Medicinal Chemistry - Volume 15, Issue 7, 2019

Background: Tyrosinase is involved in the melanin biosynthesis and the abnormal accumulation of melanin pigments leading to hyperpigmentation disorders. Controlling the melanogenesis could be an important strategy for treating abnormal pigmentation. Methods: In the present study, a series of amide derivatives (3a-e and 5a-e) were synthesized aiming to inhibit tyrosinase activity and melanin production. All derivatives were screened for tyrosinase inhibition in a cell-free system. The possible interactions of amide derivatives with tyrosinase enzyme and effect of these interactions on tyrosinase structure were checked by molecular docking in silico and by Circular Dichroism (CD) studies, respectively. The most potent amide derivative (5c) based on cell-free experiments, was further tested for cellular ROS inhibition and for tyrosinase activity using mouse skin melanoma (B16F10) cells. Results: The tyrosinase inhibitory concentration (IC50) for tested compounds was observed between the range of 68 to 0.0029 μg/ml with a lowest IC50 value of compound 5c which outperforms the reference arbutin and kojic acid. The cellular tyrosinase activity and melanin quantification assay demonstrate that 15μg/ml of 5c attenuates 36% tyrosinase, 24% melanin content of B16F10 cells without significant cell toxicity. Moreover, the zebrafish in vivo assay reveals that 5c effectively reduces melanogenesis without perceptible toxicity. Furthermore, the molecular docking demonstrates that compound 5c interacts with copper ions and multiple amino acids in the active site of tyrosinase with best glide score (-5.387 kcal/mol), essential for mushroom tyrosinase inhibition and the ability to diminish the melanin synthesis in-vitro and in-vivo. Conclusion: Thus, we propose compound 5c as a potential candidate to control tyrosinase rooted hyperpigmentation in the future.

Background: The lack of efficacious therapy for advanced melanoma and neuroblastoma makes new approaches necessary. Therefore, many scientists seek new, more effective, more selective and less toxic anticancer drugs. Objective: We propose the synthesis of the new functionalized analogs of 1-nitroacridine/4- nitroacridone connected to tuftsin/retro-tuftsin derivatives as potential anticancer agents. Methods: Acridine and acridone analogues were prepared by Ullmann condensation and then cyclization reaction. As a result of nucleophilic substitution reaction 1-nitro-9-phenoxyacridine or 1- chloro-4-nitro-9(10H)-acridone with the corresponding peptides, the planned acridine derivatives (10a-c, 12, 17-a-d, 19) have been obtained. The cytotoxic activity of the newly obtained analogs were evaluated against melanotic (Ma) and amelanotic (Ab) melanoma cell lines and neuroblastoma SH-SY5Y by using the XTT method. Apoptosis and cell cycle were analyzed by flow cytometry. Results: Among the investigated analogs compound 12 exhibited the highest potency comparable to dacarbazine action for amelanotic Ab melanoma cells. FLICA test (flurochrome-labeled inhibitors of caspases) showed that this analog significantly increased the content of cells with activated caspases (C+) among both neuroblastoma lines and only Ab melanoma line. Using phosphatidylserine (PS) externalization assay, 12 induced changes in the Ab melanoma plasma membrane structure as the externalization of phosphatidylserine (An+ cells). These changes in neuroblastoma cells were less pronounced. Conclusion: Analog 12 could be proposed as the new potential chemotherapeutic against amelanotic melanoma form especially.

Background: Breast cancer is the most prevalent cancer type in women globally. It is characterized by distinct subtypes depending on different gene expression patterns. Oncogene HER2 is expressed on the surface of cell and is responsible for cell growth regulation. Increase in HER2 receptor protein due to gene amplification, results in aggressive growth, and high metastasis in cancer cells. Methods: The current study evaluates and compares the anti-breast cancer effect of commercially available compounds against HER2 overexpressing BT-474, and triple negative MDA-MB-231 breast cancer cell lines. Results: Preliminary in vitro cell viability assays on these cell lines identified 6 lead molecules active against breast cancer. Convallatoxin (4), a steroidal lactone glycoside, showed the most potent activity with IC50 values of 0.63 ± 0.56, and 0.69 ± 0.59 μM against BT-474 and MDA-MB-231, respectively, whereas 4-[4-(Trifluoromethyl)-phenoxy] phenol (3) a phenol derivative, and Reserpine (5) an indole alkaloid selectively inhibited the growth of BT-474, and MDA-MB-231 breast cancer cells, respectively. Conclusion: These results exhibited the potential of small molecules in the treatment of HER2 amplified and triple negative breast cancers in vitro.

Background: A large number of pyrazole derivatives have different biological activities such as anticancer, antimicrobial, anti-inflammatory, analgesic and antiepileptic activity. Among them, pyrazole oximes have attracted much attention due to their potential pharmacological activities, particularly anticancer activities. Objective: Our goal is to synthesize novel thiazolyl substituted bis-pyrazole oxime derivatives with potent antitumor activities by selectively inducing apoptosis and Reactive Oxygen Species (ROS) accumulation in cancer cells. Methods: Eighteen bis-pyrazole oximes were synthesized by conjugating thiazolyl substituted pyrazoles with pyrazoxime. The target compounds were characterized by 1HNMR, 13C NMR, and HRMS, and screened for their antiproliferative activity against four cancer cells in MTT assay. The most potent compound was examined for its inhibitory effect and ROS accumulation in both cancer cells HCT116 and normal intestinal epithelial cells CCD841. Finally, the most potent compound was further evaluated for its apoptotic induction by flow cytometry analysis and immunoblot analysis of apoptosis-related proteins and DNA damage proteins. Results: Most compounds displayed potent antiproliferative activity against four cancer cell lines in vitro, displaying potencies superior to 5-FU. In particular, the most potent compound 13l selectively inhibited proliferation of colorectal cancer HCT116 cells but not normal colon CCD841 cells. Furthermore, compound 13l also selectively promoted intracellular ROS accumulation in HCT116 which was involved in 13l inhibition of cancer cell proliferation and induction of cell apoptosis. Finally, compound 13l also dose-dependently induced cancer cell apoptosis by regulating apoptotic and DNA damage related proteins expressions. Conclusion: Our synthetic bis-pyrazole oxime derivatives possess potent antitumor activities by selectively inducing apoptosis and ROS accumulation in cancer cells, which may hold great promise as therapeutic agents for the treatment of human cancers.

Background: Despite the progress in the discovery of antiretroviral compounds for treating HIV-1 infection by targeting HIV integrase (IN), a promising and well-known drug target against HIV-1, there is a growing need to increase the armamentarium against HIV, for avoiding the drug resistance issue. Objective: To develop novel HIV-1 IN inhibitors, a series of 3-hydroxy-pyrane-4-one (HP) and 3- hydroxy-pyridine-4-one (HPO) derivatives have been rationally designed and synthesized. Methods: To provide a significant characterization of the novel compounds, in-depth computational analysis was performed using a novel HIV-1 IN/DNA binary 3D-model for investigating the binding mode of the newly conceived molecules in complex with IN. The 3D-model was generated using the proto-type foamy virus (PFV) DNA as a structural template, positioning the viral polydesoxyribonucleic chain into the HIV-1 IN homology model. Moreover, a series of in vitro tests were performed including HIV-1 activity inhibition, HIV-1 IN activity inhibition, HIV-1 IN strand transfer activity inhibition and cellular toxicity. Results: Bioassay results indicated that most of HP analogues including HPa, HPb, HPc, HPd, HPe and HPg, showed favorable inhibitory activities against HIV-1-IN in the low micromolar range. Particularly halogenated derivatives (HPb and HPd) offered the best biological activities in terms of reduced toxicity and optimum inhibitory activities against HIV-1 IN and HIV-1 in cell culture. Conclusion: Halogenated derivatives, HPb and HPd, displayed the most promising anti-HIV profile, paving the way to the optimization of the presented scaffolds for developing new effective antiviral agents.

Background: Exogenous antioxidants are considered as a promising therapeutic approach to treat neurodegenerative diseases since they could prevent and/or minimize the neuronal damage by oxidation. Objective: Three series of lipophilic compounds structurally based on scutellarein (2), which is one metabolite of scutellarin (1) in vivo, have been designed and synthesized. Methods: Their antioxidant activity was evaluated by detecting the 2-thiobarbituric acid reactive substance (TBARS) produced in the ferrous salt/ascorbate-induced autoxidation of lipids, which were present in microsomal membranes of rat hepatocytes. The lipophilicity of these compounds indicated as partition coefficient between n-octanol and buffer was investigated by ultraviolet (UV) spectrophotometer. Results: This study indicated that compound 5e which had a benzyl group substituted at the C4'- OH position showed a potent antioxidant activity and good lipophilicity. Conclusion: 5e could be an effective candidate for preventing or reducing the oxidative status associated with the neurodegenerative processes.

Background: The drug formulations used to control mosquito vectors and helminth infections have resulted in the development of resistance, and negative impact on non-target organisms and environment. Objective: Plant-mediated synthesis of silver nanoparticles (P-AgNPs) using aqueous fruit peel extract of M. charantia, applications of P-AgNPs for helminthicidal activity against Indian earthworms (P. posthuma) and larvicidal activity against larvae of mosquito A. albopictus and A. aegypti. Methods: Aqueous fruit peel extract of Momordica charantia was used to reduce silver ions to silver nanoparticles (P-AgNPs). UV-Visible (UV-Vis) Spectroscopy, X-ray diffraction, Fourier Transform Infrared Spectroscopy and Transmission Electron Microscopy characterize synthesized P-AgNPs. The motility and survival rate of the worms were recorded for the helminthicidal activity. Percent mortality of larvae of A. albopictus and A. aegypti was recorded for larvicidal activity. Results: The UV-Vis absorption spectrum of P-AgNPs showed a strong surface plasmon absorption band in the visible region with a maximum absorption at 445 nm indicating the synthesis of silver nanoparticles by the addition of aqueous fruit peel extract. The XRD spectrum of P-AgNPs showed Bragg's reflection peaks 2 value characteristics for the Face-Centered Cubic (FCC) structure of silver. The sharp absorption peak in FTIR at 1659 cm-1 assigned to C=O stretching vibration in carbonyl compounds represents terpenoids, flavonoids and polyphenols in the corona of PAgNPs; a 2 mg/mL of P-AgNPs. The concentration aqueous extract and P-AgNPs showed complete death of worms (the morphological alteration/coiling of body). A 20 ppm concentration of PAgNPs showed 85% mortality in larvae of Ae. albopictus and Ae. aegypti. P-AgNPs were nontoxic at low concentrations. Conclusion: The aqueous extracts played a dual role as reducing and capping agent during the biosynthesis of AgNPs as per FTIR and XRD results. The surface reactivity facilitated by biomolecule corona attached to silver nanoparticles can further help to functionalize AgNPs in various pharmaceuticals, biomedicals, and environmental applications.

Background: Malaria remains a common life-threatening infectious disease across the globe due to the development of resistance by Plasmodium parasite against most antimalarial drugs. The situation demands new and effective drug candidates against Plasmodium. Objectives: The objective of this study is to design, synthesize and test novel quinoline based molecules against the malaria parasite. Methods: C2 and C8 modified quinoline analogs obtained via C-H bond functionalization approach were synthesized and evaluated for inhibition of growth of P. falciparum grown in human red blood cells using SYBR Green microtiter plate based screening. Computational molecular docking studies were carried out with top fourteen molecules using Autodoc software. Results: The biological evaluation results revealed good activity of quinoline-8-acrylate 3f (IC50 14.2 μM), and the 2-quinoline-α-hydroxypropionates 4b (IC50 6.5 μM), 4j (IC50 5.5 μM) and 4g (IC50 9.5 μM), against chloroquine sensitive Pf3D7 strain. Top fourteen molecules were screened also against chloroquine resistant Pf INDO strain and the observed resistant indices were found to lie between 1 and 7.58. Computational molecular docking studies indicated a unique mode of binding of these quinolines to Falcipain-2 and heme moiety, indicating these to be the probable targets of their antiplasmodial action. Conclusion: An important finding of our work is the fact that unlike Chloroquine which shows a resistance Index of 15, the resistance indices for the most promising molecules studied by us were about one indicating equal potency against drug sensitive and resistant strains of the malaria parasite.

Background: Clinical drugs for herpesvirus exhibit high toxicity and suffer from significant drug resistance. The development of new, effective, and safe anti-herpesvirus agents with different mechanisms of action is greatly required. Objective: Novel inhibitors against herpesvirus with different mechanisms of action from that of clinical drugs. Methods: A series of novel 5-(benzylamino)-1H-1,2,3-triazole-4-carboxamides were efficiently synthesized and EC50 values against Human Cytomegalovirus (HCMV), Varicella-Zoster Virus (VZV) and Herpes Simplex Virus (HSV) were evaluated in vitro. Results: Some compounds present antiviral activity. Compounds 5s and 5t are potent against both HCMV and VZV. Compounds 5m, 5n, 5s, and 5t show similar EC50 values against both TK+ and TK− VZV strains. Conclusion: 5-(Benzylamino)-1H-1, 2,3-triazole-4-carboxamides are active against herpesviruses and their activity is remarkably affected by the nature and the position of substituents in the benzene ring. The results indicate that these derivatives are independent of the viral thymidine kinase (TK) for activation, which is indispensable for current drugs. Their mechanisms of action may differ from those of the clinic anti-herpesvirus drugs.

Background: Dihydrofolate reductase is one of the important enzymes for thymidylate and purine synthesis in micro-organisms. A large number of drugs have been designed to inhibit microbial DHFR but over the period of time, some drugs have developed resistance and cross reactivity towards the enzyme. Over the past few decades, benzimidazoles, triazoles and their derivatives have been grabbing the attention of the synthetic chemists for their wide gamut of antibacterial and antifungal activities targeting microbial protein DHFR. Objective: Our goal behind present investigation is to explore benzimidazoles class of drugs as microbial DHFR inhibitors by studying ligand-receptor binding interactions, in vitro enzyme inhibition assay and confirmation of anti-microbial activity against selected pathogenic microorganisms. Methods: A library containing thirty novel 2,6-disubstituted 1H-benzimidazoles was synthesized by one pot condensation of o-nitro aniline or 2,4-dinitro aniline with series of aldehydes or acetophenones using Na2S2O4 or SnCl2 respectively and reflux for 5-6hr. Structures of compounds have been confirmed by spectroscopic methods as 1H and 13C NMR, FT-IR and MS. In vitro DHFR inhibition study was performed by using Epoch microplate reader and IC50 of the test compounds was compared with Trimethoprim. In vitro antimicrobial activity was performed against selected clinical pathogens by agar disk diffusion method and MIC (μg/mL) was reported. Results: Moderate to good level of DHFR inhibition was observed with IC50 values in the range of 7-23 μM. Compounds B1, B19, B22, B24 and B30 expressed 1.1 to 1.4 folds more prominent DHFR inhibitory activity as compared to standard Trimethoprim. Remarkable antimicrobial activity was exhibited by B1, B19, B22, B24 and B30. Molecular docking study revealed perfect binding of test ligands with key amino acids of DHFR as Phe31, Ile94, Ile5, Asp27, Gln32 and Phe36. Conclusion: Nature of 1H-benzimidazole substituents at position 2 and 6 had influence over magnitude and type of molecular binding and variation in the biological activity. The present series of 1H-benzimidazoles could be considered promising broad-spectrum antimicrobial candidates that deserve in future for preclinical antimicrobial evaluation and development of newer antimicrobial agents targeting microbial DHFR.