Dimeric 3,5-Bis(benzylidene)-4-piperidones: Tumor-Selective Cytotoxicity and Structure-Activity Relationships.

Background: The objective of this study is to find novel antineoplastic agents that display greater toxicity to malignant cells than to neoplasms. In addition, the mechanisms of action of representative compounds are sought. This report describes the cytotoxicity of a number of dimers of 3,5-bis(benzylidene)-4-piperidones against human malignant cells (promyelocytic leukemia HL-60 and squamous cell carcinoma HSC-2, HSC-3, and HSC-4). Methods: Tumor specificity was evaluated by the selectivity index (SI), that is the ratio of the mean CC50 for human non-malignant oral cells (gingival fibroblasts, pulp cells, periodontal ligament fibroblasts) to that for malignant cells. Results: The compounds were highly toxic to human malignant cells. On the other hand, these molecules were less toxic to human non-malignant cells. In particular, a potent lead molecule, 3b, was identified. A QSAR study revealed that the placement of electron-releasing and hydrophilic substituents into the aryl rings led to increases in cytotoxic potencies. The modes of action of a lead compound discovered in this study designated 3b were the activation of caspases-3 and -7, as well as causing PARP1 cleavage and G2 arrest, followed by sub-G1 accumulation in the cell cycle. This compound also depolarized the mitochondrial membrane and generated reactive oxygen species in human colon carcinoma HCT116 cells. In conclusion, this study has revealed that, in general, the compounds described in this report are tumor-selective cytotoxins.

Benzoxazole-Based Metal Complexes to Reverse Multidrug Resistance in Bacteria.

Bacteria often show resistance against antibiotics due to various mechanisms such as the expression of efflux pumps, biofilm formation, or bacterial quorum sensing (QS) controls. For successful therapy, the discovery of alternative agents is crucial. The objective of this study was to evaluate the efflux pump, anti-biofilm, and QS inhibiting, as well as antibacterial effects of 2-trifluoroacetonylbenzoxazole ligands (1-3) and their metal complexes (4-12) in bacteria. The ligand 2 and its Zn(II) complex 5, and furthermore the Cu(II) complex 7 of ligand 1, exerted remarkable antibacterial activity on the Staphylococcus aureus 272123 (MRSA) strain. In the minimum inhibitory concentration (MIC) reduction assay the ligand 3, the Zn(II) complex 5 of ligand 2, and the Cu(II), Ni(II), Mg(II), Fe(III) complexes (7, 8, 9, 12) of ligand 1 enhanced the antibacterial activity of ciprofloxacin in MRSA. An increased ethidium bromide accumulation was detected for ligand 3 in MRSA while the Fe(III) complex 12 of ligand 1 decreased the biofilm formation of the reference S. aureus ATCC 25923 strain. The Zn(II) and Ag(II) complexes (3 and 4) of ligand 1 and ligand 3 inhibited the QS. Based on our results, the ligands and their metal complexes could be potential alternative drugs in the treatment of infectious diseases.

On the Electronic Nature of Bis((Z)-1-(benzo[d]oxazol-2-yl)-3.3.3-trifluoroprop-1-en-2-ate)palladium.

The electronic nature of the recently reported complex, bis((Z)-1-(benzo[d]oxazol-2-yl)-3.3.3-trifluoroprop-1-en-2-ate)palladium, is re-investigated by a combination of spectroscopy (NMR, IR, magnetic moment, etc.) and Density Functional Theory (DFT: B3LYP 6-31G*/LANL2DZ). In contrast to the recent report, the title complex displays all the properties of diamagnetism and hence retains the properties of a formally Pd(II) square planar complex with a bis-κ2-N,O-donor ligand set. A modified synthetic route is also presented which improves the yield of the compound.

Benzoxazole-based Zn(II) and Cu(II) Complexes Overcome Multidrug-resistance in Cancer.

BACKGROUND/AIM: Multidrug resistance (MDR) represents a significant impediment to successful cancer treatment. In this study, novel metal [Zn(II), Cu(II), Mg(II), Ni(II), Pd(II), and Ag(I)] complexes of 2-trifluoroacetonylbenzoxazole previously synthesized and characterized by our group were tested for their MDR-reversing activity in comparison with the free ligands in L5178Y mouse T-lymphoma (MDR) cells transfected with human ATP-binding cassette sub-family B member 1 (ABCB1; P-glycoprotein) gene. MATERIALS AND METHODS: Cytotoxic and antiproliferative effects of the complexes were assessed by the thiazolyl blue tetrazolium bromide (MTT) method. Modulation of ABCB1 activity was measured by rhodamine 123 accumulation assay using flow cytometry. The apoptosis-inducing activity of some complexes was also tested on the multidrug resistant L5178Y mouse T-lymphoma cells, using the annexin-V/propidium iodide assay. RESULTS: When compared to the free ligand, a remarkable enhancement in MDR reversal and cytotoxic activity was found for the Zn(II) and Cu(II) complexes. The activity of the complexes proved to be up to 29- and 5-fold higher than that of the ligands and the ABCB1 inhibitor verapamil as positive control, respectively. The complexes possessed a remarkable potential to induce apoptosis of MDR cells. CONCLUSION: Our results suggest that the Zn(II) and Cu(II) complexes display significant MDR-reversing activity in a dose-dependent manner and possess strong cytotoxic activity and a remarkable potential to induce apoptosis in MDR L5178Y mouse T-lymphoma cells.

Synthesis and Antimicrobial Activity of 2-Trifluoroacetonylbenzoxazole Ligands and Their Metal Complexes.

Three 2-fluoroacetonylbenzoxazole ligands 1a-c and their new Zn(II) complexes 2a-c have been synthesized. In addition, syntheses of new metal [Mg(II), Ni(II), Cu(II), Pd(II), and Ag(I)] complexes from 1a have been also described. The molecular and crystal structures of six metal complexes 2b and 2d-h were determined by single-crystal X-ray diffraction analyses. Their antibacterial activities against six Gram-positive and six Gram-negative bacteria were evaluated by minimum inhibitory concentrations (MIC), which were compared with those of appropriate antibiotics and silver nitrate. The results indicate that some metal compounds have more antibacterial effects in comparison with free ligands and have preferred antibacterial activities that may have potential pharmaceutical applications. Noticeably, the Ag(I) complex 2h exhibited low MIC value of 0.7 µM against Pseudomonas aeruginosa, which was even superior to the reference drug, Norfloxacin with that of 1.5 µM. Against P. aeruginosa, 2h is bacteriostatic, exerts the cell surface damage observed by scanning electron microscopy (SEM) and is less likely to develop resistance. The new 2h has been found to display effective antimicrobial activity against a series of bacteria.

A Novel Methodology for Synthesis of 1,5,6-Trisubstituted 2(1H)-Pyrazinones of Biological Interest.

In this report, we describe a new method for the synthesis of densely functionalized 2(1H)-pyrazinones. Treatment of mesoionic 1,3-oxazolium-5-olates with carbanions derived from activated methylene isocyanides (p-toluenesulfonylmethyl isocyanide (TosMIC) and ethyl isocyanoacetate) causes a novel ring transformation affording 2(1H)-pyrazinones in moderate to high yields. The cytotoxicity and antibacterial activity of some of the obtained products were studied and some of the products exhibited tumor-specific cytotoxicity.

6-Benzylidene-2-[4-(pyridin-3-ylcarboxy)benzylidene]cyclohexanones: A novel cluster of tumour-selective cytotoxins.

Novel cytotoxins 3-5 containing the 1,5-diaryl-3-oxo-1,4-pentadienyl pharmacophore are disclosed. The compounds in series 3 and 5 have the potential to liberate niacin which may reduce some of the side effects of antineoplastic compounds. 3a-c emerged as the most potent cytotoxic compounds with IC50 values in the low micromolar range against human Molt4/C8 and CEM CD4+ T-lymphocytes as well as murine L1210 leukemia cells. QSAR studies revealed that cytotoxic potencies were negatively correlated with the magnitude of the Hammett sigma values of the aryl substituents. The compounds 3a-e displayed tumour-selective toxicity against human HL-60, HSC-2, HSC-3 and HSC-4 neoplasms as compared to human HGF, HPC and HPLF nonmalignant cells. A representative potent compound 3a caused PARP1 cleavage and G0/G1 cell cycle arrest in HSC-2 cells. These compounds are well tolerated in mice at doses up to and including 300mg/kg of the compounds and no mortalities were noted after 4h. The stability studies undertaken did not reveal that a representative compound 3a underwent hydrolysis to the related phenol 2a. Some guidelines for further analog development of the novel esters 3 were made.

Fluorinated Beta-diketo Phosphorus Ylides Are Novel Efflux Pump Inhibitors in Bacteria.

BACKGROUND: One of the most important resistance mechanisms in bacteria is the increased expression of multidrug efflux pumps. To combat efflux-related resistance, the development of new efflux pump inhibitors is essential. MATERIALS AND METHODS: Ten phosphorus ylides were compared based on their MDR-reverting activity in multidrug efflux pump system consisting of the subunits acridine-resistance proteins A and B (AcrA and AcrB) and the multidrug efflux pump outer membrane factor TolC (TolC) of Escherichia coli K-12 AG100 strain and its AcrAB-TolC-deleted strain. Efflux inhibition was assessed by real-time fluorimetry and the inhibition of quorum sensing (QS) was also investigated. The relative gene expression of efflux QS genes was determined by real-time reverse transcriptase quantitative polymerase chain reaction. RESULTS: The most potent derivative was Ph3P=C(COC2F5)CHO and its effect was more pronounced on the AcrAB-TolC-expressing E. coli strain, furthermore the most active compounds, Ph3P=C(COCF3)OMe, Ph3P=C(COC2F5)CHO and Ph3P=C(COCF3)COMe, reduced the expression of efflux pump and QS genes. CONCLUSION: Phosphorus ylides might be valuable EPI compounds to reverse efflux related MDR in bacteria.

Niacin esters of chalcones with tumor-selective properties.

Novel series of niacin esters of chalcones 2, 4 and 6 were designed as antineoplastic agents that have the potential to release the chemoprotectant niacin. These enones are cytotoxic to human CD4(+ )T-lymphocyte Molt 4/C8 and CEM and murine leukemia L1210 cells. Quantitative structure-activity relationship (QSAR) studies of the biodata in series 4 revealed that cytotoxic potency was enhanced by placing electron-repelling groups in one of the aryl rings. The compounds are lethal to HL-60, HSC-2, HSC-3 and HSC-4 neoplasms but less toxic to nonmalignant hepatocyte growth factor, hematopoietic progenitor cell and human periodontal ligament fibroblast cells. Hence, the compounds display tumor-selective toxicity. These chalcones are well tolerated in mice and no overt toxicity was noted. The results establish that in general the compounds in series 2, 4 and 6 have positive characteristics which warrant further studies.

Synthesis and structures of stable phosphorus zwitterions derived from mesoionic 4-trifluoroacetyl-1,3-oxazolium-5-olates.

Trialkyl phosphites were evaluated as phosphorus nucleophiles for addition to mesoionic 4-trifluoroacetyl-1,3-oxazolium-5-olates (1), thereby producing tetravalent phosphorus zwitterions (2) in good yields. The structure of 2 was determined to be a tetravalent phosphonium enolate via single crystal X-ray analysis.

Tumour-specific cytotoxicity and structure-activity relationships of novel 1-[3-(2-methoxyethylthio)propionyl]-3,5-bis(benzylidene)-4-piperidones.

A series of 1-acyl-3,5-bis(benzylidene)-4-piperidones 3-7 were designed and synthesized as novel cytotoxic agents. These compounds displayed potent cytotoxic properties towards human Molt4/C8, CEM, HSC-2, HSC-3 and HSC-4 neoplasms and also to murine L1210 cells. The majority of the compounds have sub-micromolar or very low micromolar IC50 and CC50 values and are significantly more potent than the reference alkylating drug melphalan. Evaluation of these compounds against non-malignant HGF and HPLF cells revealed the tumour-specific toxicity. In particular, 3e emerged as a promising lead cytotoxic agent which caused apoptosis and PARP1 cleavage in HSC-2 cells.

3,5-Bis(3-alkylaminomethyl-4-hydroxybenzylidene)-4-piperidones: A Novel Class of Potent Tumor-Selective Cytotoxins.

Novel 4-piperidone derivatives 2a-f are disclosed as potent cytotoxins. Many of these compounds are more potent than the reference drug melphalan. The compounds in series 2, 4-7 display selective toxicities toward various neoplasms compared to some normal cells. 2a is one of the promising lead molecules that display >11-fold higher growth inhibiting potency than 5-fluorouracil against human colon cancer cells. 2a induces apoptosis, DNA fragmentation, and cleavage of poly ADP-ribose polymerase.

Fluorinated ß-Diketo Phosphorus Ylides Are Novel Inhibitors of the ABCB1 Efflux Pump of Cancer Cells.

Efflux pump inhibitors are attractive compounds that reverse multidrug resistance (MDR) in cancer cells. In the present study, 10 phosphorus ylides (P-ylides) were compared based on their MDR-reverting activity in human ATP-binding cassette sub-family B member 1 (ABCB1; P-glycoprotein) gene-transfected L5178Y mouse T-lymphoma cells. Among them, three P-ylides, Ph3P=C(COCF3)COPh, Ph3P=C(COC2F5)COPh and Ph3P=C(COC3F7)COPh were identified as selectively modulating the ABCB1 pump. These compounds, with low cytotoxicity against mouse T-lymphoma cells, exhibited more potency than the positive control ABCB1 inhibitor verapamil.

Carotenoid composition and in vitro pharmacological activity of rose hips.

The aim of the present study was to compare carotenoid extracts of Rose hips (Rosa canina L.) with regard to their phytochemical profiles and their in vitro anti-Helicobacter pylori (H. pylori), cytotoxic, multidrug resistance (MDR) reversal and radical scavenging activity. Carotenoid composition was investigated in the different fractionation of rose hips, using extraction methods. Six main carotenoids - epimers of neochrome, lutein, zeaxanthin, rubixanthin, lycopene, ß,ß-carotene - were identified from Rose hips by their chromatographic behavior and UV-visible spectra, which is in accordance with other studies on carotenoids in this plant material. The active principles in the carotenoid extract might differ, depending upon the extraction procedures.

Dimeric 3,5-bis(benzylidene)-4-piperidones: a novel cluster of tumour-selective cytotoxins possessing multidrug-resistant properties.

A series of bis[3,5-bis(benzylidene)-4-oxo-1-piperidinyl]amides 1 display potent cytotoxic properties towards a wide range of tumours. A number of the CC(50) and IC(50) values are in the range of 10(-8) M. Specifically, these compounds have the following important properties. First, greater toxicity was demonstrated towards certain tumours than various non-malignant cells. Second, various compounds in series 1 are toxic to a number of human colon cancer and leukaemic cells. Third, these compounds reverse P-gp mediated multidrug resistance. Various prototypic molecules such as 1a,b and 1i were identified as lead molecules for further studies. A representative lead molecule 1b induces apoptosis via internucleosomal DNA fragmentation and PARP cleavage in HSC-2 and HL-60 cells while flow cytometry revealed that this compound blocked the G2/M and S-phases in the cell cycle of human colon cancer HCT-116 cells.

Inhibition of quorum sensing and efflux pump system by trifluoromethyl ketone proton pump inhibitors.

BACKGROUND: One major microbiological problem is the widespread antibiotic resistance. There is an urgent need for new antibiotics and ways to treat multi-drug-resistant infections. Inhibition of bacterial quorum sensing (QS) systems could be an effective alternative in a smuch as they regulate a broad spectrum of cell functions, including, virulence factor production, biofilm organisation and motility. Influx and efflux bacterial systems involved in quorum sensing (QS) are known to depend on the proton motive force (PMF). Thus, a new series of 12 trifluoromethyl ketones (TFs) known to inhibit the PMF, was investigated for effects on the efflux pump of a QS responding bacterium, for its subsequent effect on the response to a QS signal and its direct inhibition of the response to a QS signal. MATERIALS AND METHODS: Chromobacterium violaceum 026 (CV026) was used as the indicator strain to evaluate the QS inhibitory effect of TFs. This strain responds to the presence of short carbon chain acyl-homoserine lactones (AHLs) by the development of a purple pigment. Effect on the QS response of CV026 to externally added AHLs was evaluated. In addition, the specific activity of the TFs on the efflux pump system of the CV026 strain and a wild-type Escherichia coli strain was assessed with the aid of the automated real-time ethidium bromide method. RESULTS: From the 12 compounds, 6 proved to be effective inhibitors of the QS response by CV026, as well as inhibit the efflux pumps of CV026 and Escherichia coli. CONCLUSION: Our results show that TFs have QS inhibitory properties that are mediated through their inhibition of efflux pumps that extrude the noxious QS signal before it reaches its intended target. Because the TFs also inhibit the efflux pump of a pathogenic bacterium, the method used for the evaluation of the TFs in the current study has clinical relevance and may be exploited for the prevention of QS responses of infecting bacteria.

Quantitative structure-activity relationship (QSAR) analysis of tumor-specificity of 1,2,3,4-tetrahydroisoquinoline derivatives.

BACKGROUND: We have previously reported on the relative cytotoxicity of a total of 38 1,2,3,4-tetrahydroisoquinoline derivatives against human oral squamous cell carcinoma cell lines and human normal oral cells, and the correlation between the cytotoxicity and 17 chemical descriptors. However, the correlation between the tumor-specificity of these compounds and the chemical descriptors has never been investigated so far. Using these previous data, we investigated various parameters for their applicability in predicting tumor specificity. MATERIALS AND METHODS: Original data of 50% cytotoxic concentration (CC(50)) values exceeding the maximum concentration in experimental conditions were corrected by the introduction of a harmonic mean, reducing the number of compounds analyzed to 30. The mean pCC(50) (=-log CC(50)) values for normal and tumor cells were defined as N and T, respectively. Tumor specificity was defined as the ratio of the difference of these values to their sum: (T-N)/(T+N). The chemical descriptors were obtained by quantum chemical calculations using semi-empirical (AM1, PM3, and PM6) and density functional theory methods. The relationship between the chemical descriptors and tumor specificity was analyzed by linear regression and artificial neural networks. RESULTS: Out of 17 chemical descriptors, water-accessible surface area showed the highest correlation coefficient with tumor specificity, regardless of the method of calculation. Furthermore, neural network analysis demonstrated the importance of quantum chemical calculations in predicting the specificity of tetrahydroisoquinoline derivatives. CONCLUSION: The present study suggests the applicability of quantum chemical descriptor in the estimation of tumor specificity of related compounds.

3,5-Bis(benzylidene)-1-[3-(2-hydroxyethylthio)propanoyl]piperidin-4-ones: a novel cluster of potent tumor-selective cytotoxins.

Novel 3,5-bis(benzylidene)-1-[3-(2-hydroxyethylthio)propanoyl]piperidin-4-ones (3a-e) display potent cytotoxicity and a preferential lethality toward various neoplasms compared to some normal cells. The corresponding sulfonic acid analogues 5a-e and an isostere 4 demonstrated substantially lower activity. The leads 3d and 3e possess very high activity against colon cancer and leukemia cell lines, caused DNA fragmentation, and activated caspase-3 in HL-60 cells. The enones 3b-e were well tolerated in a short-term toxicity screen in mice.

Sequential cytotoxicity: a theory examined using a series of 3,5-bis(benzylidene)-1-diethylphosphono-4-oxopiperidines and related phosphonic acids.

The concept of sequential cytotoxicity, which states that successive chemical attacks on cellular constituents can be more deleterious to neoplasms than normal cells, was evaluated using a series of 3,5-bis(benzylidene)-1-diethylphosphono-4-oxopiperidines 1 and related phosphonic acids 2, which were screened against a panel of malignant and normal cell lines. The compounds proved to be not only potent cytotoxins (71% of the CC(50) figures are submicromolar) but to display greater cytotoxicity to the neoplastic cells. QSAR revealed that both cytotoxic potencies and selective toxicity were increased by a rise in the electron-withdrawing properties and a decrease in the hydrophobicity of the aryl substituents. Utilisation of the PL10 concept and evaluation of druglike properties revealed 1c as the lead tumour-specific cytotoxin. This molecule activated caspase-3 in HL-60 cells but not in the HSC-2 cell line. While 1c caused internucleosomal DNA fragmentation in HL-60 cells, it did not elicit this effect in either HSC-2 and HSC-4 cells. Clearly 1c exerts its cytotoxic potencies by different mechanisms and such pleiotropy is likely the principal reason for the remarkable display of preferential toxicity towards malignant cells of the compounds in series 1 and 2.

New synthesis of 3-trifluoromethylpyrroles by condensation of mesoionic 4-trifluoroacetyl-1,3-oxazolium-5-olates with phosphorus ylides.

Mesoionic 4-trifluoroacetyl-1,3-oxazolium-5-olates (1), obtained from the reaction of N-acyl-N-alkylglycines with trifluoroacetic anhydride, react with phosphorus ylides to give ß-trifluoromethylpyrroles (2) in good yields. The novel ring transformations of 1 into 2 occur via an initial attack of the ylide anions on the C-2 position of the ring.