Serine-containing 10-membered cyclodepsipeptides

As a part of a Research program aimed at studying synthesis and conformation of small ring peptides, the cyclization of diastereoisomeric N-phenylacetyl-seryl-propyl-proline tripeptides has been examined. Two 10- membered peptide lactones, and , have been isolated by treating the corresponding linear p-nitrophenyl esters with DBU in dry benzene. In these two compounds the serine lactone fragment (a common structural feature of several bioactive cyclodepsipeptides) is inserted into a highly strained small ring system. The conformation in the crystal of 5a and 5b has been studied by X-ray analysis. Both the 10-membered rings of 5a and 5b adopt an overall cis-cis-trans conformation in which the lactone junction is trans. The deviations from planarity of the peptide units vary from Δω= 30° for the DSer—Pro bond in 5b to Ao= 5-6° for the DSer-PrO bond in 5a and PrO—DPrO bond in 5b . The skeletal atoms of 5b , containing the PrO-DPrO sequence, are related by a pseudo-symmetry mirror plane passing through the Pro carbonyl and the opposite DSer C^βH₂ group. In both the molecules the exocyclic amide bond adopts an extended conformation with respect to the DSer-Pro ring junction; this arrangement gives rise to a C₅-type ring structure which is well evidenced in the case of 5a .     

银杏叶中银杏萜内酯的GC-MS定性定量分析

目的：建立银杏叶中银杏内酯A，B，C和白果内酯的定性定量分析方法。方法：银杏叶以20％乙醇超声提取，乙酸乙酯萃取，再经酸性氧化铝－活性炭－硅藻土混合柱层析，在100℃以双－三甲基硅烷三氟乙酰胺硅烷化60min后，用HP－5 MS毛细管色谱柱，柱温从180℃程序升温至300℃。采用选择离子监测（SIM）方式，以峰值最高的碎片离子作为监视离子进行定量分析。结果：银杏内酯A，B，C和白果内酯的保留时间分别为13．7，14．3，15．3和6．8min，特征（监视）离子（m/z)分别为537，625，713及455（299）；平均回收率分别为102．0％，99．4％，96．0％和96．3％，RSD分别为0．54％，2．40％，1．98％和2．43％。结论：本方法操作简便、重现性好、专属性强、准确可靠，可作为银杏萜内酯的定性定量分析方法。     

Effect of plant phenolic compounds on biofilm formation by Pseudomonas aeruginosa

In the natural environment, bacteria predominantly exist in matrix‐enclosed multicellular communities associated with various surfaces, referred to as biofilms. Bacteria in biofilms are extremely resistant to antibacterial agents thus causing serious problems for antimicrobial therapy. In this study, we showed that different plant phenolic compounds, at concentrations that did not or weakly suppressed bacterial growth, increased the capacity of Pseudomonas aeruginosa PAO1 to form biofilms. Biofilm formation of P. aeruginosa PAO1 was enhanced 3‐ to 7‐fold under the action of vanillin and epicatechin, and 2‐ to 2.5‐fold in the presence of 4‐hydroxybenzoic, gallic, cinnamic, sinapic, ferulic, and chlorogenic acids. At higher concentrations, these compounds displayed an inhibiting effect. Similar experiments carried out for comparison with Agrobacterium tumefaciens C58 showed the same pattern. Vanillin, 4‐hydroxybenzoic, and gallic acids at concentrations within the range of 40 to 400 μg/mL increased the production of N–3‐oxo‐dodecanoyl‐homoserine lactone in P. aeruginosa PAO1 which suggests a possible relationship between stimulation of biofilm formation and Las Quorum Sensing system of this bacterium. Using biosensors to detect N‐acyl‐homoserine lactones (AHL), we demonstrated that the plant phenolics studied did not mimic AHLs.     

基于UHPLC-Q-OrbitrapHRMS技术的参桂胶囊中主要化学成分研究

目的为更加全面、系统、快速地表征参桂胶囊有效化学成分谱,采用超高效液相色谱-四极杆/静电场轨道阱高分辨质谱(UHPLC-Q-OrbitrapHRMS)技术对参桂胶囊中主要化学成分进行快速识别和归属分类。方法采用ACQUITY UPLC?BEH C18色谱柱(100 mm×2.1 mm,1.7μm),以乙腈(A)-0.1%甲酸水(B)为流动相进行梯度洗脱,以实现化合物的前期分离;然后通过Q-Orbitrap MS正、负离子同时监测,一级全扫描及自动触发二级质谱扫描的模式捕捉未知成分的精确相对分子质量及碎片离子信息,同时与对照品的保留时间和质谱数据信息进行匹配,并结合相关文献以及Chemical Book、Mass Bank等数据库最终实现对中药中复杂成分的快速准确识别。结果本研究共鉴定出40种化学成分,其中包括16种皂苷类、6种有机酸类、13种内酯类及5种其他类。结论本法可快速、准确地识别参桂胶囊中主要化学成分,同时为其进一步的药效物质基础、质量控制及临床合理应用等研究奠定了科学的前期基础。     

Two new sesquiterpene lactones from leaves of yacon,Smallanthus sonchifolius

The chemical constituents of 95% EtOH extract of yacon leaves were separated to yield two new sesquiterpene lactones, together with three known compounds. The two new compounds were characterized to be 8β-angeloyloxy-13-methoxyl-11, 13-dihydromelampolid-14-oic acid methyl ester (1) and 8β-(3-methylbut-2-enoyl) oxy-13-methoxyl-11, 13-dihydromelampolid-14-oic acid methyl ester (2) on the basis of NMR spectra, HR-MS and other spectroscopic methods. The cytotoxicity of compounds 1–5 were evaluated on human hepatoma cell Bel-7402 and all the compounds showed moderate cytotoxicity.     

Cytotoxicity of Artemisinin,a Dimer of Dihydroartemisinin,Artemisitene and Eupatoriopicrin as Evaluated by the MTT and Clonogenic Assay

Artemisinin and its derivatives possess an endoperoxide bridge, which is thought to lead to the production of free-radical species. The cytotoxicity of some of these agents to a murine Ehrlich ascites (EN19) and a human HeLa S3 cancer cell line was determined using the MTT and the clonogenic assay. The MTT assay cannot distinguish between growth inhibition and cell killing, while the clonogenic assay detects actual cell death. The use of both assays to test a certain drug may give information on the mode of its cytotoxicity (i.e. growth inhibition versus cell killing). The endoperoxides artemisinin and the dimer of dihydroartemisinin showed much higher cytotoxicity in the MTT assay compared with the clonogenic assay. Thus these drugs mainly induced growth inhibition. For artemisitene and eupatoriopicrin, which possess an exocyclic methylene with alkylating properties, both tests yielded comparable results. For these compounds the MTT assay merely determined cell killing. For the reference drugs cisplatin and doxorubicin the MTT assay showed lower cytotoxicity than the clonogenic assay. This may be explained by the metabolic activity of cells that were clonogenically dead. Moreover, our experiments have shown that the MTT assay may lead to misinterpretations concerning the mode of action of certain drugs, when it is used as a substitute for the clonogenic assay.     

蒙古苍耳化学成分研究

目的:研究蒙古苍耳的化学成分.方法:采用色谱方法分离,通过波谱学方法鉴定结构.结果:从醋酸乙酯提取物中分离得到8个化合物,其中4个为倍半萜内酯类化合物,2个为三萜类化合物,2个为木质素类化合物,鉴定结构分别为:苍耳亭(1),苍耳皂素(2),11 α,13-二氢苍耳亭(3),苍术烯内酯丙(4),齐墩果酸(5),熊果酸(6),松脂素(7)和苯并二氢呋喃类木脂素(8).结论:化合物3～8为首次从蒙古苍耳中分离得到,1～3均表现出细胞黏附分子ICAM-1的诱导阻碍活性,但化合物3的活性较弱.     

不同树龄银杏叶在不同季节中总黄酮和总内酯的含量变化

目的：确定银杏叶最适宜采收季节。方法：采用HPLC法（二级管阵列检测器DAD和蒸发光散射检测器ELSD）分别测定银杏叶中总黄酮和总内酯的含量。结果：不同树龄,不同季节的银杏叶总黄酮、总内酯含量不同,结论：银杏叶的总黄酮、总内酯以二、三年生的为高,总黄酮在5月份,总内酯在9月份含量为高。     

东北红豆杉针叶中两个双重排紫杉烷内酯化合物的结构鉴定

目的研究东北红豆杉Taxuscuspidata针叶中的化学成分。方法采用硅胶柱色谱及制备薄层色谱法分离、纯化化学成分,用一维和二维核磁共振技术鉴定化合物结构。结果从东北红豆杉针叶的甲醇提取物中分离出两个罕见的双重排紫杉烷内酯类化合物wallifoliol()和tasumatrolH()。结论此两种化合物为首次从东北红豆杉中分离得到,在氘代氯仿溶液中化合物在室温下可以转化成5α-乙酰基-2α-苯甲酰氧基-4α,7β,9α,13α,20-五羟基-11(15→1),11(10→9)双重排紫杉烷-11-烯-10,15-内酯()。