Relative Mass Defect Filtering of Mass Spectra: A Path to Discovery of Plant Specialized Metabolites1[OPEN]

Metabolite masses measured using LC-MS can be sorted into structural classes using relative mass defect filtering to accelerate the annotation of novel metabolites. The rapid identification of novel plant metabolites and assignments of newly discovered substances to natural product classes present the main bottlenecks to defining plant specialized phenotypes. Although mass spectrometry provides powerful support for metabolite discovery by measuring molecular masses, ambiguities in elemental formulas often fail to reveal the biosynthetic origins of specialized metabolites detected using liquid chromatography-mass spectrometry. A promising approach for mining liquid chromatography-mass spectrometry metabolite profiling data for specific metabolite classes is achieved by calculating relative mass defects (RMDs) from molecular and fragment ions. This strategy enabled the rapid recognition of an extensive range of terpenoid metabolites in complex plant tissue extracts and is independent of retention time, abundance, and elemental formula. Using RMD filtering and tandem mass spectrometry data analysis, 24 novel elemental formulas corresponding to glycosylated sesquiterpenoid metabolites were identified in extracts of the wild tomato Solanum habrochaites LA1777 trichomes. Extensive isomerism was revealed by ultra-high-performance liquid chromatography, leading to evidence of more than 200 distinct sesquiterpenoid metabolites. RMD filtering led to the recognition of the presence of glycosides of two unusual sesquiterpenoid cores that bear limited similarity to known sesquiterpenes in the genus Solanum. In addition, RMD filtering is readily applied to existing metabolomics databases and correctly classified the annotated terpenoid metabolites in the public metabolome database for Catharanthus roseus.

[1]  Victoria L. Challinor,et al.  Open-chain steroidal glycosides, a diverse class of plant saponins. , 2013, Natural product reports.

[2]  A. D. Jones,et al.  Bioassay-directed fractionation for discovery of bioactive neutral lipids guided by relative mass defect filtering and multiplexed collision-induced dissociation. , 2010, Rapid communications in mass spectrometry : RCM.

[3]  S. Piacente,et al.  New Antifungal Terpenoid Glycosides from Alibertia edulis (Rubiaceae) , 2008 .

[4]  Chhandak Basu,et al.  Plant terpenoids: applications and future potentials , 2008 .

[5]  I. E. Woodrow,et al.  α,β-Unsaturated monoterpene acid glucose esters: structural diversity, bioactivities and functional roles. , 2011, Phytochemistry.

[6]  Nathaniel D Hawkins,et al.  Metabolomic analysis of Arabidopsis reveals hemiterpenoid glycosides as products of a nitrate ion-regulated, carbon flux overflow , 2011, Proceedings of the National Academy of Sciences.

[7]  M. Gorman,et al.  Alkaloids of Vinca rosea Linn. (Catharanthus roseus G. Don.). V. Preparation and characterization of alkaloids. , 2006, Journal of the American Pharmaceutical Association. American Pharmaceutical Association.

[8]  N. Sahu,et al.  Advances in Structural Determination of Saponins and Terpenoid Glycosides , 2001 .

[9]  M. Claeys,et al.  Characterization of flavone and flavonol aglycones by collision‐induced dissociation tandem mass spectrometry , 1997 .

[10]  R. Verpoorte,et al.  Catharanthus terpenoid indole alkaloids: biosynthesis and regulation , 2007, Phytochemistry Reviews.

[11]  Lloyd W Sumner,et al.  Metabolic profiling of saponins in Medicago sativa and Medicago truncatula using HPLC coupled to an electrospray ion-trap mass spectrometer. , 2002, Phytochemistry.

[12]  S. O’Connor,et al.  Chemistry and biology of monoterpene indole alkaloid biosynthesis. , 2006, Natural product reports.

[13]  Hong-yu Zhang,et al.  Natural products and drug discovery , 2009, EMBO reports.

[14]  A. D. Jones,et al.  Identification of methylated flavonoid regioisomeric metabolites using enzymatic semisynthesis and liquid chromatography-tandem mass spectrometry , 2013, Metabolomics.

[15]  H. Pfander,et al.  Terpenoid glycosides. , 1991, Natural product reports.

[16]  L. Xuan,et al.  Cytotoxic Terpenoid and Immunosuppressive Phenolic Glycosides from the Root Bark of Dictamnus dasycarpus , 2002, Planta medica.

[17]  D. Huhman,et al.  Mass Spectrometry Strategies in Metabolomics* , 2011, The Journal of Biological Chemistry.

[18]  M. Qiu,et al.  Two New Triterpene Glycosides with Monomethyl Malonate Groups from the Rhizome of Cimifuga foetida L. , 2011, Molecules.

[19]  V. Wray,et al.  Levels of a Terpenoid Glycoside (Blumenin) and Cell Wall-Bound Phenolics in Some Cereal Mycorrhizas , 1995, Plant physiology.

[20]  J. Chappell.  Biochemistry and Molecular Biology of the Isoprenoid Biosynthetic Pathway in Plants , 1995 .

[21]  H. Ressom,et al.  LC-MS-based metabolomics. , 2012, Molecular bioSystems.

[22]  Keith E. J. Tyo,et al.  Terpenoids: opportunities for biosynthesis of natural product drugs using engineered microorganisms. , 2008, Molecular pharmaceutics.

[23]  P. Dixon,et al.  Medicinal Plants: A Public Resource for Metabolomics and Hypothesis Development , 2012, Metabolites.

[24]  I. Baldwin,et al.  Jasmonate and ppHsystemin Regulate Key Malonylation Steps in the Biosynthesis of 17-Hydroxygeranyllinalool Diterpene Glycosides, an Abundant and Effective Direct Defense against Herbivores in Nicotiana attenuata[W] , 2010, Plant Cell.

[25]  Oliver Fiehn,et al.  Seven Golden Rules for heuristic filtering of molecular formulas obtained by accurate mass spectrometry , 2007, BMC Bioinformatics.

[26]  Banibrata Ghosh,et al.  Comparative structural profiling of trichome specialized metabolites in tomato (Solanumlycopersicum) and S. habrochaites: acylsugar profiles revealed by UHPLC/MS and NMR , 2013, Metabolomics.

[27]  B. Fraga.  Natural sesquiterpenoids. , 2012, Natural product reports.

[28]  H. Bouwmeester,et al.  The seco-iridoid pathway from Catharanthus roseus , 2014, Nature Communications.

[29]  V. Dembitsky.  Astonishing diversity of natural surfactants: 7. Biologically active hemi- and monoterpenoid glycosides , 2006, Lipids.

[30]  Nigel W. Hardy,et al.  Proposed minimum reporting standards for chemical analysis , 2007, Metabolomics.

[31]  A. D. Jones,et al.  Sesquiterpenoid glycosides from glandular trichomes of the wild tomato relative Solanum habrochaites. , 2014, Phytochemistry.

[32]  J. Juvik,et al.  Identification of α-Santalenoic and Endo β-Bergamotenoic Acids as Moth Oviposition Stimulants from Wild Tomato Leaves , 1988 .

[33]  H. Pan,et al.  Isolation and Characterization of a New Ginsenoside from the Fresh Root of Panax Ginseng , 2010, Molecules.

[34]  Daisaku Ohta,et al.  Diversification of P450 genes during land plant evolution. , 2010, Annual review of plant biology.