Medicinal Chemistry - Volume 13, Issue 1, 2017

Background: Microbes attach to surfaces and form biofilms where they are difficult to eradicate. Here they are embedded in a complex matrix of polymers and are much less sensitive against antibiotics or the immune system. Objective: This is a growing problem, especially for implants; hence, novel approaches are urgently needed to control biofilm infections. Methods: Many of these approaches interfere with the communication between the microbial cells required for biofilm formation and maintenance, a process known as quorum sensing. But microbes have also several mechanisms to disperse their own biofilms if conditions become unfavourable. Results: Recently, it has been found that the pathogen Pseudomonas aeruginosa disperses its mature biofilms using cis-2-decenoic acid. This fatty acid belongs to a group of cis-2-alkenoic acids which are known from several bacteria and are also triggering the communication between different species. In this review the biosynthesis of these compounds, their signal transduction and their role in species-species communication are presented. Examples are discussed where cis-2-alkenoic acids have been used to eradicate biofilms and enhance the sensitivity of pathogens against antibiotics, either alone or in combination with antibiotics. Conclusion: This presents an interesting approach for the control of biofilm infections but it is still in its infancy and a much broader characterization of the effects of cis-2-alkenoic acids are needed before moving to any medical application.

Assessment of toxicity is an important component of the drug discovery process. Cellbased assays are a popular choice for assessing cytotoxicity. However, these assays are complex because of the wide variety of formats and methods that are available, lack of standardization, confusing terminology and the inherent variability of biological systems and measurement. This review is intended as a guide on how to take these factors into account when planning, conducting and/or interpreting cell based toxicity assays.

Background: Group A streptococcus (GAS) is an exclusively human pathogenic bacteria. A delay in treatment of GAS infection often lead to severe diseases such as rheumatic heart disease which attributes to hundreds of thousands deaths annually. For the past few decades, the quest for a commercial GAS vaccine has been futile. Currently one of the most investigated strategies to develop vaccine against GAS includes the use of conserved epitopes from major virulent factor of GAS, M-protein. Methods: In this study, cationic liposomes of various sizes (70 nm to 1000 nm) were prepared with dimethyldioctadecylammonium bromide (DDAB) encapsulating lipopeptide bearing M-protein derived B-cell epitope (J14). Results: Smaller liposomes induced higher antibody titres, though the differences between groups were not statistically significant. Conclusion: Nonetheless, all mice which were immunized with liposome-lipopeptide delivery system elicited high levels of systemic (IgG) and mucosal antibodies (IgA), which were discernably higher than those induced with the help of commercial adjuvant (cholera toxin B subunit).

Background: Glioblastoma multiforme (GBM) is often associated with a poor survival prognostic for patients. The main reason seems to be the acquired or inherent resistance to the chemotherapeutic agent used to treat the tumor, temozolomide (TMZ). To this day, the most recognized pathway of resistance is the DNA Direct Repair pathway by the means of the protein O6- methylguanine DNA-methyltransferase (MGMT). Objectives: To design and synthesize a series of MGMT inhibitors that can sensitize GBM cells to TMZ. Methods: Twenty-five O6-alkyl, O6-aryl and O6-substituted-aryl guanine analogs including nine novel compounds were synthesized, characterized, analyzed by molecular docking and tested on the T98G GBM cells viability. Results: Following molecular modeling with MGMT, the newly designed compounds 19, 22, and 24 emerged as the most promising MGMT ligands and displayed modest cytotoxicity. Guanine analog (19), bearing a p-nitrobenzyl moiety, reduced considerably the O6-methylguanine DNAmethyltransferase expression level. When combined with TMZ (1), which is used as first line treatment for brain tumors, compounds 19, 22, and 24 decreased T98G cells proliferation by 32%, 68% and 50%, respectively. TMZ (1) displayed negligible effect on the proliferation of these cells further supporting the notion that this cell model is resistant to this alkylating agent. Conclusion: Overall, these results notably highlight a group of MGMT inhibitors that warrants further exploration in the development of therapeutic options to circumvent TMZ resistance in brain tumors.

Background: Tyrosine kinases (TK) are enzymes that catalyze the phosphorylation of tyrosine residues on proteins by the transfer of phosphate moiety of ATP. TK are key regulators of various cell functions, such as cellular growth, proliferation, migration, differentiation, and apoptosis. Src mutations and/or overexpression has been correlated with tumor growth, metastasis, and angiogenesis [4,5]. Thus, the design and the discovery of novel Src kinase inhibitors remains critically important. Methods: A series of 1,4-disubstituted 1,2,3-triazoles derivatives were designed and prepared as potential inhibitors for Src kinase. In this manuscript, all of the designed compounds were screened via molecular docking using PLANTS as virtual screening software to identify new inhibitors of Src kinase. Subsequently, all of the screened compounds were synthesized via Huisgen's 1,3-dipolar cycloaddition between terminal alkynes (1) and methyl 2-azidoacetate (2) with Cu(I) in excellent yields at room temperature. Results: In the present study, we report the design and the synthesis of a series of 1,4-disubstituted 1,2,3-triazoles involving one pot condensation of methyl 2-azidoacetate and different terminal alkynes. All the synthesized triazoles were characterized by IR, 1 H, 13 C, 19 F NMR, and HRMS. They were investigated as inhibitors of Src kinase. Conclusion: A series of 1,4-disubstituted 1,2,3-triazole compounds were synthesized through an easy, convenient Cu(I) catalyzed click reaction and evaluated for their Src kinase activity. Compound 3m exhibited significant inhibitory activity against Src Kinase. These results, along with molecular design docking observations, are significant evidence to demonstrate the compound 3m could be optimized as a potential Src kinase inhibitor in further studies.

Background: According to a review of recent literature, no previous studies have reported the dose-dependent selective inhibition of the antiproliferative activity using colony and sphere formation assays and immunoblotting in human hepatoma cells in response to doxorubicin and mitoxantrone structural analogs such as AM3. Objective: We evaluated the anticancer activity of mitoxantrone (MIT) structural analogs 1,5-bis({2- [(2-hydroxyethyl) amino]ethyl}-amino)-anthracene-9,10-dione (AM3) in human hepatoma cells (Huh-7). Methods: In this paper, we synthesized AM3 through the nucleophilic amino substitution of 1,5- dichloroanthraquinone with the corresponding dichloride groups under microwave-accelerated heating. The structural characteristics of AM3 were analyzed through ultraviolet–visible spectroscopy and nuclear magnetic resonance. In vitro activity of AM3 was measured using the dose-dependent selective inhibition of the antiproliferative activity using colony and sphere formation assays and immunoblotting in Huh-7. Results: The antiproliferative activity of AM3 was determined using IC50 values as 2.03 and 1.70 μM for hepatocellular carcinoma cell lines Huh-7 and SK-Hep-1 cells, respectively. In addition, colony formation assay of Huh-7 cells revealed that AM3 significantly suppressed the mean colony formation rate from 99.9 % to 2.5 %, and growth inhibition rate of sphere cells was significant, in which 5.0 μM of AM3 inhibited up to 28.5 % cell growth in the Huh-7 sphere cells. Immunoblotting confirmed the overexpression of CD44, COX-2, p-Akt, and Akt. Conclusion: Thus, AM3 is a novel therapeutic agent for suppressing cancer stemness and inflammation signaling in Huh-7 cells.

Background: Previously, glycopeptides antibiotics such as vancomycin, ramoplanin and an antifungal antibiotic nystatin have been studied for their diagnostic and therapeutic potential. Objective: To further explore the diagnostic and chemotherapeutic potential of other antibiotics we have now employed daptomycin, a lipopetide antibiotic and bacitracin, a polypeptide antibiotic in uptake and vitality tests on human cell lines. Method: Fluorescent conjugates of bacitracin and daptomycin were synthesized using fluorescein isothiocynate (FITC) for confocal laser scanning microscopy (CLSM) and fluorescence activated cell sorting (FACS). The cellular uptake of the synthesized daptomycin and bacitracin conjugates was studied on seven human cell lines, two healthy and five malignant using CLSM and FACS. To examine the cell membrane damage caused by the conjugates FACS experiments were carried out using propidium iodide. Results: The uptake pattern was different for both antibiotics for all the cell lines. The cytoplasmic uptake of daptomycin conjugate was lower than the bacitracin conjugate, resulting in decreased cell membrane damage. Conclusion: No preferential uptake into malignant or healthy cells was found for the two different antibiotic conjugates and the uptake patterns were also different between the two antibiotics. However, the lower cytotoxicity and different uptake mechanism makes daptomycin conjugate a prospective candidate for further study as a diagnostic agent for various intracellular infections.

Background: Antagonists to the H3 receptor are considered to be potential drugs for the treatment of Alzheimer’s disease, attention deficit-hyperactive disorder, memory and learning deficits, and epilepsy. The initial development of potent H3 receptor antagonists focused on extensive modification of the natural ligand histamine. However, it has appeared that imidazole-containing ligands are associated with inhibition of cytochrome P450 enzymes, caused by imidazole nitrogen complexation to heme iron in the active site of the enzyme. For these reasons, the development of potent non-imidazole H3 receptor antagonists was eagerly awaited. Objective: Previously, we reported the synthesis and pharmacological in vitro characterization of series of potent histamine H3-receptor non-imidazole antagonists belonging to the class of substituted 2-thiazol-4-n-propylpiperazines. A lead compound 1 of this family was a derivative carrying the ethylaminomethylpropyl chain. Methods: With the aim of increasing lipophilicity, that will help the ligands to cross the blood-brain barrier, we synthesized a series of new 2-thiazol-4-n-propylpiperazines where the ethylaminomethylpropyl moiety was replaced by a p-substituted-, an unsubstituted benzene ring, and ω-phenylalkyl substituent at positions 4 and 5 of thiazole ring, respectively. All compounds were tested for H3 antagonistic effects in vitro using the electrically contracting guinea pig jejunum. Results: The most active compounds of presented series 3d, 3e, and 3j showed lower affinity than the lead compound 1 and additionally, derivatives 3d and 3j possessed weak, competitive H1- antagonistic activity. This is in contrast to the lead compound 1 that has no affinity at H1 receptor. Conclusion: We can conclude that a side chain in the 2-thiazol-4-n-propylpiperazine scaffold should contain a basic center and should be present at a favorable position 5 of thiazole ring.

Background: The field of coordination chemistry has registered a phenomenal growth during the last few decades. It is well known that precious metals have been used for medicinal purposes for at least 3500 years. At that time, precious metals were believed to benefit health because of their rarity, but research has now well established the link between medicinal properties of inorganic drugs and specific biological properties. Methods: The current study was designed to explain the synthesis and characterization of the lanthanide (III) nitrate complexes with N-(2-hydroxynaphthalen-1-yl) methylene) nicotinohydrazide schiff base and to evaluate the antibacterial and the antioxidant activities of the schiff base and it's lanthanide ion complexes. Antimicrobial activity of the Lanthanide (III) nitrate complexes with N-(2- hydroxynaphthalen-1-yl) methylene) nicotinohydrazide schiff base was estimated by minimum inhibitory concentration (MIC, μg/mL) using a micro-broth dilution method for different clinical isolates such as Eschereshia coli and Enterococcus faecalis. The antioxidant activities of the ligand and its lanthanide complexes were tested using a UV-Visible spectrophotometer by preparing 5x10-4 M of all tested samples and DPPH in Dimethyl sulphoxide (DMSO). Results: Our present study has shown that moderate antimicrobial activity exists against both ligand and its complexes. There was no significant difference between Gram-positive and Gram-negative bacteria towards the tested ligand and its complexes. The free ligand has scavenging activity between 13-21 % while all complexes are more efficient in quenching DPPH than free ligand. Conclusion: The results obtained herein indicate that the ligand and its complexes have a considerable antibacterial activity as well as antioxidant activity in quenching DPPH.

Background: The antimicrobial activity of a synthesized series of 28 2-thioxobenzo[ g]quinazolin-4(3H)-one derivatives was evaluated in vitro against five Gram-positive bacteria, including Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus pyogenes. The antibacterial activity was extended to include five Gramnegative bacteria: Pseudomonas aeruginosa, Escherichia coli, Proteus mirabilis, Klebsiella oxytoca and Enterobacter cloacae. Furthermore, the antifungal activity was evaluated against 10 fungal strains, including Aspergillus fumigatus, Syncephalastrum racemosum, Geotricum candidum, Candida albicans, Aspergillus niger, Cryptococcus neoformans, Candida tropicalis, Penicillium expansum, Microsporum canis and Trichophyton mentagrophytes. Methods: The agar well diffusion method was adopted against Gram-positive and Gram-negative bacteria and fungi, using ampicillin, gentamicin and amphotericin B as reference drugs, respectively. Results: The findings of the antibacterial studies revealed that most of the tested compounds possess strong activity against both bacterial species. Compounds 8 and 23 were the most active on Grampositive bacteria, while several compounds demonstrated significant antibacterial activity on Gramnegative bacteria, especially Escherichia coli. Furthermore, several compounds showed strong antifungal activity against many of the investigated fungi. The obtained results were reinforced by determination of the minimum inhibitory concentration for the active compounds against Grampositive and Gram-negative bacteria, as well as fungi, compared to the reference drugs. Conclusion: Many of the investigated compounds showed potent activity against all tested microbial species. The discovery has provided a foundation for the synthesized compounds to serve as a platform for further design and development of more potent antimicrobial agents.

Background: Coumarin derivatives as dihydrocoumarins have been reported to have multiple biological activities, such as antioxidant and anti-inflammatory properties. Apocynin (APO), which is a substituted-methoxy-catechol, is the most commonly used inhibitor of the multienzymatic complex NADPH-oxidase. Objective: To increase the potency of APO as an NADPH oxidase inhibitor and its antioxidant and anti-inflammatory activities, we synthesized a compound by combining the structural features of a dihydrocoumarin and APO. Method: The dihydrocoumarin-apocynin derivative (HCA) was synthesized and evaluated in antioxidant and cell-based bioassays and compared with APO. Results: We found that HCA (IC50 = 10 μM) acted as an inhibitor of NADPH oxidase (ex vivo assays) and was more potent than APO (EC50 > 10 μM). The inhibitory effect on NADPH oxidase was not related to simple radical scavenger activity. HCA was also a more effective radical scavenger than APO, as verified in the DPPH (EC50 = 50.3 versus EC50 > 100 μM), triene degradation (slope AUC/concentration 759 ± 100 versus 101 ± 15) and FRAP (slope 0.159 versus 0.015) assays. The tested compound demonstrated a similar activity as an inhibitor of the oxidative damage provoked by peroxyl radicals in erythrocyte membranes. Conclusion: HCA showed superior capacity as inhibitor of NADPH oxidase and antioxidant activity. These findings show that HCA could be an improved substitute for APO and deserves further in vivo anti-inflammatory studies.