Analysis of phospholipid regioisomers from different food resources using ultra high performance liquid chromatography coupled with mass spectrometry and machine learning

Phospholipids (PL) play a vital role in human physiology and health. Widely present in food and diet, PL are important as both nutrients and emulsifiers, contributing to technological, nutritional and sensory properties of food. Addressing the global challenge of climate change and food security requires increasing biodiversity of food resources, which inevitably alters the PL in the diet. While many studies have revealed the sub-classes and molecular species of PL in food, the regioisomeric profiles remain largely unknown. This study aimed to analyse the regio-isomeric composition of PC as a dominating PL in a wide range of conventional and emerging food resources.

Lipid extraction using modified Foch method, and the total lipids were subjected to solid phase extraction to yield polar lipid fraction. The latter was analysed using reverse phase UHPLC-QTOF with electron spray ionization in negative mode, and the PC regioisomer composition was quantified based on collision-induced dissociation mass spectra using a machine learning software recently developed by our group. The findings demonstrated the suitability of the novel methods for nontargeted analysis of PC regioisomers in varying matrices. Milk of human, pig, and camel contained high content of PC 18:0/18:2. Within the molecular species PC 16_18:1, PC 18:1/16:0 dominated in human, pig and dog milk, whereas cow, goat and sheep milk had PC 16:0/18:1 as the major isomer. Food rich in plant proteins, such as legumes and cereals showed different PL isomer composition compared to food rich in animal proteins such as meat, egg, and fish, and significant variation was also found among species within each group. The significance of PL isomeric composition for food quality, nutrition and health deserves further study. The findings of this study improve the understanding of lipid biochemistry and has strong relevance to sustainable food and healthy diet.