Analysis of the Amine Submetabolome Using Novel Isotope-Coded Pyrylium Salt Derivatization and LC-MS: Herbs and Cancer Tissues as Cases.

The amine submetabolome, including amino acids (AAs) and biogenic amines (BAs), is a class of small molecular compounds exhibiting important physiological activities. Here, a new pyrylium salt named 6,7-dimethoxy-3-methyl isochromenylium tetrafluoroborate ([ d 0 ]-DMMIC) with stable isotope-labeled reagents ([ d 3 ]-/[ d 6 ]-DMMIC) was designed and synthesized for amino compounds. [ d 0 ]-/[ d 3 ]-/[ d 6 ]-DMMIC-derivatized had a charged tag and formed a set of molecular ions with an increase of 3.02 m / z and the characteristic fragment ions of m / z 204.1:207.1:210.1. When DMMIC coupled with liquid chromatography-mass spectrometry (LC-MS), a systematic methodology evaluation for quantitation proved to have good linearity ( R 2 between 0.9904 and 0.9998), precision (interday: 2.2-21.9%; intraday: 1.0-19.7%), and accuracy (recovery: 71.8-108.8%) through the test AAs. Finally, the methods based on DMMIC and LC-MS demonstrated the advantaged application by the nontargeted screening of BAs in a common medicinal herb Senecio scandens and an analysis of metabolic differences among the amine submetabolomes between the carcinoma and paracarcinoma tissues of esophageal squamous cell carcinoma (ESCC). A total of 20 BA candidates were discovered in S. scandens as well as the finding of 13 amine metabolites might be the highest-potential differential metabolites in ESCC. The results showed the ability of DMMIC coupled with LC-MS to analyze the amine submetabolome in herbs and clinical tissues.