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.