Diazo-carboxyl click chemistry enables rapid and sensitive quantification of carboxylic acid metabolites

Carboxylic acids are central metabolites in bioenergetics, signal transduction and post-translation protein regulation. Unlike its genomic and transcriptomic counterparts, the quest for metabolomic profiling in trace amounts of biomedical samples is prohibitively challenging largely due to the lack of sensitive and robust quantification schemes for carboxylic acids. Based on diazo-carboxyl click chemistry, here we demonstrate DQmB-HA method as a rapid derivatization strategy for the sensitive analysis of hydrophilic, low-molecular-weight carboxylic acids. To the investigated metabolites, DQmB-HA derivatization method renders 5 to 2,000-fold higher response on mass spectrometry along with improved chromatographic separation on commercial UHPLC-MS machines. Using this method, we present the near-single-cell analysis of carboxylic acid metabolites in mouse egg cells before and after fertilization. Malate, fumarate and {beta}-hydroxybutyrate were found to decrease in mouse zygotes. We also showcase the kinetic profiling of TCA-cycle intermediates inside adherent cells cultured in one well of 96-well plates during drug treatment. FCCP and AZD3965 were shown to have overlapped but different effects on the isotope labeling of carboxylic acids. Finally, we apply DQmB-HA method to plasma or serum samples (down to 5 L) from mice and humans collected on pathological and physiological conditions. The measured changes of succinate, {beta}-hydroxybutyrate, and lactate in blood corroborate previous literatures in ischemia-reperfusion injury mouse model, acute fasting-refeeding mouse model, and human individuals diagnosed with mitochondrial dysfunction diseases, respectively. Overall, DQmB-HA method offers a sensitive, rapid and user-friendly quantification scheme for carboxylic acid metabolites, paving the road toward the ultimate goals of single-cell metabolomic analysis and bedside monitoring of biofluid samples.