benzofurans and phenethylamine

Phenethylamine-based designer drugs are prevalent within the new psychoactive substance market. Characterisation of their metabolites is important in order to identify suitable biomarkers which can be used for better monitoring their consumption. Careful design of in vitro metabolism experiments using subcellular liver fractions will assist in obtaining reliable outcomes for such purposes. The objective of this study was to stepwise investigate the in vitro human metabolism of seven phenethylamine-based designer drugs using individual families of enzymes. This included para-methoxyamphetamine, para-methoxymethamphetamine, 4-methylthioamphetamine, N-methyl-benzodioxolylbutanamine, benzodioxolylbutanamine, 5-(2-aminopropyl) benzofuran and 6-(2-aminopropyl) benzofuran. Identification and structural elucidation of the metabolites was performed using liquid chromatography-quadrupole-time-of-flight mass spectrometry. The targeted drugs were mainly metabolised by cytochrome P450 enzymes via O-dealkylation as the major pathway, followed by N-dealkylation, oxidation of unsubstituted C atoms and deamination (to a small extent). These drugs were largely free from Phase II metabolism. Only a limited number of metabolites were found which was consistent with the existing literature for other phenethylamine-based drugs. Also, the metabolism of most of the targeted drugs progressed at slow rate. The reproducibility of the identified metabolites was assessed through examining formation patterns using different incubation times, substrate and enzyme concentrations. Completion of the work has led to a set of metabolites which are representative for specific detection of these drugs in intoxicated individuals and also for meaningful evaluation of their use in communities by wastewater-based drug epidemiology.

Topics: 3,4-Methylenedioxyamphetamine; Amines; Amphetamines; Benzodioxoles; Benzofurans; Butylamines; Catalysis; Chromatography, Liquid; Cytochrome P-450 Enzyme System; Cytosol; Designer Drugs; Dose-Response Relationship, Drug; Female; Humans; Likelihood Functions; Liver; Male; Mass Spectrometry; Methamphetamine; Microsomes, Liver; Models, Chemical; Phenethylamines; Propylamines; Reproducibility of Results; Substance Abuse Detection; Wastewater; Water Purification

An allosteric binding site with high affinity for imidazoline I(2) ligands has been proposed to exist on monoamine oxidase-B (MAO-B). However, enzyme inhibition only occurs at ligand concentrations far higher than are required to saturate this site. We here confirm previous reports that inactivation of recombinant human MAO-B with tranylcypromine results in the formation of a high affinity I(2) site on the enzyme, measured as an increase in binding of [(3)H]2-BFI. Incubation of MAO-B with 2-phenylethylamine, an endogenous trace amine and MAO-B substrate, resulted in a progressive loss of enzyme activity, increased enzyme mass, distinct spectral changes and, as was observed with tranylcypromine, a parallel increase in high affinity binding of [(3)H]2-BFI. Kinetic studies of the mechanism by which 2-BFI inhibits MAO-B activity suggested binding of 2-BFI, at micromolar concentrations, to a site distinct from the active site on at least two forms of the pure enzyme, probably corresponding to oxidised and reduced enzyme states. Studies with mutant enzymes revealed a pattern of changes consistent with binding of 2-BFI to the substrate entrance channel of human MAO-B. Structural data confirm that high affinity binding of I(2) ligands occurs within the entrance channel of inactive enzyme, while lower affinity binding at the same location in catalytically active enzyme results in mixed inhibition of MAO-B activity. High affinity I(2) sites may form in vivo due to inactivation of a portion of MAO-B during amine oxidation, while the low affinity I(2) site on active enzyme is a target for novel MAO-B inhibitor drugs.

Topics: Allosteric Regulation; Benzofurans; Binding Sites; Humans; Imidazoles; Imidazoline Receptors; Ligands; Models, Molecular; Monoamine Oxidase; Monoamine Oxidase Inhibitors; Mutation; Phenethylamines; Protein Binding; Recombinant Proteins; Tranylcypromine

1. The brain constituents beta-phenylethylamine (PEA) and tryptamine enhance the impulse propagation mediated transmitter release (exocytosis) from the catecholaminergic and serotoninergic neurons in the brain ('catecholaminergic/serotoninergic activity enhancer, CAE/SAE, effect'). (-)Deprenyl (Selegiline) and (-)1-phenyl-2-propylaminopentane [(-)PPAP] are amphetamine derived CAE substances devoid of the catecholamine releasing property. 2. By changing the aromatic ring in PPAP we developed highly potent and selective CAE/SAE substances, structurally unrelated to the amphetamines. Out of 65 newly synthetized compounds, a tryptamine derived structure, (-)1-(benzofuran-2-yl)-2-propylaminopentane [(-)BPAP] was selected as a potential follower of (-)deprenyl in the clinic and as a reference compound for further analysis of the CAE/SAE mechanism in the mammalian brain. 3. (-)BPAP significantly enhanced in 0.18 micromol 1(-1) concentration the impulse propagation mediated release of [(3)H]-noradrenaline and [(3)H]-dopamine and in 36 nmol 1(-1) concentration the release of [(3)H]-serotonin from the isolated brain stem of rats. The amount of catecholamines and serotonin released from isolated discrete rat brain regions (dopamine from the striatum, substantia nigra and tuberculum olfactorium, noradrenaline from the locus coeruleus and serotonin from the raphe) enhanced significantly in the presence of 10(-12) - 10(-14) M (-)BPAP. BPAP protected cultured hippocampal neurons from the neurotoxic effect of beta-amyloid in 10(-14) M concentration. In rats (-)BPAP significantly enhanced the activity of the catecholaminergic and serotoninergic neurons in the brain 30 min after acute injection of 0.1 microg kg(-1) s.c. In the shuttle box, (-)BPAP in rats was about 130 times more potent than (-)deprenyl in antagonizing tetrabenazine induced inhibition of performance.

Topics: Animals; Benzofurans; Brain; Cells, Cultured; Dopamine; Electric Stimulation; Mice; Norepinephrine; Phenethylamines; Psychotropic Drugs; Rabbits; Rats; Receptors, Catecholamine; Receptors, Serotonin; Serotonin; Tryptamines

Peripheral postsynaptic alpha-adrenoceptor blocking properties of six new dihydrobenzofurane and imidazoline derivatives have been investigated in pithed rat against the pressor effects of phenylephrine and cirazoline (alpha 1-agonists) and clonidine and azepexole (alpha 2-agonists). Except for (N-methylimidazolinyl-2)-2 dihydro-2,3 benzofurane (II) that acted neither on alpha 1- nor alpha 2-adrenoceptors, all the compounds revealed blocking effects - plus or minor - on both alpha 1- and alpha 2-adrenoceptors. (Imidazolinyl-2)-2-chloro-7 dihydro-2,3-benzofurane (IV) is equipotent in blocking both alpha 1- and alpha 2-adrenoceptors. 7-Methoxy-(imidazolinyl-2)-2 dihydro-2,3-benzofurane (III) and (imidazolinyl-2)-2-fluoro-7-dihydro-2,3-benzofurane (V) block more effectively alpha 1- than alpha 2-adrenoceptors whereas (imidazolinyl-2)-2-benzocyclobutane (VI) is more potent in blocking alpha 2- than alpha 1-adrenoceptors. (Imidazolinyl-2)-2-dihydro-2,3-benzofurane (I) is a preferential alpha 2-adrenoceptor blocking agent. The most effective agents on alpha 2-adrenoceptors are under further pharmacological investigations.

Topics: Adrenergic alpha-Agonists; Adrenergic alpha-Antagonists; Animals; Azepines; Benzofurans; Blood Pressure; Clonidine; Drug Interactions; Imidazoles; Male; Phenethylamines; Phenylephrine; Rats; Rats, Inbred Strains; Receptors, Neurotransmitter