title: Function and stability of abscisic acid acyl hydrazone conjugates by LC-MS2 of ex vivo samples.
abstract: We prepare a biotinylated conjugate of the ubiquitous plant hormone (S)-(+)-abscisic acid via an acyl hydrazone linkage at the C4' position and demonstrate in vivo cleavage of the otherwise stable acyl hydrazone linkage using LC-MS2. As part of a wider chemical genomic study, biological activity of the conjugate was assessed using standard epidermal peel and gravimetric transpiration assays, showing significant activity but at a level lower than the unconjugated hormone. When deuterated samples of the conjugate were fed to the plant, however, it was apparent by LC-MS2 experiments that significant levels of hydrolysis of the acyl hydrazone had taken place, contrary to in vitro stability assays in artificial sap. We conclude that abscisic acid is liberated in sufficient quantities to account for the observed physiological response and that LC-MS2 monitoring of conjugates is a simple and practical method by which such events may be assessed, whether in plants or other organisms.
authors.affiliation: Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Smith
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Clark
authors.forename: Richard
authors.initials: R
authors.lastname: Napier
authors.forename: Paul C
authors.initials: PC
authors.lastname: Taylor
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Thompson
authors.forename: Andrew
authors.initials: A
authors.lastname: Marsh
mesh_terms: D000040:Abscisic Acid / Q000737:chemistry* / Q000494:pharmacology*; D002853:Chromatography, Liquid; D034822:Commelina / Q000378:metabolism*; D006835:Hydrazones / Q000737:chemistry* / Q000494:pharmacology*; D006868:Hydrolysis; D018551:Solanum lycopersicum / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D010936:Plant Extracts / Q000032:analysis; D018515:Plant Leaves / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D018526:Plant Transpiration / Q000187:drug effects; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D006835:Hydrazones; D010936:Plant Extracts; D000040:Abscisic Acid