Analysis of Fatty Acid Esters of Hydroxyl Fatty Acid in Nut Oils and Other Plant Oils

Oils and lipids are common food components and efficient sources of energy. Both the quantity and the quality of oils and lipids are important with regard to health and disease. Fatty acid ester of hydroxy fatty acid (FAHFA) is a novel lipid class that was discovered as an endogenous lipid; FAHFAs have shown anti-diabetic effects in a mammalian system. We analyzed the overall FAHFA composition in nut oils and other common oils: almond (raw, roasted), walnut, peanut, olive, palm, soybean, and rapeseed oils. We developed a method of liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry (LC-ESI/MS/MS) for a comprehensive target analysis of FAHFAs. The analysis revealed wide variation in the FAHFA profiles (15 compounds and 62 peaks). For 7-11 compounds of FAHFA, a total level of 8-29 pmol/mg oil was detected in nuts oils; for 11 compounds, 4.9 pmol/mg oil was detected in olive oil, and for 4-9 compounds, < 2 pmol/mg oil was detected in palm, soy, and rapeseed oils. The major FAHFAs were FAHFA 36:3, FAHFA 36:2, and FAHFA 36:4 in nut oil, FAHFA 36:2, FAHFA 34:1, and FAHFA 36:1 in olive oil, and FAHFA 32:1, FAHFA 34:0, FAHFA 36:0, and FAHFA 36:1 in all of the common oils. The composition of FAHFAs in nut oils is mainly unsaturated fatty acids, whereas those in olive oil are unsaturated fatty acids and saturated fatty acids. The composition of FAHFAs in common oils was mainly saturated fats. This is the first report to demonstrate the quality and quantity of the FAHFAs in the nut oils. Nuts have been described to be a great source of many nutrients and to be beneficial for our health. Our present findings comprise additional evidence that the intake of nuts in daily diets may prevent metabolic and inflammatory-based diseases.