Environmentally directed mutations in the dehalogenase system of Pseudomonas putida strain PP3

Favourable mutations involving the two dehalogenases (DehI and DehII) of Pseudomonas putida PP3 and derivative strains containing the cloned gene for DehI (dehI) occurred in response to specific environmental conditions, namely: starvation conditions; the presence of dehalogenase substrates (halogenated alkanoic acids — HAAs) which were toxic to P. putida; and/or the presence of a potential growth substrate. Fluctuation tests showed that these mutations were environmentally directed by the presence of HAAs. the mutations were associated with complex DNA rearrangements involving the movement of dehI located on a transposon DEH. Some mutations resulted in switching off the expression of either one or both of the dehalogenases, events which were effective in protecting P. putida from toxic compounds in its growth environment. Other mutations partially restored P. putida's dehalogenating capability under conditions where toxic substrates were absent. Restoration of the capability to untilize HAAs was favoured when normal growth substrates were present in the environment.     

Inhibition of penicillin biosynthetic enzymes by halogen derivatives of phenylacetic acid

Summary The effect of phenylacetic acid (PAA) and several analogs on the activity of isopenicillin N synthase (IPNS) and acyl-CoA: 6-APA acyltransferase (AT) fromPenicillium chrysogenum Wis 54-1255 has been tested. Whereas the substitution on the ring of a hydrogen atom by hydroxy-, methyl- or methoxy- groups did not cause any effect, the presence of halogens (Cl or Br) at positions 3 and/or 4 of PAA strongly inhibited these two enzymes. The replacement of hydrogen atoms by fluorine in certain positions also caused inhibition, but to a lesser extent.     

Novel flavonoids from the stem of Popowia cauliflora

Six flavonoids, five of them novel, have been isolated from the whole stem of Popowia cauliflora and identified as: baicalein trimethyl ether, 5-hydroxy-6,7-dimethoxyflavone, 5,7,8-trimethoxyflavanone, 2′-hydroxy-3′,4′,6′-trimethoxychalcone, 2′,3′,4′,6′-tetramethoxychalcone and 2′,4-dihydroxy-3′,4′,6′-trimethoxychalcone, on the basis of spectral data and simple chemical modifications. The value of ¹³C NMR in assigning the positions of methoxy substituents is briefly discussed.     

粘质沙雷氏菌AS-1中SpnR功能及卤化呋喃对其群体感应的抑制

通过分泌和感知一系列信号分子,细菌能够根据自身菌体密度的变化调控基因的表达,从而控制一系列重要的表现型,包括毒力因子的产生,生物膜的形成以及菌体发光等.这种广泛存在的信号机制被称为群体感应.在沙雷氏菌种中已经发现了多套群体感应机制.粘质沙雷氏菌AS-1从土壤中分离,其中含有LuxI/LuxR的同类蛋白,被称为SpnI/SpnR.粘质沙雷氏菌AS-1合成AHLs分子N-hexanoy1-L-homoserinelactone(C6-HSL)和N-(3.oxohexanoyl)-L-homoserine lactone(3-oxo-C6-HSL)作为其信号分子,通过群体感应感知菌体密度来控制基因的表达.通过基因替代的方法制得了spnR基因破坏的变异株,命名为粘质沙雷氏菌AS-1R.对粘质沙雷氏菌AS-1R的研究表明SpnR蛋白消极的调控沙雷氏菌红色色素的产生,运动性以及生物膜的形成等一系列由群体感应控制的性状:另一方面,作为一种天然的群体感应抑制剂,卤化呋喃能够有效的抑制粘质沙雷氏菌AS-1的群体感应,但并不干扰AHL-SpnR的相互作用.为运用粘质沙雷氏菌群体感应调节抑制其致病性提供了方法和依据,同时也为卤化呋喃对群体感应抑制机理的研究提供了新的思路.     

宽泛底物谱色氨酸脱羧酶体外合成卤代色胺衍生物和血清素

【背景】色氨酸脱羧酶在自然界有高度特异性,行使催化色氨酸为色胺的功能。一个色氨酸脱羧酶BaTDC参与南海海绵共生菌Bacillus atrophaeus C89次级代谢产物bacillamides的生物合成过程。【目的】探究BaTDC酶学特征和底物谱,建立体外合成色胺衍生物的方法。【方法】通过构建系统发育树揭示BaTDC在进化中的地位。在温度梯度和pH梯度下进行酶反应,利用不同的色氨酸衍生物为底物,通过HPLC和UPLC-MS检测酶反应过程,表征BaTDC活性。【结果】系统发育分析显示BaTDC与肠道菌Ruminococcus gnavus亲缘关系相近。纯化重组BaTDC的最适温度为40?45 °C,最适pH值为8.0。BaTDC可以催化羟代色氨酸和卤代色氨酸包括4-氟色氨酸和5,6,7-氯色氨酸及4-溴色氨酸,得到相应的卤代色胺衍生物和血清素。【结论】本研究分析了BaTDC的特性,发现BaTDC表现出宽泛的底物耐受性,可为前体喂养或定向生物合成新型药用色胺衍生物和下游复杂天然产物奠定基础。     

Cardamonin Presents in Vivo Activity against Schistosoma mansoni and Inhibits Potato Apyrase

Schistosomiasis, a neglected tropical disease caused by Schistosoma species, harms over 250 million people in several countries. The treatment is achieved with only one drug, praziquantel. Cardamonin, a natural chalcone with in vitro schistosomicidal activity, has not been in vivo evaluated against Schistosoma. In this work, we evaluated the in vivo schistosomicidal activities of cardamonin against Schistosoma mansoni worms and conducted enzymatic apyrase inhibition assay, as well as molecular docking analysis of cardamonin against potato apyrase, S. mansoni NTPDase 1 and S. mansoni NTPDase 2. In a mouse model of schistosomiasis, the oral treatment with cardamonin (400 mg/kg) showed efficacy against S. mansoni, decreasing the total worm load in 46.8 % and reducing in 54.5 % the number of eggs in mice. Cardamonin achieved a significant inhibition of the apyrase activity and the three-dimensional structure of the potato apyrase, obtained by homology modeling, showed that cardamonin may interact mainly through hydrogen bonds. Molecular docking studies corroborate with the action of cardamonin in binding and inhibiting both potato apyrase and S. mansoni NTPDases.     

Design,synthesis and preliminary structure–activity relationship investigation of nitrogen-containing chalcone derivatives as acetylcholinesterase and butyrylcholinesterase inhibitors: a further study based on Flavokawain B Mannich base derivatives

In order to study the structure–activity relationship of Flavokawain B Mannich-based derivatives as acetylcholinesterase (AChE) inhibitors in our recent investigation, 20 new nitrogen-containing chalcone derivatives (4?a–8d) were designed, synthesized, and evaluated for AChE inhibitory activity in vitro. The results suggested that amino alkyl side chain of chalcone dramatically influenced the inhibitory activity against AChE. Among them, compound 6c revealed the strongest AChE inhibitory activity (IC₅₀ value: 0.85?μmol/L) and the highest selectivity against AChE over BuChE (ratio: 35.79). Enzyme kinetic study showed that the inhibition mechanism of compound 6c against AChE was a mixed-type inhibition. The molecular docking assay showed that this compound can both bind with the catalytic site and the peripheral site of AChE.     

Synthesis of novel chalcones through palladium-catalyzed CO cross-coupling reaction of bromo-chalcones with ethyl acetohydroxamate and their antiplasmodial evaluation against Plasmodium falcipuram in vitro

An efficient method for palladium-catalyzed CO cross-coupling of ethyl acetohydroxamate (EAcHO) with 4-bromo-chalcones has been developed to synthesize novel chalcones. The two supporting ligands, namely tBuXPhos (L7), and cataCXium®PIntB (L16) were found to be effective ligands towards the Pd-catalyzed CO cross-coupling reaction to afford the desired product in moderate to excellent yields (50–99%). The coupled products were screened for in vitro blood stage antiplasmodial activity against Plasmodium falciparum (3D7) using the [³H] hypoxanthine incorporation inhibition assay. Of the twenty two compounds screened, eleven showed good antiplasmodial activity with IC₅₀ values ranging from 6–16 μg/mL. The selected active molecules 11, 16, 22, (IC₅₀ 12 μg/mL) and 19 (IC₅₀ 6 μg/mL) were studied for their cytotoxic effect against HepG2 Cells (human hepatocellular liver carcinoma cell lines), showing the selectivity index (SI) values are greater than 4 except chalcone 22. Our result demonstrates a methodology for synthesizing novel chalcones as a new class of antiplasmodial agent.     

Synthesis and biological activity of 4-alkoxy chalcones: potential hydrophobic modulators of P-glycoprotein-mediated multidrug resistance

A series of 4-alkoxy-2′,4′,6′-trihydroxychalcones have been synthesized and evaluated for their ability to inhibit P-glycoprotein-mediated multidrug resistance (MDR) by direct binding to a purified protein domain containing an ATP-binding site and a modulator-interacting region. The introduction of hydrophobic alkoxy goups at position 4 led to much more active compounds as compared to the parent chalcone. The binding affinity increased as a function of the chain length, up to the octyloxy derivative for which a K_D of 20 nM was obtained.     

Diprenylated chalcones and other constituents from the twigs of Dorstenia barteri var. subtriangularis

The twigs of Dorstenia barteri var. subtriangularis yielded three diprenylated chalcones: (-)-3-(3,3-dimethylallyl)-5'-(2-hydroxy-3-methylbut-3-enyl)-4,2',4'-trihydroxychalcone, (+)-3-(3,3-dimethylallyl)-4',5'-[2'-(1-hydroxy-1-methylethyl)-dihydrofurano]-4,2'-dihydroxychalcone and 3,4-(6",6"-dimethyldihydropyrano)-4',5'-[2',-(1-hydroxy-1-methylethyl)-dihydrofurano]-2'-hydroxychalcone for which the names bartericins A, B and C, respectively, are proposed. Stipulin, beta-sitosterol and its 3-beta-D-glucopyranosyl derivative were also isolated. The structures of these secondary metabolites were determined on the basis of spectroscopic analysis, especially, NMR spectra in conjunction with 2D experiments, COSY, HMQC and HMBC. The structural relationship of bartericins B and C was further established by the chemical cyclization of one to the other.