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OBJECTIVE：To study the inhibitor y effects of cajanonic acid A on 5 kinds of cytochrome P 450（CYP）enzyme，in human liver microsomes in vitro . METHODS ：By Cocktail probe substrate method ，50.0，15.0，5.0，1.5，0.5，0.15，0.05 μmol/L cajanonic acid A were added into liver microsomes ， and incubated with mixed probe substrates [including phenacetin ， dextromethorphan，omeprazole，testosterone and toluenesulfonbutylurea （probe substrates of CYP 1A2，CYP2D6，CYP2C19， CYP3A4，CYP2C9，respectively）]. On the basis of setting up blank group and positive control group [ α-naphthalene brass ， quinidine，（+）-N-3-benzyl vanillin ，ketoconazole and sulfabendazole （specific inhibitors of CYP 1A2，CYP2D6，CYP2C19， CYP3A4，CYP2C9，respectively）]，using puerarin as internal standard ，UPLC-MS/MS method was adopted to determine the contents of corresponding metabolites （acetaminophen， dextrophane， 5-hydroxy omeprazole ， 6 β-hydroxytestosterone， hydroxytolbutamide）. The determination was performed on ACQUITY UPLC ® BEH C 18 column，with mobile phase consisted of 0.01％ formic acid aqueous solution- 0.01％ acetonitrile formic acid （gradient elution ）at the flow rate of 0.4 mL/min. The column temperature was 40 ℃，and the sample size was 2 μL. An electrospray ionization source was used to conduct positive and negative ion scanning in the multiple reaction monitoring mode. The data acquisition range was m/z 100-1 200，the collision gas was argon ， the atomized gas was nitrogen ，the gas flow rate of the cone hole was 50 L/h，the desorption gas flow rate was 800 L/h，the capillary voltage under positive and negative mode was 2.0， 1.5 kV，and the ion source temperature was 120 ℃，110 ℃， respectively. The desolvent temperature were 400 ℃ and 450 ℃ ， respectively. Non linear regression analysis was performed by using Graphpad Prism 5.0 software and IC 50 wascalculated. RESULTS ：The linear ranges of above metabolifes were 0.26-8.35，0.36-34.56，0.10-3.09, 3.67-117.37，0.15-4.88 μmol/L（R2＞0.99）. The limits of quantitation were 0.26，0.36， 0.10，3.67，0.15 μmol/L，respectively. The IC 50 values of specific inhibitors in positive control group to CYP 1A2，CYP2D6， CYP2C19，CYP3A4 and CYP 2C9 in human liver microsomes were all within the acceptable range reported in the literature. The IC50 values of cajanonic acid A to CYP 1A2，CYP2D6 and CYP 3A4 in human liver microsomes were all more than 50 μmol/L，and the IC 50 values of CYP 2C9 and CYP 2C19 were 4.94 and 18.00 μmol/L，respectively. CONCLUSIONS ：Cajanonic acid A has no inhibitory effect on CYP 1A2，CYP2D6 and CYP 3A4，but has a certain inhibitory effect on CYP 2C9 and CYP 2C19.
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The aim of this study is to establish the in vitro methods for the study of induction and inhibition on CYP450 by drugs, and to validate the analytical method and incubation system. A method for the simultaneous determination of eight metabolites of seven subtypes of CYP450 enzymes probe substrates in human liver microsomes (HLM) was established and validated. The incubation system was optimized to confirm the incubation time and protein concentration of HLM, the enzyme activity of seven subtypes of CYP450 enzymes in HLM was determined, and the inhibition effects on each CYP450s were checked by positive controls. The method for the simultaneous determination of three metabolites of subtypes of CYP450 enzymes was established and validated in human primary cultured hepatocytes (HPCH) using the incubation medium. The enzyme activity of three subtypes of CYP450 enzymes in HPCH was determined, and the total RNA was extracted from HPCH after incubation. The expression of CYP450 enzymes were measured by Taqman fluorescence probe method. The induction effects on each CYP450s were examined using the positive controls. The established methods for the determination of metabolites of probe substrates were fully validated, and the results were conformed to the requirements of bioanalytical method validation. The induction and inhibition effects on each CYP450s were checked by positive controls. The established in vitro methods for the study of drug induction and inhibition on CYP450 were simple and reliable, which could be used in the investigation of enzyme induction or inhibition properties of new drug candidates and to evaluation the metabolic interactions of concomitant medication in clinical.
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OBJECTIVE: To establish a UPLC-Q-TOF-MS method to characterize the metabolites of phillygenin in human liver microsomal incubation system for the first time. METHODS: The chromatography separation was performed on a C18 reversed phase LC column (Phenomenex Kinetex C18, 2.1 mm×100 mm, 2.6 μm). The mobile phase consisted of water-formic acid (100:0.1, V/V) and acetonitrile and a gradient elution program was adopted at the flow rate of 400 μL·min-1. The mass spectral analysis was performed in a positive electrospray ionization mode, and the turbo spray temperature was 550℃. The full MS experiment was run with a scan range from m/z100 to m/z 1 000. RESULTS: The possible fragmentation pathways of phillygein were speculated in a positive electrospray ionization mode, and eight metabolites was identified in human liver microsomal incubation system. CONCLUSION: The UPLC-Q-TOF-MS method is very convenient and efficient for detecting phillygein in human liver mirosomes. The developed method is suitable for the metabolism research of phillygein in human liver microsomes, which providing valuable reference for pharmacokinetic study of phillygenin.
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OBJECTIVE: To study the hepatotoxicity of Polygonum multiflorum on the basic of the bilirubin metabolism mediated by glucuronidation of UGT1A1 enzyme. METHODS: Inspected the enzyme kinetic parameters after giving the rats Polygonum multiflorum extract orally(in vivo), and added the Polygonum multiflorum extract into the human liver microsome(rat liver microsome; human recombinant UGT1A1 enzyme) to test the hepatotoxicity using the bilirubin as UGT1A1 enzyme substrate, investigating the inhibition of the UGT1A1 enzyme(in vitro). Apparent inhibition constant Ki and enzyme kinetic parameters were used to evaluate the hepatotoxicity. RESULTS: Polygonum multiflorum extract has a strong inhibiton to the UGT1A1 enzyme in all the three systems in vitro. All the type of inhibition is the competitive inhibition. While Polygonum multiflorum extract has a strong inhibiton to the UGT1A1 enzyme in vivo, but the type of inhibition is the uncompetitive inhibition. CONCLUSION: The method we had established in our study provides a new idea and a new method to evaluate the hepatotoxicity and the safety of Chinese herbs.
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To study the hepatotoxicity of emodin based on bilirubin metabolism mediated by glucuronidation of UGT1A1 enzyme. In this study, three different incubation systems were established by using RLM, HLM, and rUGT1A1, with bilirubin as the substrate. Different concentrations of bilirubin and emodin were added in the incubation systems. The double reciprocal Michaelis equation was drawn based on the total amount of bilirubin glucuronidation. The apparent inhibition constant Ki was then calculated with the slope curve to predict the hepatotoxicity. The results indicated that emodin had a significant inhibition to the UGT1A1 enzyme in all of the three systems, with Ki=5.400±0.956(P<0.05) in HLM system, Ki =10.020±0.611(P<0.05) in RLM system, Ki=4.850±0.528(P<0.05) in rUGT1A1 system. Meanwhile, emodin had no significant difference between rat and human in terms of inhibition of UGT1A1 enzyme. Emodin had a potential risk of the hepatotoxicity by inhibiting the UGT1A1 enzyme activity. And the method established in this study provides a new thought and new method to evaluate hepatotoxicity and safety of traditional Chinese medicines.
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No abstract available.
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Humans , Catechols , Cytochrome P-450 Enzyme System , Cytochromes , Fatty Alcohols , Liver , Microsomes, LiverABSTRACT
0.05). Conclusions In human liver microsome system in vitro,CYP1A2,2B6 and CYP2A6 contribute to the metabolism of 629.It is very important for bioreduction drugs design and development,and provide the basic experimental and theoretical profiles for extensive application in clinic.
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AIMTo evaluate CYP3A activity of hum an liver microsomes by the ratio of lidocaine(LDC) to its metabolites. M ETHODSIn 1 g?L -1 microsomal protein lidocaine was incubated at 37 ℃ for 1 hour. Lidocaine, monoethylglycinexylidide(MEGX) and glycinexylidide(GX) were determined by HPLC. RESULTSThe linear regress equations fo r LDC, MEGX and GX were = 0 293 4 X- 0 005 661 (r= 0 9 99 7 )、= 0 791 3 X- 0 008 916 (r= 0 999 3 ) and = 0 679 9 X- 0 007 770 (r= 0 998 5 ). The best conditio n for the incubation test in vitro was 2 0 mg?L -1 LDC plus 1 0 g ?L -1 microsomal protein for 60 min. The mean (MEGX+GX)/LDC ratio was 3 2 8. CONCLUSIONThe (MEGX+GX)/LDC ratio can be used to evaluate C YP3A activity of human liver microsomes.