Current Topics in Medicinal Chemistry - Volume 13, Issue 16, 2013

Pradimicins (PRM) are a unique class of nonpeptidic carbohydrate-binding agents that inhibit HIV infection by efficiently binding to the HIV-1 envelope gp120 glycans in the obligatory presence of Ca2+. Surface plasmon resonance (SPR) data revealed that addition of EDTA dose-dependently results in lower binding signals of PRM-A to immobilized gp120. Pradimicin derivatives that lack the free carboxylic acid group on the C-18 position failed to bind gp120 and were devoid of significant antiviral activity. Ca2+ was much more efficient for PRM-A binding to gp120 than Cd2+, Ba2+ or Sr2+. Instead, calcium could not be replaced by any other mono- (i.e. K+), di- (i.e. Cu2+ Mg2+, Mn2+, Fe2+, Zn2+) or trivalent (i.e. Al,3+, Fe3+) cation without complete loss of gp120 binding. However, Zn2+, Mg2+ and Mn2+ added to a Ca2+- pradimicin mixture, prevented pradimicin from efficient binding to gp120 glycans. These data suggest that these bivalent cations may bind to pradimicins but lead to pradimicin-cation complexes that are unable to further coordinate with the glycans of gp120. Thus, in order to afford antiviral activity, only a few cations can (i) bind to pradimicin to form a dimeric complex and (ii) subsequently coordinate the pradimicin/cation interaction with gp120 glycans

Viruses coopt host intracellular Ca2+ signaling pathways to optimize timing and effectiveness of infection stages against barriers to invasion, pathogenesis, replication, and release. Virus-induced changes in free cytosolic Ca2+ levels facilitate virus adsorption, uncoating, catalysis, toxin production, structural assembly and stabilization, trafficking, and fusion and budding. Ca2+-associated alterations in virus status also selectively precipitate host cytopathologies through, among other events, retardation or induction of apoptosis, elevation of metabolic stress and reactive oxygen species production, and promotion of proinflammatory cytokine and chemokine synthesis and release. Viral particles and proteins tune spatiotemporal dynamics of host free cytosolic Ca2+ concentrations by modulating Ca2+ entry from the extracellular environment, upstream first or second messengers, ion- and ATP-dependent Ca2+ pumps that sequester or extrude free cytosolic Ca2+, store-operated Ca2+ mobilization and leakage, and viral capsid/envelope and downstream host Ca2+ binding proteins and sensors. Each of these major viral mechanisms, briefly reviewed in this article, presents a suitable drug target capable of mitigating the severity and incidence of viral infections. Given its pivotal role in cellular response regulation, bioenergetics, posttranslational protein and lipid modification and transport, homeostasis, cell motility and morphogenesis, and T lymphocyte proliferation, targeting virally stimulated inositol 1,4,5-trisphoshate (IP3)-mediated store-operated Ca2+ release especially offers unique, predictable benefits for augmenting immunoprotection in vertebrate clinical populations. We appraise possibilities of modulating this system with experimental proteins that gate activation kinetics of endoplasmic-reticulum-localized Ca2+-conducting IP3 receptors via allosteric protein-protein interactions. Such compounds are expected to be valuable in treating primary disease symptoms and sequelae, including virus-associated dementia.

Successful pharmaceutical development of a drug molecule depends not only on its potency and selectivity but also on its solid state. Thus the properties of active pharmaceutical ingrdient depend on the identity of its constituents as well as on their arrangement. It is quite common for a drug molecule to exist in more than one crystalline arrangement leading to polymorphism. The various polymorphs differ from each other in dissolution rate, bioavailability, oral absorption, toxicology and clinical trial results. Ultimately both safety and efficacy are impacted by properties that vary among different solid forms. In the recent years screening of polymorphs is increasingly emphasised in the pharmaceutical industry not only because of the valuable knowledge obtained provides necessary guidance for further development but also because of the issue of intellectual property rights. Cocrystallization is an emerging area of research and provides a unique opportunity to enhance marketed products or to pursue compounds that had otherwise been deemed non developable. This review discusses that how common polymorphism among anti- retroviral and its effect on their efficacy. Prevalence of cocrystallization in improving the bioavailability and efficacy of these pharmaceutically important drugs is also incorporated.

Azole compounds are an important class of nitrogen heterocycles with electron-rich property. This special structure endows azole-based derivatives easily bind with the enzymes and receptors in organisms through noncovalent interactions such as hydrogen bonds, coordination bonds, ion-dipole, cation-π,π-π stacking and hydrophobic effect as well as van der Waals force etc., thereby possessing various applications in medicinal chemistry, especially their protrudent effects such as imidazoles and triazoles against fungal strains. The design, synthesis and antimicrobial activity of azole derivatives have been extensively investigated and have become one of the highly active highlights in recent years, and the progress is quite rapid. In particular, a large number of azole-based antibacterial and antifungal agents have been penetratingly studied as candidates and even some of them have been used in clinic, which have shown the great potential and development value of azole compounds. Based on our researches on azole compounds and referring to other literature, this work scientifically reviewed the researches and developments of azole-based compounds as antibacterial and antifungal agents, including oxazole, imidazole, benzimidazole, triazole, benzotriazole, pyrazole, thiazole, carbazole as well as tetrazole in recent three years. It is hopeful that azole compounds may continue to serve as an important direction for the exploitation of azole-based antibacterial and antifungal drugs with better curative effect, lower toxicity, less side effects, especially fewer resistances and so on.

Thiourea and guanidine substructural units are of significant importance as the compounds containing these core units either in the open or the cyclic form are known to display an array of pharmacological properties. This brief review assimilates the literature on the medicinal significance of thiourea and guanidine derivatives with respect to antimalarial and antimicrobial activities.

Antimicrobial peptides are a group of natural or semi-synthetic molecules possessing antimicrobial activities against bacteria, fungi, viruses, parasites, etc. They are considered as promising candidates for treatment of microbial infections and suppression of microbial resistance. The increasing emergence of bacterial resistance has required development of new efficient antibiotics that can be added to the antibacterial armamentarium. The marine world provides a rich source of antimicrobial peptides. That world has not been highly explored yet, and much more effort is required in order to discover new efficient antimicrobial peptides. In the present article, we have reviewed the recent progress in the field of marine antimicrobial peptides from 2009 until the mid of 2012.

A series of 3-(5-(arylidene)-2-(aryl)-4-oxothiazolidin-3-yl)-2-phenylquinazolin-4(3H)-one derivatives (1-18) was synthesized in appreciable yield and characterized by physicochemical and spectral means. The synthesized compounds were evaluated for their in vitro antimicrobial and anticancer potentials. Antimicrobial properties of the title compounds were investigated against Gram positive and Gram negative bacterial as well fungal strains. 3-(5-(3- Methoxybenzylidene)-2-(4-(dimethylamino)phenyl)-4-oxothiazolidin-3-yl)-2-phenyl quinazolin-4(3H)-one (16, pMICam = 1.71 µM/ml) was found to be the most active antimicrobial agent. The anticancer evaluation of synthesized compounds against human colon (HCT116) cancer cell line indicated that 3-(5-(4-bromobenzylidene)-2-(3-chlorophenyl)-4- oxothiazolidin-3-yl)-2-phenylquinazolin-4(3H)-one (7, IC50 = 5.27 µM) was the most active anticancer agent and was more potent than standard drug, 5-fluorouracil (IC50 = 6.00 µM). QSAR models developed for antimicrobial activity of synthesized compounds indicated that antimicrobial activity of synthesized 4-thiazolidinone derivatives was governed by the topological parameters, valence first and second order molecular connectivity indices (1Χv and 2Χv) and the electronic parameters, total energy (Te) and cosmic energy (Cos E).

We herein report the synthesis of 3β-substituted amides of 17a-aza-D-homo-4-androsten-17-one (11a-11r) from commercially available Diosgenin as the starting material. The structures of newly synthesized compounds were confirmed by IR, 1H NMR, 13C NMR and mass spectrometry. All the synthesized analogues were tested for their 5α- reductase inhibitory and antimicrobial activity, some of them exhibit moderate to potent activity comparable to the reference drugs. Among the synthesized derivatives the analogue (11r) 3β-(indonlylbutanamido)-17a-aza-D-homo-4- androsten-17-one was found to be active against both 5-reductase enzyme and microbial strains, whereas the analogue (11i) 3β-(3,4-dimethoxy-benzamido)-17a-aza-D-homo-4-androsten-17-one was found to be the least active. The detailed 5-reductase inhibitors and antimicrobial activities of the synthesized compounds were reported.

A series of novel derivatives of 1,3-oxazolidin-2-one 12a-12n has been synthesized starting from 4-nitro-(L)- phenylalanine by involving five-step reaction sequence. All the compounds were screened for their in vitro antibacterial activity against four pathogenic bacterial strains namely, Staphylococcus aureus, Bacillus subtilis (Gram-positive), Escherichia coli, Pseudomonas aeruginosa (Gram-negative) and in vitro antifungal activity against two pathogenic fungal strains namely, Candida albicans and Saccharomyces cerevisiae. All the synthesized compounds showed activity against Gram-positive bacteria. Compounds 12c and 12l exhibited maximum antibacterial activity against Gram-positive bacteria. However, against Gram-negative bacteria only five of screened compounds were found to be active. Compounds 12c and 12i displayed best antifungal activity against the tested fungi. Docking studies were carried out in order to gain insight into the mechanism of action and the binding mode of these compounds. These studies were in agreement with the biological data.

Cancer is a disease without limits turning out to be prime cause for raising death toll around the world. Several treatment strategies including chemotherapy, surgery and radiotherapy are being employed worldwide to combat this disease. Due to the unwanted effects of currently available therapies, scientific community is immensely interested in exploring newer alternative pathways. Fluoroquinolones have been employed as potent anti-microbial agents for last few decades and now being looked up as potential therapeutic agents in the other ailments also. Several research endeavours are carried out in different parts of the world to focus on the prospective role of fluoroquinolones in carcinogenesis and mutagenesis. This article is an earnest attempt to present recent research work carried out on fluoroquinolones in the context to cancer treatment therapies.