Short-chain carboxylic acids, aldehydes, and ketones are important intermediates and end products of many metabolic processes. Their levels in biofluids and tissues can reflect the status of specific metabolic reactions, the homeostasis of whole metabolic system, and the well-being of a biological entity. Traditionally, GC-MS has been widely used for analyzing carboxylic acids, aldehydes, and ketones in biological samples after chemical derivatization. However, due to poor compatibility of common GC columns with water, the derivatization process in GC-MS is often complicated and time consuming, especially for the metabolites in biofluids and tissues. Recently, new chemical derivatization techniques have been developed to enhance the sensitivity and performance of LC-MS for analyzing these metabolites. In this study, the use of 2-hydrazinoquinoline (HQ) as a novel derivatization agent for LC-MS analysis of carboxylic acids, aldehydes, and ketones in biological samples was explored, and the conditions for the derivatization reaction were optimized. The metabolites in urine, serum, and tissue extracts can be conveniently derivatized in a 60-min process. The formation of carboxylic acid derivatives is attributed to the esterification reaction between HQ and carboxyl group, while the production of aldehyde and ketone derivatives is through the formation of Schiff bases between HQ and carbonyl group. Compared to other known hydrazine derivatization agents, including 2-hydrazinopyridine, 2-picolylamine and dansyl hydrazine, HQ can react with a broader spectrum of intermediary metabolites in biological samples, and can achieve better chromatographic performance in reversed phase LC system and higher ionization efficiency in electrospray source. Using this HQ-based approach, the metabolic disorder induced by streptozotocin-elicited diabetes was examined by the LC-MS-based metabolomics. The results showed the time-dependent separation of mouse urine samples from STZ treatment in a multivariate model of urinary metabolites. Both known and novel small-molecule biomarkers associated with STZ-induced ketoacidosis were conveniently identified and subsequently elucidated, reflecting the dramatic changes in nutrient (glucose, amino acid, and lipid) and energy metabolism after STZ treatment. Overall, HQ derivatization of carboxylic acids, aldehydes, and ketones can be an effective platform for the LC-MS-based metabolomic investigation of endogenous metabolism.
University of Minnesota M.S. thesis July 2013. Major: Nutrition. Advisor: Chi Chen. 1 computer file (PDF); x, 84 pages.
2-hydrazinoquinoline as a novel derivatization agent for LC-MS-based metabolomic investigation of ketoacidosis in streptozotocin-elicited diabetes.
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