Structural characterization of a case-implicated contaminant, "Peak X," in commercial preparations of 5-hydroxytryptophan.

Abstract

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. 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). 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. 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.