Evaluation of the antimicrobial activity of ebselen: role of the yeast plasma membrane H+-ATPase

Ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one) is a selenium-containing antioxidant demonstrating anti-inflammatory and cytoprotective properties in mammalian cells and cytotoxicity in lower organisms. The mechanism underlying the antimicrobial activity of ebselen remains unclear. It has recently been proposed that, in lower organisms like yeast, the plasma membrane H+-ATPase (Pma1p) could serve as a potential target for this synthetic organoselenium compound. Using yeast and bacteria, the present study found ebselen to inhibit microbial growth in a concentration- and time-dependent manner, and yeast and Gram-positive bacteria to be more sensitive to this action (IC50 approximately 2-5 microM) than Gram-negative bacteria (IC50 < 80 microM). Washout experiments and scanning electron microscopic analysis revealed ebselen to possess fungicidal activity. In addition, ebselen was found to inhibit medium acidification by PMA1-proficient haploid yeast in a concentration-dependent manner. Additional studies comparing PMA1 (+/-) and PMA1 (+/+) diploid yeast cells revealed the mutant to be more sensitive to treatment with ebselen than the wild type. Ebselen also inhibited the ATPase activity of Pma1p from S. cerevisiae in a concentration-dependent manner. The interaction of ebselen with the sulfhydryl-containing compounds L-cysteine and reduced glutathione resulted in the complete and partial prevention, respectively, of the inhibition of Pma1p ATPase activity by ebselen. Taken together, these results suggest that the fungicidal action of ebselen is due, at least in part, to interference with both the proton-translocating function and the ATPase activity of the plasma membrane H+-ATPase.     

In vitro assessment of the growth and plasma membrane H+‐ATPase inhibitory activity of ebselen and structurally related selenium‐ and sulfur‐containing compounds in Candida albicans

Ebselen (EB, compound 1) is an investigational organoselenium compound that reduces fungal growth, in part, through inhibition of the fungal plasma membrane H⁺‐ATPase (Pma1p). In the present study, the growth inhibitory activity of EB and of five structural analogs was assessed in a fluconazole (FLU)‐resistant strain of Candida albicans (S2). While none of the compounds were more effective than EB at inhibiting fungal growth (IC₅₀ ～ 18 μM), two compounds, compounds 5 and 6, were similar in potency. Medium acidification assays performed with S2 yeast cells revealed that compounds 4 and 6, but not compounds 2, 3, or 5, exerted an inhibitory activity comparable to EB (IC₅₀ ～ 14 μM). Using a partially purified Pma1p preparation obtained from S2 yeast cells, EB and all the analogs demonstrated a similar inhibitory activity. Taken together, these results indicate that EB analogs are worth exploring further for use as growth inhibitors of FLU‐resistant fungi.     

Novel selenoorganic compounds as modulators of oxidative stress in blood platelets

Many selenoorganic compounds play an important role in biochemical processes and act as antioxidants, enzyme inhibitors, or drugs. The effects of five new synthesized selenoorganic compounds (2-(5-chloro-2-pyridyl)-7-azabenzisoselenazol-3(2H)-one; 2-phenyl-7-azabenzisoselenazol-3(2H)-one; 2-(pyridyl)-7-azabenzisoselenazol-3(2H)-one; 7-azabenzisoselenazol-3(2H)-one; bis(2-aminophenyl) diselenide) on oxidative changes in human blood platelets and in plasma were studied in vitro and compared with those of ebselen, a well known antioxidant. Our studies demonstrated that bis(2-aminophenyl) diselenide has distinctly protective effects against oxidative stress in blood platelets and in plasma. It might have greater biological relevance and stronger pharmacological effects than ebselen.     

Density functional theory molecular modelling,DNA interactions,antioxidant, antimicrobial,anticancer and biothermodynamic studies of bioactive water soluble mixed ligand complexes

A novel series of bioactive water soluble mixed ligand complexes (1–5) [M^II(L)(phen)AcO]. nH₂O {where M?=?Cu (1) n?=?2; Co (2), Mn (3), Ni (4), n?=?4 and Zn (5) n?=?2} were synthesized from 2-(2-Morpholinoethylimino) methyl)phenol Schiff base ligand (LH), 1, 10-phenanthroline and metal(II) acetate salt in a 1:1:1 stoichiometric ratio and characterized by several spectral techniques. The obtained analytical and spectral data suggest the octahedral geometry around the central metal ion. Density functional theory calculations have been further supportive to explore the optimized structure and chemical reactivity of these complexes from their frontier molecular orbitals. Gel electrophoresis result indicates that complex (1) manifested an excellent DNA cleavage property than others. The observed binding constants with free energy changes by electronic absorption technique and DNA binding affinity values by viscosity measurements for all compounds were found in the following order (1)?>?(2)?>?(4)?>?(5)?>?(3) > (LH). The binding results and thermodynamic parameters are described the intercalation mode. In vitro antioxidant properties disclose that complex (1) divulges high scavenging activity against DPPH^?, ^?OH, O₂^?? NO^?, and Fe³⁺. The antimicrobial reports illustrate that the complexes (1–5) were exhibited well defined inhibitory effect than ligand (LH) against the selected different pathogenic species. The observed percentage growth inhibition against A549, HepG2, MCF-7, and NHDF cell lines suggest that complex (1) has exhibited superior anticancer potency than others. Thus, the complex (1) may contribute as potential anticancer agent due to its unique interaction mode with DNA.GRAPHICAL ABSTRACT

Communicated by Ramaswamy H. Sarma     

Regulation of <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> Plasma membrane H<Superscript>+</Superscript>-ATPase (Pma1) by Dextrose and Hsp30 during Exposure to Thermal Stress

Pma1p is an essential plasma membrane H⁺-pump in Saccharomyces cerevisiae that pumps out H⁺ at the expense of cellular ATP. Its activity is induced by glucose at 30°C and is inhibited by Hsp30 during exposure to heat shock conditions. To further investigate the regulation of Pma1 function by glucose and Hsp30 during exposure to thermal stress, we estimated Pma1 activity, its protein levels and ser-phosphorylation status in membrane fractions isolated from BY4741 and hsp30Δ cells grown in dextrose and sorbitol at 30°C, and following exposure at 40°C for 30 min. Our results demonstrate that Pma1 activity and protein levels were reduced in Hsp30⁺ cells following exposure to thermal stress in dextrose media. The above was not observed in hsp30Δ cells wherein Pma1 activity did not decrease following exposure to similar conditions. Although Pma1p levels decreased in heat-shocked hsp30Δ cells, it was lower compared to that observed in Hsp30⁺ cells. Total ser-phosphorylation of Pma1 also showed a decrease following exposure to heat shock condition in dextrose media in both BY4741 and hsp30Δ cells. Its levels were also reduced in BY4741 cells upon heat shock treatment in sorbitol unlike that observed in hsp30Δ cells wherein it was increased. Taken together the above indicate that heat shock induced reduction in Pma1 activity and protein levels in dextrose media required Hsp30. To examine functional interactions between dextrose utilization, Hsp30 and the regulation of various aspects of Pma1, we determined if dextrose regulated other functions attributed to Hsp30. Results demonstrate that the deletion of HSP30 rendered cells dependent on dextrose utilization for survival during exposure to lethal heat stress. Our study has hence been able to establish a functional relationship between glucose utilization, Hsp30 function and the regulation of Pma1 activity. Finally, since the deletion of HSP30 renders Pma1p levels and its activity unresponsive to thermal stress in dextrose media, we concluded that Hsp30 is necessary to maintain Pma1 in a regulation competent conformation. Hsp30 may thus act as a chaperone in the S. cerevisiae plasma membrane.     

2,4,5-Triphenylisothiazol-3(2H)-one 1,1-dioxides as inhibitors of human leukocyte elastase

A series of substituted 2,4,5-triphenylisothiazol-3(2H)-one 1,1-dioxides 9 was synthesized and investigated as inhibitors of human leukocyte elastase (HLE). All compounds were found to inhibit HLE in a time-dependent manner and most of them exhibited k_obs/[I] values > 300 M^{? 1}s^{? 1}. The most potent 3-oxosultam of this series was 9l (k_obs/[I] = 2440 M^{? 1}s^{? 1}). Kinetic investigations performed with 9g and different substrate concentrations did not allow to clearly distinguish between a competitive or noncompetitive mode of inhibition. A more complex interaction is supported by the failure of a linear dependency of k_obs values on the inhibitor concentration.     

Microwave assisted synthesis and antimicrobial activity of 2-quinoxalinone-3-hydrazone derivatives

A simple and efficient method has been developed for the synthesis of various 2-quinoxalinone-3-hydrazone derivatives using microwave irradiation technique. The series of 2-quinoxalinone-3-hydrazone derivatives synthesized, were structurally confirmed by analytical and spectral data and evaluated for their antimicrobial activities. The results showed that this skeletal framework exhibited marked potency as antimicrobial agents. The most active antibacterial agent was 3-{2-[1-(6-chloro-2-oxo-2H-chromen-3-yl)ethylidene]hydrazinyl}quinoxalin-2(1H)-one, 7 while 3-[2-(propan-2-ylidene)hydrazinyl]quinoxalin-2(1H)-one, 2 appeared to be the most active antifungal agent.     

Synthesis and biological evaluation of 3-acyl-2-phenylamino-1,4-dihydroquinolin-4(1H)-one derivatives as potential MERS-CoV inhibitors

3-Acyl-2-phenylamino-1,4-dihydroquinolin-4(1H)-one derivatives were synthesized and evaluated to show high anti-MERS-CoV inhibitory activities. Among them, 6,8-difluoro-3-isobutyryl-2-((2,3,4-trifluorophenyl)amino)quinolin-4(1H)-one (6u) exhibits high inhibitory effect (IC₅₀ = 86 nM) and low toxicity (CC₅₀ > 25 μM). Moreover, it shows good metabolic stability, low hERG binding affinity, no cytotoxicity, and good in vivo PK properties.     

Comparison of engineered <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> and engineered <Emphasis Type="Italic">Escherichia coli</Emphasis> for the production of an optically pure keto alcohol

In this study, the production of enantiomerically pure (1R,4S,6S)-6-hydroxy-bicyclo[2.2.2]octane-2-one ((−)-2) through stereoselective bioreduction was used as a model reaction for the comparison of engineered Saccharomyces cerevisiae and engineered Escherichia coli as biocatalysts. For both microorganisms, over-expression of the gene encoding the NADPH-dependent aldo-keto reductase YPR1 resulted in high purity of the keto alcohol (−)-2 (>99% ee, 97–98% de). E. coli had three times higher initial reduction rate but S. cerevisiae continued the reduction reaction for a longer time period, thus reaching a higher conversion of the substrate (95%). S. cerevisiae was also more robust than E. coli, as demonstrated by higher viability during bioreduction. It was also investigated whether the NADPH regeneration rate was sufficient to supply the over-expressed reductase with NADPH. Five strains of each microorganism with varied carbon flux through the NADPH regenerating pentose phosphate pathway were genetically constructed and compared. S. cerevisiae required an increased NADPH regeneration rate to supply YPR1 with co-enzyme while the native NADPH regeneration rate was sufficient for E. coli. Nádia Skorupa Parachin and Magnus Carlquist have contributed equally to the paper.     

Chemical constituents from the fungus Monascus purpureus and their antifungal activity

One new cyclohex-2-enone derivative, purpureusone (1), together with seven known compounds (2–8) were isolated from the n-BuOH-soluble fraction of the 95% EtOH extract of the red yeast rice fermented with the yellow mutant of the fungus Monascus purpureus BCRC 38038. Their structures were characterized by direct interpretation of their spectroscopic methods, including 1D NMR (¹H, ¹³C NMR, DEPT), 2D NMR (COSY, NOESY, HSQC and HMBC), and HRESIMS. Purpureusone (1) contains a cyclohex-2-enone skeleton connected with one γ-lactone ring, one octanoyl, and 2-oxopentyl side chains. Some isolates were evaluated for their antifungal effect against Candida albicans and Saccharomyces cerevisiae using a TLC bioautographic method. Compound 1 showed antifungal inhibitory activity in vitro.     

Synthesis,characterization, antiamoebic activity and cytotoxicity of new pyrazolo[3, 4-d]pyrimidine-6-one derivatives

A new series of pyrazolo[3,4-d]pyrimidine-6-one derivatives (2a–2j) were prepared by using the Biginelli multicomponent cyclocondensation of 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one (1a), different aromatic aldehydes, and urea with a catalytic amount of HCl at reflux temperature. These compounds were characterized by IR, ¹H NMR, ¹³C NMR, and Mass spectral data. In vitro antiamoebic activity was performed against HM1:IMSS strain of Entamoeba histolytica. The results showed that the compounds 2b, 2i, and 2j with IC₅₀ values of 0.37 µM, 0.04 µM, and 0.06 µM, respectively, exhibited better antiamoebic activity than the standard drug metronidazole (IC₅₀?=?1.33 µM). The toxicological studies of these compounds on human breast cancer MCF-7 cell line showed that the compounds 2b, 2i, and 2j exhibited >80% viability at the concentration range of 1.56–50 µM.     

α-Glucosidase inhibitory activity and cytotoxic effects of some cyclic urea and carbamate derivatives

The inhibitory activities of selected cyclic urea and carbamate derivatives (1–13) toward α-glucosidase (α-Gls) in in vitro assay were examined in this study. All examined compounds showed higher inhibitory activity (IC₅₀) against α-Gls compared to standard antidiabetic drug acarbose. The most potent was benzyl (3,4,5-trimethoxyphenyl)carbamate (12) with IC₅₀?=?49.85?±?0.10?µM. In vitro cytotoxicity of the investigated compounds was tested on three human cancer cell lines HeLa, A549 and MDA-MB-453 using MTT assay. The best antitumour activity was achieved with compound 2 (trans-5-phenethyl-1-phenylhexahydro-1H-imidazo[4,5-c]pyridin-2(3H)-one) against MDA-MB-453 human breast cancer cell line (IC₅₀?=?83.41?±?1.60?µM). Cyclic ureas and carbamates showed promising anti-α-glucosidase activity and should be further tested as potential antidiabetic drugs. The PLS model of preliminary QSAR study indicated that, in planing the future synthesis of more potent compounds, the newly designed should have the substituents capable of polar interactions with receptor sites in various positions, while avoiding the increase of their lipophilicity.     

Efficient Synthesis of a New L-Shaped Dimer of Naphthalene,and Its Analogs

Efficient syntheses of 14H-dinaphtho[1,8-bc:1′,8′-fg]oxocin-14-one (2), 14H-dinaphtho[1,8-bc:1′,2′-f]oxepin-14-one (3), and 2,2′(2H,2′H)-spirobi[naphtho[1,8-bc]furan] (9) are described. The putative structure of 2 has been reported previously, but the synthetic route was not reproducible. 7H-Dibenzo[c,h]xanthen-7-one (4), a known compound, was obtained by a different method. Possible reaction mechanism are proposed.     

柯拉斯那沉香的生物活性成分研究

为了解柯拉斯那(Aquilaria crassna)的化学成分,从其所产沉香中分离得到10个化合物,经波谱分析分别鉴定为:6,8-羟基-2-(2-苯乙基)色酮(1),6,8-二羟基-2-[2-(4-甲氧基苯)乙基]色酮(2),rel-(1a R,2R,3R,7b S)-1a,2,3,7b-tetrahydro-2,3-dihydroxy-5-(2-phenylethyl)-7H-oxireno[f][1]benzopyran-7-one(3),rel-(1a R,2R,3R,7b S)-1a,2,3,7b-tetrahydro-2,3-dihydroxy-[2-(4-methoxyphenyl)-ethyl]-7H-oxireno[f][1]benzopyran-7-one(4),rel-(1a R,2R,3R,7b S)-1a,2,3,7b-tetrahydro-2,3-dihydroxy-5-[2-(3-hydroxy-4-methoxyphenyl)-ethyl]-7H-oxireno[f][1]benzopyran-7-one(5),oxidoagarochromone B(6),oxidoagarochromone C(7),(5S,6R,7S,8R)-2-[2-(3′-hydroxy-4′-methoxyphenyl)ethyl]-5,6,7,8-tetrahydroxy-5,6,7,8-tetrahydrochromone(8),6,7-cis-dihydroxy-2-(2-phenylethyl)-5,6,7,8-tetrahydrochromone(9),N-trans-feruloyltyramine(10)。化合物3~5和8~10为首次从柯拉斯那沉香中分离得到。化合物1,3,6,7,9和10对乙酰胆碱酯酶具有一定的抑制活性,化合物4对人慢性髓原白血病细胞株K-562和人胃癌细胞株SGC-7901均具有较小的抑制作用,化合物1和3对人肝癌细胞株BEL-7402也有抑制活性。     

Antifungal secondary metabolites from endophytic Verticillium sp.

Endophytes were isolated from roots of wild Rehmannia glutinosa to screen the strains with antifungal metabolites. A strain identified as Verticillium sp. was selected for chemical and biological investigations because of the strong antifungal activity of the crude extract against Pyricularia oryzae P-2b. Chemical investigations of culture broth afforded three compounds: 2,6-dihydroxy-2-methyl-7-(prop-1E-enyl)-1-benzofuran-3(2H)-one, massariphenone and ergosterol peroxide. The metabolites were isolated by silica gel and Sephadex LH-20, 2,6-dihydroxy-2-methyl-7-(prop-1E-enyl)-1-benzofuran-3(2H)-one was reported for the first time and the chemical structure was established following the analysis of NMR, UV, IR, MS data. 2,6-Dihydroxy-2-methyl-7-(prop-1E-enyl)-1-benzofuran-3(2H)-one and ergosterol peroxide displayed clear inhibition of the growth of three pathogens as well as Verticillium sp.     

Synthesis and antibacterial activity of a new series of 3-[3-(substituted phenyl)-1-phenyl-1H-pyrazol-5-yl]-2H-chromen-2-one derivatives

A series of 3-[3-(substituted phenyl)-1-phenyl-1H-pyrazol-5-yl]-2H-chromen-2-one (4a–k) were synthesized by reaction of 3-[2,3-dibromo-3-(substituted phenyl)propanoyl]-2H-chromen-2-one (3 a-k) with phenyl hydrazine in presence of triethylamine in absolute ethanol, characterized by spectral data and screened for their in vitro antibacterial activity against gram-positive and gram-negative bacteria. Among the series, compounds 4d, 4h and 4i displayed an encouraging antibacterial activity profile as compared to reference standard drug ciprofloxacin against tested bacterial strains.     

Antifungal quinazolinones from marine-derived Bacillus cereus and their preparation

Two new quinazolinones alkaloids, R(+)-2-(heptan-3-yl)quinazolin-4(3H)-one (1) and (2R,3′R)+(2S,3′R)-2-(heptan-3-yl)-2,3-dihydroquinazolin-4(1H)-one (2) (a pair of epimers), as well as seven known analogues, 2-methylquinazolin-4(3H)-one (3), 2-benzylquinazolin-4(3H)-one (4), cyclo-(Pro-Ile), cyclo-(Pro-Leu), cyclo-(Pro-Val), cyclo-(Pro-Phe), and cyclo-(Tyr-Pro) were isolated from the n-butyl alcohol extract of the marine-derived bacterium Bacillus cereus 041381. The new compounds were identified by spectroscopic analysis and chemical synthesis. Four optical isomers 5−8 were also synthesized. Compounds 1−8 all showed moderate antifungal activity against Candida albicans with MIC values of 1.3−15.6 μM. Compound 5 exhibits the most powerful antifungal activity, which may reveal that S-configuration and 2,3-double bond were necessary for antifungal activity, and the racemization at C-2 and C-3′ reduced the antifungal activity.     

Design and synthesis of potent and selective pyridazin-4(1H)-one-based PDE10A inhibitors interacting with Tyr683 in the PDE10A selectivity pocket

Utilizing structure-based drug design techniques, we designed and synthesized phosphodiesterase 10A (PDE10A) inhibitors based on pyridazin-4(1H)-one. These compounds can interact with Tyr683 in the PDE10A selectivity pocket. Pyridazin-4(1H)-one derivative 1 was linked with a benzimidazole group through an alkyl spacer to interact with the OH of Tyr683 and fill the PDE10A selectivity pocket. After optimizing the linker length, we identified 1-(cyclopropylmethyl)-5-[3-(1-methyl-1H-benzimidazol-2-yl)propoxy]-3-(1-phenyl-1H-pyrazol-5-yl)pyridazin-4(1H)-one (16f) as having highly potent PDE10A inhibitory activity (IC₅₀ = 0.76 nM) and perfect selectivity against other PDEs (>13,000-fold, IC₅₀ = >10,000 nM). The crystal structure of 16f bound to PDE10A revealed that the benzimidazole moiety was located deep within the PDE10A selectivity pocket and interacted with Tyr683. Additionally, a bidentate interaction existed between the 5-alkoxypyridazin-4(1H)-one moiety and the conserved Gln716 present in all PDEs.     

Cytotoxic activity of 4′-hydroxychalcone derivatives against Jurkat cells and their effects on mammalian DNA topoisomerase I

Chalcones (1,3-diaryl-2-propen-1-ones) are α, β-unsaturated ketones with cytotoxic and anticancer properties. Several reports have shown that compounds with cytotoxic properties may also interfere with DNA topoisomerase functions. Five derivatives of 4′-hydroxychalcones were examined for cytotoxicity against transformed human T (Jurkat) cells as well as plasmid supercoil relaxation experiments using mammalian DNA topoisomerase I. The compounds were 3-phenyl-1-(4′-hydroxyphenyl)-2-propen-1-one (I), 3-(p-methylphenyl)-1-(4′-hydroxyphenyl)-2-propen-1-one (II), 3-(p-methoxyphenyl)-1-(4′-hydroxyphenyl)-2-propen-1-one (III), 3-(p-chlorophenyl)-1-(4′-hydroxyphenyl)-2-propen-1-one (IV), and 3-(2- thienyl)-1-(4′-hydroxyphenyl)-2-propen-1-one (V). The order of the cytotoxicity of the compounds was; IV > III > II > I > V. Compound IV, had the highest Hammett and log P values (0.23 and 4.21, respectively) and exerted both highest cytotoxicity and strongest DNA topoisomerase I inhibition. Compounds I and II gave moderate interference with the DNA topoisomerase I while III & V did not interfere with the enzyme.