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Structural characterization of a case-implicated contaminant, "Peak X," in commercial preparations of
Klaus Klarskov1, Kenneth L Johnson, Linda M Benson
1Biomedical Mass Spectrometry and Functional Proteomics Facility, Mayo Clinic, Rochester, Minnesota, USA.
Objective:
To determine the chemical structure of a contaminant, X1, previously found in eosinophilia myalgia syndrome case-implicated 5-hydroxytryptophan (5-OHTrp), and also present in over-the-counter (OTC) commercially available 5-OHTrp.
Methods:
Case-implicated 5-OHTrp as well as 6 OTC samples were subjected to accurate mass HPLC-mass spectrometry and HPLC-electrochemical detection, and reacted with reduced glutathione. Peak X1 was subsequently subjected to HPLC-tandem mass spectrometry (MS/MS), as well as the resulting nucleophilic glutathione product. All these data were compared with analysis carried out under identical conditions on authentic 4,5-tryptophan-dione (Trp-4,5D).
Results:
Based on accurate mass, tandem mass spectrometric analysis, and comparision with authentic standard compound analysis, X1 was determined to be 4,5-tryptophan-dione, a putative neurotoxin. The presence of X1 in OTC samples varied from 0.5 to 10.3% of the amount of Trp-4,5D present in case-implicated 5-OHTrp.
Conclusion:
Peak X1 was identified as the putative neurotoxin Trp-4,5D. It was found in case-implicated 5-OHTrp as well as 6 OTC samples. This gives some cause for concern in terms of the safety of such commercial preparations of 5-OHTrp.