title: A facile means for the identification of indolic compounds from plant tissues.
abstract: The bulk of indole-3-acetic acid (IAA) in plants is found in the form of conjugated molecules, yet past research on identifying these compounds has largely relied on methods that were both laborious and inefficient. Using recent advances in analytical instrumentation, we have developed a simple yet powerful liquid chromatography-mass spectrometry (LC-MS)-based method for the facile characterization of the small IAA conjugate profile of plants. The method uses the well-known quinolinium ion (m/z 130.0651) generated in MS processes as a signature with high mass accuracy that can be used to screen plant extracts for indolic compounds, including IAA conjugates. We reinvestigated Glycine max (soybean) for its indoles and found indole-3-acetyl-trytophan (IA-Trp) in addition to the already known indole-3-acetyl-aspartic acid (IA-Asp) and indole-3-acetyl-glutamic acid (IA-Glu) conjugates. Surprisingly, several organic acid conjugates of tryptophan were also discovered, many of which have not been reported in planta before. These compounds may have important physiological roles in tryptophan metabolism, which in turn can affect human nutrition. We also demonstrated the general applicability of this method by identifying indolic compounds in different plant tissues of diverse phylogenetic origins. It involves minimal sample preparation but can work in conjunction with sample enrichment techniques. This method enables quick screening of IAA conjugates in both previously characterized as well as uncharacterized species, and facilitates the identification of indolic compounds in general.
authors.affiliation: Plant Biological Sciences Graduate Program, Department of Horticultural Science, Microbial and Plant Genomics Institute, University of Minnesota, 1970 Folwell Avenue, Saint Paul, MN, 55108, USA.
authors.forename: Peng
authors.initials: P
authors.lastname: Yu
authors.forename: Adrian D
authors.initials: AD
authors.lastname: Hegeman
authors.forename: Jerry D
authors.initials: JD
authors.lastname: Cohen
mesh_terms: D000596:Amino Acids / Q000737:chemistry / Q000302:isolation & purification; D001224:Aspartic Acid / Q000737:chemistry / Q000302:isolation & purification; D002853:Chromatography, Liquid; D003059:Cocos / Q000737:chemistry; D035264:Flowers / Q000737:chemistry; D020441:Ginkgo biloba / Q000737:chemistry; D007210:Indoleacetic Acids / Q000737:chemistry* / Q000302:isolation & purification; D007211:Indoles / Q000737:chemistry* / Q000302:isolation & purification; D018551:Solanum lycopersicum / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D018515:Plant Leaves / Q000737:chemistry; D010944:Plants / Q000737:chemistry*; D014364:Tryptophan / Q000737:chemistry
chemical_list: D000596:Amino Acids; D007210:Indoleacetic Acids; D007211:Indoles; D001224:Aspartic Acid; C030737:indoleacetic acid; D014364:Tryptophan
keywords: Cocos nucifera; Ginkgo biloba; Glycine max; IAA conjugates; LC-MS; Orbitrap; Solanum lycopersicum; auxin; indole-3-acetyl-trytophan; technical advance