Analysis of nonvolatile lipid oxidation products in vegetable oils by normal‐phase high‐performance liquid chromatography with mass spectrometric detection

Abstract

Nonvolatile triacylglyceride (TAG) oxidation products play an important role in the oxidative degradation of lipids. They serve as a reservoir of oxygen-containing species and hence can act as off-flavor precursors or as initiators for further oxidation reactions. Possible nonvolatile lipid oxidation products are TAG with a hydroperoxy, hydroxy, epoxy, or oxo (ketone or aldehyde) group or combination of these groups. The breakdown of TAG hydroperoxides yields nonvolatile glyceride species with two intact fatty acid chains and one short chain mostly ending in an aldehyde or hydroxy group (2 1 / 2 glycerides). By means of normal-phase high-performance liquid chromatography (HPLC) with mass spectrometric (MS) detection, nonvolatile lipid oxidation products can be separated according to polarity. This results in separation into classes of TAG oxidation products, such as epoxy-TAG, oxo-TAG, hydroperoxy-TAG, hydroxy-TAG and 2 1 / 2 glycerides, which can be identified using selected ion chromatograms. The retention times of TAG oxidation products on the normal-phase HPLC system and the signal intensity of the MS detector are stable enough to enable quantitative analysis based on external calibration. The normal-phase HPLC-MS method is very suitable for the characterization and quantitation of nonvolatile TAG oxidation products in oxidized TAG reference compounds as well as in real oils or oil phases isolated from emulsions, spreads, or other fat-based food products. This method can give detailed information for the study of lipid oxidation mechanisms.

Formation of triacylglycerol core aldehydes during rapid oxidation of corn and sunflower oils with tert‐butyl hydroperoxide/Fe2+

“…On the basis of previous work with standard oxotriacylglycerols (22,42), the earlier eluted peak was attributed to an aldehyde in the secondary position and the later eluted peak to an aldehyde in the primary position of the oxidized triacylglycerol molecule. A functional group in the sn-2 position is known to exert higher polarity than a similar group in the sn-1 or sn-3 position of the triacylglycerol molecule (22,43,44).…”

“…These compounds could have been formed in a termination reaction between a tert-butylhydroperoxy radical and an alkenyl radical or between a lipid hydroperoxy radical and the tert-butyl radical. The formation of the tert-butyl derivatives of the lipid hydroperoxides has a precedent in the existence of di-tert-butyl peroxide (40), as well as in the formation of cyclic peroxides during decomposition of linoleate hydroperoxides (31,48) and tocopherol adducts (42). Furthermore, Miyashita et al (31) have demonstrated that oxygenation of methyl linoleate hydroperoxides yields dimers composed of octadecadienoate and octadecenoate moieties crosslinked through either ether or peroxy linkages across the 9-or 13-positions.…”

Quantitative Profiling of Major Neutral Lipid Classes in Human Meibum by Direct Infusion Electrospray Ionization Mass Spectrometry

“…[60][61][62][63][64][65] In our study, NaI appeared to be ideal for the detection of these neutral lipids in the mixture of chloroform and methanol. NaI has been used as the additive by two groups for enhanced ESI-MS detection of polar plasmenyl phosphati- 66 and phosphatidylethanolamine 67 and one group for nonpolar triacylglycerols 68 ; however, no rationale for choosing NaI over other sodium salts as the additive was offered by these groups. We attribute such enhancement primarily to two reasons.…”

Neutral lipids in non‐starch lipid and starch lipid extracts from Portuguese sourdough bread

“…The putative assignment of non-identified peaks (NIP) to core aldehydes and other non-volatile oxidation products was excluded by comparing to the NP-HPLC data made available by SteenhorstSlikkerveer et al [49]. Table 3.…”