In vitro inhibition of rat monoamine oxidase by liquiritigenin and isoliquiritigenin isolated from Sinofranchetia chinensis.
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.
Pan
X
X
Institute of Functional Biomolecules, State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, Nanjing 210093, China.
Kong
L D
LD
Zhang
Y
Y
Cheng
C H
CH
Tan
R X
RX
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
D047188:Chalcones; D004365:Drugs, Chinese Herbal; D044950:Flavanones; D005419:Flavonoids; D008996:Monoamine Oxidase Inhibitors; D002599:Chalcone; C040920:isoliquiritigenin; D008995:Monoamine Oxidase; C083152:liquiritigenin