人参皂苷生物转化及其产物的活性研究进展

现代药理研究表明,人参中的稀有人参皂苷具有多种生物活性。稀有人参皂苷天然含量低,可以通过生物转化获得。本文着重综述了人参皂苷生物转化的最新研究成果,及其转化产物的药理活性。     

二萜类化合物微生物转化研究进展

二萜类化合物是一类重要的天然产物,研究发现微生物能对该类化合物进行多种类型的结构修饰。本文根据十年来二萜类化合物生物转化研究的报道,对二萜类化合物的生物转化菌种及催化反应类型进行综述,以期为二萜类化合物生物转化研究与应用提供参考。     

天然药物化学成分的生物转化研究进展

目的:天然药物的化学成分是天然药物研究及天然药物发挥疗效的基础,很难采用常规化学法进行合成或结构改造得到具有新颖活性的化合物,因此采用生物转化的方法对其化学结构进行修饰。文章对天然药物化学成分及其生物转化的研究进展进行概括介绍。方法:查阅国内外及校图书数据库相关文献,以常见天然药物化学成分为基础,将近年来生物转化技术用于如苷类,萜类及生物碱等研究情况进行归纳、总结、评述。结果:国内外学者对天然药物中某种单一有效成分的转化研究较为深入,得到了一些新化合物,其中部分新化合物的活性甚至超过了转化母体。结论:用生物转化的方法处理天然药物,将其用于复杂活性成分的筛选和研制,并与高效快速的药物筛选手段相结合,是发掘天然高活性低毒先导化合物的重要途径。     

天然产物化学的课程教学研究改革

天然产物化学是一门以有机化学为基础的学科,使用化学和物理方法来研究生物体的代谢次级产物,其发展越来越受当代科学家的重视.从目前我国天然产物化学研究中所存在的问题以及面临的机遇与挑战出发,结合天然产物化学的课程特点,对如何开展天然产物化学的教学内容和教学方法进行改革和探索,并提出了对天然产物化学的体会与思考.     

植物天然产物的微生物合成与转化

植物天然产物是一类结构复杂、性能多样的次级代谢产物,广泛应用于食品、药品、化妆品等多个领域。目前植物天然产物的主要来源依赖于从植物中提取,这种生产方式周期长且占用大量耕地。微生物细胞因其生长周期短、操作简便、环境友好、大规模发酵可控等优势而被广泛研究用以替代传统的植物提取法。目前利用微生物细胞工厂合成和转化植物天然产物已成为研究的热点,实现了萜类、黄酮、生物碱、皂苷等多种植物天然产物的合成和转化。本文分别从从头合成和生物转化的角度综述了微生物细胞工厂在植物天然产物合成中的应用,为更加系统、深入地研究植物天然产物的微生物合成与转化提供参考。     

《天然产物化学》课程教学改革研究

天然产物化学以有机化学为基础,是研究天然产物的学科。设立该课程的目的是为了获得新的生物活性物质,服务于人类健康和经济社会发展。作为化学专业学生的重要课程,天然产物化学课程教学尚存在诸多的问题,影响了教学效果和质量。文章分析了天然产物化学课程教学存在的问题,在此基础上提出了天然产物化学课程教学的改革对策,以期更好地促进天然产物化学课程的发展。     

《天然产物化学实验》教学改革初探

天然产物化学实验是天然产物化学理论课程的重要组成部分,本文提出并分析了天然产物化学实验课程中存在的问题,针对优化天然产物化学实验的教学内容,从调整教学方法和模式等方面出发,初步探索了天然产物化学实验的教学改革。     

植物天然产物的微生物合成与转化

植物天然产物是一类结构复杂、性能多样的次级代谢产物,广泛应用于食品、药品、化妆品等多个领域。目前植物天然产物的主要来源依赖于从植物中提取,这种生产方式周期长且占用大量耕地。微生物细胞因其生长周期短、操作简便、环境友好、大规模发酵可控等优势而被广泛研究用以替代传统的植物提取法。目前利用微生物细胞工厂合成和转化植物天然产物已成为研究的热点,实现了萜类、黄酮、生物碱、皂苷等多种植物天然产物的合成和转化。本文分别从从头合成和生物转化的角度综述了微生物细胞工厂在植物天然产物合成中的应用,为更加系统、深入地研究植物天然产物的微生物合成与转化提供参考。     

面手性配体参与的催化氢化合成手性药物研究进展

在天然手性化合物参与下，利用手性诱导外消旋化合物进行拆分或化学计量不对称合成、天然产物转化、生物转化等等是获得手性化合物的重要方法，但这些方法操作繁琐、成本高、产量小，远远达不到工业化生产的要求。不对称催化氢化被认为是最具工业化应用前景的反应，也是目前最成熟的不对称催化反应，已经有许多工业化的实例。综述了面手性二茂铁配体参与的不对称催化氢化反应在手性药物生产过程中应用的研究进展，并对其未来发展方向进行了展望。     

天然产物抑藻活性研究进展

近几年来,环境水体中的有害藻类的频频爆发使得水环境面临着巨大的挑战。而天然产物因其独特的化学结构和生物活性而受到社会各界的广泛关注,多种天然代谢产物对水体中的有害藻华和赤潮有较强的抑制作用,具有较大的防治潜力。本文将从抑藻机理和天然产物的抑藻活性物质等方面进行初步探讨,为天然产物抑藻活性研发提供一定的理论依据。     

Enhancement of Gluconobacter oxydans catalyzing D‐lactic acid production by coupling of synthesis and separation

BACKGROUND: Gluconobacter oxydans was applied for enantioselective oxidation of racemic‐1,2‐propanediol. Accumulation of product in the biotransformation reactor inhibited the activity and enantioselectivity of oxidative enzymes, and it also led to overproduction of lactaldehyde as an intermediate of incomplete oxidation. It was important to improve the enzymatic activity and ee value of the chiral product. RESULTS: The coupling of biotransformation and separation was studied with an in situ product removal method. Anion exchange resin was applied to remove D ‐lactic acid on line. The ee value achieved was 95% and product yield increased by 50%, compared with the control result without coupling system. CONCLUSION: Coupling of biotransformation and separation effectively decreased the free D ‐lactic acid concentration in the system. Product inhibition of enzyme activity and enantioselectivity was reduced, and the ee value and product yield were improved. Copyright © 2009 Society of Chemical Industry     

Intensification of 1‐phenylethanol production by periodical membrane extraction of the product from fermentation broth

BACKGROUND: Enantioselective bioreduction of acetophenone to S‐(?)‐1‐phenylethanol by Saccharomyces cerevisiae under non‐growth conditions is inhibited by the product created. This study investigated the possibility of intensification and mathematical simulation of 1‐phenylethanol production using periodic product removal carried out by membrane extraction in a hollow fiber membrane module. RESULTS: The highest reaction rate was observed at the beginning of the biotransformation. With increased product concentration in the reaction medium, the reaction rate gradually decreased by about 50% after 20 h of biotransformation. The low concentration of product maintained in the reaction medium using membrane extraction had positive influence on the 1‐phenylethanol production with a high yield (96%) and mean reaction rate of 0.226 mg h^?1g^?1, 35% higher than biotransformation without product removal. The equilibrium change and membrane fouling caused by biomass were not significant. It was possible to mathematically simulate the whole course of the extractive biotransformation with good agreement with experimental data. CONCLUSION: Bioreductive production of 1‐phenylethanol is more effective when using periodic membrane extraction of the product from the fermentation broth, which gives higher reaction rate, higher yield and simpler downstream process than biotransformation without product removal. Copyright © 2012 Society of Chemical Industry     

分子印迹技术应用研究

分子印迹技术是在近年来才发展起来的一项新兴技术,具备分子特异识别的功能.本文对其发展历程、基本原理及其在分析化学、天然产物化学、生物学、膜分离、有机合成等方面在国内外应用现状进行综述.     

Rearrangements of electrochemically generated cation radicals: The quest for regiochemical control and an application to total synthesis

Herein we provide an overview of our efforts to achieve regiochemical control in the rearrangement of the cation radicals derived from housanes, and to apply the chemistry to the total synthesis of a natural product.     

A Photoexcited Porphyrin System as a Biomimetic Catalyst for D-limonene Biotransformation

A photoexcited porphyrin system has been found to be an efficient catalyst for D-limonene biotransformation. The catalyst showed high selectivity in hydroxylation of D-limonene. The best catalyst for limonene biotransformation was 5,10,15,20-Tetraphenylporphyrin (H₂TPP), which gave the highest accumulation of carvone and an unknown product with a verbenone-like mass spectrum. The highest conversion yield of these products was favoured at 1:2 molar ratio of H₂TPP to limonene. Some factors affecting the biotransformation yield were also investigated. Maximal yield of carvone was obtained in the medium containing 90% of the substrate, within the period of 18–36 h. Mechanism involved in limonene biotransformation catalysed by H₂TPP is also discussed.     

Maitotoxin: An Inspiration for Synthesis

Maitotoxin holds a special place in the annals of natural products chemistry as the largest and most toxic secondary metabolite known to date. Its fascinating, ladder-like, polyether molecular structure and diverse spectrum of biological activities elicited keen interest from chemists and biologists who recognized its uniqueness and potential as a probe and inspiration for research in chemistry and biology. Synthetic studies in the area benefited from methodologies and strategies that were developed as part of chemical synthesis programs directed toward the total synthesis of some of the less complex members of the polyether marine biotoxin class, of which maitotoxin is the flagship. This account focuses on progress made in the authors' laboratories in the synthesis of large maitotoxin domains with emphasis on methodology development, strategy design, and structural comparisons of the synthesized molecules with the corresponding regions of the natural product. The article concludes with an overview of maitotoxin's biological profile and future perspectives.     

反式茴脑生物降解菌株的筛选及其生物转化

以广西特色香料资源茴油为碳源,开展了反式茴脑生物降解菌株的筛选工作,并对反式茴脑生物转化过程进行了初步研究,以期获得的菌株能催化茴油中的主要成分反式茴脑,合成高附加值的天然香料或医药中间体。通过富集培养的方法,从八角树下土壤中筛选能将反式茴脑转化生成茴香醛或茴香酸的细菌菌株,采用薄层层析法、分光光度法和HPLC法相结合对转化液进行分析。结果筛选到一株细菌菌株BT-13能以茴油为碳源高产茴香酸。从形态、生理生化实验和16S rDNA序列分析,初步鉴定细菌菌株BT-13为假单胞菌属（Pseudomonas sp.）。     

Process integration aspects for the production of fine chemicals illustrated with the biotransformation of γ-butyrobetaine into l-carnitine

l-carnitine is a fine chemical with pharmaceutical, nutritional and animal food applications. Thus, the product purification forms an essential part of the production process. Consequently, process optimization of biotransformation and downstream processing should be done in an integral way. There are several options for the process design of the biotransformation, e.g. chemostat with cell recycling, one-stage or multistage, fed-batch. Blackman kinetics for the product formation of the biotransformation of γ-butyrobetaine into l-carnitine provided adequate modelling of the bioprocess in order to define the optimal process design with respect to productivity, downstream processing and cost. With respect to these criteria, the fed-batch biotransformation of γ-butyrobetaine into l-carnitine appeared to be superior over several modes of operation of the continuous process with cell recycling. A lower productivity of the fed-batch process was compensated by a disproportionally cheaper downstream processing or a lower investment cost.Furthermore, process integration considerations determined the choice of raw materials for the biotransformation, such as carbon and nitrogen sources, resulting in optimized or even a reduced number of unit operations of the downstream processing.     

Discovery of a Short‐Chain Dehydrogenase from Catharanthus roseus that Produces a New Monoterpene Indole Alkaloid

Plant monoterpene indole alkaloids, a large class of natural products, derive from the biosynthetic intermediate strictosidine aglycone. Strictosidine aglycone, which can exist as a variety of isomers, can be reduced to form numerous different structures. We have discovered a short‐chain alcohol dehydrogenase (SDR) from plant producers of monoterpene indole alkaloids (Catharanthus roseus and Rauvolfia serpentina) that reduce strictosidine aglycone and produce an alkaloid that does not correspond to any previously reported compound. Here we report the structural characterization of this product, which we have named vitrosamine, as well as the crystal structure of the SDR. This discovery highlights the structural versatility of the strictosidine aglycone biosynthetic intermediate and expands the range of enzymatic reactions that SDRs can catalyse. This discovery further highlights how a sequence‐based gene mining discovery approach in plants can reveal cryptic chemistry that would not be uncovered by classical natural product chemistry approaches.     

Transformation of Biomass Products into Fine Chemicals Catalyzed by Solid Lewis- and Brønsted-acids

β-Pinene is a biomass product that can be obtained from turpentine oil and transformed into its epoxide by a standard reaction of synthetic organic chemistry. This epoxide can be used as cheap and easily available entry for other natural products with an added value employing different solids as catalysts. Hence, the Lewis acidic mesoporous molecular sieve Sn-MCM-41 provides predominantly myrtanal as product whereas commercial nitrogen containing resins treated with an acid convert β-pinene oxide into perillyl alcohol as main product.