Lipidome mapping of natural rubber: Detailed investigation into the influence of geographical origin and treatment using liquid chromatography and high-resolution tandem mass spectrometry

Discovering the non-isoprene components retained within the natural rubber (NR) matrix is essential to elucidate their role in modulating the viscoelastic properties of the raw material and the rheological behavior of the rubber-based materials, such as tyres in the automotive industry. Here, lipid's content, their identification and quantification were achieved by hydrophilic interaction liquid chromatography (HILIC) coupled to Fourier-transform (FT) orbital-trap tandem mass spectrometry (MS/MS) through electrospray ionization (ESI). Overall, 10 classes of phospholipids (PLs) and a few glycolipids (GLs) were characterized also in terms of regiochemistry including 7 species of fatty acids (FAs), 107 PLs and 6 GLs. Among the identified PLs, phosphatidylcholines (PCs), phosphatidylinositols (PIs), phosphatidylethanolamines (PEs) were detected, with a marked predominance of their lyso-forms, including lyso-N-acyl phosphatidylethanolamines (LNAPEs), lyso-phosphatidylserines (LPSs), and lyso-phosphatidic acids (LPAs). In addition, the presence of digalactosyl monoacylglycerols (DGMGs) was established. The identified FA species predominantly contained even numbers of carbon atoms, mainly C16 and C18, with varying degrees of unsaturation. By comparing various types of NR in terms of geographical origin (Thailand, Cameroon, Brazil) and different raw material treatment (acid, neutral and basic), a dissimilar content of lipids was reflected across the different sample groups.