Study on metabolic dynamics,metabolic enzyme phenotype and species difference of hepatic and intestinal microsome of psoralidin / 中国中药杂志

This study aims to investigate metabolic activities of psoralidin in human liver microsomes( HLM) and intestinal microsomes( HIM),and to identify cytochrome P450 enzymes( CYPs) and UDP-glucuronosyl transferases( UGTs) involved in psoralidin metabolism as well as species differences in the in vitro metabolism of psoralen. First,after incubation serial of psoralidin solutions with nicotinamide adenine dinucleotide phosphate( NADPH) or uridine 5'-diphosphate-glucuronic acid( UDPGA)-supplemented HLM or HIM,two oxidic products( M1 and M2) and two conjugated glucuronides( G1 and G2) were produced in HLM-mediated incubation system,while only M1 and G1 were detected in HIM-supplemented system. The CLintfor M1 in HLM and HIM were 104. 3,and57. 6 μL·min~(-1)·mg~(-1),respectively,while those for G1 were 543. 3,and 75. 9 μL·min~(-1)·mg~(-1),respectively. Furthermore,reaction phenotyping was performed to identify the main contributors to psoralidin metabolism after incubation of psoralidin with NADPH-supplemented twelve CYP isozymes( or UDPGA-supplemented twelve UGT enzymes),respectively. The results showed that CYP1 A1( 39. 5 μL·min~(-1)·mg~(-1)),CYP2 C8( 88. 0 μL·min~(-1)·mg~(-1)),CYP2 C19( 166. 7 μL·min~(-1)·mg~(-1)),and CYP2 D6( 9. 1 μL·min~(-1)·mg~(-1)) were identified as the main CYP isoforms for M1,whereas CYP2 C19( 42. 0 μL·min~(-1)·mg~(-1)) participated more in producing M2. In addition,UGT1 A1( 1 184. 4 μL·min~(-1)·mg~(-1)),UGT1 A7( 922. 8 μL·min~(-1)·mg~(-1)),UGT1 A8( 133. 0 μL·min~(-1)·mg~(-1)),UGT1 A9( 348. 6 μL·min~(-1)·mg~(-1)) and UGT2 B7( 118. 7 μL·min~(-1)·mg~(-1)) played important roles in the generation of G1,while UGT1 A9( 111. 3 μL·min~(-1)·mg~(-1)) was regarded as the key UGT isozyme for G2. Moreover,different concentrations of psoralidin were incubated with monkey liver microsomes( MkLM),rat liver microsomes( RLM),mice liver microsomes( MLM),dog liver microsomes( DLM) and mini-pig liver microsomes( MpLM),respectively. The obtained CLintwere used to evaluate the species differences.Phase Ⅰ metabolism and glucuronidation of psoralidinby liver microsomes showed significant species differences. In general,psoralidin underwent efficient hepatic and intestinal metabolisms. CYP1 A1,CYP2 C8,CYP2 C19,CYP2 D6 and UGT1 A1,UGT1 A7,UGT1 A8,UGT1 A9,UGT2 B7 were identified as the main contributors responsible for phase Ⅰ metabolism and glucuronidation,respectively. Rat and mini-pig were considered as the appropriate model animals to investigate phase Ⅰ metabolism and glucuronidation,respectively.

Resveratrol inhibits metabolism of tryptophan in human liver microsomes / 中国药理学通报

Aim To study the effect of resveratrol on the metabolism of tryptophan to kynurenine in human liver microsomes.Methods High performance liquid chromatography-tandem mass spectrometry ( LC-MS/ MS) was used to detect the concentration of tryptophan and kynurenine in the microsome incubation system, and the incubation time, tryptophan concentration, and microsomal protein concentration were investigated respectively.The optimal tryptophan incubation system obtained above was used to explore the effect of resveratrol on the kynurenine pathway.Results The optimal incubation time of tryptophan in human liver mi-crosomes in vitro was 90 min,the concentration of tryptophan and liver microsomal protein was 8 mg • L"1 and 1 g • L"1, respectively.The enzyme reaction rate constant Km was 95.91 ±22.29 jxmol • L'1, and the maximum reaction rate V

Identification of human cytochrome P450 and UGT enzymes involved in the metabolism of ferulic acid, a major bioactive component in traditional Chinese medicines / 中国天然药物

Ferulic acid (FA) is an active component of herbal medicines. One of the best documented activities of FA is its antioxidant property. Moreover, FA exerts antiallergic, anti-inflammatory, and hepatoprotective effects. However, the metabolic pathways of FA in humans remain unclear. To identify whether human CYP or UGT enzymes are involved in the metabolism of FA, reaction phenotyping of FA was conducted using major CYP-selective chemical inhibitors together with individual CYP and UGT Supersomes. The CYP- and/or UGT-mediated metabolism kinetics were examined simultaneously or individually. Relative activity factor and total normalized rate approaches were used to assess the relative contributions of each major human CYPs towards the FA metabolism. Incubations of FA with human liver microsomes (HLM) displayed NADPH- and UDPGA-dependent metabolism with multiple CYP and UGT isoforms involved. CYPs and UGTs contributed equally to the metabolism of FA in HLM. Although CYP1A2 and CYP3A4 appeared to be the major contributors in the CYP-mediated clearance, their contributions to the overall clearance are still minor (< 25%). As a constitute of many food and herbs, FA poses low drug-drug interaction risk when co-administrated with other herbs or conventional medicines because multiple phase I and phase II enzymes are involved in its metabolism.

Analysis of metabolites and metabolic pathway of 5F-AMB in vitro using UPLC-HR-MS / 药学学报

This study was designed to investigate the metabolites of 5F-AMB by human liver microsomes model in vitro. 5F-AMB was added in the reaction mixture to simulate the metabolic process in human hepatocytes in vivo, and then to determine the reaction points and pathways of metabolism by ultra performance liquid chromatography (UPLC) coupled to high resolution mass spectrum (HR-MS). 5F-AMB generated 9 metabolites in total in the human liver microsomes model. Ester hydrolysis, combination of ester hydrolysis and oxidative defluorination, combination of ester hydrolysis and hydroxylation on pentyl chain moiety and combination of ester hydrolysis and hydroxylation on indazole ring moiety reactions were its main metabolic pathways. The method is fast and efficient so that the ester hydrolysis, combination of ester hydrolysis and oxidative defluorination, combination of ester hydrolysis and hydroxylation on pentyl chain moiety and combination of ester hydrolysis and hydroxylation on indazole ring moiety metabolites of 5F-AMB can be used as the suitable and potential biomarkers in the urine samples.

Effects of isorhamnetin on human liver microsomes CYPs and rat primary hepatocytes / 药物评价研究

Objective To study the inhibitory effects ofisorhamnetin on six kinds of CYPs of liver in vitro,and the toxic effect on rat hepatocytes Methods This report uses warm incubation of human liver microsomes in vitro to investigate the inhibition of isorhamnetin on 6 kinds of CYPs (CYP2C19,CYP2D6,CYP3A4,CYP2E1,CYP1A2 and CYP2C9),and using HPLC-MS/MS to detect product of metabolism as well as analysing of the pathways of metabolic.At the same time,using rat primary hepatocytes which has low CYPs activity in vitro to explore whether the use of isorhamnetin will cause effects on the ALT,AST and LDH of hepatocytes.Results Isorhamnetin has inhibition effects on CYP2E1 and CYP1A2,the inhibition rate were 59.48％ and 39.91％,respectively.Methylated metabolite is produced after incubating of isorhamnetin and HLMs.The isorhmnetin becomes high polarity and water solubility metabolite 3,3',4',5,7-hydroxyflavone.Isorhamnetin of 30,100 and 300 μmol/L cause a significant rise of ALT and LDH in primary cultured rat hepatocytes cultured (P ＜ 0.01).isorharnnetin of 100 μmol/L cause a rise of AST in primary cultured rat hepatocytes cultured (P ＜ 0.05) and 300 μmol/L cause a significant rise (P ＜ 0.01).It was a dose-dependent manner.Conclusion Isorhamnetin in vitro mainly metabolized by HLMs,and at the same time have a certain inhibitory effect on CYP2E1 and CYP1A2,which may cause the drugs which are metabolized by CYP2E1 and CYP1A2 in vivo accumulation that lead to a series of drug interactions.The results also indicate that heavy use of isorhamnetin cause some adverse effects on hepatocytes,and it was a dose-dependent manner.Individuals need to pay attention to the dose ofisorhamnetin and the potential drug interactions.

Inhibition of Cytochrome P450 by Nomilin and Obacunone and Potential Mechanism in Human Liver Microsomes / 中草药·英文版

Objective Nomilin and obacunone are two important limonoids that are well known for their anticancer effect. Previous studies showed that limonoids had inhibitory effect on cytochrome P450 3A4 (CYP3A4). However these effects are inconclusive with regards to prediction of potential drug interactions. Methods Nomilin or obacunone was pre-incubated with HLMs for 30 min. Following 10-fold dilution from the pre-incubation concentration, a second incubation was performed in the presence of NADPH and cytochrome P450 substrates for 15 min. The reaction was quenched and the supernatants were analyzed by chromatography/mass spectrometry. Results In this study, nomilin and obacunone showed potent inhibitory effect on CYP3A4 with the IC50 values of 3.50 and 6.08 µmol/L, respectively. The inhibition of CYP3A4 was in a time-, concentration- and NADPH-dependent manner with Ki values of 2.92 and 1.25 µmol/L and Kinact values of 0.033 and 0.078 min−1 for nomilin and obacunone respectively. These results elucidated that they were time-dependent inhibitors for CYP3A4. Conclusion Concomitant use of limonoids and other drugs may call for extra caution for purposes of clinical safety.

In vitro inhibitory effects of plumbagin, the promising antimalarial candidate, on human cytochrome P450 enzymes

OBJECTIVE@#To investigate the propensity of plumbagin to inhibit the three isoforms of human cytochrome P450 (CYP), i.e., CYP1A2, CYP2C19, and CYP3A4 using human liver microsomes in vitro.@*METHODS@#Inhibitory effects of plumbagin on the three human CYP isoforms were investigated using pooled human liver microsomes. Phenacetin O-deethylation, omeprazole hydroxylation and nifedipine oxidation were used as selective substrates for CYP1A2, CYP2C19 and CYP3A4 activities, respectively. Concentrations of paracetamol, 5-hydroxyomeprazole, and oxidized nifedipine were determined in microsomal incubation mixture using high-performance liquid chromatography.@*RESULTS@#Plumbagin showed significant inhibitory effects on all CYP isoforms, but with the most potent activity on CYP2C19-mediated omeprazole hydroxylation. The IC50 (concentration that inhibits enzyme activity by 50%) values of plumbagin and nootkatone (selective inhibitor) for CYP2C19 were (0.78 ± 0.01) and (27.31 ± 0.66) μM, respectively. The inhibitory activities on CYP1A2-mediated phenacetin O-deethylation and CYP3A4-mediated nifedipine oxidation were moderate. The IC50 values of plumbagin and α-naphthoflavone (selective inhibitor) for CYP1A2 were (1.39 ± 0.01) and (0.02 ± 0.36) μM, respectively. The corresponding IC50 values of plumbagin and ketoconazole (selective inhibitor) for CYP3A4 were (2.37 ± 0.10) and (0.18 ± 0.06) μM, respectively.@*CONCLUSIONS@#Clinical relevance of the interference of human drug metabolizing enzymes should be aware of for further development scheme of plumbagin as antimalarial drug when used in combination with other antimalarial drugs which are metabolized by these CYP isoforms.

In vitro inhibitory effects of plumbagin, the promising antimalarial candidate, on human cytochrome P450 enzymes

Objective: To investigate the propensity of plumbagin to inhibit the three isoforms of human cytochrome P450 (CYP), i.e., CYP1A2, CYP2C19, and CYP3A4 using human liver microsomes in vitro. Methods: Inhibitory effects of plumbagin on the three human CYP isoforms were investigated using pooled human liver microsomes. Phenacetin O-deethylation, omeprazole hydroxylation and nifedipine oxidation were used as selective substrates for CYP1A2, CYP2C19 and CYP3A4 activities, respectively. Concentrations of paracetamol, 5-hydroxyomeprazole, and oxidized nifedipine were determined in microsomal incubation mixture using high-performance liquid chromatography. Results: Plumbagin showed significant inhibitory effects on all CYP isoforms, but with the most potent activity on CYP2C19-mediated omeprazole hydroxylation. The IC

Inhibitory mechanism of tetrahydropalmatine enantiomers on cytochrome P450 in human liver microsomes / 中草药

Objective: To investigate the inhibition of tetrahydropalmatine (THP) enantiomers on main cytochrome P450 (CYP450) in human liver microsomes and the mechanism. Methods: The effects of (-)-THP and (+)-THP on the activies of main phase I metabolic enzymes in human liver microsomes, CYP1A2, CYP2C9, CYP2C19, CYP3A1, CYP2E1, and CYP2D6 were investigated using Cocktail probe drugs method; The effect of preincubation with (-)-THP on the CYP2D6 substrate dextromethorphan demethylation activity in human liver microsomes were investigated using a two-step incubation scheme and study its inhibitory mechanism was studied; The enzyme inhibitory kinetic parameters of CYP2D6 by (-)-THP were investigated using time-dependent incubation with human liver microsomes. Results: The inhibitory effect of (+)-THP on CYP450 subtype was not significant, while.CYP2D6 activity was significantly inhibited by (-)-THP (IC50 = 0.46 μmol/L). The value of IC50 preincubation with or without NADPH were 2.40 and 0.46 μmol/L, respectively, IC50 (-) NADPH/IC50 (+) NADPH = 5.22. And the enzyme inhibitory kinetic parameters of Ki and Kinact were 0.690 μmol/L and 0.0846 min-1, respectively. Conclusion: (-)-THP has a strong inhibition on CYP2D6, and the type of inhibition is mechanism-based inhibiton (MBI), which should indicate a potential metabolic drug-drug interaction mediated by (-)-THP in clinical application.

Enzyme reaction kinetics, metabolic enzyme phenotype, and metabolites of berberine / 中草药

Objective: To study the metabolic characteristics of berberine using the pooled human liver microsomes and recombinant human cytochrome enzymes P450 (CYP) isozymes, to identify CYP isozymes responsible for berberine metabolism and its contribution, and to determine the structures of metabolism. Methods: Pooled human liver microsomes were incubated with berberine (20, 100, 200, 400, 600, 800, and 1 200 ng/mL). The Michaelis-Menten parameters (Km), maximum velocity (Vmax), and clearance (CLint) of pooled liver microsomes were initially estimated by analyzing Lineweave-Brurk plot. Various selective CYP inhibitors were used to investigate their inhibitory effects on the metabolism of berberine and the certain concentration of berberine was incubated with recombinant human CYP isozymes (CYP3A4, CYP1A2, CYP2D6, and CYP2C9). The concentration of berberine and metabolites in the incubation pool was determined by UPLC method. The P450 isozymes were ranked with the method of total normalized rate (TNR) and the related metabolites were identified by LC-MS/MS. Results: The Vmax, Km, and CLint of berberine in pooled human liver microsomes were 1.51 nmol·mg-1·h-1, 2.69 nmol/mL, and 0.56 mL·mg-1·h-1, respectively. Quinidine (the specific inhibitor of CYP2D6) and Furafylline (the specific inhibitor of CYP1A2) could significantly inhibit the berberine metabolism, and the other CYP inhibitors had no significant effect on the metabolism of berberine. CYP2D6 and CYP1A2 were responsible for 75.253 9% and 23.323 6% of the berberine metabolite M1 (demethyleneberberine), and responsible for 46.893 8% and 8.679 5% of M2 (thalifendine or berberrubine). The major metabolic pathway of berberine in pooled human liver microsomes incubation system is O-demethylated, demethyleneberberine, thalifendine, or berberrubine could be generated in vitro. Conclusion: Bererine is metabolized by CYP2D6 and CYP1A2 in human liver, the metabolites of berberine are demethyleneberberine and thalifendine or berberrubine.

In vitro Metabolism of Strychnine by Human Cytochrome P450 and Its Interaction with Glycyrrhetic Acid / 中草药·英文版

Objective To investigate the metabolism of strychnine (STN) and the metabolic interaction between STN and glycyrthetic acid (GA) in vitro.MethodsHuman liver microsomes (HLM) and human recombinant cytochrome P450 (CYP) isoforms were employed to study the metabolism of STN and the metabolic interaction of STN with GA in vitro.ResultsIn HLM,the Km,Vmax,and clearance of STN were 88.50 μmol/L,0.88 nmol/(mg·min),and 9.93 mL/(mg·min),respectively.STN was metabolized mainly by CYP3A4.However,STN noncompetitively inhibited CYP3A4-catalyzed testosterone 6β-hydroxylation with IC50 value of 5.9 μtmol/L and Ki value of 5.5μmol/L.Moreover,GA competitively inhibited STN metabolism with IC5o value of 10.6 μmol/L and Ki value of 17.7 μmol/L.ConclusionAlthough STN is mainly metabolized by CYP3A4 in vitro,STN has noncompetitive inhibition on CYP3A4-catalyzed testosterone 6β-hydroxylation.Moreover,GA could competitively inhibit STN metabolism.The present work is helpful to elucidate the metabolic interaction between STN and GA.

Study on the metabolites of phenoprolamine hydrochloride in human body and human liver microsomes by LC-MS/MS / 中国药学杂志

OBJECTIVE: To study the metabolites of phenoprolamine hydrochloride in human body and in human liver microsomes. METHODS: Two volunteers were administrated with 60 mg of phenoprolamine hydrochloride, and plasma samples were collected in specified time points; phenoprolamine hydrochloride was incubated in human liver microsomes. All the metabolites were identified with the LC-MS/MS system. RESULT: One key metabolite was detected in human plasma which m/z was 212.1. Six metabolites were detected in human liver microsomes and the m/z were separately 360.1, 342.2, 415.1, 281.4 and 330.2. Based on metabolite analysis, several metabolic pathways in human body and human liver microsomes were proposed. CONCLUSION: The metabolites of phenoprolamine hydrochloride in human body were different with that in human liver microsomes. We assumed phenoprolamine hydrochloride would metabolize mainly through other pathway but not in the liver. Copyright 2012 by the Chinese Pharmaceutical Association.

Determination of the activity of human hepatic cytochromes P450 CYP2C8/9, CYP2E1 / 中国药理学通报

AIM: To establish the methods for assaying the activities of tolbutamide hydroxylase (CYP2C8/9) and chlorzoxazone 6-hydroxylase (CYP2E1) from adult human livers microsomes. METHODS: The microsomes was isolated from human adults liver and the contents of microsomal protein were determined. Using the tolbutamide and chlorzoxazone as substrates, the amount of hydroxytoblbutamide and hydroxychlorzoxazone formed during the incubation period was quantified by extroppolating from the standard curve and the specific activity of CYP2C8/9 and CYP2E1 were calculated. RESULTS: There was no siginificant influence on the activities of CYP2C8/9 and CYP2E1 in different times. CONCLUSIONS: The methods utilized to estimate the activity of CYP2C8/9 and CYP2E1 were simple, stable, and repeatable. These methods can be used in new drug screening, safety evaluation and reseasch on pathology and toxicology of liver.

Determination of the activity of human hepatic cytochromes P450 CYP2C8/9,CYP2E1 / 中国药理学通报

AIM To establish the methods for assaying the activities of tolbutamide hydroxylase (CYP2C8/9) and chlorzoxazone 6-hydroxylase(CYP2E1) from adult human livers microsomes. METHODS The microsomes was isolated from human adults liver and the contents of microsomal protein were determined. Using the tolbutamide and chlorzoxazone as substrates, the amount of hydroxytoblbutamide and hydroxychlorzoxazone formed during the incubation period was quantified by extroppolating from the standard curve and the specific activity of CYP2C8/9 and CYP2E1 were calculated. RESULTS There was no siginificant influence on the activities of CYP2C8/9 and CYP2E1 in different times. CONCLUSIONS The methods utilized to estimate the activity of CYP2C8/9 and CYP2E1 were simple, stable, and repeatable. These methods can be used in new drug screening, safety evaluation and reseasch on pathology and toxicology of liver.