Identification of methylhexaneamine by GC high-resolution TOFMS and soft ionization.

UNLABELLED: Methylhexaneamine (MHA) is a stimulant that is added to dietary supplements and its safety is an on-going debate, prompting the World Anti-Doping Agency to add it to the 2010 prohibited list. Gas chromatography-low resolution mass spectrometry (GC-MS) with electron ionization (EI) requires derivatization to convert MHA into a less volatile compound, and a 2-3 min solvent delay to prevent filament damage. Without derivatization, the EI mass spectrum of MHA, which exhibits an abundant immonium ion at m/z 44 and no other fragment ions with relative intensity >10%, is very similar to the EI mass spectra of 2-aminoheptane, 1,4-dimethylamylamine, and n-hexylmethylamine. When using derivatization with trifluoroacetic anhydride (TFAA) and GC-high resolution time-of-flight mass spectrometry with soft ionization, the derivatized MHA diastereoisomers can be distinguished from the trifluoroacetyl-derivatives of 1-aminoheptane, 2-aminoheptane, 1,4-dimethylamylamine (1,4-DMAA) and n-hexylmethylamine. Several nutritional supplements were analysed for MHA by this technique and the results of the measurements are presented here. KEYWORDS: GC high-resolution TOFMS; Soft-ionization; Methylhexaneamine; Nutritional supplements.

Unexpected contribution of cytochrome P450 enzymes CYP11B2 and CYP21, as well as CYP3A4 in xenobiotic androgen elimination - insights from metandienone metabolism.

The metabolism of a variety of anabolic steroids frequently misused for doping purposes has been investigated in the last years. This research mainly focused on main and long-term metabolites suitable for detection, but detailed clearance mechanisms have rarely been elucidated. Recent studies on metandienone focused on the identification of 17ß-hydroxymethyl-17α-methyl-18-norandrosta-1,4,13-trien-3-one (20ßOH-NorMD) as long-term metabolite, however, the metabolic pathway of its generation remained unclear. Metandienone and its Wagner-Meerwein rearrangement product 17,17-dimethyl-18-norandrosta-1,4,13-trien-3-one (NorMD) were hydroxylated by different human cytochrome P450 enzymes (CYPs). Some of their hydroxylation products were chemically synthesized and characterized by mass spectrometry to allow for their trace detection in urine samples. Following oral administration of metandienone or NorMD in one human volunteer each the post administration urines were checked for the presence of those hydroxylated metabolites using GC-MS/MS analysis. The human mitochondrial steroid hydroxylating enzymes CYP11B1 and CYP11B2 were capable to metabolize metandienone leading to the formation of 11ß-hydroxymetandienone and 18-hydroxymetandienone. Following Wagner-Meerwein rearrangement, the resulting products could be assigned to 20ßOH-NorMD and 11ßOH-NorMD. The contribution of CYP11B1 and CYP11B2 in human metabolism of metandienone was confirmed by analysis of post-administration samples of metandienone and NorMD. Combined with the results from a previous study, enzymatic pathways were identified that involve CYP21 and CYP3A4 in the hydroxylation of NorMD, while CYP21, CYP3A4 and CYP11B2 take part in 20ßOH-NorMD generation from MD. The current study represents a valuable contribution to the elucidation of clearance mechanisms of anabolic steroids and also indicates that mainly non-liver CYPs seem to be involved in these processes.