Epoxidation of the methamphetamine pyrolysis product, trans-phenylpropene, to trans-phenylpropylene oxide by CYP enzymes and stereoselective glutathione adduct formation.

Pyrolytic products of smoked methamphetamine hydrochloride are well established. Among the various degradation products formed, trans-phenylpropene (trans-beta-methylstyrene) is structurally similar to styrene analogues known to be bioactivated by CYP enzymes. In human liver microsomes, trans-phenylpropene was converted to the epoxide trans-phenylpropylene oxide (trans-2-methyl-3-phenyloxirane) and cinnamyl alcohol. Incubation of trans-phenylpropene with microsomes in the presence of enzyme-specific P450 enzyme inhibitors indicated the involvement of CYP2E1, CYP1A2, and CYP3A4 enzymes. Both (R,R)-phenylpropylene oxide and (S,S)-phenylpropylene oxide were formed in human liver microsomal preparations. Enantiomers of trans-phenylpropylene oxide were stereoselectively and regioselectively conjugated in a Phase II drug metabolism reaction catalyzed by human liver cytosolic enzymes consisting of conjugation with glutathione. The structure of the phenylpropylene oxide-glutathione adduct is consistent with nucleophilic ring-opening by attack at the benzylic carbon. Exposure of cultured C6 glial cells to (S,S)-phenylpropylene oxide produced a cytotoxic response in a concentration-dependent manner based on cell degeneration and death.

Conversion of methamphetamine to N-methyl-methamphetamine in formalin solutions.

Embalming is common, and yet it can create problems for the forensic scientist if a drug has been the cause of death and if this drug is also reactive toward the embalming fluid. Previous studies have focused on the amines such as nortriptyline, desipramine, and fenfluramine. In the presence of formalin, a typical component of embalming fluid, these compounds can be rapidly converted to their methylated derivatives amitriptyline, imipramine, and N-methyl-fenfluramine, respectively. We have begun a larger project designed to determine the reactivity and reactions of a wide range of drugs with formalin and have extended it to amphetamines. We report here our results from methamphetamine, which is converted into its N-methyl derivative in the presence of formalin. The rate of conversion is dependent upon pH and formalin concentration with the greatest conversion occurring under basic conditions and the highest formalin concentration. Up to 100% conversion in 24 h was observed under certain conditions. When studied in human tissue exposed to methamphetamine and treated with formalin, again, conversion to N-methyl-methamphetamine was readily apparent as early as 30 min after exposure to formalin. Finally, we note that the reactions of methamphetamine with formalin studied here are probably general and should be considered when performing postmortem/postembalming forensic analysis.