Identification of methylated flavonoid regioisomeric metabolites using enzymatic semisynthesis and liquid chromatography-tandem mass spectrometry |
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Authors: | Chao Li Adam Schmidt Eran Pichersky Feng Shi A. Daniel Jones |
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Affiliation: | 1.Department of Chemistry,Michigan State University,East Lansing,USA;2.Department of Molecular, Cellular, and Developmental Biology,University of Michigan,Ann Arbor,USA;3.Department of Biochemistry and Molecular Biology,Michigan State University,East Lansing,USA;4.Department of Biochemistry and Molecular Biology,Michigan State University,East Lansing,USA |
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Abstract: | Discrimination of isomeric methylated metabolites is an important step toward identifying genes responsible for methylation, but presents substantial challenges because authentic standards are often unavailable and mass spectra of isomers have been considered indistinguishable. In this report, an approach is described for identifying methyl group positions in multiply methylated flavonoid metabolites using combinations of tandem mass spectrometry, liquid chromatography retention, and site-selective methylation by recombinant O-methyltransferases from Solanum habrochaites LA1777. The basis for observed fragment ions in tandem mass spectra of multiply methylated myricetin was further established using enzymatic incorporation of deuterium-labeled methyl groups using S-adenosylmethionine-d 3 as precursor. |
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