Investigations on the stereoselectivity of the phase II metabolism of the 3,4-methylenedioxyethylamphetamine (MDEA) metabolites 3,4-dihydroxyethylamphetamine (DHEA) and 4-hydroxy-3-methoxyethylamphetamine (HMEA).
Different elimination was reported for the two enantiomers of the designer drug 3,4-methylenedioxyethylamphetamine (MDEA) in vivo. In the present work, the enantioselectivity of glucuronidation and sulfation of the MDEA phase I metabolites 3,4-dihydroxyethylamphetamine (DHEA) and 4-hydroxy-3-methoxyethylamphetamine (HMEA) was investigated. First, glucuronide standards were synthesized using rat liver microsomes. Incubations were performed with recombinant human UDP-glucuronyltransferases (UGT) and pooled human liver microsomes (pHLM) for glucuronidation and using recombinant human sulfotransferases (SULT) and pooled human liver cytosol (pHLC) for sulfation. Product formation experiments were performed by quantification of the phase II metabolites using liquid chromatography-high-resolution mass spectrometry. Additionally, substrate depletion experiments were conducted by gas chromatography-mass spectrometry after chiral derivatization for sulfation. UGT2B7, 2B15, and 2B17 were involved in glucuronidation of HMEA and SULT1A1 and SULT1A3 and SULT1A3 and SULT1E1 in the sulfation of DHEA and HMEA, respectively. SULTs provided much higher affinity, whereas UGTs showed higher capacities. Marked stereoselectivity could be observed for UGT2B15, UGT2B17, and pHLM toward S-HMEA, for SULT1A3 and pHLC toward S-DHEA and for SULT1A3 and pHLC toward R-HMEA. In conclusion, the phase II metabolism might also contribute to the observed different pharmacokinetic properties of MDEA.