title: Metabolomics meets functional assays: coupling LC-MS and microfluidic cell-based receptor-ligand analyses.
abstract: BACKGROUND
  Metabolomics has become a valuable tool in many research areas. However, generating metabolomics-based biochemical profiles without any related bioactivity is only of indirect value in understanding a biological process. Therefore, metabolomics research could greatly benefit from tools that directly determine the bioactivity of the detected compounds.
  
  
  OBJECTIVE
  We aimed to combine LC-MS metabolomics with a cell based receptor assay. This combination could increase the understanding of biological processes and may provide novel opportunities for functional metabolomics.
  
  
  METHODS
  We developed a flow through biosensor with human cells expressing both the TRPV1, a calcium ion channel which responds to capsaicin, and the fluorescent intracellular calcium ion reporter, YC3.6. We have analysed three contrastingCapsicumvarieties. Two were selected with contrasting degrees of spiciness for characterization by HPLC coupled to high mass resolution MS. Subsequently, the biosensor was then used to link individual pepper compounds with TRPV1 activity.
  
  
  RESULTS
  Among the compounds in the crude pepper fruit extracts, we confirmed capsaicin and also identified both nordihydrocapsaicin and dihydrocapsaicin as true agonists of the TRPV1 receptor. Furthermore, the biosensor was able to detect receptor activity in extracts of bothCapsicumfruits as well as a commercial product. Sensitivity of the biosensor to this commercial product was similar to the sensory threshold of a human sensory panel.
  
  
  CONCLUSIONS
  Our results demonstrate that the TRPV1 biosensor is suitable for detecting bioactive metabolites. Novel opportunities may lie in the development of a continuous functional assay, where the biosensor is directly coupled to the LC-MS.
authors.affiliation: BU Bioscience, WageningenUR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: M G L
authors.initials: MGL
authors.lastname: Henquet
authors.affiliation: BU Bioscience, WageningenUR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.|Laboratory of Plant Physiology, WageningenUR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Roelse
authors.affiliation: BU Bioscience, WageningenUR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.|Netherlands Metabolomics Centre, Einsteinweg 55, 3335 CC Leiden, The Netherlands.
authors.forename: R C H
authors.initials: RCH
authors.lastname: de Vos
authors.affiliation: BU Bioscience, WageningenUR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Schipper
authors.affiliation: BU Bioscience, WageningenUR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: G
authors.initials: G
authors.lastname: Polder
authors.affiliation: Laboratory of Cell Biology, WageningenUR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: N C A
authors.initials: NCA
authors.lastname: de Ruijter
authors.affiliation: BU Bioscience, WageningenUR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.|Netherlands Metabolomics Centre, Einsteinweg 55, 3335 CC Leiden, The Netherlands.|Laboratory of Plant Physiology, WageningenUR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: R D
authors.initials: RD
authors.lastname: Hall
authors.affiliation: BU Bioscience, WageningenUR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: M A
authors.initials: MA
authors.lastname: Jongsma
keywords: Bioactivity; Capsaicin; Functional metabolomics; Receptor-ligand screening; TRPV1