Discovery of novel AHLs as potent antiproliferative agents

Design, synthesis, and biological activity studies on benzimidazole derivatives targeting myeloperoxidase

Myeloperoxidase (MPO) plays a key role in human antimicrobial system by oxidizing vital molecules of microorganisms in phagolysosomes through produced hypochlorous acid (HOCl). However, MPO can be released outside the phagocyte and produces reactive intermediates leading to tissue damage. MPO, as a local mediator of tissue damage, has been associated with inflammatory diseases such as renal injury, multiple sclerosis, cardiovascular and neurodegenerative diseases. Therefore, the enzyme currently draws attention as a potential therapeutic target. In this study, isomeric 1,3-dihydro-2H-benzo[d]imidazole-2-thione derivatives having amide, hydrazide and hydroxamic acid groups either on nitrogen or on sulphur atom were designed and their inhibitory activity was determined on chlorination and peroxidation cycles of MPO. Among the compounds, 2-(2-thioxo-2,3-dihydro-1H-benzo[d]imidazole-1-yl)acetohydrazide(C19) was found as the most active inhibitor on both cycles.

Chemical probe of AHL modulators on quorum sensing in Gram-Negative Bacteria and as antiproliferative agents: A review

Pathogenic bacteria use an intercellular chemical communication system called quorum sensing (QS) to control the expression of cellular functions such as virulence factors, biofilm formation, toxin production, and antibiotic resistance in a manner that is highly dependent on population density. Hence, since the emergence of QS, there has been a great interest in exploiting the QS mechanism as a new drug target. Therefore, blocking the QS mechanism can be an effective strategy to control infection and solve the problem of drug resistance. So far, there is no clinically approved anti-QS drug that can disable the circuits of QS systems. This review discusses the quorum-sensing network systems and novel anti-QS inhibitors in some Gram-negative bacteria.

Emerging applications of bacteria as antitumor agents

Bacteria are associated with the human body and colonize the gut, skin, and mucous membranes. These associations can be either symbiotic or pathogenic. In either case, bacteria derive more benefit from their host. The ability of bacteria to enter and survive within the human body can be exploited for human benefit. They can be used as a vehicle for delivering or producing bioactive molecules, such as toxins and lytic enzymes, and eventually for killing tumor cells. Clostridium and Salmonella have been shown to infect and survive within the human body, including in tumors. There is a need to develop genetic circuits, which enable bacterial cells to carry out the following activities: (i) escape the human immune system, (ii) invade tumors, (iii) multiply within the tumorous cells, (iv) produce toxins via quorum sensing at low cell densities, and (v) express suicide genes to undergo cell death or cell lysis after the tumor has been lysed. Thus, bacteria have the potential to be exploited as anticancer agents.

Synthesis of γ-Hydroxy-α-amino Acid Derivatives by Enzymatic Tandem Aldol Addition-Transamination Reactions

Three enzymatic routes toward γ-hydroxy-α-amino acids by tandem aldol addition–transamination one-pot two-step reactions are reported. The approaches feature an enantioselective aldol addition of pyruvate to various nonaromatic aldehydes catalyzed by trans-o-hydroxybenzylidene pyruvate hydratase-aldolase (HBPA) from Pseudomonas putida. This affords chiral 4-hydroxy-2-oxo acids, which were subsequently enantioselectively aminated using S-selective transaminases. Three transamination processes were investigated involving different amine donors and transaminases: (i) l-Ala as an amine donor with pyruvate recycling, (ii) a benzylamine donor using benzaldehyde lyase from Pseudomonas fluorescens Biovar I (BAL) to transform the benzaldehyde formed into benzoin, minimizing equilibrium limitations, and (iii) l-Glu as an amine donor with a double cascade comprising branched-chain α-amino acid aminotransferase (BCAT) and aspartate amino transferase (AspAT), both from E. coli, using l-Asp as a substrate to regenerate l-Glu. The γ-hydroxy-α-amino acids thus obtained were transformed into chiral α-amino-γ-butyrolactones, structural motifs found in many biologically active compounds and valuable intermediates for the synthesis of pharmaceutical agents.

Dinuclear zinc-catalyzed asymmetric [3 + 2] cyclization reaction for direct assembly of chiral α-amino-γ-butyrolactones bearing three stereocenters

A highly atom-economic and novel enantioselective [3 + 2] cyclization reaction for the construction of optical α-amino-γ-butyrolactones possessing three stereocenters.

Synthesis and Biological Evaluation of Novel L-Homoserine Lactone Analogs as Quorum Sensing Inhibitors of Pseudomonas aeruginosa

In this study, we synthesized four series of novel L-homoserine lactone analogs and evaluated their in vitro quorum sensing (QS) inhibitory activity against two biomonitor strains, Chromobacterium violaceum CV026 and Pseudomonas aeruginosa PAO1. Studies of the structure-activity relationships of the set of L-homoserine lactone analogs indicated that phenylurea-containing N-dithiocarbamated homoserine lactones are more potent than (Z)-4-bromo-5-(bromomethylene)-2(5H)-furanone (C30), a positive control for biofilm formation. In particular, compared with C30, QS inhibitor 11f significantly reduced the production of virulence factors (pyocyanin, elastase and rhamnolipid), swarming motility, the formation of biofilm and the mRNA level of QS-related genes regulated by the QS system of PAO1. These results reveal 11f as a potential lead compound for developing novel antibacterial quorum sensing inhibitors.

Crystal structure and Hirshfeld surface analysis of 2-[(1,3-benzoxazol-2-yl)sulfan-yl]-N-(2-meth-oxy-phen-yl)acetamide

In the title compound, C16H14N2O3S, the 1,3-benzoxazole ring system is essentially planar (r.m.s deviation = 0.004 Å) and makes a dihedral angle of 66.16 (17)° with the benzene ring of the meth-oxy-phenyl group. Two intra-molecular N-H⋯O and N-H⋯N hydrogen bonds occur, forming S(5) and S(7) ring motifs, respectively. In the crystal, pairs of C-H⋯O hydrogen bonds link the mol-ecules into inversion dimers with R 2 2(14) ring motifs, stacked along the b-axis direction. The inversion dimers are linked by C-H⋯π and π-π-stacking inter-actions [centroid-to-centroid distances = 3.631 (2) and 3.631 (2) Å], forming a three-dimensional network. Two-dimensional fingerprint plots associated with the Hirshfeld surface show that the largest contributions to the crystal packing come from H⋯H (39.3%), C⋯H/H⋯C (18.0%), O⋯H/H⋯O (15.6) and S⋯H/H⋯S (10.2%) inter-actions.

Design and synthesis of novel xanthone-triazole derivatives as potential antidiabetic agents: α-Glucosidase inhibition and glucose uptake promotion

Inhibiting the decomposition of carbohydrates into glucose or promoting glucose conversion is considered to be an effective treatment for type 2 diabetes. Herein, a series of novel xanthone-triazole derivatives were designed, synthesized, and their α-glucosidase inhibitory activities and glucose uptake in HepG2 cells were investigated. Most of the compounds showed better inhibitory activities than the parental compound a (1,3-dihydroxyxanthone, IC₅₀ = 160.8 μM) and 1-deoxynojirimycin (positive control, IC₅₀ = 59.5 μM) towards α-glucosidase. Compound 5e was the most potent inhibitor, with IC₅₀ value of 2.06 μM. The kinetics of enzyme inhibition showed that compounds 5e, 5g, 5h, 6c, 6d, 6g and 6h were noncompetitive inhibitors, and molecular docking results were consistent with the noncompetitive property that these compounds bind to allosteric sites away from the active site (Asp214, Glu276 and Asp349). On the other hand, the glucose uptake assays exhibited that compounds 5e, 6a, 6c and 7g displayed high activities in promoting the glucose uptake. The cytotoxicity assays showed that most compounds were low-toxic to human normal hepatocyte cell line (LO2). These novel xanthone triazole derivatives exhibited dual therapeutic effects of α-glucosidase inhibition and glucose uptake promotion, thus they could be use as antidiabetic agents for developing novel drugs against type 2 diabetes.

Multicomponent synthesis of some new (1S,4S)-2,5-diazabicyclo[2.2.1]heptane-dithiocarbamates and their in vitro anti-proliferative activity against CaSki, MDA-MB-231 and SK-Lu-1 tumour cells as apoptosis inducing agents without necrosis

Identification of a new class of antitumor agent capable to induce apoptosis without triggering necrotic cell death event is challenging. The present communication describes the multicomponent synthesis of seven new (1S,4S)-2,5-diazabicyclo[2.2.1]heptane-dithiocarbamates and their in vitro antiproliferative activity on cervical cancer cell line (CaSki), breast cancer cell line (MDA-MB231), lung cancer cell line (SK-Lu-1) and human lymphocytes. Among the synthesized dithiocarbamates, compound 9e displayed significant antiproliferative activity without inducing any necrotic cell death (both on tumour cells and lymphocytes) and induced apoptosis in tumor cells by the caspase dependent apoptotic pathway. The compound 9e also exhibited greater tumor selectivity than human lymphocytes. In silico ADME predictions revealed that compound 9e has the potential to be developed as a drug candidate. Rapid chemical modifications of this lead are thus highly necessary for further investigation as a drug like safer antitumor candidate and also to achieve compounds with better activity profile.

Design, Synthesis and Antiproliferative Evaluation of 3-Aminopropyloxy Derivatives of Chalcone

A series of 3-aminopropyloxy derivatives of chalcone were synthesised and evaluated for their antiproliferative activity against liver, gastric and neuroendocrine cancer cell lines. Most of the synthesised compounds exhibited moderate to good activity against all three cancer cell lines, but in particular, a 3-(pyrrolidin-1-yl)propyloxy chalcone containing a 3,4,5-trimethoxyphenyl group showed the highest antiproliferative activity with an IC50 value of 2.74 μM against liver cancer cells.

Design, synthesis and antiproliferative activity studies of novel dithiocarbamate-chalcone derivates

A series of novel dithiocarbamate-chalcone derivates were designed, synthesized and evaluated for antiproliferative activity against three selected cancer cell lines (EC-109, SK-N-SH and MGC-803). Majority of the synthesized compounds exhibited moderate to potent activity against all the cancer cell lines assayed. Particularly, compounds II2 and II5 exhibited the excellent growth inhibition against SK-N-SH with IC50 values of 2.03μM and 2.46μM, respectively. Further mechanism studies revealed that compound II2 could obviously inhibit the proliferation of SK-N-SH cells by inducing apoptosis and arresting the cell cycle at G0/G1 phase.

Multicomponent assembly of novel antiproliferative steroidal dihydropyridinyl spirooxindoles

Multicomponent assembly of steroidal dihydropyridinyl spirooxindoles from pregnenolone, isatins, malononitrile, and ammonium acetate is described, which involves the formation of two C-C bonds, two C-N bonds, and an all-carbon quaternary stereogenic center in a single operation. MTT assays showed that some of these compounds had moderate to excellent cytotoxicity against the tested cancer cell lines and were more potent than 5-FU. Particularly, compound 5o represented excellent inhibitory effect toward EC-109 (IC50=0.3 μM), being about 33-fold more potent than 5-FU.

Discovery of novel heteroarylmethylcarbamodithioates as potent anticancer agents: Synthesis, structure-activity relationship analysis and biological evaluation

A series of new analogs based on the structure of lead compound 10 were designed, synthesized and evaluated for their in vitro anti-cancer activities against four selected human cancer cell lines (HL-60, Bel-7402, SK-BR-3 and MDA-MB-468). Several synthesized compounds exhibited improved anti-cancer activities comparing with lead compound 10. Among them, 1,3,4-oxadiazole analogs 17o showed highest bioactivity with IC50 values of 1.23, 0.58 and 4.29 μM against Bel-7402, SK-BR-3 and MDA-MB-468 cells, respectively. It is noteworthy that 17o has potent anti-proliferation activity toward a panel of cancer cells with relatively less cytotoxicity to nonmalignant cells. The further mechanistic study showed that it induced apoptosis and cell cycle arrest through disrupting spindle assembly in mitotic progression, indicating these synthesized dithiocarbamates represented a novel series of anti-cancer compounds targeting mitosis.

Synthesis of α-Benzyloxyamino-γ-butyrolactones via a Polar Radical Crossover Cycloaddition Reaction

A direct catalytic synthesis of substituted α-benzyloxyamino-γ-butyrolactones is reported, starting from simple oxime acids and alkenes. The substituted O-benzyloxime acid starting materials are cyclized with oxidizable alkenes, via Polar Radical Crossover Cycloaddition (PRCC) reactions. The catalytic reaction is carried out using the Fukuzumi acridinium photooxidant and substoichiometric amounts of a redox-active cocatalyst. The utility of this method has been demonstrated through the use of 3 oxime acids and 19 oxidizable olefins.

Efficient synthesis of novel antiproliferative steroidal spirooxindoles via the [3+2] cycloaddition reactions of azomethine ylides

A series of novel steroidal spirooxindoles 3a-h were synthesized from pregnenolone in a high regioselective manner using the 1,3-dipolar cycloaddition as the key step. This protocol resulted in the formation of two C-C bonds, one C-N bond and the creation of one pyrrolidine ring and three contiguous stereocenters in a single operation. Biological evaluation showed that these synthesized steroidal spirooxindoles exhibited moderate to good antiproliferative activity against the tested cell lines and some of them were more potent than 5-FU. Among them, compounds 3e and 3f displayed the best antiproliferative activity against MCF-7 cells with the IC50 values of 4.0 and 3.9μM, respectively. Flow cytometry analysis demonstrated that compound 3d caused the cellular apoptosis and cell cycle arrest at G2/M phase in a concentration-dependent manner. Docking results indicated that compound 3d fitted well into the MDM2 active site 1RV1 by interacting with Lys94 and Thr101 residues.