RESUMO
We attempted to isolate the constituent(s) responsible for the suppressive effect of the juice of shekwasha, a citrus produced in Okinawa Prefecture, on D-galactosamine (GalN)-induced liver injury in rats. Liver injury-suppressive activity, as assessed by plasma alanine aminotransferase and aspartate aminotransferase activities, was found only in the fraction that was extracted with n-hexane when three fractions were added to the diet and fed to rats. Of five compounds isolated from the n-hexane-soluble fraction by silica gel column chromatography, three compounds had liver injury-suppressive effects when five compounds were singly force-fed to rats at a level of 300 mg/kg body wt 4 h before the injection with GalN. The structures of the three active compounds were determined as 3',4',5,6,7,8-hexamethoxyflavanone (citromitin), 4',5,6,7,8-pentamethoxyflavone (tangeretin) and 3',4',5,6,7,8-hexamethoxyflavone (nobiletin), which are known flavonoids mainly existing in citrus. Nobiletin, the most important compound in the n-hexane-soluble fraction, also had suppressive effects on liver injuries induced by carbon tetrachloride, acetaminophen and GalN/lipopolysaccharide (LPS) in addition to liver injury induced GalN. Nobiletin suppressed GalN/LPS-induced increases in plasma tumor necrosis factor (TNF)-alpha and nitric oxide (NO) concentrations and hepatic mRNA levels for inducible NO synthase and DNA fragmentation. These results suggest that nobiletin suppressed GalN/LPS-induced liver injury at least by suppressing the production of both TNF-alpha and NO. The results obtained here indicate that the hepatoprotective effect of shekwasha juice is mainly ascribed to several polymethoxy flavonoids included in the juice.
Assuntos
Doença Hepática Induzida por Substâncias e Drogas/tratamento farmacológico , Citrus/química , Flavonas/uso terapêutico , Flavonoides/uso terapêutico , Fígado/efeitos dos fármacos , Fitoterapia , Extratos Vegetais/uso terapêutico , Acetaminofen , Alanina Transaminase/sangue , Animais , Aspartato Aminotransferases/sangue , Intoxicação por Tetracloreto de Carbono/tratamento farmacológico , Fragmentação do DNA/efeitos dos fármacos , Flavonas/farmacologia , Flavonoides/farmacologia , Galactosamina , Lipopolissacarídeos , Fígado/enzimologia , Masculino , Estrutura Molecular , Óxido Nítrico/sangue , Óxido Nítrico Sintase Tipo II/genética , Óxido Nítrico Sintase Tipo II/metabolismo , Extratos Vegetais/química , Extratos Vegetais/farmacologia , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Fator de Necrose Tumoral alfa/sangueRESUMO
To evaluate the protective effects of fruit juices against D-galactosamine (GalN)-induced liver injury, lyophilized fruit juices (total 12 kinds) were fed to rats for 7 d, and then we evoked liver injury by injecting GalN. The juice of camu-camu (Myrciaria dubia) significantly suppressed GalN-induced liver injury when the magnitude of liver injury was assessed by plasma alanine aminotransferase and aspartate aminotransferase activities, although some other juices (acerola, dragon fruit, shekwasha, and star fruit) also tended to have suppressive effects. An active compound was isolated from camu-camu juice by solvent fractionation and silica gel column chromatography. The structure was determined to be 1-methylmalate. On the other hand, malate, 1,4-dimethylmalate, citrate, and tartrate had no significant effect on GalN-induced liver injury. It is suggested that 1-methylmalate might be a rather specific compound among organic acids and their derivatives in fruit juices in suppressing GalN-induced liver injury.
