山姜素在人肝微粒体的葡萄糖醛酸化反应研究

目的研究体外肝微粒体孵育体系中山姜素的葡萄糖醛酸化代谢情况,鉴定参与山姜素葡萄糖醛酸化代谢的UGT亚型。方法用体外肝微粒体孵育体系,用HPLC-UV检测方法,检测山姜素的葡萄糖醛酸化代谢情况。将代谢产物进行纯化后,用质谱(MS)和核磁共振(NMR)法进一步鉴定其结构。用商业化重组表达的UGT单酶,鉴定代谢产物的结构和归属可能参与山姜素葡萄糖醛酸化代谢反应的葡萄糖醛酸转移酶(UGTs)亚型。结果山姜素葡萄糖醛酸代谢产生一个代谢产物,经结构鉴定为山姜素-氧-单葡萄糖醛酸化产物。人肝微粒体代谢山姜素的动力学行为,符合米方程且动力学参数:Vmax=(101.9±3.0)nmol·min-1·mg-1·pro,Km=(40.6±3.6)μmol·L-1。UGT1A1、UGT1A3、UGT1A9和UGT2B15均参与了山姜素的葡萄糖醛酸化反应。结论山姜素在人肝微粒体孵育体系中会被代谢成为一个单葡萄糖醛酸化产物,且归属了参与的UGT酶。     

黄芩素在人及不同种属肝微粒体中的UDP-glucuronosyltransferase代谢差异（摘要）

目的：研究黄芩素在不同种属肝微粒体中的UDP-葡萄糖醛酸转移酶（UDP-glucuronosyltransferase, UDPGA）代谢差异特性。方法使用肝微粒体体外代谢孵育法、HPLC-UV分析方法,选用不同种属的肝微粒体进行黄芩素UDPGA体外代谢研究。结果黄芩素在人肝微粒体及不同种属的肝微粒中,加入UDPGA进行37℃恒温孵育,孵育结束后离心,取上清液,经HPLC-UV分离检测得到3个代谢产物,分别是：黄芩素-7-O-β-葡萄糖醛酸结合物、黄芩素-6-O-β-葡萄糖醛酸结合物和黄芩素-6-O-葡萄糖醛酸结合物-7-O-β-葡萄糖醛酸结合物;通过与标准品对照确定黄芩素的三个代谢产物都是葡萄糖醛酸化的代谢产物。同时,不同种属间UGT代谢物的活性表现出较大差异,黄芩素-7-O-β-葡萄糖醛酸结合物在人肝微粒体中的代谢活性最强,Km=1.61,Vmax=0.77（BG在人肝微粒体中的代谢活性是SD雌鼠的25.2倍）;黄芩素-6-O-β-葡萄糖醛酸结合物在比格犬肝微粒体中代谢活性最强,Km=3.05,Vmax=3.51（雄性比格犬肝微粒体的活性是雄性恒河猴肝微粒体的2.6倍）;黄芩素-6-O-葡萄糖醛酸-7-O-β-葡萄糖醛酸结合物在猪肝微粒体中代谢活性最强,Km=5.38, Vmax=0.17（猪肝微粒体的活性是人肝微粒体的13.6倍）,其他依次是犬、恒河猴、鼠和人。结论黄芩素在人及不同种属肝微粒体UGT代谢中均生成上述三种葡萄糖醛酸化代谢产物,但是不同种属间的代谢表现出酶动力学的差异。     

去甲斑蝥新型衍生物N-14NCTDA大鼠肝微粒体酶代谢

目的初步阐明十四烷基去甲斑蝥素酰亚胺(tetradecyl derivative of norcantharidin,简称N-14NCTDA)肝微粒体酶代谢情况,鉴定该药物体外Ⅰ相代谢产物,并推测其主要代谢途径。方法以超速离心法制备大鼠肝微粒酶并以二辛可酸(butyleyanoacrylate,BCA)法测定微粒体蛋白浓度。药物与肝微粒体在一定条件下孵育,使用飞行时间质谱(UPLC/Q-TOF MS)进行分析。结果制备的大鼠肝微粒体酶蛋白质量浓度约为6.4 g·L~(-1)。代谢研究结果显示,孵育后反应液中主要检测到3个代谢产物,其分子离子峰相对分子质量分别为380.280 6、378.264 8和394.259 7,分别对应原型药羟基化、醛基化及羧化产物。结论 UPLC/Q-TOF MS方法适用于N-14NCTDA和其代谢产物的定性鉴别。体外初步代谢结果表明,N-14NCTDA的酰亚胺键难以在肝脏水解释放出NCTD,其主要以末端烷基氧化的方式进行Ⅰ相代谢。     

聚乙二醇400对黄芩素在不同种属肝微粒体上代谢转化的影响

目的:建立一种UPLC-MS/MS的分析方法,考察PEG400对肝微粒体孵育黄芩素后其代谢转化的影响,并比较其在不同种属肝微粒体中的代谢特征。方法:基于体外肝微粒体孵育体系,分别将不同摩尔浓度(2.5,5,10,20μmol·L^-1)的黄芩素于不同摩尔浓度(0,2,4,8μmol·L^-1)的PEG400干预下的肝微粒体中进行37℃恒温孵育60 min,再加入含有内标(染料木素)的冰冷乙腈终止反应,以UPLC-MS/MS正离子模式监测孵育体系中黄芩素及其代谢产物的质量浓度,并根据质量浓度求算酶活性剩余百分含量及其参数。用于定量分析的离子对分别为m/z 447～271(黄芩苷和B6G);m/z 271～172(黄芩素);m/z 271～153(内标)。结果:基于肝微粒体体外孵育结果分析,在鼠、人和犬的肝微粒体孵育后B6G的v_max与黄芩苷的v_max都存在不同,表明黄芩素在不同种属肝微粒中的代谢转化存在差异;PEG400共孵育后,B6G与黄芩苷的v_max分别得到提高,表明了黄芩素的葡...     

芫花主要黄酮成分对肝微粒体UGTs及UGT1A1活性的体外抑制作用

目的 考察芫花主要黄酮成分芫花素和芹菜素对尿苷二磷酸葡萄糖醛酸转移酶（UGTs）及UGT1A1活性的影响。方法 采用体外肝微粒体孵育模型,以4-硝基酚（4-nitrophenol,4-NP）为底物检测UGTs活性,胆红素为底物检测UGT1A1活性;利用UV及UPLC-MS/MS测定底物或代谢产物的含量。结果 对UGTs,在大鼠肝微粒体、小鼠肝微粒体以及人肝微粒体孵育体系中,芫花素和芹菜素均能不同程度地抑制UTGs活性;抑制强弱顺序：在大鼠肝微粒体温孵体系中,芫花素>芹菜素;在小鼠肝微粒体以及人肝微粒体温孵体系中,芹菜素>芫花素。对UGT1A1,在人肝微粒体孵育体系中,芫花素和芹菜素均表现为中等强度的竞争性抑制作用,抑制强弱顺序：芹菜素（IC₅₀=12.40 μmol·L^-1）>芫花素（IC₅₀=23.21 μmol·L^-1）。结论 芫花素和芹菜素对不同肝微粒体孵育体系中UGTs及UGT1A1均可产生显著抑制作用且存在种属差异。芫花素及芹菜素可能存在基于UGT酶的药物相互作用。     

大鼠微粒体代谢酶对黄芩素葡萄糖醛酸化代谢物影响的实验研究

目的 观察大鼠微粒体代谢酶对黄芩素(治疗呼吸道感染中药)代谢作用的影响.方法 用体外微粒体药物代谢酶孵育法;用HPLC法测定黄芩素及其葡萄糖醛酸化代谢物的含量,在不同孵育时间和不同浓度下,观察大鼠肝肠不同微粒体对黄芩素葡萄糖醛酸化代谢产物生成速率的影响.结果 5种不同微粒体药物代谢酶对黄芩素均有代谢作用,且随孵育时间延长,代谢作用也相应增加,呈较好的时间和剂量依赖关系.在5种微粒体中,十二指肠微粒体代谢作用最强;而肝代谢作用最弱.结论 黄芩素主要代谢部位是肠道.     

基于淫羊藿次苷Ⅱ代谢行为的体外药物相互作用研究

目的 应用体外实验方法筛选淫羊藿次苷Ⅱ在肝微粒体中的尿苷二磷酸葡萄糖醛酸转移酶（UGT）抑制剂,为改善淫羊藿次苷Ⅱ生物利用度提供新思路。方法 首先选择槲皮素、山柰酚、桔皮素、柚皮素、水飞蓟素、草质素、胡椒碱、甘草查尔酮A以及异银杏双黄酮作为抑制剂筛选对象,对以上9种化合物在人肝微粒体、人肠微粒体、大鼠肝微粒体、猴肝微粒体及小型猪肝微粒体中对淫羊藿次苷Ⅱ葡萄糖醛酸化反应的抑制作用进行初步研究。抑制剂分别选择低、中、高3个浓度（1、10、100 μmol/L）,采用超快速高效液相色谱（UFLC）法测定代谢产物生成速率,以UGT代谢酶残余活性评价抑制能力。从中筛选出抑制能力较强的化合物（半数抑制浓度IC₅₀≤10 μmol/L）,对其在人肝微粒体中的抑制机制进行系统研究并计算IC₅₀及抑制常数（K_i）值。IC₅₀值的测定采用单一底物浓度法,在不同浓度代谢酶抑制剂的孵育体系中,代谢产物的生成速率不同,应用非线性回归分析计算而得。K_i的测定需在孵育体系中设计3～4个底物浓度以及4～5个包括0点在内的抑制剂浓度,抑制动力学类型通过Dixon作图法和Lineweaver-Burk作图法确定,采用二次作图法计算K_i。结果 山柰酚、槲皮素及甘草查尔酮A对淫羊藿次苷Ⅱ在不同种属肝微粒体及人肠微粒体中的葡萄糖醛酸化反应均具有较强的抑制作用;对在人肝微粒体中的葡萄糖醛酸化反应抑制作用的IC₅₀值分别为（1.01±0.26）、（4.65±0.51）、（5.34±1.00） μmol/L;Dixon作图法及Lineweaver-Burk作图法表明,甘草查尔酮A能够竞争性抑制淫羊藿次苷Ⅱ在人肝微粒体中的葡萄糖醛酸化反应,K_i值为0.18 μmol/L;槲皮素遵循混合型抑制动力学模型,K_i值为0.23 μmol/L;山柰酚符合非竞争型抑制动力学模型,K_i值为0.36 μmol/L。结论 山柰酚、槲皮素及甘草查尔酮A能够降低淫羊藿次苷Ⅱ在不同种属肝微粒体中的葡萄糖醛酸化反应速率,使代谢产物生成减少,清除减慢。     

黄芩素在正常及早期肝纤维化模型小鼠体外肝、肠微粒体中Ⅱ相代谢差异

目的考察肝纤维化模型小鼠肝、肠微粒体对黄芩素体外葡萄糖醛酸化代谢影响和酶促反应动力学研究。方法小鼠每周3次灌胃20%CCl4油溶液,持续6周,检测血清肝功能指标ALT和AST,ELISA试剂盒检测血清中HA,天狼猩红染色和免疫组化染色α-SMA评估肝纤维化模型。检测正常和肝纤维小鼠肠道内容物β-葡萄糖醛酸苷酶活性,同时建立小鼠肝、肠微粒体孵育体系对黄芩素葡萄糖醛酸化反应的酶促反应动力学进行研究,评估其代谢动力学类型,并对比在正常和肝纤维化模型中最大反应速率(Vmax)和米氏常数(Km)。结果经过6周CCl4诱导后,模型组的血清、病理和免疫组化检测结果显示肝纤维化模型复制成功。体外实验结果显示,黄芩素在小鼠肝微粒体中的代谢方式符合米氏方程,而在肠微粒体中属于底物抑制型。与正常组相比,黄芩素在肝纤维化后的肝微粒体中的代谢速率要显著提高(P<0.01),而在肠微粒体中则相反,但差异无统计学意义,同时发现肝纤维化后肠道菌群中的β-葡萄糖醛酸苷酶活性要显著高于正常组(P<0.01)。结论肝纤维化状态对葡萄糖醛酸苷转移酶等Ⅱ相代谢酶的活性带来显著的改变,这值得我们关注肝纤维化疾病状态下药物的代谢特征和临床疗效,促进安全合理用药。     

三重四级杆复合线性离子阱质谱对丹皮酚经大鼠肝微粒体体外代谢产物的分析

[摘要] 目的：以丹皮酚为研究对象,系统分析丹皮酚在体外经大鼠肝微粒体代谢的Ι相以及Ⅱ相代谢产物。方法：借助HPLC-DAD与三重四级杆复合线性离子阱高分辨质谱,采用LightSight软件辅助建立丹皮酚及2,4-二羟基苯乙酮经肝微粒体代谢产物的pMRM-IDA分析方法,分析了丹皮酚在体外经大鼠肝微粒体代谢的Ι相以及Ⅱ相代谢产物。结果：结果发现,丹皮酚在大鼠肝微粒体中经Ι相代谢后产物主要为的4位去甲基的2,4-二羟基苯乙酮和4种氧化代谢产物,而2,4-二羟基苯乙酮Ⅱ相代谢产物主要为4位葡萄糖醛酸化的糖苷化代谢产物。结论：建立了丹皮酚Ι相以及Ⅱ相代谢产物的分析方法,为丹皮酚进一步的代谢研究以及临床合理化用药提供新的方向。     

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。     

Characterization of cardamonin metabolism by P450 in different species via HPLC-ESI-ion trap and UPLC-ESI-quadrupole mass spectrometry

Aim:

To characterize the metabolism of cardamonin by the P450 enzymes in human and animal liver microsomes.

Methods:

Cardamonin was incubated with both human and animal liver microsomal incubation systems containing P450 reaction factors. High performance liquid chromatography coupled with ion trap mass spectrometry was used to identify the metabolites. Serial cardamonin dilutions were used to perform a kinetic study in human liver microsomes. Selective inhibitors of 7 of the major P450 isozymes were used to inhibit cardamonin hydroxylation to identify the isozymes involved in cardamonin metabolism. The cardamonin hydroxylation metabolic capacities of human and various other animals were investigated using the liver microsomal incubation system.

Results:

Two metabolites generated by the liver microsome system were detected and identified as hydroxylated cardamonin. The K_m and V_max values for cardamonin hydroxylation were calculated as 32 μmol/L and 35 pmol·min⁻¹·mg⁻¹, respectively. Furafylline and clomethiazole significantly inhibited cardamonin hydroxylation. Guinea pigs showed the highest similarity to humans with respect to the metabolism of cardamonin.

Conclusion:

CYP 1A2 and 2E1 were identified as the P450 isozymes involved in the metabolism of cardamonin in human liver microsomes. Furthermore, our research suggests that guinea pigs could be used in the advanced pharmacokinetic studies of cardamonin in vivo.     

Involvement of UDP-Glucuronosyltransferases in the Extensive Liver and Intestinal First-Pass Metabolism of Flavonoid Baicalein

Purpose The present study aims to investigate the involvement of UDP-glucuronosyltranferase (UGT) in the extensive liver and intestinal first-pass glucuronidation of baicalein (B) in both rats and humans and also to study sulfation and P450 mediated hydroxylation of B.Materials and Methods B was incubated with liver and intestine microsome, cytosol, S9 fractions from human, rat and various human recombinant UGT isozymes, respectively. The generated metabolites were identified by HPLC/MS/MS and quantified by HPLC/UV.Results Three metabolites of B namely baicalein 7-O-glucuronide (BG), the isomer of baicalein 7-O-glucuronide (BG’), and baicalein sulfate were found. BG, the predominant metabolite of B, was extensively generated in liver and jejunum microsomes in both humans and rats. Its formation was mainly catalyzed by UGT 1A9 and also mediated by UGT 1A1, 1A3, 1A8, 1A7 and 2B15 with different kinetic profiles. UGT 1A8 mediated formation of BG’ was mainly found in human intestine and rat liver microsomes. Sulfation and P450 mediated hydroxylation of B were much less significant than glucuronidation.Conclusions Extensive liver and intestinal first-pass glucuronidation of B were found in both humans and rats. Under the current experimental conditions, UGT 1A9 and UGT 1A8 demonstrated the fastest formation rate of BG in human liver preparations and BG’ in human intestine preparations, respectively.     

苦碟子注射液对大鼠肝微粒体CYP450酶5个亚型的体外抑制作用

目的研究苦碟子注射液对大鼠肝微粒体CYP450酶的体外抑制作用。方法制备大鼠肝微粒体。将苦碟子注射液分别与混合探针药物非那西丁、甲苯磺丁脲、奥美拉唑、睾酮和氯唑沙宗共同孵育,UPLC-MS/MS法检测各探针药物的代谢物。结果在测定浓度范围内,苦碟子注射液对CYP2E1、CYP2C9和CYP2C19的活性抑制率小于50%;对CYP1A2、CYP3A4的IC_(50)值分别为12.68%、8.11%,远高于临床日用药浓度0.20%~0.80%。结论在正常剂量下,苦碟子注射液对大鼠CYP2E1、CYP2C9、CYP2C19几乎不显示抑制作用,对CYP1A2、CYP3A4几乎没有抑制作用。     

苯环喹溴铵在大鼠肝微粒体中的代谢转化研究

目的:建立检测大鼠肝微粒体中苯环喹溴铵代谢产物的方法,验证其在大鼠体内的代谢途径。方法:采用大鼠肝微粒体体外温孵法,建立液相色谱-质谱法测定并分析肝微粒体中苯环喹溴铵及其代谢物。色谱及质谱条件如下:色谱柱为TSK-gelODS-80Ts,流动相为甲醇-40mmol·L-1的乙酸铵水溶液(含0.1%甲酸)梯度洗脱;正离子模式,扫描型离子检测。结果:在体外代谢系统中,根据质谱碎片信息检测出6个代谢产物,分别是苯环喹溴铵的二羟基、单羟基和氧化产物。结论:建立的液相色谱-质谱法能够准确灵敏地测定大鼠肝微粒体中苯环喹溴铵的代谢产物,验证了在大鼠体内苯环喹溴铵的代谢部位在环戊烷基上。     

Determination of the human cytochrome P450s involved in the metabolism of 2n -propylquinoline

1 2 n -Propylquinoline (2 n PQ) is a newly developed drug for visceral antileishmaniasis and its activity has been previously evaluated in mice following oral administration. The study was carried out to investigate the kinetic formation of 2 n PQ metabolites and to characterize the human liver CYP forms involved in its oxidative metabolism. 2. The inhibition of 2 n PQ metabolite formation by specific substrates or inhibitors of CYP forms and correlation studies were performed in human liver microsomes. 2 n PQ biotransformation was then studied in human lymphoblasts expressing specific CYPs and microsomal epoxide hydrolase. 3. Three major metabolites were produced by human liver microsomes and their structures were identified by ESI-LC/MS: dihydroxy-2 n -propylquinoline, 3'-hydroxy-2 n -propylquinoline and 1'-hydroxy-2 n -propylquinoline. An intermediary metabolite, epoxy-2 n -propylquinoline, formed by CYP was also biotransformed by microsomal epoxide hydrolase into dihydroxy-2 n -propylquinoline. 4. 2 n PQ oxidation follows Michaelis-Menten kinetics. In human liver microsomes, its metabolism was extremely inhibited by pilocarpine, coumarin and diethyldithiocarbamate. From a panel of 12 human liver microsome samples, the rate of 2 n PQ oxidation was highly correlated with the activities of CYP2A6 and CYP2E1. Human lymphoblasts expressing specific CYPs showed the involvement of CYP2A6, CYP2E1 and CYP2C19. 5. The results indicate that 2 n PQ metabolites are 3'- and 1'-hydroxylated by human liver microsomes and an epoxy-2 n -propylquinoline is biotransformed into a dihydroxy-2 n -propylquinoline by microsomal epoxide hydrolase.     

Comparison of genistein metabolism in rats and humans using liver microsomes and hepatocytes.

Species differences and metabolism are the most crucial factors in considering the effects of genistein. The aim of this study was to have a better knowledge of the metabolic fate of genistein in humans as compared with rats. For this purpose, radiolabeled genistein was incubated with human and rat liver microsomes and with cryopreserved hepatocytes from both species. Incubations were performed using a wide range of genistein concentrations to analyze the kinetics of formation of the metabolites. Metabolite profiling was obtained using an HPLC system connected to a radioactivity detector. Identification of the metabolites was based on their retention times as compared with those of authentic standards and on LC-MS (ESI-MS/MS) or NMR analyses. In both species, liver microsomes produced the same three hydroxylated metabolites (8-OH, 6-OH and 3'-OH-genistein) whereas cryopreserved hepatocytes produced the same glucurono- and sulfo-conjugates (genistein 4'-O-sulfate 7-O-glucuronide, genistein 7-O-glucuronide, genistein 4'-O-glucuronide, genistein 7-O-sulfate and genistein 4'-O-sulfate). The rate of metabolism varied with species. 3'-Hydroxygenistein was the predominant metabolite produced by rat liver microsomes, whereas in humans 3'-hydroxy and 8-hydroxygenistein were produced in the same range. In both human and rat hepatocyte incubations, genistein 7-O-glucuronide represented more than 50% of the incubated dose. Our results on hepatocytes confirmed the predominance of conjugation reaction compared to oxidative reaction observed in vivo.     

Determination of the human cytochrome P450s involved in the metabolism of 2n-propylquinoline

1 2n-Propylquinoline (2nPQ) is a newly developed drug for visceral antileishmaniasis and its activity has been previously evaluated in mice following oral administration. The study was carried out to investigate the kinetic formation of 2nPQ metabolites and to characterize the human liver CYP forms involved in its oxidative metabolism. 2. The inhibition of 2nPQ metabolite formation by specific substrates or inhibitors of CYP forms and correlation studies were performed in human liver microsomes. 2nPQ biotransformation was then studied in human lymphoblasts expressing specific CYPs and microsomal epoxide hydrolase. 3. Three major metabolites were produced by human liver microsomes and their structures were identified by ESI-LC/MS: dihydroxy-2n-propylquinoline, 3'-hydroxy-2n-propylquinoline and 1'-hydroxy-2n-propylquinoline. An intermediary metabolite, epoxy-2n-propylquinoline, formed by CYP was also biotransformed by microsomal epoxide hydrolase into dihydroxy-2n-propylquinoline. 4. 2nPQ oxidation follows Michaelis-Menten kinetics. In human liver microsomes, its metabolism was extremely inhibited by pilocarpine, coumarin and diethyldithiocarbamate. From a panel of 12 human liver microsome samples, the rate of 2nPQ oxidation was highly correlated with the activities of CYP2A6 and CYP2E1. Human lymphoblasts expressing specific CYPs showed the involvement of CYP2A6, CYP2E1 and CYP2C19. 5. The results indicate that 2nPQ metabolites are 3'- and 1'-hydroxylated by human liver microsomes and an epoxy-2n-propylquinoline is biotransformed into a dihydroxy-2n-propylquinoline by microsomal epoxide hydrolase.     

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。     

Characterization of benzimidazole and other oxidative and conjugative metabolites of brimonidine in vitro and in rats in vivo using on-line H/D exchange LC-MS/MS and stable-isotope tracer techniques

The characterization of brimonidine metabolites presents some challenges since brimonidine and its metabolites generate few structurally informative fragment ions in the LC-MS/MS spectra. The objective of the current study is to use on-line hydrogen/deuterium (H/D) exchange LC-MS/MS and stable-isotope tracer techniques to further characterize unknown brimonidine metabolites in vitro and in vivo. Brimonidine and D₄-brimonidine were co-incubated in rat and human microsomes and rabbit aldehyde oxidase in vitro. In addition, the urine was collected from rats co-administered orally with brimonidine and D₄-brimonidine. The hepatic microsomal and urinary metabolites were then characterized by H/D LC-MS/MS system. In addition to previously characterized 2-oxobrimonidine, 3-oxobrimonidine and 2,3-dioxobrimonidine, the results show that oxidation occurs at quinoxaline ring producing oxo-hydroxybrimonidine and hydroxyquinoxaline metabolites. The hydroxyquinoxaline metabolite was only observed in microsomal incubations with hydroxylation at the 7- or 8- position. The dehydro-hydroxybrimonidine metabolites were characterized as 2-oxo or 3-oxo -4′,?5′-dehydrobrimonidine. A novel metabolite ((4-bromo-1H-benzoimidazol-5-yl)-imidazolidin-2-ylidene-amine) of benzimidazole derivative of brimonidine in rats in vivo was identified and confirmed with reference standard. In conclusion, on-line H/D exchange LC-MS/MS and stable-isotope tracer techniques are useful for the characterization of brimonidine metabolites.     

罗通定在人、比格犬和大鼠肝微粒体代谢转化的体外比较研究

目的体外研究罗通定(rotundine,RTD)在大鼠、比格犬和人肝微粒体中酶代谢动力学及代谢产物差异。方法优化3个种属肝微粒体与RTD反应体系,应用LC-MS测定RTD在3种肝微粒体中的体外代谢消除,应用LC-MS/MS分析比较RTD在3种肝微粒体中代谢产物种类和生成量的差异,计算并比较相应的活性值。结果RTD在人肝微粒体中代谢转化最慢,其相应的动力学参数为Km=2.67μmol·L-1、Vmax=0.095μmol·L-1·min-1、T21=298±18.0min、CLint=14.6±0.91ml·min-1·kg-1;大鼠中相应的动力学参数为Km=3.24μmol·L-1、Vmax=0.122μmol·L-1·min-1、T12=71.0±2.30min、CLint=87.5±2.79ml·min-1·kg-1;比格犬中相应的动力学参数为Km=5.31μmol·L-1、Vmax=0.228μmol·L-1·min-1、T21=62.3±0.647min、CLint=139±1.43ml·min-1·kg-1。RTD在3个种属肝微粒体中均代谢产生4个O-去甲基后的羟基化同分异构体产物,但4个产物的相对生成百分比在不同种属肝微粒体中有一定差异。结论罗通定在体外人、大鼠和比格犬肝微粒体中主要的I相代谢途径相同,但是酶代谢动力学性质及代谢产物的生成量存在着一定的差异。