Microbial/enzymatic synthesis of chiral pharmaceutical intermediates

Chirality is a key factor in the efficacy of many drugs; thus, the production of single enantiomers of drug intermediates has become increasingly important in the pharmaceutical industry. Chiral intermediates and fine chemicals are in high demand from the pharmaceutical and agrochemical industries for the preparation of bulk drug substances and agricultural products. There has been an increasing awareness of the enormous potential of microorganisms and enzymes for the transformation of synthetic chemicals with high chemo-, regio- and enantioselectivity. In this article, biocatalytic processes for the synthesis of chiral pharmaceutical intermediates are described.     

LC—MS／MS高通量快速筛查中成药和保健品中未知非法添加药物

目的建立LC—MS／MS的筛查方法,高通量快速筛查中成药和保健品中的非法添加药物。方法色谱条件采用ZORBAXXDB—C18柱,乙腈：1mM甲酸铵（含0．1％甲酸）梯度洗脱;质谱条件采用电喷雾离子化源正离子化筛查方式（ESI＋）,通过相关信息扫描模式（IDA）,最终在已建立的谱库中自动搜索出中成药和保健品中未知的非法添加物。结果对于怀疑有未知的非法添加物样本,经18min的快速筛查,可以同时筛查到包括降糖、镇静催眠、解热镇痛、非甾体抗炎、抗生素、抗癫痫等多种类的非法添加药物。结论本文建立的LC—MS／MS方法简单、快速、准确、高通量,可用于筛查中成药和保健品中未知的非法添加物。     

Genetic aspects of metabolic processing of chemical substances.

The Ah locus in the mouse controls the induction of cytochrome P1-450 and at least 10 associated monooxygenase activities. These enzyme systems metabolically potentiate and detoxify chemical carcinogens, environmental pollutants, drugs, and other chemicals, as well as numerous endogenous substrates. With certain substrates cytochrome P1-450 is known to produce a predominance of reactive intermediates and products that differ from those formed by other cytochrome P-450 species. Numerous conditions in the mouse, including cancer, drug toxicity, and birth defects, are directly associated with the Ah locus, which is considered to be a single gene or a small number of genes.     

Conventional and novel approaches in generating and characterization of reactive intermediates from drugs/drug candidates

Despite several thousands of drugs are in use currently, research on new drug molecules is continuing. Because, there are diseases still without medication, successor/better drugs make the predecessor ones obsolete, and advancement in both life sciences and analytical technologies provide identification of previously unknown mechanisms of diseases, and discovery of novel drug targets. The two main criteria which a drug candidate should meet are high affinity for the target, and no or acceptable/tolerable toxicity in humans. Among these two, toxicity is the limiting one; developing a drug candidate with unacceptable toxicity has to be discontinued, even if it has an extremely high pharmacological activity. Drug would be withdrawn, if serious toxicity arises after marketing. Since drug development is a long (approximately 10 years), expensive, and infertile (one lead in 10.000 molecules) process, it is extremely important to detect the potential toxicity of drug candidate as early as possible. Today, it is believed that a great majority of toxic effects are caused by reactive intermediates generated by biotransformation of the parent drug. However, there are experimental difficulties in identifying such metabolite(s) in vivo. Their formation is affected by multi-factorial events; they can further be metabolized to structurally different products, and/or they may bind to a huge variety of biological sites or macromolecules. Hence, some reactive intermediates and their corresponding stable derivatives are generated in trace amounts, which make their determination more difficult. The ability of cytochrome P450s (CYP450) and other biotransformation enzymes to function in vitro offers a great flexibility to researchers, biotransformation of any compound can be simulated in a test tube, and metabolites/reactive intermediates are generated in an environment which has relatively much less background and less interfering multi-factorial events compared to in vivo. To simulate biotransformation, microsomal fraction is used most frequently from human and non-human sources. Purified or recombinant enzymes are used in determining the individual isoenzymes responsible for certain metabolites. Because of the chemical reactivity of intermediates, relevant, usually nucleophilic trapping agent(s) such as glutathione (GSH), N-acetylcysteine (NAC) and cyanide (CN-) are used to stabilize the metabolite. Trapped metabolites are subjected to spectrometric and/or nuclear magnetic resonance spectroscopic analyses for structural identification. Vertiginous advances especially in mass spectrometric technologies offer researchers new challenges in this area. This review is aimed at briefly summarizing the state of the art and compiling the highlighted studies in characterization of the reactive metabolites from drug molecules.     

Role of cyclic tertiary amine bioactivation to reactive iminium species: structure toxicity relationship

Cytochrome P450-mediated bioactivation of drugs to reactive metabolites has been reported to be the first step in many adverse drug reactions. Metabolic activation of cyclic tertiary amines often generates a number of oxidative products including N-dealkylation, ring hydroxylation, α-carbonyl formation, N-oxygenation, and ring opening metabolites that can be formed through iminium ion intermediates. Therapeutic pharmaceuticals and their metabolites containing a cyclic tertiary amine structure have the potential to form iminium intermediates that are reactive toward nucleophilic macromolecules. Examples of cyclic tertiary amines that have the potential for forming reactive iminium intermediates include the piperazines, piperidines, 4-hydroxypiperidines, 4-fluoropiperidines and related compounds, pyrrolidines and N-alkyltetrahydroquinolines. Major themes explored in this review include bioactivation reactions for cyclic tertiary amines, which are responsible for the formation of iminium intermediates, together with some representative examples of drugs and guidance for discovery scientists in applying the information to minimize the bioactivation potential of cyclic amine-based compounds in drug discovery. Potential strategies to abrogate reactive iminium intermediate formation are also discussed.     

Characterization and validation of an in silico toxicology model to predict the mutagenic potential of drug impurities

Control and minimization of human exposure to potential genotoxic impurities found in drug substances and products is an important part of preclinical safety assessments of new drug products. The FDA's 2008 draft guidance on genotoxic and carcinogenic impurities in drug substances and products allows use of computational quantitative structure-activity relationships (QSAR) to identify structural alerts for known and expected impurities present at levels below qualified thresholds. This study provides the information necessary to establish the practical use of a new in silico toxicology model for predicting Salmonella t. mutagenicity (Ames assay outcome) of drug impurities and other chemicals. We describe the model's chemical content and toxicity fingerprint in terms of compound space, molecular and structural toxicophores, and have rigorously tested its predictive power using both cross-validation and external validation experiments, as well as case studies. Consistent with desired regulatory use, the model performs with high sensitivity (81%) and high negative predictivity (81%) based on external validation with 2368 compounds foreign to the model and having known mutagenicity. A database of drug impurities was created from proprietary FDA submissions and the public literature which found significant overlap between the structural features of drug impurities and training set chemicals in the QSAR model. Overall, the model's predictive performance was found to be acceptable for screening drug impurities for Salmonella mutagenicity.     

Do You Get What You Paid For? An Examination of Products Advertised as Kratom

Although some novel psychoactive substances (NPS) are newly discovered chemicals, others are traditional or indigenous substances that are introduced to new markets. One of these latter substances is a plant many people refer to as kratom. Indigenous to Southeast Asia and used for a variety of instrumental and recreational purposes, kratom has recently become available to Western drug users. Kratom is somewhat unique in that the plant contains two different psychoactive chemicals, which have both stimulant (mitragynine) and narcotic (7-hydroxymitragynine) properties. Thus, kratom may appeal to different types of drug users for reasons other than curiosity. In the current study, 15 samples of products that were either directly advertised as kratom or were listed in the results of a web search (but were not directly advertised as kratom) were purchased for testing. After laboratory testing, it was determined that all products advertised as kratom contained the active chemical mitragynine, but 7-hydroxymitragynine was not detected in any of the samples. Implications are discussed.     

Evaluation of action mechanisms of toxic chemicals using JFCR39, a panel of human cancer cell lines

We previously established a panel of human cancer cell lines, JFCR39, coupled to an anticancer drug activity database; this panel is comparable with the NCI60 panel developed by the National Cancer Institute. The JFCR39 system can be used to predict the molecular targets or evaluate the action mechanisms of the test compounds by comparing their cell growth inhibition profiles (i.e., fingerprints) with those of the standard anticancer drugs using the COMPARE program. In this study, we used this drug activity database-coupled JFCR39 system to evaluate the action mechanisms of various chemical compounds, including toxic chemicals, agricultural chemicals, drugs, and synthetic intermediates. Fingerprints of 130 chemicals were determined and stored in the database. Sixty-nine of 130 chemicals ( approximately 60%) satisfied our criteria for the further analysis and were classified by cluster analysis of the fingerprints of these chemicals and several standard anticancer drugs into the following three clusters: 1) anticancer drugs, 2) chemicals that shared similar action mechanisms (for example, ouabain and digoxin), and 3) chemicals whose action mechanisms were unknown. These results suggested that chemicals belonging to a cluster (i.e., a cluster of toxic chemicals, a cluster of anticancer drugs, etc.) shared similar action mechanism. In summary, the JFCR39 system can classify chemicals based on their fingerprints, even when their action mechanisms are unknown, and it is highly probable that the chemicals within a cluster share common action mechanisms.     

Chemical toxicology of reactive intermediates formed by the glutathione-dependent bioactivation of halogen-containing compounds

The concept that reactive intermediate formation during the biotransformation of drugs and chemicals is an important bioactivation mechanism was proposed in the 1970s and is now accepted as a major mechanism for xenobiotic-induced toxicity. The enzymology of reactive intermediate formation as well as the characterization of the formation and fate of reactive intermediates are now well-established. The mechanism by which reactive intermediates cause cell damage and death is, however, still poorly understood. Although most xenobiotic-metabolizing enzymes catalyze the bioactivation of chemicals, glutathione-dependent biotransformation has been largely associated with detoxication processes, particularly mercapturic acid formation. Abundant evidence now shows that glutathione-dependent biotransformation constitutes an important bioactivation mechanism for halogen-containing drugs and chemicals and has for many compounds been implicated in their organ-selective toxicity and in their mutagenic and carcinogenic potential. The glutathione-dependent biotransformation of haloalkenes is the first step in the cysteine S-conjugate beta-lyase pathway for the bioactivation of nephrotoxic haloalkenes. This pathway has been a rich source of reactive intermediates, including thioacyl halides, alpha-chloroalkenethiolates, 3-halo-alpha-thiolactones, 2,2,3-trihalothiiranes, halothioketenes, and vinylic sulfoxides. Glutathione-dependent bioactivation of gem-dihalomethanes and 1,2-, 1,3-, and 1,4-dihaloalkanes leads to the formation of alpha-chlorosulfides, thiiranium ions, sulfenate esters, and tetrahydrothiophenium ions, respectively, and these reactions lead to reactive intermediate formation.     

诱导性多能干细胞体外诱导的现状和展望

鉴于人的胚胎干细胞在再生医学、组织工程学和药物研发等领域有极高的应用价值,科学家尝试通过各种途径获得胚胎干细胞样的多能干细胞。其中Yamanaka等率先在体外通过病毒载体诱导的方式实现体细胞重新编程,由此得到诱导性多能干细胞。多种无遗传修饰的诱导方式正在尝试和改进中,例如用小分子化合物来代替外源基因进行重编程引起了很大的兴趣。用基于细胞水平的表型筛选法和信号通路筛选法,已筛选出特异小分子或天然产物,也可以特异地将成熟细胞去分化为干细胞,有望运用于组织修复和再生。而利用重组蛋白在体外将体细胞诱导为干细胞,也获得了初步成功。由诱导性多能干细胞在体外诱导分化出的细胞在治疗相应疾病方面展示出一定疗效。不同类型的干细胞向体细胞的定向分化策略都是基于目前对发育生物学的认识,这些研究揭示了一些共同的可能线索。     

奥洛他定原料药中间体中乙醇、正丁醇的气相色谱测定方法研究

目的:研究奥洛他定原料药中间体中乙醇、正丁醇的测定方法.方法:采用气相色谱法,对乙醇、正丁醇进行了测定.结果:乙醇、正丁醇可用相应的测定方法准确测出.结论:测定方法准确可靠、重现性好,产品中未检出乙醇、正丁醇.     

专利视角下我国医药中间体应用技术发展态势研究

目的:协助企业了解医药中间体行业相关的技术点和发展趋势,为医药中间体应用技术提供新的发展思路和技术支持.方法:将医药中间体涉及的核心技术列为研究对象并分为四级,检索国家知识产权局专利检索系统(SIPO)及合享(INCOPAT)、智慧芽(PatSnap)专利数据库中2020年2月2日之前公开/公告的医药中间体专利数据.运...     

Novel chemical permeation enhancers for transdermal drug delivery

Transdermal drug delivery has been accepted as a potential non-invasive route of drug administration, with advantages of prolonged therapeutic action, decreased side effect, easy use and better patient compliance. However, development of transdermal products is primarily hindered by the low permeability of the skin. To overcome this barrier effect, numerous new chemicals have been synthesized as potential permeation enhancers for transdermal drug delivery. In this review, we presented an overview of the investigations in this field, and further implications on selection or design of suitable permeation enhancers for transdermal drug delivery were also discussed.     

Life and times in biochemical toxicology

The biochemical facets of toxicology have always had a major role in providing insight into mechanisms. Some of the history of the development of this area is summarized, including metabolism, enzymology, and the chemistry of reactive intermediates. Knowledge in these fields has had a major impact in the areas of drug metabolism and safety assessment, which are both critical steps in the development of pharmaceuticals and the rational use of commodity chemicals. The science of toxicology has developed considerably with input from other disciplines and today is poised to emerge as a predictive science with even more dramatic impact. The challenges ahead are considerable but there is renewed excitement in the potential of the field. As in the past, further advances in the field of toxicology will require the input of knowledge from many disciplines.     

Narrow-and-sharp or broad-and-blunt--regulations of hazardous chemicals in consumer products in the European Union

Chemicals are incorporated into a vast number of consumer products, and it has been recognized that considerable exposures of humans and the environment to chemicals are due to diffuse emissions from everyday products. Different approaches to the management of risks concerning chemicals in products are discussed on the international arena, but no general strategy has yet been adopted. The aim of this study is to investigate how health and environmental risks associated with chemicals in consumer products are currently managed in European Union legislations, mainly by the Toys Directive, the RoHS Directive, and REACH. Significant differences were found between the risk reduction strategies in these legislations, including substance prioritization, type of restrictions and requirements, and information dissemination to consumers. REACH regulates chemicals in products to a limited extent, and via quite complicated processes. Product-specific rules are therefore useful supplements to REACH for regulating chemicals in products. The combined effects of the RoHS and WEEE directives seem to be effective in promoting substitution of substances identified as problematic in electrical and electronic equipment, and it is recommended that the possibility to develop similar systems should be considered also for other product categories.     

Green synthesis and properties of arginine derived complexes for assorted drug delivery systems: A review

In the current scenario, green technologies in chemistry and various fields create attention to every researcher. The green synthesis provides environmentally and eco-friendly raw materials and intermediate products, making a simple process without using harmful and toxic reactants. Amino acids are one of the reactants from which the intermediates or excipients can be made using the straightforward methodology, and these are utilized in drug delivery via a different route of Administration. By employing such medication at a cellular level, we can eliminate the adverse events and toxicity of chemically synthesized excipients and achieve a better therapeutic effect. In the present paper, Arginine was reviewed as the starting material from which the greener excipients can be synthesized, and these materials were employed for drug delivery systems. However, some of the synthetic processes employed chemicals, and also usage of the synthesized green material in the formulation of different dosage forms may require proper guidelines, but still, the research is going on for the application of green excipients for therapeutic purposes. Moreover, Arginine, as such, is an amino acid. It can also be utilized in different formulations as an active ingredient, which was also emphasized in the review paper from past research and patents.This review aims to be comprehensive and have general interest for chemists as it involves the various routes by which excipients were synthesized and the study, including the properties of different excipients and their application.     

A rapid bioassay for chemicals that induce pro-oxidant states

A new bioassay has been developed that allows rapid, sensitive detection of chemicals such as paraquat and adriamycin, which manifest their acute toxicity, mutagenicity or carcinogenicity by inducing a pro-oxidant state in vivo. Submitochondrial particles isolated from bovine myocardium are used to catalyze NADH-dependent enzymatic reduction of these chemicals to free radicals. The highly reactive species generated in this system reduce molecular dioxygen to the superoxide anion radical, which is detected spectrophotometrically using the adrenochrome reaction. The anticancer drug adriamycin, the herbicides paraquat and diquat, the analytical dye sulfonazo III, and the experimental carcinogen 4-nitroquinoline-N-oxide have been used to test the sensitivity of this new method. This assay can be used to screen fresh water samples for the presence of pollutants that can generate oxygen-centered free radicals in vivo, or to test newly synthesized chemicals for this activity, and may therefore be valuable for environmental monitoring and preliminary toxicity evaluation of industrial or pharmaceutical products.     

氮杂环类抗凝血药的有关物质分析方法研究进展

含氮杂环化合物是许多化学药物、天然药物、生物活性大分子的中间体,在抗凝血领域也具有独特的生物活性。药物的质量安全与杂质的含量密切相关,开发一种有效、快速的杂质检测方法变得尤为重要。本文对抗凝血药中的含氮杂环化合物：吡啶及吡啶类衍生物类(硫酸氯吡格雷、普拉格雷、阿加曲班)、咪唑及咪唑衍生物类(阿那格雷、阿哌沙班)、嘧啶类(替卡格雷)的有关物质进行了总结,并归纳了此类药物的杂质结构和国内外现行的分离检测方法,为开发快速有效的含氮杂环化合物检出方法和氮杂环类抗凝药的制备和工艺优化提供参考。     

Development of a consumer product ingredient database for chemical exposure screening and prioritization

Consumer products are a primary source of chemical exposures, yet little structured information is available on the chemical ingredients of these products and the concentrations at which ingredients are present. To address this data gap, we created a database of chemicals in consumer products using product Material Safety Data Sheets (MSDSs) publicly provided by a large retailer. The resulting database represents 1797 unique chemicals mapped to 8921 consumer products and a hierarchy of 353 consumer product “use categories” within a total of 15 top-level categories. We examine the utility of this database and discuss ways in which it will support (i) exposure screening and prioritization, (ii) generic or framework formulations for several indoor/consumer product exposure modeling initiatives, (iii) candidate chemical selection for monitoring near field exposure from proximal sources, and (iv) as activity tracers or ubiquitous exposure sources using “chemical space” map analyses. Chemicals present at high concentrations and across multiple consumer products and use categories that hold high exposure potential are identified. Our database is publicly available to serve regulators, retailers, manufacturers, and the public for predictive screening of chemicals in new and existing consumer products on the basis of exposure and risk.     

The stability studies and in vitro hepatic microsomal metabolism of some alpha-phenyl-N-substituted nitrones in rats.

Nitrones are a very important class of synthetic chemicals as synthetic intermediates, antioxidant agents, and metabolic oxidation products of secondary amines and imines used drug, food, cosmetic and printing industry. In the present study, the stability experiments and in vitro metabolism studies using rat microsomal preparations fortified with NADPH were carried out using three different alpha-phenyl-N-substituted nitrones ie alpha-phenyl-N-tert-butylnitrone (PTBN), alpha-(2,6-dichlorophenyl)-N-phenylnitrone (DCPPN) and alpha-phenyl-N-adamantanylnitrone (PADN). The separation of these compounds from the potential degradation, isomerization and metabolic products were performed using a reverse phase HPLC system with a diodearray uv detection. Following stability experiments at 37 degrees C using methanolic nitrone solutions, it was observed that PTBN produced trace amounts of benzaldehyde and the corresponding amide. DCPPN also produced trace amounts of amide. After 12 hours, the amount of the amide significantly increased. PADN produced trace amount of benzaldehyde but not any amide. The proposed compounds were incubated with rat microsomal preparations fortified with NADPH, extracted into dichloromethane (DCM) and finally evaporated under nitrogen in the dark conditions. PTBN was metabolized into corresponding amide whereas DCPPN and PADN did not. With all of the substrates, the corresponding aldehydes are observed with both test and control tubes using denaturated microsomes and without co-factors.