ORIGINAL PAPER Analysis of Fatty Acid Esters of Hydroxyl Fatty Acid in Selected Plant Food Ana-Marija Liberati-Čizmek 1 & Mirna Biluš 2 & Antun Lovro Brkić 3 & Irena Colić Barić 4 & Miro Bakula 1 & Amela Hozić 5 & Mario Cindrić 5 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Metabolic syndrome, characterized by obesity, low-grade inflammation, insulin resistance, hyperglycemia, dyslipidemia and hypertension, is a major risk factor for cardiovascular mortality. Preclinical studies on recently discovered classes of lipids – fatty acid esters of hydroxy fatty acids (FAHFA) have revealed their anti-inflammatory and insulin-sensitizing potential. The FAHFA levels are significantly decreased in insulin-resistant individuals, their application exhibited anti-inflammatory effects and restor- ing the glucose-insulin homeostasis. The aim of our research was to analyze the overall FAHFA composition in a common diet, as only a partial FAHFA composition has been revealed so far (only the PAHSA subclass was analyzed in a few foods). A new approach to the FAHFAs analysis includes nano-LC and post-column modifier followed by negative ion mass spectrometry, in order to obtain maximum sensitivity. Analysis of different foods – oat (whole grain, coarse flakes and fine flakes), apple, clementine, lemon, strawberry, blueberry, mango, kiwi, avocado, pineapple, banana, onion, garlic, cherry tomato, carrot, parsley root, pepper and radish – exhibited wide inter-food variation in the FAHFA profiles. Sixteen analyzed FAHFAs (palmitic, oleic, palmitoleic and stearic hydroxy-esters) showed microgram to low nanogram levels (0.165 ng/g – 32 μg/g FW), with the highest abundancy in oat, clementine, garlic and pineapple. Stearic acid hydroxy stearic acid (SAHSA) was the most abundant FAHFA, especially in the food with antioxidative, anti-inflammatory and beneficial metabolic effects. In contrary, the PAHSA - previously proven to have the strongest antihyperglycemic and insulin-sensitizing effects, was not present in some foods (radish, avocado, mango, lemon, cherry tomato, kiwi). Our study proves the importance of overall FAHFA analysis in food (especially in a functional food), because of their potential metabolic benefits and possible future incorporation in special diets. Keywords Bioactive food compounds . Fatty acid esters of hydroxyl fatty acids . FAHFA composition . Food analysis . Negative ion mass spectrometry Abbreviations FAHFA Fatty acid esters of hydroxy fatty acids OAHOA Oleic acid hydroxy oleic acid OAHPA Oleic acid hydroxy palmitic acid OAHPO Oleic acid hxdroxy palmitoleic acid OAHSA Oleic acid hydroxy stearic acid PAHPA Palmitic acid hydroxy palmitic acid PAHPO Palmitic acid hydroxy palmitoleic acid PAHOA Palmitic acid hydroxy oleic acid PAHSA Palmitic acid hydroxy stearic acid POHOA Palmitoleic acid hydroxy oleic acid POHPA Palmitoleic acid hydroxy palmitic acid POHPO Palmitoleic acid hydroxy palmitoleic acid POHSA Palmitoleic acid hydroxy stearic acid SAHOA Stearic acid hydroxy oleic acid SAHPA Stearic acid hydroxy palmitic acid Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11130-019-00728-8) contains supplementary material, which is available to authorized users. * Mario Cindrić mcindric@irb.hr 1 Department for Endocrinology and Diabetology in Clinical Hospital Sveti Duh, Zagreb, Croatia 2 BIOCentre, Central Lab Services, Zagreb, Croatia 3 Department of Physics, Faculty of Science, Zagreb, Croatia 4 Department for Food Quality Control, Faculty of Food Technology and Biotechnology, Zagreb, Croatia 5 Division of Molecular Medicine Ruđer Bošković Institute, Zagreb, Croatia Plant Foods for Human Nutrition https://doi.org/10.1007/s11130-019-00728-8