4-hydroxy-3-methoxymethamphetamine and 3-4-dihydroxymandelic-acid

3,4-Methylenedioxymethamphetamine (MDMA, Ecstasy) is excreted in human urine mainly as conjugates of its metabolites 3,4-dihydroxymethamphetamine (DHMA) and 4-hydroxy-3-methoxymethamphetamine (HMMA). The glucuronidation kinetics of HMMA showed high capacities, but also high K(m) values, unlikely to be reached after recreational user's doses. Therefore, the aim of the present work was to investigate the sulfation of DHMA and HMMA by human sulfotransferases (SULTs) in pooled human liver cytosol (pHLC). The kinetic data showed deviation from typical Michaelis-Menten kinetics. The overall efficiency for HMMA sulfation was calculated to be 2-10 times higher than for glucuronidation. As the sulfation of both MDMA metabolites showed substrate inhibition effects, their inhibitory potential towards typical sulfation reactions in pHLC was tested. The following substrates for typical sulfation reactions were used: nitrophenol, dopamine, estradiol, and dehydroepi androsten dione. Inhibition was observed towards dopamine sulfation by DHMA and HMMA, but not by MDMA. The 1/V vs. 1/S plots indicated a mixed-type or competitive inhibition model for DHMA and HMMA, respectively. In conclusion, the presented data indicated that sulfation of HMMA should be the major conjugation reaction observed in humans. Furthermore, both, DHMA and HMMA, were identified as inhibitors of dopamine sulfation.

Topics: Cytosol; Dopamine; Hallucinogens; Humans; Kinetics; Mandelic Acids; Methamphetamine; N-Methyl-3,4-methylenedioxyamphetamine; Sulfotransferases

Different pharmacokinetic properties are known for the two enantiomers of the entactogen 3,4-methylendioxy-methamphetamine (MDMA), most likely due to enantioselective metabolism. The aim of the present work was 1) the investigation of the main sulfotransferases (SULT) isoenzymes involved in the sulfation of the main MDMA phase I metabolites 3,4-dihydroxymethamphetamine (DHMA) and 4-hydroxy-3-methoxymethamphetamine (HMMA) and 2) the evaluation of a possible enantioselectivity of this phase II metabolic step. Therefore, racemic DHMA and HMMA were incubated with heterologously expressed SULTs, and quantification of the sulfates by liquid chromatography-high-resolution mass spectrometry was conducted. Because separation of DHMA and HMMA sulfate could not be achieved by liquid chromatography, enantioselective kinetic parameters were determined using the substrate-depletion approach with enantioselective quantification of substrate consumption by gas chromatography-negative ion chemical ionization mass spectrometry. SULT1A1 and SULT1A3 catalyzed sulfation of DHMA, and SULT1A3 and SULT1E1 catalyzed sulfation of HMMA. SULT1A1 and SULT1E1 revealed classic Michaelis-Menten kinetics, whereas SULT1A3 kinetics showed deviation from the typical Michaelis-Menten kinetics, resulting in a concentration-dependent self-inhibition. SULT1A3 showed the highest affinity and capacity of the SULT isoforms. Marked enantioselectivity could be observed for S-DHMA sulfation by SULT1A3 and in human liver cytosol, whereas no differences were observed for HMMA sulfation. Finally, comparison of K(m) and V(max) values calculated using achiral product formation and chiral substrate depletion showed good correlation within 2-fold of each other. In conclusion, preferences for S-enantiomers were observed for DHMA sulfation, but not for HMMA sulfation.

Topics: Chromatography, Gas; Chromatography, Liquid; Humans; Isoenzymes; Kinetics; Lactates; Mandelic Acids; Mass Spectrometry; Metabolic Detoxication, Phase I; Metabolic Detoxication, Phase II; Methamphetamine; N-Methyl-3,4-methylenedioxyamphetamine; Sulfates; Sulfotransferases