA and -ALA. Concentrations in sunflower oil were lower but increased when oil was pressed from preheated seeds. Overall, this study provides fundamental new information about the occurrence of oxidized fatty acids in plant oils, having the potential to characterize their quality and authenticity.

中文翻译：

超越自氧化和脂氧合酶：植物油中的脂肪酸氧化产物

几十年来，植物油中亚油酸（LA，C18：2 n6）和α-亚麻酸（ALA，C18：3 n3）氧化的研究重点是自动氧化形成和脂加氧酶衍生的9-氢（过）xy-和13-氢(过)氧基-LA和-ALA。在这里，我们使用非靶向方法表明，其他羟基脂肪酸在植物油中含量更丰富。液相色谱-质谱和气相色谱-质谱分析揭示了亚麻籽油和菜籽油中高度丰富的峰。使用可靠的参考标准，其中七个峰被确定为 9-、10-、12-、13- 和 15-HODE 以及 9- 和 13-HOTrE。此外，还根据保留时间、[M–H] ⁻离子及其碎片离子（16-OH-C18:3、18-OH-C18:3、12 的三种异构体）对六个峰进行了表征。 -OH-C18:2，和15-OH-C18:2之一。基于使用 CYP4F2 对 ALA 进行自氧化和末端羟基化，16-OH-C18:3 和 18-OH-C18:3 分别初步鉴定为 16-OH-ALA 和 18-OH-ALA。对形成途径的研究表明，脂肪酸去饱和酶 3 参与 12-OH-C18:2 异构体、15-HODE 及其异构体的形成。根据合成标准，主要存在的 12-OH-C18:2 异构体被鉴定为 12 R , S -OH-9 Z ,15 Z -十八碳二烯酸（densipolilic 酸）。冷榨亚麻籽油和菜籽油中存在的特征性氧脂质浓度高达 0.1 g/100 g，因此比众所周知的 9-氢（过）xy- 和 13-氢（过）xy-LA 高约六倍和-ALA。葵花籽油的浓度较低，但当从预热的种子中压榨油时，葵花籽油的浓度会增加。总体而言，这项研究提供了有关植物油中氧化脂肪酸发生情况的基本新信息，有可能表征其质量和真实性。

更新日期：2023-08-25

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