title: Analysis of monoamine oxidase enzymatic activity by reversed-phase high performance liquid chromatography and inhibition by beta-carboline alkaloids occurring in foods and plants.
abstract: Monoamine oxidase (MAO) is a flavin adenine dinucleotide (FAD)-containing enzyme located at the outer membranes of mitochondria that catalyzes the oxidative deamination of biogenic and xenobiotic amines. We have used a chromatographic method to measure MAO-enzymatic activity by using kynuramine as a non-selective substrate with its MAO-oxidation product subsequently analyzed by RP-HPLC-DAD and HPLC-mass spectrometry (MS). This method was applied to study the kinetic parameters, inhibition and reaction products of MAO recombinant enzymes in presence of tetrahydro-beta-carboline and beta-carboline alkaloids occurring in foods, plants and mammals. Analysis by HPLC showed that tetrahydro-beta-carbolines or beta-carbolines were not modified by MAO. Several beta-carbolines such as tryptoline (1,2,3,4-tetrahydro-beta-carboline) and 1-methyltryptoline (1-methyl-1,2,3,4-tetrahydro-beta-carboline) were inhibitors of MAO-A; instead their corresponding 6-hydroxy-derivatives (6-hydroxytryptoline and 6-hydroxy-1-methyltryptoline) lacked this activity. Tetrahydro-beta-carboline-3-carboxylic acids were unable to inhibit MAO enzymes. In contrast, their oxidation products, i.e. the fully aromatic beta-carbolines (norharman and harman), acted as good inhibitors of MAO. Two tetrahydro-beta-carbolines (i.e. tryptoline and 1-methyltryptoline) occurring in foods were isolated by solid-phase extraction (SPE) and RP-HPLC from selected samples of sausages and the corresponding extracts exhibited good inhibition properties over MAO-A. These results suggest that beta-carbolines from foods, plants, and mammals may exert inhibitory actions on MAO enzymes.
authors.affiliation: Spanish Council for Scientific Research, CSIC, Instituto de Fermentaciones Industriales, Juan de la Cierva 3, 28006 Madrid, Spain. therraiz@ifi.csic.es
authors.forename: Tomas
authors.initials: T
authors.lastname: Herraiz
authors.forename: Carolina
authors.initials: C
authors.lastname: Chaparro
mesh_terms: D000470:Alkaloids / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D000818:Animals; D002243:Carbolines / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D002460:Cell Line; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005504:Food Analysis / Q000379:methods*; D006801:Humans; D007700:Kinetics; D015394:Molecular Structure; D008995:Monoamine Oxidase / Q000235:genetics / Q000378:metabolism*; D008996:Monoamine Oxidase Inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D010944:Plants / Q000737:chemistry*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D000470:Alkaloids; D002243:Carbolines; D008996:Monoamine Oxidase Inhibitors; D011994:Recombinant Proteins; D008995:Monoamine Oxidase