Lipidomics of Algae and Human Plasma by Chromatography and Mass Spectrometry Techniques

The word lipidomics aims to characterize and quantify the lipids and as well as study their pathways and interactions with other biological molecules. In this thesis study, a GC-MS methodology was developed to analyze the fatty acid methyl esters produced by the algae, Scenedesmus dimorphus. This method involved extraction of the total lipids by modified Folch method, fractionation of these lipids by aminopropyl cartridges and their derivatization by BCl3-methanol. The method developed has been validated in terms of linear calibration ranges (0.500 to 500 muM for fatty acids, and 0.200 to 200 muM for glycerolipids), recoveries (≥ 86%), precision (≤ 9% CV) and accuracy (≤+/- 6% RE), and applied for the quantitation of fatty acids and glycerolipids in algae Scenedesmus dimorphus dried mass. This method was then extended to determine the quality of biodiesel. A linear regression modeling was performed using digestate, magnesium sulfate and potassium phosphates as the factors to determine their optimum levels. An optimum level of 1% digestate concentration supplemented with magnesium sulfate and potassium phosphates concentrations of 0.75 mM and 1.5 mM was determined from the predictions of the model. These procedures of lipid analysis were further used for the development of the shotgun methodology. A series of precursor and neutral loss scans were developed to determine the relative amounts of the glycerophospholipids and glycerolipids produced by the algae, S. dimorphus grown under two different growth media. Our results demonstrated significant changes in the levels of triacylglycerols (TAGs) between the cultures in the two media.;In the second part of the study, lipidomics approach was used to compare the compositional changes of lipids in plasma of Alzheimer's (AD) patients and normal cognitive controls. Statistical analysis of lipids (e.g. , principal component analysis and t-test) between the two groups revealed 14 glycerophospholipid species that had significant differences (p<0.005). Semi-quantitative analyses of these identified glycerophospholipids was achieved using internal standards specific for each lipid sub-class. These findings suggest that the perturbations in the Kennedy pathway due to oxidative stress in the brain of the AD patients was primarily responsible for the changes in the lipid species.