Effects Of Quercetin On The Metabonome Of Portal And Hepatic Venous Plasma And Urine In Rats

Quercetin, one of the common polyphenolic compounds, is widely present in vegetables, fruit, tea, and red wine. Quercetin has a wide range of biological activities, including anti-inflammatory, antioxidant, cancer-preventing, DNA damage preventive, and cardioprotective activities. On the basis of previous studies, the biochemical effects of quercetin on rats were investigated using 1H NMR spectroscopy. The work finished in this study included the following parts:1. The effects of quercetin on metabolic profiles of portal venous plasma were investigated. Sixty male Wistar rats were administered orally with 40 mg/kg quercetin (quercetin group) or solvent (2% DMSO, control group). The portal venous plasma was collected before and 0.5, 1, 2, 4 and 8h after administration. The data of 1H NMR spectra were subjected to principal component analysis (PCA) or partial least square-discriminant analysis (PLS-DA). The FRAP values of portal venous plasma, duodenum and jejunum were determined. The DAO activity of portal venous plasma was also measured. The results showed that the FRAP values of duodenum and jejunum were increased after adminstration. The plasma DAO activity did not change significantly. The results of PCA and PLS-DA revealed the inherent clustering behavior. The detectable biochemical effects associated with quercetin dosing included increased plasma concentrations of lactate, alanine, glutamate, succinate,β-hydroxybutyrate, acetone, HDL and decreased plasma concentrations of citrate, tyrosine and LDL. It is concluded that quercetin can change the intestinal endogenous metabolism significantly in rats. The decreased LDL and increased HDL may contribute to the preventive action of quercetin on cardiovascular diseases.2. The effects of quercetin on metabolic profiles of hepatic venous plasma were investigated. Fifty male Wistar rats were administered orally with 40 mg/kg quercetin (quercetin group) or solvent (2% DMSO, control group). The hepatic venous plasma was collected before and 0.5, 1, 2 and 4h after administration. The data of 1H NMR spectra were treated similarly as previous study. The activities of AST, ALT and hepatic FRAP value were measured. The results showed that the AST and ALT activities in hepatic venous plasma did not change significantly. The hepatic FRAP value was increased after adminstration. The results of PCA or PLS-DA indicated an inherent clustering behavior. The PLS-DA plot showed a metabolic trajectory in hepatic venous plasma after giving quercetin. The metabolic changes identified after giving quercetin included increased plasma concentrations of lactate, alanine, threonine,β-hydroxybutyrate, acetone, PC and decreased plasma concentrations of glucose and lipoprotein (a). It is concluded that hepatic endogenous metabolism is changed by quercetin. The decreased lipoprotein (a) and increased PC may be contributed to the prevention of atherosclerosis by quercetin.3. The effects of quercetin on urine metabolic profiles were investigated. Twelve male Wistar rats were administered orally with 40 mg/kg quercetin (quercetin group) or solvent (2% DMSO, control group). The urinary samples were collected -12-0h before and 0-12, 12-24, 24-36 and 36-48h after administration, and analyzed by 1H NMR. The urinary spectral data derived from PLS-DA presented an inherent clustering behavior. The PLS-DA plot showed a trajectory of metabolic shift. The metabolic changes associated with giving quercetin included increased concentrations of lactate,β-hydroxybutyrate, alanine, glutamine and decreased concentrations of citrate, 2-oxoglutarate, creatinine. Several peaks were not identified. It was demonstrated that the urinary metabolites profile was changed significantly after giving quercetin.4. The main metabolites of quercetin in portal venous plasma were analysed. Fifteen male Wistar rats were administered orally with 40 mg/kg quercetin (quercetin group) or solvent (2% DMSO, control group). Portal venous plasma was collected 1h after administration and analyzed by LC-MS. The analytes were treated by formic acid and acetone precipitation to remove protein from plasma, and then were separated on C18 column. The mobile phase consisted of acetonitrile - 1% acetic acid aqueous solution(40:60) at a flow rate of 0.3 mL·min-1. A mass spectrometer equipped with quadrupole mass analyzer was used as detector and operated in negative ion mode. In select ion reaction (SIR) mode, the ion combinations of m/z 301, m/z 315, m/z 381, m/z 463, m/z 477, m/z 557 and m/z 653 were used to identify the derivatives of quercetin, methylquercetin, quercetin sulfate, quercetin-3-glucoside, quercetin-3-glucuronide, quercetin glucuronide sulfate, quercetin diglucuronide. Identification of quercetin, methylquercetin, quercetin sulfate, quercetin-3-glucuronide, and quercetin glucuronide sulfate. It was concluded that quercetin is metabolised extensively during absorption, giving rise to the glucuronidated, methoxylated and sulfated derivatives.In summary, there were significant metabolic changes induced by quercetin administration, including increased glucolysis and production of ketone bodies, changes of concentration of some intermediates in Kreb's cycle, lipoproteins and PC. It is shown that quercetin is bioavailable and subjected to metabolism and subsequent urinary excretion. Metabonomic analysis indicated that exposure to quercetin induced changes in endogenous metabolic profiles. The NMR-based metabonomic analysis has good prospect in application for nutrition research in the future.