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


CONCLUSIONS
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.
Klarskov
Klaus
K
Biomedical Mass Spectrometry and Functional Proteomics Facility, Mayo Clinic, Rochester, Minnesota, USA.
Johnson
Kenneth L
KL
Benson
Linda M
LM
Cragun
Jennifer D
JD
Gleich
Gerald J
GJ
Wrona
Monika
M
Jiang
Xiang-Rong
XR
Dryhurst
Glenn
G
Naylor
Stephen
S
D006916:5-Hydroxytryptophan / Q000009:adverse effects* / Q000032:analysis / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D004340:Drug Contamination; D016603:Eosinophilia-Myalgia Syndrome / Q000139:chemically induced*; D006801:Humans; D013058:Mass Spectrometry
D006916:5-Hydroxytryptophan