Application of high-resolution, two-dimensional H-1 and C-13 nuclear magnetic resonance techniques to the characterization of lipid oxidation products in autoxidized linoleoyl/linolenoylglycerols

Subjection of polyunsaturated fatty acid (PUFA)rich culinary oils to standa rd frying episodes generates a range of lipid oxidation products (LOP), inc luding saturated and alpha,beta-unsaturated aldehydes which arise from the thermally induced fragmentation of conjugated hydroperoxydiene precursors. Since such LOP are damaging to human health, we have employed high-resoluti on, two-dimensional H-1-H-1 relayed coherence transfer, H-1-H-1 total corre lation, H-1-C-13 heteronuclear multiple quantum correlation, and H-1-H-1 J- resolved nuclear magnetic resonance (NMR) spectroscopic techniques to furth er elucidate the molecular structures of these components present in (i) a model linoleoylglycerol compound (1,3-dilinolein) allowed to autoxidize at ambient temperature and (ii) PU FA-rich culinary oils subjected to repeated frying episodes. The above techniques readily facilitate the resolution of selected vinylic and aldehydic resonances of LOP which appear as complex o verlapping patterns in conventional one-dimensional spectra, particularly w hen employed in combination with solvent-induced spectral shift modificatio ns. Hence; much useful multicomponent information regarding the identity an d/or classification of glycerol-bound conjugated hydroperoxydiene and hydro xydiene adducts, and saturated and alpha,beta-unsaturated aldehydes, presen t in autoxidized PUFA matrices is provided by these NM methods. Such molecu lar information is of much value to researchers investigating the deleterio us health effects of LOP available in the diet.