6-甲氧基正丁苯酞在大鼠肝微粒体中的代谢研究

报道了用GC/MS方法及衍生化技术研究6-甲氧基正丁苯酞(MBP)在大鼠肝微粒体中的代谢转化结果。6-甲氧基正丁苯酞在苯巴比妥(PB)诱导的大鼠肝微粒体中主要转化为3-羟基、γ-羟基取代物,6-羟基正丁苯酞与一个环氧化代谢产物。     

抗焦虑新药AF-5及其代谢物在人肝微粒体体外温孵体系中代谢研究

目的研究一类抗焦虑新药AF-5及其代谢物(I,II)在人肝微粒体体外温孵体系中代谢情况.方法自制人肝微粒体,用Lowry法测定酶活性为8.79mg·mL^-1.以此配制人肝微粒体体外温孵体系,加入药物,温孵后,提取分离,GC-MS测定.结果鉴定了AF-5在人肝微粒体体外温孵体系中的两个主要代谢物,并阐明了其体外代谢途径为AF-5的4位首先氧化为羟基,然后氧化成羰基.结论AF-5在体外人肝微粒体温孵体系中,100min后完全代谢成羟基代谢物I及羰基代谢物II,以羟基代谢物为主要代谢产物.AF-5代谢物I在人肝微粒体温孵体系中,可转化为代谢物II,而代谢物II在人肝中则不再代谢.     

蓝萼甲素在大鼠体内外的代谢转化

目的研究蓝萼甲素在大鼠体内外的代谢转化。方法采用大鼠肝微粒体体外温孵法,研究对蓝萼甲素的代谢转化。采用RP-HPLC法同时分离检测蓝萼甲素及其体外代谢产物。结果用液-液萃取、制备HPLC法,从大鼠胆汁中分离了一个代谢产物,经质谱分析推测结构为羟基化蓝萼甲素,并采用HPLC-MS连用,分析了肝微粒体体外温孵样品中的代谢产物,推测了蓝萼甲素的可能代谢转化途径。结论蓝萼甲素在大鼠肝微粒体和胆汁中可被代谢转化,主要代谢产物为羟基化蓝萼甲素。     

左旋黄皮酰胺在大鼠肝微粒体中的代谢转化研究

用大鼠肝微粒体体外温孵法进行了左旋黄皮酰胺[(-)-clausenamide]代谢转化研究,优化了温孵体系,建立了反相HPLC-DAD同时分离检测左旋黄皮酰胺及其体外代谢产物的分析方法。用硅胶低压柱色谱、制备TLC及制备HPLC分离纯化了两个代谢产物并进行了光谱鉴定。结果表明,两个代谢物分别确定为6-和5-位羟基取代的黄皮酰胺。     

右旋黄皮酰胺在大鼠肝微粒体中的代谢转化

目的：研究黄皮酰胺的主要代谢途径,为进一步研究黄皮酰胺代谢的立体选择性打下基础。方法：用大鼠肝微粒体体外温孵法对右旋黄皮酰胺((+)-clausenamide)进行温孵,用硅胶柱色谱、制备TLC分离纯化代谢产物并通过光谱分析鉴定其结构。结果：分离得到5个代谢产物CM1,CM3,CM4,CM5及CM6,其结构分别鉴定为6-羟基,4-羟基,4,6-二羟基,4-苯环邻位羟基,4,7-苯环间位-二羟基黄皮酰胺。结论：黄皮酰胺的代谢主要发生羟化或双羟化,CM3是其主要代谢产物,量较少的CM4,CM6为其进一步代谢产生的双羟基代谢产物;另2个代谢产物CM1,CM5产生的量也较少;CM2未分离得到,但通过HPLC分析知其为右旋黄皮酰胺的微量代谢产物。     

6－甲氧基正丁苯酞在大鼠肝微粒体中的代谢研究

报道了用ＧＣ／ＭＳ方法及衍生化技术研究６甲氧基正丁苯酞（ＭＢＰ）在大鼠肝微粒体中的代谢转化结果。６甲氧基正丁苯酞在苯巴比妥（ＰＢ）诱导的大鼠肝微粒体中主要转化为３羟基、γ羟基取代物，６羟基正丁苯酞与一个环氧化代谢产物     

6-甲氧基正丁苯酞的体内代谢转化研究

大鼠用6-甲氧基正丁苯酞(MBP)灌胃,收集0～24h尿液,经酶水解、提取浓缩、衍生化处理后用GC/MS分析。在大鼠0～24h尿液中,6-甲氧基正丁苯酞原药含量很低,主要以代谢物形式存在,依次为C-6脱甲基产物、C₃-C_α环氧化物、γ-羟化物、β-羟化物以及两个次级代谢产物。6-甲氧基正丁苯酞体内代谢结果与其在肝微粒体中代谢结果基本一致。     

左旋一叶碱的代谢转化

目的研究一叶碱［securinine,(-)SE］在大鼠体内外的代谢转化。方法采用大鼠肝微粒体体外温孵法对(-)SE的代谢转化进行了研究,优化了代谢体系,建立了反相HPLC法同时分离检测(-)SE及其体外代谢产物的分析方法。用液液萃取,制备TLC及半制备HPLC分离纯化了4个代谢产物并进行了光谱鉴定。在此基础上,建立了生物体液中(-)SE及其代谢物的反相HPLC分析方法,并用该法检测了ip给药后大鼠的胆汁、尿样及其经β-葡糖醛酸苷酶水解后的样品。结果代谢物分别鉴定为6-位羟基,6-位羰基及5-位α及β羟基取代的(-)SE,还证实了体内6-位羟基代谢物进一步形成了二相结合型产物。结论基本阐明(-)SE在大鼠体内外代谢转化的途径。     

左旋一叶萩碱的代谢转化

目的　研究一叶碱 [securinine ,( - )SE]在大鼠体内外的代谢转化。方法　采用大鼠肝微粒体体外温孵法对 ( - )SE的代谢转化进行了研究 ,优化了代谢体系 ,建立了反相HPLC法同时分离检测 ( - )SE及其体外代谢产物的分析方法。用液液萃取 ,制备TLC及半制备HPLC分离纯化了 4个代谢产物并进行了光谱鉴定。在此基础上 ,建立了生物体液中 ( - )SE及其代谢物的反相HPLC分析方法 ,并用该法检测了ip给药后大鼠的胆汁、尿样及其经 β 葡糖醛酸苷酶水解后的样品。结果　代谢物分别鉴定为 6 位羟基 ,6 位羰基及 5 位α及 β羟基取代的 ( - )SE ,还证实了体内 6 位羟基代谢物进一步形成了二相结合型产物。结论　基本阐明 ( - )SE在大鼠体内外代谢转化的途径     

去氢厄弗酚在小鼠肝微粒体中代谢产物及CYP450酶亚型的鉴定

目的建立去氢厄弗酚(DHE)小鼠体外肝微粒体孵育方法,鉴定DHE在小鼠肝微粒体中的代谢产物及参与DHE代谢的CYP450酶亚型。方法采用UPLC-Q-TOF-MS/MS分析鉴定DHE在体外肝微粒体共温孵后的代谢产物,筛选7种CYP450酶亚型,并通过特异性化学抑制剂法,鉴别参与DHE代谢的主要CYP450酶亚型。结果在体外肝微粒体共温孵后,检测到4个代谢产物;所筛选的7种CYP450酶亚型中,CYP1A2、CYP2C8和CYP2D2对DHE体外肝微粒体代谢的参与度较高。结论在肝脏中,有多种代谢酶亚型参与DHE的代谢,表明DHE在临床上不易与其他药物产生相互作用。     

Stereoselective glucuronidation and hydroxylation of etodolac by UGT1A9 and CYP2C9 in man

1.?In vitro metabolic studies with etodolac were performed. S- and R-etodolac were converted to the acylglucuronide and hydroxylated metabolites by UDP-glucuronosyltransferase (UGT) and cytochrome P450 in microsomes. However, the stereoselectivities of UGT and P450 for the isomers were opposite. S-etodolac was glucuronidated preferentially than R-etodolac by UGT. In contrast, R-etodolac was hydroxylated preferentially than S-etodolac by P450.

2.?Of several human P450 enzymes, CYP2C9 had the greatest activity for hydroxylation of R-etodolac. Sulfaphenazole, an inhibitor of CYP2C9, and anti-CYP2C9 antibody inhibited the hydroxylation of R-etodolac in human liver microsomes. CYP2C9 therefore contributes to the stereoselective hydroxylation of R-etodolac.

3.?Of several human UGT enzymes, UGT1A9 had the greatest activity for glucuronidation of S-etodolac. Propofol and thyroxine, inhibitors of UGT1A9, inhibited the glucuronidation of S-etodolac in human liver microsomes. Therefore, UGT1A9 is mainly responsible for the stereoselective glucuronidation of S-etodolac.

4.?Because S-etodolac was metabolized more rapidly than R-etodolac in human cryopreserved hepatocytes, the stereoselectivities of UGT1A9 for etodolac substantially influenced the overall metabolism of S- and R-etodolac in man.     

Roles of two allelic variants (Arg144Cys and Ile359Leu) of cytochrome P4502C9 in the oxidation of tolbutamide and warfarin by human liver microsomes

1. Tolbutamide methyl hydroxylation and racemic warfarin 7-hydroxylation activities were determined in liver microsomes of 39 Japanese and 45 Caucasians genotyped for the cytochrome P450 (P450 or CYP) 2C9 gene into three groups, namely the wild-type (Arg144·Ile359), and two heterozygous Cys allele (Cys144·Ile359) and Leu allele (Arg144·Leu359) variants. 2. Good correlations were found between tolbutamide methyl hydroxylation and racemic warfarin 7-hydroxylation activities in liver microsomes of Japanese and Caucasians. Humans with the Cys allele CYP2C9 variant, which was detected in 22% of Caucasians, were found to have similar catalytic rates to those of the wild-type in the oxidations of tolbutamide and racemic warfarin, whereas humans with the Leu allele, which was detected in 8% Japanese and 7% Caucasian samples, had lower catalytic rates than those of other two groups. 3. The rates of 6- and 7-hydroxylation of racemic warfarin were correlated well with those of S-warfarin, but not R-warfarin, in human liver microsomes. 4. Both human liver microsomes and recombinant CYP2C9 catalysed 7-hydroxylation of S-warfarin more extensively than those of R-warfarin. K_m's for the 7-hydroxylation of S-warfarin were not very different in liver microsomes of humans with these three genotypes. Anti-CYP2C9 antibodies and sulphaphenazole inhibited the 6- and 7- hydroxylation of S-warfarin, but not R-warfarin,by > 90% and the methyl hydroxylation of tolbutamide by about 50%. 5. These results suggest that humans with Leu allele of CYP2C9 have lower V_max's for S-warfarin 7-hydroxylation and tolbutamide methyl hydroxylation than those with wildtype and Cys allele CYP2C9, although the K_m's are not very different in liver microsomes m of these three groups of humans. R-warfarin hydroxylation may be catalysed by P450 enzymes other than CYP2C9 in man.     

Stereoselective N-Demethylation of Chlorpheniramine by Rat-liver Microsomes and the Involvement of Cytochrome P450 Isozymes

Previous studies have suggested that degradation of the two stereoisomers of chlorpheniramine in the liver might be catalysed by different types of cytochrome P450. Stereoselective N-demethylation of chlorpheniramine and the involvement of cytochrome P450 (CYP) isozymes have, therefore, been investigated in the liver microsomes of eight-week-old male rats. Incubation of racemic chlorpheniramine with liver microsomes from the male rat resulted in the formation of both enantiomers of monodesmethylchlorpheniramine (DMChp). Further metabolism of DMChp to didesmethylchlorpheniramine (DDMChp) did not, however, occur. The S/R enantiomeric ratio for intrinsic clearance (V_max/K_m) was approximately 2.0, suggesting that the N-demethylation was stereoselective for S-(+)-chlorpheniramine. On the other hand, although the V_max/K_m value for the formation of S-(+)- and R-(–)-DMChp increased with phenobarbitone-inducible rat-liver microsomes, there was no difference between the rates of N-demethylation of the enantiomers. In contrast, 3-methylcholanthrene reduced the intrinsic clearance of S-(+)-chlorpheniramine by N-demethylation and increased its value for R-(–)-chlorpheniramine, showing no stereoselectivity for the N-demethylation of chlorpheniramine. The difference between the intrinsic clearance of the two enantiomers by N-demethylation was because of differences in affinity for the catalysing enzyme. This is indicative of stereoselective involvement of the main enzyme concerned in the N-demethylation of the enantiomers, considered to be CYP 2C11. Anti-CYP 2C11 also partially inhibited the N-demethylation of racemic chlorpheniramine in rat-liver microsomes exposed to phenobarbitone and 3-methylcholanthrene. That CYP 2B1 was involved in the N-demethylation of both enantiomers was also supported by results from an experiment using phenobarbitone-inducible rat-liver microsomes. CYP1A1 did not, however, catalyse the N-demethylation of either enantiomer. These results indicate that N-demethylation of the S-(+)-enantiomer of chlorpheniramine occurs preferentially in the microsomes, demonstrating the stereoselective contribution of CYP2C11. Immunoinhibition studies suggest, moreover, that the N-demethylation of both chlorpheniramine enantiomers is catalysed by CYP2B1, but not by CYP1A1.     

Stereoselectivity in metabolism of ifosfamide by CYP3A4 and CYP2B6

The aim was to identify the hepatic cytochromes P450 (CYPs) responsible for the enantioselective metabolism of ifosfamide (IFA). The 4-hydroxylation, N²- and N³-dechloroethylation of IFA enantiomers were monitored simultaneously in the same metabolic systems using GC/MS and pseudoracemate techniques. In human and rat liver microsomes, (R)-IFA was preferentially metabolized via 4-hydroxylation, whereas its antipode was biotransformed in favour of N-dechloroethylation. CYP3A4 was the major enzyme responsible for metabolism of IFA enantiomers in human liver. The study also revealed that CYP3A (human CYP3A4/5 and rat CYP3A1/2) and CYP2B (human CYP2B6 and rat CYP2B1/2) enantioselectively mediated the 4-hydroxylation, N²- and N³-dechloroethylation of IFA. CYP3A preferentially supported the formation of (R)-4-hydroxyIFA (HOIF), (R)-N²-dechloroethylIFA (N2D) and (R)-N³-dechloroethylIFA (N3D), whereas CYP2B preferentially mediated the generation of (S)-HOIF, (S)-N2D and (S)-N3D. The enantioselective metabolism of IFA by CYP3A4 and CYP2B1 was confirmed in cDNA transfected V79 cells.     

Enantioselective N-Demethylation and Hydroxylation of Sibutramine in Human Liver Microsomes and Recombinant Cytochrome P-450 Isoforms

The enantioselective metabolism of sibutramine was examined using human liver microsomes (HLM) and recombinant cytochrome P-450 (CYP) isoforms. This drug is metabolized to N-mono-desmethyl- (M1) and N,N-di-desmethylsibutramine (M2), and subsequent hydroxylation results in hydroxyl M1 (HM1) and hydroxyl M2 (HM2). No significant difference was noted in formation of M1from sibutramine between R- and S-sibutramine in HLM. However, S-enantiomers of M1 and M2 were preferentially metabolized to M2, HM1, and HM2compared to R-enantiomers in HLM, and intrinsic clearance (Cl_int) ratios of S-enantiomers/R-enantiomers were 1.97, 4.83, and 9.94 for M2, HM1, and HM2, respectively. CYP3A4 and CYP3A5 were only involved in the formation of M1, whereas CYP2B6 and CYP2C19 were responsible for all metabolic reactions of sibutramine. CYP2C19 and CYP3A5 displayed catalytic preference for S-sibutramine to S-M1, whereas CYP2B6 and CYP3A4 showed little or no stereoselectivity in metabolism of sibutramine to M1. In the case of M2 formation, CYP2B6 metabolized S-M1 more rapidly than R-M1 with a Cl_int ratio of 2.14. However, CYP2C19 catalyzed less S-M1 than R-M1 and the Cl_int ratio of S-M1 to R-M1 was 0.65. The most significant enantioselectivity was observed in formation of HM1 from M1, and HM2 from M2. CYP2B6 and CYP2C19 exhibited preferential catalysis of formation of hydroxyl metabolites from S-enantiomers rather than R-enantiomers. These results indicate that S-sibutramine was more rapidly metabolized by CYP isoforms than R-sibutramine, and that enantioselective metabolism needs to be considered in drug interactions involving sibutramine and co-administered drugs.     

Polymorphism in stereoselective hydroxylations of mephenytoin and hexobarbital by Japanese liver samples in relation to cytochrome P-450 human-2 (IIC9)

1. Stereoselective 4′-hydroxylations of R-(—)-mephenytoin and S-(+)-mephenytoin were determined in liver microsomes of 19 Japanese subjects.

2. The content of P-450 human-2 assessed by Western blots correlated with micro-somal S-(+)-mephenytoin 4′-hydroxylation. Antibody raised against P-450 human-2 effectively inhibited microsomal S-(+)-mephenytoin 4′-hydroxylation, but was less efficient for inhibition of R-(—)-mephenytoin 4′-hydroxylation in extensive metabolizers, and 4′-hydroxylation of both mephenytoin enantiomers in poor metabolizers.

3. Similar results were observed on the stereoselective hydroxylations of R-(+)- and S-(+)-hexobarbital. Clear correlations were observed for the content of P-450 human-2 and microsomal R-(—)-hexobarbital 3′α-hydroxylation and S-(+)-hexobarbital 3′β-hydroxylation.

4. Moreover, yeast microsomes expressing P-450 human-2 cDNA showed high stereoselectivities for hydroxylations of mephenytoin and hexobarbital similar to those observed in human liver.

5. Two other cytochromes P-450(IIC 9/10) expressed in yeast, whose cDNA were synthesized by site-directed mutagenesis from human-2 cDNA, showed no stereo-selectivity for the hydroxylations of mephenytoin and hexobarbital, in spite of the modification of only two amino acid substitutions or deletions in the whole sequence.

6. Only a cytochrome derived from P-450 human cDNA corresponding to P-450 human-2 was expressed in human livers, the two cytochromes of the three related IIC9/10 forms were not expressed.

7. These findings indicate that P-450 human-2 is the major cytochrome P-450 responsible for the polymorphisms in stereoselective hydroxylations of mephenytoin and hexobarbital.     

Species differences in the stereochemistry of the metabolism of isoprene in vitro

1. Comparative studies on the stereochemistry of the metabolism of isoprene in vitro have been carried out using liver microsomes from rats, mice, monkeys, dogs, rabbits and humans. Differences between strains and gender were also investigated. 2. In the production of the isoprene monoepoxides,microsomes from the livers of the male Sprague- Dawley or Wistar rat showed an approximately 2:1 preference for the formation of (S)-2-(1-methylethenyl)o xirane compared with the (R)-enantiomer. No enantioselectiv ity was observed for mouse or rabbit. In contrast, liver microsomes from dog, monkey or male human preferentially formed (R)-2-1(1-methylethenyl)axirane. There was no enantioselectivity observed with microsomes from female human liver. 3. The significant differences between species in the in vitro metabolism of isoprene indicate that stereochemical and mechanistic data should be taken into account when evaluating the results of animal studies designed to assess the carcinogenic risks to humans that may be associated with exposure to isoprene.     

In vitro study of fenoprofen chiral inversion in rat: comparison of brain versus liver

1. The extent and the overall stereoselectivity of the combined steps involved in the chiral inversion of fenoprofen, a non-steroidal anti-inflammatory drug, was investigated in rat brain microsomes and cytosol. Results were compared with those obtained with the same liver subcellular compartments. 2. Brain microsomes catalysed the stereoselective activation of the R(-)-enantiomer to its coenzyme A thioester with a specific activity ~10-fold less than that obtained with liver microsomes. 3. Rat brain microsomes and cytosol mediated the racemization and hydrolysis of both R(-)- and S(+)-fenoprofenoyl-CoA. In brain fractions the epimerase activity was lower than in liver, whereas the hydrolysis process appeared more efficient. 4. Thus, the data indicated that the three-step mechanism occurred in brain subcellular compartments leading to a minor chiral inversion of fenoprofen compared with that in liver.     

Stereoselective Taurine Conjugation of (<Emphasis Type="Italic">R</Emphasis>)-Benoxaprofen Enantiomer in Rats: <Emphasis Type="Italic">In Vivo</Emphasis> and <Emphasis Type="Italic">in Vitro</Emphasis> Studies Using Rat Hepatic Mitochondria and Microsomes

No HeadingPurpose. Identify (R)-BOP-T in rat bile after administration of (R)-BOT over a 12 h period.Methods. Each benoxaprofen (BOP) enantiomer was administered i.v. to bile duct-cannulated rats at a dose of 5 mg/kg. The optical isomers of BOP and its metabolites in plasma, urine, and bile were quantified using a chiral HPLC column. The amounts of BOP glucuronide (BOP-G), BOP taurine conjugate (BOP-T), and BOP enantiomers excreted into the bile over 12 h after administration of (R)-BOP were as follows: (R)-BOP-G and (S)-BOP-G, 2.1 ± 0.5 and 6.2 ± 1.4% of the dose; (R)-BOP-T and (S)-BOP-T, 5.6 ± 1.8 and 0.7 ± 0.3% of the dose; (R)-BOP and (S)-BOP, 0.7 ± 0.1 and 1.7 ± 0.2% of the dose, respectively, whereas after (S)-BOP administration, (S)-BOP-G and (S)-BOP were mainly excreted into the bile (14.3 ± 1.8 and 3.0 ± 0.4% of the dose, respectively). Only after (R)-BOP administration was the taurine conjugate of BOP found in the bile, and the configuration was R. BOP-T could not be found in the bile after (S)-BOP administration. To investigate the stereoselectivity of the conjugation enzymes responsible for BOP-T formation, in vitro studies were performed using rat hepatic organelles.Results. When (R)-BOP was used as a substrate, rat hepatic mitochondrial and microsomal fractions exhibited stereoselective BOP-T formation activity, with microsomal activity approximately 3.0 times greater than that of the mitochondria. That of (S)-BOP was approximately 2.1. Mean (R)/(S) ratios of BOP enantiomer for BOP-T formation in the mitochondrial and microsomal incubations were approximately 1.7 and 2.4, respectively.Conclusion. Although in the in vivo studies, only (R)-BOP-T originated from (R)-BOP was found in the bile, the configuration of BOP-T formed by the incubations of (R)-BOP or (S)-BOP with rat hepatic mitochondria or microsomes was S for both.     

Stereo‐Selective Metabolism of Methadone by Human Liver Microsomes and cDNA‐Expressed Cytochrome P450s: A Reconciliation

Abstract: In vitro metabolism of methadone was investigated in cytochrome P450 (CYP) supersomes and phenotyped human liver microsomes (HLMs) to reconcile past findings on CYP involvement in stereo‐selective metabolism of methadone. Racaemic methadone was used for incubations; (R)‐ and (S)‐methadone turnover and (R)‐ and (S)‐EDDP formation were determined using chiral liquid chromatography–tandem mass spectrometry. CYP supersome activity for methadone use and EDDP formation ranked CYP2B6 > 3A4 > 2C19 > 2D6 > 2C18, 3A7 > 2C8, 2C9, 3A5. After abundance scaling, CYP3A4, 2B6 and 2C19 accounted for 63–74, 12–32 and 1. 4–14% of respective activity. CYP2B6, 2D6 and 2C18 demonstrated a preference for (S)‐EDDP formation; CYP2C19, 3A7 and 2C8 for (R)‐EDDP; 3A4 none. Correlation analysis with 15 HLMs supported the involvement of CYP2B6 and 3A. The significant correlation of S/R ratio with CYP2B6 activity confirmed its stereo‐selectivity. CYP2C19 and 2D6 inhibitors and monoclonal antibody (mAb) did not inhibit EDDP formation in HLM. Chemical and mAb inhibition of CYP3A in high 3A activity HLM reduced EDDP formation by 60–85%; inhibition of CYP2B6 in 2B6 high‐activity HLM reduced (S)‐EDDP formation by 80% and (R)‐EDDP formation by 55%. Inhibition changed methadone metabolism in a stereo‐selective manner. When CYP3A was inhibited, 2B6 mediated (S)‐EDDP formation predominated; S/R stereo‐selectivity increased. When 2B6 was inhibited (S)‐EDDP formation fell and stereo‐selectivity decreased. The results confirmed the primary roles of CYPs 3A4 and 2B6 in methadone metabolism; CYP2C8 and 2C9 did not appear involved; 2C19 and 2D6 have minimal roles. CYP2B6 is the primary determinant of stereo‐selective metabolism; stereo‐selective inhibition might play a role in varied plasma concentrations of the two enantiomers.