【作者】 董瑞华；

【导师】 宋三泰； 刘泽源；

【作者基本信息】 中国人民解放军军事医学科学院 ， 药理学， 2011， 博士

【摘要】 百里酚和异百里酚是百里香属、薄荷香属等药用植物中广泛分布的单酚类化合物,它们在结构上互为同分异构体。作为百里香属、薄荷香属植物的主要活性成分,百里酚和异百里酚显示了良好的抗氧化、抗炎、抗菌及抗肿瘤等药理学活性,是多味中药产生疗效的物质基础。此外,这两个化合物还作为食品添加剂(FDA和欧盟批准)被广泛应用于食品工业中。借助体外技术体系开展中药活性成分在人体及动物组织的吸收、分布、代谢及排泄(ADME)等性质研究,不仅有助于揭示中药的活性物质基础及其在人体及动物体内的处置进程,进而选择适宜动物模型来开展整体药代、药理及毒理研究;还对科学解释中药体内作用机制以及中草药药物的相互作用具有重大作用。百里酚和异百里酚作为多种药食同源中草药的主要活性成分,其在人体内的代谢转化及其对代谢酶活性的影响对临床安全用药至关重要。然而,到目前为止,对上述两个单酚类化合物的体内代谢途径尚不清楚,其代谢稳定性及代谢行为、以及是否引发药物药物相互作用(DDⅠ)等科学问题至今未得到很好的研究,而这些性质对中药自身以及与其共服药物的有效性和安全性均会产生重大影响。同时,百里酚和异百里酚在多种食物和中草药中大量存在,在人们食用富含百里酚和异百里酚的食物时其与其它食物和药物的相互作用,非常值得我们关注,尤其是对患者在临床用药中的药物膳食结构更应引起我们的注意。酚类化合物在中草药中广泛存在且结构多样、而且多具有抗氧化、抗炎、抗菌等活性,其不但为新药研发提供了广阔的资源,同时其代谢产物又进一步丰富了化合物的结构多样性。药物代谢性质的研究,对先导化合物的优化、中药作用机理的发现及药物的安全有效使用均具有重要意义。同时多数酚类化合物均是Ⅱ相代谢酶的天然底物,包括磺酸化酶,甲基化酶,葡萄糖醛酸化酶(UGT)等Ⅱ相代谢酶;但作为人体主要代谢酶的细胞色素氧化酶P450更倾向于代谢含有疏水基的化合物,然而既含有酚羟基又具有疏水基的物质其在人体内代谢行为,及在特定化合物中CYP与UGT代谢的重要性至今鲜有报道。本研究利用人肝及动物肝微粒体等体外孵育体系,对百里酚和异百里酚的体外代谢稳定性、代谢酶动力学、种属差异、药物相互作用以及化合物结构对药物代谢行为的影响进行了系统研究。本论文首先建立了百里酚和异百里酚的高效液相检测方法;所建立的方法具有很好的特异性;精密度和准确度及稳定性等研究均符合方法学的要求;经过方法学验证,该方法可以满足百里酚和异百里酚两种化合物在后续研究中的定量要求。在此基础上,论文着重对百里酚和异百里酚进行了体外Ⅰ、Ⅱ相酶代谢研究,阐明了两化合物的代谢途径;同时考察了两化合物代谢的种属差异及药物相互作用的效应。本论文系统研究了百里酚和异百里酚体外Ⅰ相代谢,阐明了两化合物在人肝中的Ⅰ相代谢途径。在人肝微粒体孵育体系中,百里酚在能生成一个羟化代谢产物(M 1),异百里酚能够生成两个羟化代谢产物(M 1,M 2)。进一步研究证实,CYP1A2、CYP2A6和CYP2B6参与了百里酚的Ⅰ相代谢,CYP1A2、CYP2A6参与了异百里酚Ⅰ相代谢M 1的生成,CYP1A2、CYP2A6和CYP2B6则参与介导了M 2的生成。在不同种属间的代谢能力表现出较大的差异,依据研究的不同目的,可以选择不同的实验动物作为模型。在研究原形的毒性时,可能要考虑清除比较慢的动物。在研究代谢产物的毒性时,可能要考虑代谢转化较快的动物。各种属对百里酚和异百里酚CYP代谢能力的差异,也提示在未来工作中,深入研究代谢物的活性及毒性是非常有必要的。本论文同时研究了百里酚和异百里酚体外Ⅱ相代谢,阐明了两化合物在人肝和人肠中的Ⅱ相代谢途径。在人肝和人肠微粒体孵育体系中,百里酚和异百里酚都能生成一个单葡萄糖醛酸结合物。进一步研究证实,两化合物的葡萄糖醛酸结合代谢都是多酶参与的过程,其中UGT1A3、UGT1A7、UGT1A8、UGT1A9和UGT2B7能催化百里酚的葡萄糖醛酸化代谢,UGT1A3,UGT1A6,UGT1A7,UGT1A9和UGT2B7能催化异百里酚的葡萄糖醛酸化代谢。通过抑制剂研究发现,UGT1A9在人肝脏代谢中起主要作用,UGT1A7在人肠代谢中起主要代谢作用。两个化合物在不同种属间的葡萄糖醛酸化代谢酶谱尽管没有区别,但是代谢活性还是存在着较大的差异,需要在后续研究中依照不同的研究目的选择合适的动物代谢模型。通过比较百里酚和异百里酚的Ⅰ、Ⅱ相代谢发现,异百里酚无论在Ⅰ相还是Ⅱ相酶代谢过程中,均表现出了比百里酚较高的代谢活性和相对高的代谢清除率。尤其是在Ⅱ相葡萄糖醛酸化代谢中表现更为明显。同时发现,在百里酚的Ⅰ相、Ⅱ相代谢比较中,CYP代谢路径的代谢清除率占有更大优势,可能是其主要的代谢途径。在异百里酚的代谢中,UGT代谢所起的作用更加重要,暗示疏水集团和酚羟基的空间距离在决定药物代谢途径和代谢快慢上具有重要作用。本论文还考察了百里酚和异百里酚引发DDⅠ的可能性,研究发现异百里酚能够抑制UGT1A9的活性。该抑制表现出了明显依赖于酶或底物的特点。通过异百里酚对UGT特异性探针底物4 MU和异丙酚抑制作用的能力来评价其导致DDⅠ的可能性。结果发现,异百里酚对4 MU在UGT1A9代谢中产生了竞争性的抑制作用(Ki=5.7 M),而在对异丙酚在UGT1A9单酶代谢中产生了非竞争性的抑制作用(Ki=25.0 M)。所以在临床或者食用异百里酚的过程中需要注意DDI的可能性作用。比较两种化合物的结构并结合国内外已有文献,发现疏水基远离酚羟基的化合物更趋向于发生Ⅱ相化代谢;同时其代谢酶谱也产生一定的差异,代谢能力也发生很大的变化;这可能是由于疏水基空间位阻的作用产生了上述的影响。以上发现提示小分子化合物结构上的微小变化,都可能会导致代谢途径的巨大差异。在模式实验动物选择中应选择与人具有相似代谢行为和代谢能力的动物来开展整体动物实验,若利用了不合适的动物模型进行临床前研究可能会产生较大差异、从而影响临床实验的设计及数据的可靠性。本研究对百里酚和异百里酚的体外代谢系统研究,首次报道揭示了它们的代谢通路,有助于对该类化合物在药物早期研究中的‘成药性’进行评估。同时丰富了单酚类化合物的药代动力学研究,对此类化合物的后续研究提供了理论依据和实验支持。也对临床药物膳食结构具有一定的指导意义。更多还原

【Abstract】 Thymol and carvacrol are isomers in structure, which are predominant monoterpenic phenol widely distributed in thyme and oregano. Thymol and carvacrol are the major component of thyme and oregano essential oils, which have many diverse pharmacology activities such as antioxidant, anti inflammatory, antibacterial and anti tumor. In addition, the two compounds are also widely used as a food additive in the food industry. The study of absorption, distribution, metabolism and excretion (ADME) properties in the human body and animals tissues of the main active ingredients of Chinese medicine, which carry out in vitro technology system, not only helps to reveal the material basis of the activity of traditional Chinese medicine and its disposal of human and animal body process, then select the appropriate animal model to carry out the overall pharmacokinetics, pharmacology and toxicology; also have a significant role to explain the mechanism of traditional Chinese medicine in the human body and Chinese herbal medicine drug interactions. Thymol and carvacrol are the main active ingredients of Chinese herbal medicine homology as many different variety of food and medicine; and which the contribution of its metabolic transformation in the human body and its effects on the metabolic enyme activity is essential for the clinical safety of drugs. However, so far, metabolic pathway of the two monoterpene in vivo is not clear, the metabolic stability and metabolic behavior, and whether the cause of drug drug interactions (DDI) and other scientific issues has not been well study; and these properties for the safety and effectiveness of the Chinese medicine itself and co administer drug will have a significant impact.Phenolics compounds is widespread in Chinese herbal medicine and structurally diverse, and most have antioxidant, anti inflammatory, antibacterial activity; which not only furnish the extensive resources for the new drug development, and its metabolites further enrich the structure of various compounds. The study is to investigate the metabolic stability in vitro, enzyme pharmacokinetics, species differences, drug drug interaction and structure pharmacokinetics of thymol and carvacrol, which use human liver microsomes, animal liver microsomes and other in vitro incubation systems The different methods of high performance liquid detection for thymol and carvacrol were established at first. The method has good specificity, which the precision & accuracy and stability of it are in line with methodology requirements; and the method can meet the quantitative requirements for the follow up study. On this basis, the paper focuses on in vitro phase I andⅡmetabolism of thymol and carvacrol, and the metabolic pathways of the two compounds have been elucidation.In vitro phase I of thymol and carvacrol were investigated in this study, and the phase I pathway of the two compounds in HLMs were illustrated. There were one hydroxylated metabolite (M 1) found in the metabolic reaction of thymol and two hydroxylated metabolites (M 1, M 2) generated in the metabolic reaction of carvacrol. Throughout the investigation of recombine CYP and inhibitory effects, we found CYP1A2, CYP2A6 and CYP2B6 were involved in the metabolism of thymol in the hydroxylation reaction; CYP1A2, CYP2A6 involved in the formation of M 1, and CYP1A2, CYP2A6 and CYP2B6 were involved in the formation of M 2. The diversity of the ability of metabolism was shown in different species, so we can select animal model according as the object of the study. For the toxicity study of former drug, the animal which have the comparatively slow clear rate was the better choice; but for the metabolite, the quicker the better. The diversity of the CYP in the different species prompt us the study of pharmacodynamics and toxicity of metabolite were very essentialMeanwhile, the investigation of the in vitro phaseⅡof thymol and carvarol were carried out, the phaseⅡpathyway of it in HLMs and HIMs were clarified. There were one glucuronidation metabolite found in the HLMs and HIMs. The study also validated there were more enzymes involoved the reaction. Chmical inhibition studies and related screening of recombinant human enzyme were experimented, and found UGT1A3, UGT1A7, UGT1A8, UGT1A9, and UGT2B7 involoved in the thymol glucuronidation metabolic response, UGT1A3, UGT1A6, UGT1A7, UGT1A9 and UGT2B7 in carvacrol. Furthermore, we indentified UGT1A9 as the major isozyme responsible for carvacrol glucuronidation in HLMs; and the UGT1A7 as the major isozyme responsible in HIMs. In dispite of there is not much different in zymogram between the different spices, the ability of metabolism have shown the huge diversity. So, the selection of the animal model should be in line with the orders.The kinetic paraments showed that carvacrol have own the relatively high metabolic activities and clearance rate than thymol in terms of phase I or II metabolic reactions, especially in the glucuronidation of carvacrol. Meanwhile, the higher clearance rate of thymol hydroxylation in the phase I and II shown that the CYP might be the main metabolic pathway of thymol in human; and the result of the carvacrol in the phase I and II indicate the CYP and UGT metabolism might have the identical contribution in human body. The results shown that the interspace between the hydrophobic group and hydroxyl group have the significant effects in determining the pathyway and speed of metabolism.The study also extremely investigated the inhibitory effects of carvacrol and thymol on major CYP and UGT isoformes, and the carvacrol have the ability of inhibition on UGT1A9 isoformes. The probe substrate for all tested UGT isoforms is 4 MU which is a nonselective substrate of UGTs, and the Propofol, mainly metabolized by UGT1A9, could be used as a probe substrate for UGT1A9. The results showed that carvacrol could inhibit the activity of UGT1A9 with negligible effects on other UGT isoforms. The carvacrol competitively inhibit UGT1A9 mediated 4 MU glucuronidation reaction (Ki=5.7 M), but the noncompetitively inhibiton found in carvacrol towards UGT1A9 mediated propofol glucuronidation(Ki=25.0 M). To date, mechanism of substrate dependent inhibition of drug metabolizing enzymes was still unclear. Therefore, in vitro data on the inhibition of UGT1A9 by carvacrol should be interpreted with caution.We found the compounds that the hydrophobic group far from the phenolic hydroxyl group have the tendency of occurrence of phase II, through compare the structure between the two compounds and analysis the literature at home and abroad. Meanwhile, there were some different on the metabolic enzyme and metabolic capability, which may be due to the stereospecific blockade effects of hydrophobic group. These findings suggest that small changes in the structure of small molecule compounds, may lead to a huge difference in the metabolic pathways. It should be selected with the people with similar metabolic behavior and metabolic capability to carry out the whole animal experiments, if the inappropriate animal models were be use, the pre clinical study may generate vary significantly, thus affecting the design of clinical trials and data reliability.In this study, the in vitro metabolism of thymol and carvacrol were carried out, and the metabolism pathway of the two compounds were first clarified, and the consequence is very useful to asses the‘medicine’for the candidate compounds in the early development. However, the result enriches the pharmacokinetic study of monoterpenic phenol, and provide a theoretical basis and experimental support for such compounds in the follow up study.更多还原