title: In vitro inhibition of rat monoamine oxidase by liquiritigenin and isoliquiritigenin isolated from Sinofranchetia chinensis.
abstract: OBJECTIVE
  To study the inhibition of liquiritigenin (1) and isoliquiritigenin (2) isolated from Sinofranchetia chinensis on rat monoamine oxidase A and B (MAO A and B).
  
  
  METHODS
  Rat brain mitochondrial fraction, prepared by differential centrifugation, was utilized as a source of MAO activity. MAO activity was determined radiochemically with [14C]5-hydroxytryptamine (5-HT) and [14C]beta-phenylethylamine (beta-PEA) used as MAO A or B specific radiolabled substrates, respectively. The Ki and KI values were obtained from Lineweaver-Burk plot using linear regression analysis.
  
  
  RESULTS
  Liquiritigenin and isoliquiritigenin were found to be inhibitory against both MAO A and B in a dose-dependent manner. IC50 (95% of confidence limits) of liquiritigenin and isoliquiritigenin were 32 (26-36) and 13.9 (12.8-15.6) mumol/L for the inhibition of MAO A, and 104.6 (89.0-118.9) and 47.2 (39.5-54.5) mumol/L for that of MAO B, respectively. Lineweaver-Burk transformation of the MAO A inhibition data indicated that the inhibition was non-competitive for both liquiritigenin and isoliquiritigenin whereas their inhibition of MAO B was of mixed type. Regarding MAO A inhibition, the Ki values of liquiritigenin and isoliquiritigenin were 31.5 mumol/L and 14.3 mumol/L, respectively. As to the inhibition of MAO B, the Ki and KI data for liquiritigenin were 164.7 and 15.2 mumol/L, and those for isoliquiritigenin were 62.2 and 9.3 mumol/L, respectively.
  
  
  CONCLUSIONS
  Liquiritigenin and isoliquiritigen inhibited the activity of MAO A and B in rat brain mitochondria, and the latter was more active than the former.
authors.affiliation: Institute of Functional Biomolecules, State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210093, China.
authors.forename: X
authors.initials: X
authors.lastname: Pan
authors.forename: L D
authors.initials: LD
authors.lastname: Kong
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: C H
authors.initials: CH
authors.lastname: Cheng
authors.forename: R X
authors.initials: RX
authors.lastname: Tan
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D002599:Chalcone / Q000031:analogs & derivatives* / Q000302:isolation & purification / Q000494:pharmacology*; D047188:Chalcones; D004365:Drugs, Chinese Herbal / Q000737:chemistry / Q000494:pharmacology; D044950:Flavanones; D005419:Flavonoids / Q000302:isolation & purification / Q000494:pharmacology*; D008928:Mitochondria / Q000201:enzymology; D008995:Monoamine Oxidase / Q000378:metabolism*; D008996:Monoamine Oxidase Inhibitors / Q000494:pharmacology; D010946:Plants, Medicinal / Q000737:chemistry; D051381:Rats
chemical_list: D047188:Chalcones; D004365:Drugs, Chinese Herbal; D044950:Flavanones; D005419:Flavonoids; D008996:Monoamine Oxidase Inhibitors; D002599:Chalcone; C040920:isoliquiritigenin; D008995:Monoamine Oxidase; C083152:liquiritigenin