Medicinal Chemistry - Volume 14, Issue 4, 2018

Background: Although the expression levels of many P450s differ between tumour and corresponding normal tissue, CYP1B1 is one of the few CYP subfamilies which is significantly and consistently overexpressed in tumours. CYP1B1 has been shown to be active within tumours and is capable of metabolising a structurally diverse range of anticancer drugs. Because of this, and its role in the activation of procarcinogens, CYP1B1 is seen as an important target for anticancer drug development. Objective: To synthesise a series of chalcone derivatives based on the chemopreventative agent DMU-135 and investigate their antiproliferative activities in human breast cancer cell lines which express CYP1B1 and CYP1A1. Method: A series of chalcones were synthesised in yields of 43-94% using the Claisen-Schmidt condensation reaction. These were screened using a MTT assay against a panel of breast cancer cell lines which have been characterised for CYP1 expression. Result: A number of derivatives showed promising antiproliferative activities in human breast cancer cell lines which express CYP1B1 and CYP1A1, while showing significantly lower toxicity towards a non-tumour breast cell line with no CYP expression. Experiments using the CYP1 inhibitors acacetin and α-naphthoflavone provided supporting evidence for the involvement of CYP1 enzymes in the bioactivation of these compounds. Conclusion: Chalcones show promise as anticancer agents with evidence suggesting that CYP1 activation of these compounds may be involved.

Background: Chalcones, natural products produced by plants as a natural defense mechanisms against various pathogens, are molecules with structures that include two aromatic rings joined by an α, β unsaturated carbonyl system. Previous research has demonstrated that chalcones exhibit a wide variety of biological activities, including anticancer, antifungal, and antibiotic properties. Objective: Our goal is to synthesize novel heterocyclic-containing chalcones and have their biological activities evaluated. Methods Sixteen chalcones were synthesized by the crossed aldol condensation of substituted tetralones with substituted pyridinylaldehydes. The products were purified by recrystallization in MeOH/H2O and characterized by 1H NMR, 13C NMR, and HRMS. Anticancer assays were performed by NCI (National Cancer Institute) against the NCI-60 panel of 60 different human cancer cell lines, including leukemia, non-small-cell lung cancer, colon, central nervous system, melanoma, ovarian, renal, prostate, and breast cancer. Antimicrobial assays were performed by COADD (Community for Open Antimicrobial Drug Discovery) against Escherichia coli, Klebsiella pneumonia, Acinetobacter baumannii, Pseudomonas aeruginosa, Staphylococcus aureus, Cryptococcus neoformans var. grubii, and Candida albicans. Result: Chalcone 3d had demonstrated growth inhibition greater than 60% against a variety of cancers: leukemia (MOLT-4, SR), non-small cell lung cancer (NCI-H522), colon cancer (HCT- 116), prostate cancer (DU-145), and breast cancer (MCF7, MDA-MB-468) and was also cytotoxic to three different cell lines (CCRF-CEM, RPMI-8226, and KM12). 5c was active against leukemia (CCRF-CEM, RPMI-8226, SR) and breast cancer (MCF7) and 5e was active only against leukemia (RPMI-8226, SR). 5h was partially active and the best compound with growth inhibition of MRSA by 75%. 3b was the best compound against EC, KP, and PA and 3f had the greatest activity against AB. For fungi, 3f and 3e demonstrated the best growth inhibition. Conclusion: A small library of heterocyclic-containing chalcones was developed and initial screening demonstrates modest activity against cancers, bacteria, and fungi.

Background: Chalcones, 2-pyrazolines and thiazoles have been reported to possess various pharmacological activities. Objective: Synthesis of new chalcones and utilizing them as a building block for constructing a series of thiazole derivatives and evaluating some of them as anticancer agents. Method: The new compounds were synthesized via stirring at room temperature or thermal heating. Cytotoxic evaluation of the new synthesized compounds was tested using the method of Skehan et al. Moreover, the computational studies were performed using MOE 2014.09 software. Result: A series of new chalcones were prepared by the reaction of ethyl 3-acetyl-1-aryl-5-methyl- 1H-pyrazole-4-carboxylate with a number of substituted benzaldehydes. One of these chalcones was used as a building block for constructing a pyrazoline ring via its reaction with thiosemicarbazide. The produced carbothioamide derivative was used for the preparation of two series of thiazole derivatives by its reaction with a number of hydrazonoyl chlorides. Moreover, reaction of 3- acetylpyrazole thiosemicarbazone derivative with a number of N-aryl-2-oxopropane hydrazonoyl chlorides afforded 5-arylazothiazole derivatives. The assigned structures for all the newly synthesized compounds were confirmed on the basis of elemental analyses and spectral data. Some of the newly synthesized chalcones and thiazoles were tested for their cytotoxicity against human colon carcinoma cell line (HCT-116) and the molecular docking was carried out on the most active compound 3f. Conclusion: The results of the anticancer activity revealed that compounds 3f, 3e, 3c and 3b have promising activities compared with the standard drug Doxorubicin. Moreover, the computational studies confirm the results of biological activity. Also, the ADME profile study showed that compound 3f can be considered as a promising drug by conducting good pharmacokinetic and medicinal chemistry tests.

Background: Isoxazoles, pyridazines, and pyrimidopyrazines have recently attracted attention due to their potent pharmacological activities. They exhibited anticancer, neuroprotective, analgesic and anti-inflammatory effects. Objective: The study aimed to synthesize novel isoxazoles, pyridazines, and pyrimidopyrazines through efficient high yield protocol for evaluating their analgesics and anti-inflammatory activities. Method: A series of novel isoxazole-, pyridazine-, pyrimidopyrazine derivatives was prepared from 5,8-alkyl-1,3-dimethyl-5,6-dihydropyrimido[5,6-e]pyrazine-2,4,7-trione (1a,b) as the starting material. Results: The prepared derivatives were synthesized in moderate to good yields (60-75%) in a stepwise efficient protocol under mild condition. These new compounds have been proven by several spectroscopic techniques as IR, 1D and 2D NMR techniques and mass analysis. The in vivo anti-inflammatory was assessed for the synthesized compounds using carrageenan-induced rat hind paw edema model. Also, the in vivo analgesic activity for these products was examined utilizing hot-plate and acetic acid-induced writhing response assays. Conclusion: The isoxazole derivatives (3a-f) showed the most forceful anti-inflammatory and analgesic activities. Pyrimidopyrazines (4a-f) demonstrated weaker but comparable antiinflammatory and analgesic activities to the positive controls.

Background: A new series of 13 piperazinyl flavone derivatives has been synthesized and examined for their in vitro antiradical and antioxidant activities in response to the pharmacy industry's increasing demand for new non-toxic anti-inflammatory and anticancer drugs. Method: Their antioxidant activity was evaluated by the reactive oxygen species (ROS) scavenging assays, 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH•) and 2,2'-azino-bis(3- ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS+•) scavenging assays, and the ferric reducing antioxidant potency (TAC) method, and was compared to known positive controls, herbal infusions, and penicillins. Chemiluminescence, spectrophotometry, electron spin resonance (ESR) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) as the spin trap were the measurement techniques. Result: It was seen that synthesized compounds have a wide spectrum of antioxidant property. Some of the test compounds proved to be extremely efficient scavengers of H2O2 exhibiting, in some cases, EC50 of about 2 μM. The values of antioxidant status (TAS) were in the range of 49 ± 3.9 to 1283 ± 51.3 μM TE/g (TE = Trolox equivalent) and were lower than that of butylated hydroxytoluene (BHT) (1304 ± 43.2 μM TE/g) and green tea (1356 ± 40.0 μM TE/g), but for several synthesized compounds, they were higher than chamomille infusion and penicillins. Ferric reducing antioxidant powers (TAC) for the piperazinyl flavone derivatives were in the range 7 ± 0.5 to 104 ± 0.6 μM TE/g and were weaker than that of BHT (217 ± 5.3 μM TR/g ). Conclusion: Carboxylic or hydroxamic acid substituted piperazinyl flavones are potentially active as antioxidants, thus may be suggested as pharmacologically interesting ones.

Background: Adenosine triphosphate (ATP) is the energy currency of the body; it takes part in various and indispensable metabolic processes for the maintenance of cell homeostasis, degrading to its hydrolysis product, adenosine diphosphate (ADP). Efficient ways to restore ATP are therefore necessary in the cells. When the cell lacks energy due to ischemic conditions or high ATP demand, phosphocreatine gives its phosphate group to ADP that converts to ATP, in a reaction catalyzed by the enzyme creatine kinase. For this reason, phosphocreatine is utilized as a pharmacological treatment in human diseases that involve a failure of the cellular energy, most notably in coronary artery disease. Objective: Commercially available phosphocreatine is currently synthesized using different methods, each of one characterized by a rather low yield of the final product, probably due to the low reactivity of the guanylating reagent. The aim of this work is to overcome the drawbacks of the synthetic methods currently employed, devising a novel synthetic route to obtain phosphocreatine and phosphocreatine prodrugs in higher yields and purity. Method: To obtain a higher yield of the final product and a lower number of sub-products, this method utilizes a new guanylating agent characterized by high reactivity, endowed with a protecting group t-Boc on one of the two nitrogen atoms of the guanidinic function and a protected phosphate on the other one; that compound is then conjugated with an opportune secondary amine. The obtained product is cleaved first with acidic conditions to obtain the phosphocreatine prodrug (phosphocreatine ethyl ester) and then with an enzymatic method to obtain the phosphocreatine. Result: Have been obtained in good yield and purity as demonstrated by HPLC and mass spectrometry analysis. Conclusion: This novel synthetic route permits to obtain the phosphocreatine molecule in higher yield and purity compared to the methods currently employed with a combination of chemical and enzymatic methods.

Background: Mycobacterium abscessus causes a wide range of clinical diseases that are difficult to treat. This microorganism is resistant not only to the classical antituberculosis agents but also to most of the antimicrobials that are currently available, resulting in limited therapeutic options and treatment failure. This scenario stresses the need to search for new drugs with activity against M. abscessus. Objective: To evaluate in vitro the antimycobacterial activity and cytotoxicity of rifabutin (RFB 1) and ten derivatives (2-11) against M. abscessus ATCC 19977. Method: The minimum inhibitory concentration (MIC) of the molecules was determined by the microdilution broth method according to the guideline described in CLSI. The toxicity evaluation was carried in 96-well microplates, using the cell line J774A.1 (ATCC TIB-67). Result: From the eleven molecules tested, RFB 1 and RFB 4 were the compounds showing higher activities against M. abscessus, with MICs of 0.9 and 1.0 μM, respectively. The R1 and R2 moieties seem to have deciding influence over the final activity. Furthermore, N-oxide derivatives 9, 10, and 11 were also active against M. abscessus, with MICs of 7.2 μM, 1.8 μM and 3.8 μM, respectively. An explanatory hypothesis for the better activities of compounds RFB 1, RFB 4, RFB 10 and RFB 11 considers the likely hydrogen bonding between ligands and receptor, balancing the global flexibility and interaction energies. RFB 1 and its most effective derivatives were found to be not toxic. Conclusion: Besides RFB 1, its derivatives 4, 10 and 11 show potential for clinical development in the M. abscessus treatment.

Background: Benzazepines received great attention in the field of medicinal chemistry since this scaffold has been recognized to belong to the important family of privileged templates. More specifically, the 4-amino-1,2,4,5-tetrahydro-2-benzazepin-3-one (Aba) is used as a core structure in a variety of constrained therapeutic peptide (turn) mimetics.Most of the synthetic approaches towards this template have focused on cyclizations which form the central 7-membered azepine ring. Objective: Previous investigations in our group allowed an expansion of the substitution patterns in the 4-amino-benzazepin-3-one scaffold by introduction of methyl substituents at positions 4 and 5 of the azepinone ring system, but also to 1-aryl substituted compounds. These were the only trisubstituted analogues obtained to date. To introduce an additional point of diversification and conformational constraint useful for peptide mimicry, one can use bifunctional substrates in the Ugi reaction as reported in the present manuscript. Method: The 1-carboxamido-substituted Aba scaffold has been synthesized via the Ugi-3CR reaction starting from N-Phth-protected 2-formyl-L-Phe-OH with a set of amine and isocyanide derivatives. The most suited reaction conditions were applied, involving preformation of the imine in MeOH (0.1 M) in the presence of anhydrous Na2SO4 during 2 hours at room temperature, followed by the addition of an equimolar quantity of isocyanide prior to heating the reaction mixture at 80 °C for 20 hours, using sealed vial reaction conditions. Results: The substituted Aba scaffolds were isolated in moderate yields (and diastereomeric ratio). This is due to the requirement for a double N-phthaloyl protection of the bifunctional building block, which prevents the use of an excess of amine reagent to drive the reaction conversion to completion, and some starting substrate always remains. Despite the moderate yields, the methodology is efficient since it only requires a limited number of synthetic steps in a final one-pot reaction. In most cases, the diastereomers could be separated by preparative RP-HPLC or via silica gel column chromatography. This is interesting from a medicinal chemistry point of view, since access is provided to the individual diastereomers. Conclusion: We have developed an efficient and useful one-pot strategy to access 1-substituted 4- aminobenzazepinone (Aba) derivatives via the Ugi-3CR reaction. To the best of our knowledge, these scaffolds are only accessible through the presented methodology. The obtained structural complexity, as well as the substitution versatility of these trisubstituted scaffolds, will allow their use in various biological applications.

Background: Nipecotic acid is considered to be one of the most potent inhibitors of neuronal and glial γ-aminobutyric acid (GABA) uptake in vitro. However, nipecotic acid does not readily cross the blood-brain barrier (BBB) following peripheral administration, owing to its hydrophilic nature. Objective: A series of substituted acetonaphthones tethered nipecotic acid derivatives were designed and synthesized with an aim to improve the lipophilicity and the blood-brain barrier (BBB) permeation. Methods: Synthesized compounds were tested in mice models of PTZ, pilocarpine, and DMCM induced epilepsy, in vivo. The rota-rod test was performed to determine the acute neurotoxicity of the potential leads (4a, 4b, and 4i). These potential hybrids were also evaluated for their ability to cross the BBB by an in vitro parallel artificial membrane permeability BBB assay (PAMPA-BBB). The leads were subjected to in silico molecular docking and dynamics studies on homology modelled protein of human GABA (γ-amino butyric acid) transporter 1 (GAT1) and prediction of their pharmacokinetic properties. Result: Amongst the synthesized derivatives, compounds 3a, 3b, 3i, 4a, 4b, and 4i exhibited increased latency of seizures against subcutaneous pentylenetetrazole (scPTZ) induced seizures in mice. Derivatives 4a, 4b, 4i were more effective compared to nipecotic acid ester counterparts 3a, 3b and 3i placing the importance of the presence of free carboxyl group in the centre. The findings revealed that 4i was comparatively more permeable (Pe= 8.89) across BBB than the standard tiagabine (Pe= 7.86). In silico studies proved the consensual interactions of compound 4i with the active binding pocket. Conclusion: Some nipecotic acid-acetonaphthone hybrids with considerable anti-epileptic activity, drug like properties and the ability to permeate the BBB have been successfully synthesized.