Antimycobacterial Activities of Hydroxamic Acids and Their Iron(II/III), Nickel(II), Copper(II) and Zinc(II) Complexes.

Hydroxamic acid (HA) derivatives display antibacterial and antifungal activities. HA with various numbers of carbon atoms (C2, C6, C8, C10, C12 and C17), complexed with different metal ions, including Fe(II/III), Ni(II), Cu(II) and Zn(II), were evaluated for their antimycobacterial activities and their anti-biofilm activities. Some derivatives showed antimycobacterial activities, especially in biofilm growth conditions. For example, 20-100 µM of HA10Fe2, HA10FeCl, HA10Fe3, HA10Ni2 or HA10Cu2 inhibited Mycobacterium tuberculosis, Mycobacterium bovis BCG and Mycobacterium marinum biofilm development. HA10Fe2, HA12Fe2 and HA12FeCl could even attack pre-formed Pseudomonas aeruginosa biofilms at higher concentrations (around 300 µM). The phthiocerol dimycocerosate (PDIM)-deficient Mycobacterium tuberculosis H37Ra was more sensitive to the ion complexes of HA compared to other mycobacterial strains. Furthermore, HA10FeCl could increase the susceptibility of Mycobacterium bovis BCG to vancomycin. Proteomic profiles showed that the potential targets of HA10FeCl were mainly related to mycobacterial stress adaptation, involving cell wall lipid biosynthesis, drug resistance and tolerance and siderophore metabolism. This study provides new insights regarding the antimycobacterial activities of HA and their complexes, especially about their potential anti-biofilm activities.

Stimuli Responsive Materials Supported by Orthogonal Hydrogen and Halogen Bonding or I···Alkene Interaction.

Smart materials represent an elegant class of (macro)-molecules endowed with the ability to react to chemical/physical changes in the environment. Herein, we prepared new photo responsive azobenzenes possessing halogen bond donor groups. The X-ray structures of two molecules highlight supramolecular organizations governed by unusual noncovalent bonds. In azo dye I-azo-NO2, the nitro group is engaged in orthogonal H···O···I halogen and hydrogen bonding, linking the units in parallel undulating chains. As far as compound I-azo-NH-MMA is concerned, a non-centrosymmetric pattern is formed due to a very rare I···π interaction involving the alkene group supplemented by hydrogen bonds. The Cambridge Structural Database contains only four structures showing the same I···CH2=C contact. For all compounds, an 19F-NMR spectroscopic analysis confirms the formation of halogen bonds in solution through a recognition process with chloride anion, and the reversible photo-responsiveness is demonstrated upon exposing a solution to UV light irradiation. Finally, the intermediate I-azo-NH2 also shows a pronounced color change due to pH variation. These azobenzenes are thereby attractive building blocks to design future multi-stimuli responsive materials for highly functional devices.

Synthesis, structure and anticancer properties of new biotin- and morpholine-functionalized ruthenium and osmium half-sandwich complexes.

Ruthenium (Ru) and osmium (Os) complexes are of sustained interest in cancer research and may be alternative to platinum-based therapy. We detail here three new series of ruthenium and osmium complexes, supported by physico-chemical characterizations, including time-dependent density functional theory, a combined experimental and computational study on the aquation reactions and the nature of the metal-arene bond. Cytotoxic profiles were then evaluated on several cancer cell lines although with limited success. Further investigations were, however, performed on the most active series using a genetic approach based on RNA interference and highlighted a potential multi-target mechanism of action through topoisomerase II, mitotic spindle, HDAC and DNMT inhibition.

New Folate-Grafted Chitosan Derivative To Improve Delivery of Paclitaxel-Loaded Solid Lipid Nanoparticles for Lung Tumor Therapy by Inhalation.

Inhaled chemotherapy for the treatment of lung tumors requires that drug delivery systems improve selectivity for cancer cells and tumor penetration and allow sufficient lung residence. To this end, we developed solid lipid nanoparticles (SLN) with modified surface properties. We successfully synthesized a new folate-grafted copolymer of polyethylene glycol (PEG) and chitosan, F-PEG-HTCC, with a PEG-graft ratio of 7% and a molecular weight range of 211-250 kDa. F-PEG-HTCC-coated, paclitaxel-loaded SLN were prepared with an encapsulation efficiency, mean diameter, and zeta potential of about 100%, 250 nm, and +32 mV, respectively. The coated SLN entered folate receptor (FR)-expressing HeLa and M109-HiFR cells in vitro and M109 tumors in vivo after pulmonary delivery. The coated SLN significantly decreased the in vitro half-maximum inhibitory concentrations of paclitaxel in M109-HiFR cells (60 vs 340 nM, respectively). We demonstrated that FR was involved in these improvements, especially in M109-HiFR cells. After pulmonary delivery in vivo, the coated SLN had a favorable pharmacokinetic profile, with pulmonary exposure to paclitaxel prolonged to up to 6 h and limited systemic distribution. Our preclinical findings therefore demonstrated the positive impact of the coated SLN on the delivery of paclitaxel by inhalation.

Discovery of Novel Potent Reversible and Irreversible Myeloperoxidase Inhibitors Using Virtual Screening Procedure.

The heme enzyme myeloperoxidase (MPO) participates in innate immune defense mechanism through formation of microbicidal reactive oxidants. However, evidence has emerged that MPO-derived oxidants contribute to propagation of inflammatory diseases. Because of the deleterious effects of circulating MPO, there is a great interest in the development of new efficient and specific inhibitors. Here, we have performed a novel virtual screening procedure, depending on ligand-based pharmacophore modeling followed by structure-based virtual screening. Starting from a set of 727842 compounds, 28 molecules were selected by this virtual method and tested on MPO in vitro. Twelve out of 28 compounds were found to have an IC50 less than 5 µM. The best inhibitors were 2-(7-methoxy-4-methylquinazolin-2-yl)guanidine (28) and (R)-2-(1-((2,3-dihydro-1H-imidazol-2-yl)methyl)pyrrolidin-3-yl)-5-fluoro-1H-benzo[d]imidazole (42) with IC50 values of 44 and 50 nM, respectively. Studies on the mechanism of inhibition suggest that 28 is the first potent mechanism-based inhibitor and inhibits irreversibly MPO at nanomolar concentration.

From Dynamic Combinatorial Chemistry to in Vivo Evaluation of Reversible and Irreversible Myeloperoxidase Inhibitors.

The implementation of dynamic combinatorial libraries allowed the determination of highly active reversible and irreversible inhibitors of myeloperoxidase (MPO) at the nanomolar level. Docking experiments highlighted the interaction between the most active ligands and MPO, and further kinetic studies defined the mode of inhibition of these compounds. Finally, in vivo evaluation showed that one dose of irreversible inhibitors is able to suppress the activity of MPO after inducing inflammation.

A survey of the mechanisms of action of anticancer transition metal complexes.

Metal complexes have been the subject of numerous investigations in oncology but, despite the plethora of newly synthesized compounds, their precise mechanisms of action remain generally unknown or, for the best, incompletely determined. The continuous development of efficient and sensitive techniques in analytical chemistry and molecular biology gives scientists new tools to gather information on how metal complexes can be effective toward cancer. This review focuses on recent findings about the anticancer mechanism of action of metal complexes and how the ligands can be used to tune their pharmacological and physicochemical properties.

Novel bis-arylalkylamines as myeloperoxidase inhibitors: Design, synthesis, and structure-activity relationship study.

Human myeloperoxidase (MPO) plays an important role in innate immunity but also aggravates tissue damage by oxidation of biomolecules at sites of inflammation. As a result from a recent high-throughput virtual screening approach for MPO inhibitors, bis-2,2'-[(dihydro-1,3(2H,4H) pyrimidinediyl)bis(methylene)]phenol was detected as a promising lead compound for inhibition of the MPO-typical two-electron oxidation of chloride to hypochlorous acid (IC50 = 0.5 µM). In the present pharmacomodulation study, 37 derivatives of this lead compound were designed and synthesized driven by comprehensive docking studies and the impact on the chlorination activity of MPO. We describe the structural requirements for optimum (i) binding to the heme periphery and (ii) inhibition capacity. Finally, the best three inhibitors (bis-arylalkylamine derivatives) were probed for interaction with the MPO redox intermediates Compound I and Compound II. Determined apparent bimolecular rate constants together with determination of reduction potential and nucleophilicity of the selected compounds allowed us to propose a mechanism of inhibition. The best inhibitor was found to promote the accumulation of inactive form of MPO-Compound II and has IC50 = 54 nM, demonstrating the successful approach of the drug design. Due to the similarity of ligand interactions between MPO and serotonine transporter, the selectivity of this inhibitor was also tested on the serotonin transporter providing a selectivity index of 14 (KiSERT/IC50MPO).

New dry powders for inhalation containing temozolomide-based nanomicelles for improved lung cancer therapy.

Besides the numerous advantages of a chemotherapy administered by the inhalation route for lung cancer therapy, dry powder for inhalation (DPI) offers many advantages compared to other techniques and seems to be a technique that is well-adapted to an anticancer treatment. DPI formulations were developed using the cytotoxic drug temozolomide and a new folate-grafted self-assembling copolymer, a conjugate of three components, folate-polyethylene glycol-hydrophobically-modified dextran (F-PEG-HMD). F-PEG-HMD was synthesized using carbodiimide-mediated coupling chemistry in three main steps. F-PEG-HMD was characterized by 1H-NMR, mass spectrometry and thermal analysis. F-PEG-HMD presented a critical micellar concentration in water of 4x10-7 M. F-PEG-HMD nanomicelles were characterized by a trimodal particle size distribution with Z-average diameter of 83±1 nm in water. Temozolomide-loaded nanomicelles were prepared by solubilization of F-PEG-HMD in the presence of temozolomide. Temozolomide solubility in water was increased in the presence of F-PEG-HMD (2-fold increase in molar solubility) which could potentially lead to increased local concentrations in the tumor site. The temozolomide-loaded F-PEG-HMD nanomicelles were characterized by a Z-average diameter of ~50 to ~60 nm, depending on the F-PEG-HMD concentration used. The nanomicelles were then spray-dried to produce dry powders. Temozolomide remained stable during all the formulation steps, confirmed by similar in vitro anticancer properties for the DPI formulations and a raw temozolomide solution. Two of the developed DPI formulations were characterized by good aerodynamic properties (with a fine particle fraction of up to 50%) and were able to release the F-PEG-HMD nanomicelles quickly in aqueous media. Moreover, in vitro, the two DPI formulations showed wide pulmonary deposition in the lower respiratory tract where adenocarcinomas are more often found. The present study, therefore, shows that F-PEG-HMD-based dry powders for inhalation could constitute an interesting drug delivery system able to release nanomicelles that are useful in adenocarcinomas that overexpress folate receptors.

Ferulaldehyde and lupeol as direct and indirect antimicrobial compounds from Cordia gilletii (Boraginaceae) root barks.

Cordia gilletii De Wild (Boraginaceae), a medicinal plant used against infectious diseases in the Democratic Republic of Congo, was investigated for direct and indirect antimicrobial properties. On one hand, the methanol extract is active against many pathogenic bacteria, including resistant strains. Its bio-guided fractionation led to the isolation of ferulaldehyde; this compound showed antimicrobial and antioxidant properties that may support the activity we observed for the methanol extract and some of the traditional uses of C. gilletii. On the other hand, the n-hexane extract of root barks possesses indirect antimicrobial properties, enhancing the activity of antibiotics against methicillin-resistant Staphylococcus aureus (MRSA). The fractionation of this extract led to the isolation of lupeol, which decreases the minimum inhibitory concentration of several antibiotics (4 to 8 fold) against MRSA and contributes to the effects observed for the raw n-hexane extract.

Synthesis and in vitro characterization of platinum(II) anticancer coordinates using FTIR spectroscopy and NCI COMPARE: A fast method for new compound discovery.

Platinum-based drugs have been used for several decades to treat various cancers successfully. Cisplatin is the original compound in this class; it cross-links DNA, resulting in cell cycle arrest and cell death via apoptosis. Cisplatin is effective against several tumor types but exhibits toxic side effects; in addition, tumors often develop resistance. An original in vitro approach is proposed to determine whether platinum-based research compounds are good candidates for further study by comparing them to marketed drugs using FTIR spectroscopy and the COMPARE analysis from the NCI. Both methods can produce fingerprints and highlight differences between the compounds, classifying the candidates and revealing promising derivatives.

Hybrid molecules inhibiting myeloperoxidase activity and serotonin reuptake: a possible new approach of major depressive disorders with inflammatory syndrome.

OBJECTIVES: Major depressive disorder (MDD) is accompanied with an imbalance in the immune system and cardiovascular impairments, such as atherosclerosis. Several mechanisms have been pointed out to underlie this rather unexpected association, and among them the activity of myeloperoxidase (MPO). The aim of our study was to find compounds that inhibit both MPO and serotonin transporter (SERT) for treating MDD associated with cardiovascular diseases. METHODS: SERT inhibition was assessed with measuring of [(3) H]-serotonin uptake using HEK-293 MSR cells. MPO inhibition was determined by taurine chloramine test on 3-(aminoalkyl)-5-fluoroindole derivatives and on clinically relevant antidepressants. All kinetic measurements were performed using a temperature-controlled stopped-flow apparatus (model SX-18 MV). Promising lead compounds were docked onto SERT 3D structure modelled using the LeuT structure complexed to tryptophan (PDB code 3F3A). Their toxicological profile was also assessed. KEY FINDINGS: 3-(aminoalkyl)-5-fluoroindole derivative with 5 carbons on the side chain and paroxetine showed the best activity on both MPO and SERT at the nanomolar range. Paroxetine was found to be the first irreversible MPO inhibitor at nanomolar concentrations. CONCLUSIONS: Our results put forward the first hybrid molecule (compound 25) and drug (paroxetine) that can be especially used in MDD associated with inflammatory syndrome.

Structure-activity relationship analysis of bufadienolide-induced in vitro growth inhibitory effects on mouse and human cancer cells.

The in vitro growth inhibitory effects of 27 bufadienolides and eight degradation products, with two cardenolides (ouabain and digoxin) chosen as reference compounds, were analyzed by means of an MTT colorimetric assay in six human and two mouse cancer cell lines. A structure-activity analysis was then performed to highlight the most important substituents relating to the in vitro growth inhibitory activity of bufadienolides in cancer cells. Thus, the current study revealed that various bufadienolides, including gamabufotalin rhamnoside (1a), bufotalin (2a), and hellebrin (3a), displayed higher growth inhibitory activities for various human cancer cell lines when compared to ouabain and digoxin. Gamabufotalin rhamnoside (1a) was the only compound that displayed growth inhibitory effects of <1 µM in mouse cancer cells that expressed mutated forms of the Na(+),K(+)-ATPase α-1 subunit. In addition, all genins and degradation products displayed weaker (if any) in vitro growth inhibitory effects on cancer cells when compared to their respective glycosylated homologue, with the exception of hellebrigenin (3b), which was as active as hellebrin (3a).

Design, synthesis, and structure-activity relationship studies of novel 3-alkylindole derivatives as selective and highly potent myeloperoxidase inhibitors.

Due to its production of potent antimicrobial oxidants including hypochlorous acid, human myeloperoxidase (MPO) plays a critical role in innate immunity and inflammatory diseases. Thus MPO is an attractive target in drug design. (Aminoalkyl)fluoroindole derivatives were detected to be very potent MPO inhibitors; however, they also promote inhibition of the serotonin reuptake transporter (SERT) at the same concentration range. Via structure-based drug design, a new series of MPO inhibitors derived from 3-alkylindole were synthesized and their effects were assessed on MPO-mediated taurine chlorination and low-density lipoprotein oxidation as well as on inhibition of SERT. The fluoroindole compound with three carbons in the side chain and one amide group exhibited a selectivity index of 35 (Ki/IC50) with high inhibition of MPO activity (IC50 = 18 nM), whereas its effect on SERT was in the micromolar range. Structure-function relationships, mechanism of action, and safety of the molecule are discussed.

N-(2-{3-[3,5-bis(trifluoromethyl)phenyl]ureido}ethyl)-glycyrrhetinamide (6b): a novel anticancer glycyrrhetinic acid derivative that targets the proteasome and displays anti-kinase activity.

18-ß-Glycyrrhetinic acid (GA; 1) and many of its derivatives are cytotoxic in cancer cells. The current study aims to characterize the anticancer effects of 17 novel 1 derivatives. On the basis of these studies, N-(2-{3-[3,5-bis(trifluoromethyl)phenyl]ureido}ethyl)-glycyrrhetinamide (6b) appeared to be the most potent compound, with IC(50)in vitro growth inhibitory concentrations in single-digit micromolarity in a panel of 8 cancer cell lines. Compound 6b is cytostatic and displays similar efficiency in apoptosis-sensitive versus apoptosis-resistant cancer cell lines through, at least partly, the inhibition of the activity of a cluster of a dozen kinases that are implicated in cancer cell proliferation and in the control of the actin cytoskeleton organization. Compound 6b also inhibits the activity of the 3 proteolytic units of the proteasome. Compound 6b thus represents an interesting hit from which future compounds could be derived to improve chemotherapeutic regimens that aim to combat cancers associated with poor prognoses.

Quinone methides and their prodrugs: a subtle equilibrium between cancer promotion, prevention, and cure.

The importance of reactive drug metabolites in the pathogenesis of drug-induced toxicity has been investigated since the early 1950s, mainly to reveal the link between toxic metabolites and chemical carcinogenesis. This review mainly focuses on biologically active compounds, which generate reactive quinone methide (QM) intermediates either directly or after bioactivation. Several examples of anticancer drugs acting through the generation of QM electrophiles are given. The use of those drugs for chemotherapeutic purposes is also discussed. The key feature of those QM-generating drugs is their reactivity toward specific nucleophilic biological targets. Modulation of their reactivity represents a challenge for medicinal chemists because, depending on the reactivity of these QM intermediates, their interaction with critical proteins can alter the function of these key proteins and induce a wide variety of responses with functional consequences. Among the possible consequences, antiproliferative effects could be exploited for chemotherapeutic purposes. Information on how such QM-generating drugs can affect individual target proteins and their functional consequences are required to help the medicinal chemist in the design of more specific QM-generating molecules for chemotherapeutic use.

Structure-based design, synthesis, and pharmacological evaluation of 3-(aminoalkyl)-5-fluoroindoles as myeloperoxidase inhibitors.

Oxidized low-density lipoproteins (LDLs) accumulate in the vascular wall and promote local inflammation, which contributes to the progression of the atheromatous plaque. The key role of myeloperoxidase (MPO) in this process is related to its ability to modify APO B-100 in the intima and at the surface of endothelial cells. A series of 3-(aminoalkyl)-5-fluoroindole analogues was designed and synthesized by exploiting the structure-based docking of 5-fluorotryptamine, a known MPO inhibitor. In vitro assays were used to study the effects of these compounds on the inhibition of MPO-mediated taurine chlorination and oxidation of LDLs. The kinetics of the interaction between the MPO redox intermediates, Compounds I and II, and these inhibitors was also investigated. The most potent molecules possessed a 4- or 5-carbon aminoalkyl side chain and no substituent on the amino group. The mode of binding of these analogues and the mechanism of inhibition is discussed with respect to the structure of MPO and its halogenation and peroxidase cycles.

Fourier transform infrared (FTIR) spectroscopy to monitor the cellular impact of newly synthesized platinum derivatives.

Platinum complexes remain widely used to combat various types of cancers. Three platinum complexes, cisplatin, carboplatin and oxaliplatin, are marketed for various oncological purposes. Additionally, nedaplatin, lobaplatin and heptaplatin have gained regionally limited approval for oncology purposes. Furthermore, various platinum derivatives are currently under clinical trials. More than 40 years after their discovery, however, the precise mechanism of action of platinum antitumor complexes remains elusive, partly because these compounds display numerous intracellular targets. Structure-activity-relationship analyses are therefore difficult to conduct to optimize the synthesis of novel platinum derivatives. The aim of the present study is to illustrate the potential of using Fourier Transform Infrared (FTIR) analyses to monitor the cellular modifications induced by the new platinum derivatives that we have synthesized. We show in the present study the advantages of combining an in vitro assay to determine the IC50 growth inhibition concentrations of a series of compounds belonging to a given chemical series and FTIR analyses carried out at the IC50 concentrations for each compound to identify potential hits within this series of compounds. The original pharmacological approach proposed here could, therefore, avoid large-scale pharmacological experiments to find hits within a given chemical series.

Simple di- and trivanillates exhibit cytostatic properties toward cancer cells resistant to pro-apoptotic stimuli.

A series of 33 novel divanillates and trivanillates were synthesized and found to possess promising cytostatic rather than cytotoxic properties. Several compounds under study decreased by >50% the activity of Aurora A, B, and C, and WEE1 kinase activity at concentrations <10% of their IC(50) growth inhibitory ones, accounting, at least partly, for their cytostatic effects in cancer cells and to a lesser extent in normal cells. Compounds 6b and 13c represent interesting starting points for the development of cytostatic agents to combat cancers, which are naturally resistant to pro-apoptotic stimuli, including metastatic malignancies.

1H-nuclear magnetic resonance determination of the enantiomeric purity of aliphatic primary amines, beta-aminoalcohols, beta-diamines and alpha-amino-acids with 1R-(-)-myrtenal: scope and limitations.

1R-(-)-myrtenal was tested as a chiral derivatising agent for the determination of the enantiomeric purity of aliphatic primary amines, beta-aminoalcohols, beta-diamines and alpha-amino-acids. Derivatisation procedure consists in mixing one equivalent each of the amine and 1R-(-)-myrtenal directly into the nuclear magnetic resonance (NMR) tube before addition of the appropriate deuterated solvent and, for alpha-amino-acids, one equivalent of NaOH was added to neutralise the acidic function. Diastereoisomeric imines were completely formed after 12 h and analysed by 1H-NMR except for N-methyl beta-diamines for which imidazolidines were obtained. The method gave satisfactory results only for alpha- and beta-arylalkylamines for which CDCl(3) could be advantageously replaced by C(6)D(6) or pyridine-d(5) in order to increase the difference between the chemical shifts. The main advantage of the procedure is its simplicity as it does not involve steps such as activation, heating, solvent evaporation and isolation of the product. Its limitations are the limited series of compounds susceptible to be analysed and the small difference between the chemical shifts of the diastereoisomeric imines obtained.