Liquid chromatography electrospray tandem mass spectrometry of amino acid conjugates of jasmonic acid under positive and negative ionisation

The positive and negative ion electrospray mass spectra of a series of (N)-jasmonoyl amino acid conjugates were measured by combined high performance liquid chromatography (HPLC)/mass spectrometry (MS), The mass spectra obtained of both positive and negative ions exhibit mostly a single abundant peak of [M + H](+) and [M - H](-), respectively, which indicates the molecular mass of the conjugate, From these ions detailed structural information can be obtained by liquid chromatography/tandem mass spectrometry. The positive daughter ion mass spectra obtained by collision-induced dissociation (CID) of [M + H](+) give information about both the jasmonoyl moiety and the amino acid component. The negative ion daughter spectra of [M - H](-) are dominated by an ion originating from the deprotonated amino acid. Therefore, the conjugating amino acid can structurally be assigned by both the positive and negative ion CID mass spectra.