Antiviral activity of an N-allyl acridone against dengue virus

Newly synthesized acridone derivatives targeting lung cancer: A toxicity and xenograft model study

AKT is one of the overexpressed targets in nonsmall cell lung cancer (NSCLC) and plays an important role in its progression and offers an attractive target for the therapy. The PI3K/AKT/mTOR pathway is upregulated in NSCLC. Acridone is an important heterocycle compound which treats cancer through various mechanisms including AKT as a target. In the present work, the study was designed to evaluate the safety profile of three acridone derivatives (AC-2, AC-7, and AC-26) by acute and repeated dose oral toxicity. In addition to this, we also checked the pAKT overexpression and its control by these derivatives in tumor xenograft model. The results from acute and repeated dose toxicity showed these compounds to be highly safe and free from any toxicity, mortality, or significant alteration in body weight, food, and water intake in the rats. In the repeated dose toxicity, compounds showed negligible variations in a few hematological parameters at 400 mg/kg. The histopathology, biochemical, and urine parameters remained unchanged. The xenograft model study demonstrated AC-2 to be inhibiting HOP-62 induced tumor via reduction in p-AKT1 (Ser473) expression significantly. In immunofluorescence staining AC-2 treated tissue section showed 2.5 fold reduction in the expression of p-AKT1 (Ser473). Histopathology studies showed the destruction of tumor cells with increased necrosis after treatment. The study concluded that AC-2 causes cell necrosis in tumor cells via blocking the p-AKT1 expression. The findings may provide a strong basis for further clinical applications of acridone derivatives in NSCLC.

Synthesis of acridones via Ir(III)-catalyzed amination annulation of oxazoles with anthranils

An unprecedented Ir(III)-catalyzed C-H activation/amination/annulation of 2-phenyloxazoles with anthranils for the highly selective preparation of acridone derivatives in one-pot under controlled conditions is reported. This protocol is characterized by atom economy and high regioselectivity. A wide range of anthranils with 2-phenyloxazoles were well tolerated and afforded the desired products in moderate to good yields, in which the anthranil serves as a convenient amination reagent.

N-Heterocycles as Promising Antiviral Agents: A Comprehensive Overview

Viruses are a real threat to every organism at any stage of life leading to extensive infections and casualties. N-heterocycles can affect the viral life cycle at many points, including viral entrance into host cells, viral genome replication, and the production of novel viral species. Certain N-heterocycles can also stimulate the host's immune system, producing antiviral cytokines and chemokines that can stop the reproduction of viruses. This review focused on recent five- or six-membered synthetic N-heterocyclic molecules showing antiviral activity through SAR analyses. The review will assist in identifying robust scaffolds that might be utilized to create effective antiviral drugs with either no or few side effects.

Acridones as promising drug candidates against Oropouche virus

Oropouche virus (OROV) is an emerging vector-borne arbovirus found in South America that causes Oropouche fever, a febrile infection similar to dengue fever. It has a high epidemic potential, causing illness in over 500,000 cases diagnosed since the virus was first discovered in 1955. Currently, the prevention of human viral infection depends on vaccination, but availability for many viruses is limited, and they are classified as neglected viruses. At present, there are no vaccines or antiviral treatments available. An alternative approach to limiting the spread of the virus is to selectively disrupt viral replication mechanisms. Here, we demonstrate the inhibitory effect of acridones, which efficiently inhibited viral replication by 99.9 % in vitro. To evaluate possible mechanisms of action, we conducted tests with dsRNA, an intermediate in virus replication, as well as MD simulations, docking, and binding free energy analysis. The results showed a strong interaction between FAC21 and the OROV endonuclease, which possibly limits the interaction of viral RNA with other proteins. Therefore, our results suggest a dual mechanism of antiviral action, possibly caused by ds-RNA intercalation. In summary, our findings demonstrate that a new generation of antiviral drugs could be developed based on the selective optimization of molecules.

Plant-derived alkaloids acting on dengue virus and their vectors: from chemistry to pharmacology

Dengue is a mosquito-borne viral infection, with its prevention and control depending on effective vector control measures. At present, dengue virus (DENV) is an epidemic in more than 100 countries of Southeast Asia, Africa, Eastern Mediterranean, the Americas and the Western Pacific. Several alkaloids isolated from natural herbs can serve as a reservoir for antiDENV drug development. Traditionally, plant extracts rich in alkaloids are used for the treatment of fever and have also revealed antimicrobial activity against various pathogenic bacteria, fungi and virus. The present narrative review collates the literature-based scenario of alkaloids and derivatives acting on DENV. The mechanism of action of such alkaloids with antiDENV and vector activity is also discussed.

Synthesis of novel cytotoxic tetracyclic acridone derivatives and study of their molecular docking, ADMET, QSAR, bioactivity and protein binding properties

Acridone based synthetic and natural products with inherent anticancer activity advancing the research and generating a large number of structurally diversified compounds. In this sequence we have designed, synthesized a series of tetracyclic acridones with amide framework viz., 3-(alkyloyl/ aryloyl/ heteroaryloyl/ heteroaryl)-2,3-dihydropyrazino[3,2,1-de]acridin-7(1H)-ones and screened for their in vitro anti-cancer activity. The in vitro study revealed that compounds with cyclopropyl-acetyl, benzoyl, p-hydroxybenzoyl, p-(trifluoromethyl)benzoyl, p-fluorobenzoyl, m-fluorobenzoyl, picolinoyl, 6-methylpicolinoyl and 3-nicotinoyl groups are active against HT29, MDAMB231 and HEK293T cancer cell lines. The molecular docking studies performed for them against 4N5Y, HT29 and 2VWD revealed the potential ligand-protein binding interactions among the neutral aminoacid of the enzymes and carbonyl groups of the title compounds with a binding energy ranging from - 8.1394 to - 6.9915 kcal/mol. In addition, the BSA protein binding assay performed for them has confirmed their interaction with target proteins through strong binding to BSA macromolecule. The additional studies like ADMET, QSAR, bioactivity scores, drug properties and toxicity risks ascertained them as newer drug candidates. This study had added a new collection of piperazino fused acridone derivatives to the existing array of other nitrogen heterocyclic fused acridone derivatives as anticancer agents.

Application of Lanthanide Shift Reagent to the 1H-NMR Assignments of Acridone Alkaloids

This study investigates the application of the paramagnetic shift reagent tris(dipivaloylmethanato)-europium(III) in NMR spectral studies of permethoxyacridone alkaloids (1–3) and pyranoacridone alkaloids (4–6). The induced chemical shifts (∆δ) of all protons were observed for the same molecule, and were compared to deduce the positions resulting from the distance nearby the Eu(dpm)₃. Assignment of the H-2, H-4 and H-8 of polysubstituted acridones could be distinguished based on the least-squares method of lanthanide-induced shifts plotted against the mole ratios of Eu(dpm)₃ to the substrate. The developed method is not only potentially useful for determining the planar structures of polysubstituted compounds, such as acridones, anthraquinones, xanthones, flavonoids, and phenanthrenes, but also applicable for their stereochemistry.

Recent advances in antiviral drug development towards dengue virus

Despite the high disease burden of dengue virus, there is no approved antiviral treatment or broadly applicable vaccine to treat or prevent dengue virus infection. In the last decade, many antiviral compounds have been identified but only few have been further evaluated in pre-clinical or clinical trials. This review will give an overview of the direct-acting and host-directed antivirals identified to date. Furthermore, important parameters for further development that is, drug properties including efficacy, specificity and stability, pre-clinical animal testing, and combinational drug therapy will be discussed.

Contemporary Strategies and Current Trends in Designing Antiviral Drugs against Dengue Fever via Targeting Host-Based Approaches

Dengue virus (DENV) is an arboviral human pathogen transmitted through mosquito bite that infects an estimated ~400 million humans (~5% of the global population) annually. To date, no specific therapeutics have been developed that can prevent or treat infections resulting from this pathogen. DENV utilizes numerous host molecules and factors for transcribing the single-stranded ~11 kb positive-sense RNA genome. For example, the glycosylation machinery of the host is required for viral particles to assemble in the endoplasmic reticulum. Since a variety of host factors seem to be utilized by the pathogens, targeting these factors may result in DENV inhibitors, and will play an important role in attenuating the rapid emergence of other flaviviruses. Many experimental studies have yielded findings indicating that host factors facilitate infection, indicating that the focus should be given to targeting the processes contributing to pathogenesis along with many other immune responses. Here, we provide an extensive literature review in order to elucidate the progress made in the development of host-based approaches for DENV viral infections, focusing on host cellular mechanisms and factors responsible for viral replication, aiming to aid the potential development of host-dependent antiviral therapeutics.

De novo design approaches targeting an envelope protein pocket to identify small molecules against dengue virus

Dengue fever is a mosquito-borne viral disease that has become a major public health concern worldwide. This disease presents with a wide range of clinical manifestations, from a mild cold-like illness to the more serious hemorrhagic dengue fever and dengue shock syndrome. Currently, neither an approved drug nor an effective vaccine for the treatment are available to fight the disease. The envelope protein (E) is a major component of the virion surface. This protein plays a key role during the viral entry process, constituting an attractive target for the development of antiviral drugs. The crystal structure of the E protein reveals the existence of a hydrophobic pocket occupied by the detergent n-octyl-β-d-glucoside (β-OG). This pocket lies at the hinge region between domains I and II and is important for the low pH-triggered conformational rearrangement required for the fusion of the virion with the host's cell. Aiming at the design of novel molecules which bind to E and act as virus entry inhibitors, we undertook a de novo design approach by "growing" molecules inside the hydrophobic site (β-OG). From more than 240000 small-molecules generated, the 2,4 pyrimidine scaffold was selected as the best candidate, from which one synthesized compound displayed micromolar activity. Molecular dynamics-based optimization was performed on this hit, and thirty derivatives were designed in silico, synthesized and evaluated on their capacity to inhibit dengue virus entry into the host cell. Four compounds were found to be potent antiviral compounds in the low-micromolar range. The assessment of drug-like physicochemical and in vitro pharmacokinetic properties revealed that compounds 3e and 3h presented acceptable solubility values and were stable in mouse plasma, simulated gastric fluid, simulated intestinal fluid, and phosphate buffered saline solution.

Recent update on anti-dengue drug discovery

Dengue is the most important arthropod-borne viral disease of humans, with more than half of the global population living in at-risk areas. Despite the negative impact on public health, there are no antiviral therapies available, and the only licensed vaccine, Dengvaxia^®, has been contraindicated in children below nine years of age. In an effort to combat dengue, several small molecules have entered into human clinical trials. Here, we review anti-DENV molecules and their drug targets that have been published within the past five years (2014-2018). Further, we discuss their probable mechanisms of action and describe a role for classes of clinically approved drugs and also an unclassified class of anti-DENV agents. This review aims to enhance our understanding of novel agents and their cognate targets in furthering innovations in the use of small molecules for dengue drug therapies.

Dengue Virus and Its Inhibitors: A Brief Review

The global occurrence of viral infectious diseases poses a significant threat to human health. Dengue virus (DENV) infection is one of the most noteworthy of these infections. According to a WHO survey, approximately 400 million people are infected annually; symptoms deteriorate in approximately one percent of cases. Numerous foundational and clinical investigations on viral epidemiology, structure and function analysis, infection source and route, therapeutic targets, vaccines, and therapeutic drugs have been conducted by both academic and industrial researchers. At present, CYD-TDV or Dengvaxia^® is the only approved vaccine, but potent inhibitors are currently under development. In this review, an overview of the viral life circle and the history of DENVs is presented, and the most recently reported antiviral candidates and newly discovered promising targets are focused and summarized. We believe that these successes and failures have enabled progress in anti-DENV drug discovery and hope that our review will stimulate further innovation in this area.

Hepatitis C virus in vitro replication is efficiently inhibited by acridone Fac4

Hepatitis C virus (HCV) affects about 170 million people worldwide. The current treatment has a high cost and variable response rates according to the virus genotype. Acridones, a group of compounds extracted from natural sources, showed potential antiviral actions against HCV. Thus, this study aimed to evaluate the effect of a panel of 14 synthetic acridones on the HCV life cycle. The compounds were screened using an Huh7.5 cell line stably harbouring the HCV genotype 2a subgenomic replicon SGR-Feo-JFH-1. Cells were incubated in the presence or absence of compounds for 72 h and cell viability and replication levels were assessed by MTT and luciferase assays, respectively. At a concentration of 5 µM the acridone Fac4 exhibited a >90 % inhibition of HCV replication with no effect on cell viability. The effects of Fac4 on virus replication, entry and release steps were evaluated in Huh7.5 cells infected with the JFH-1 isolate of HCV (HCVcc). Fac4 inhibited JFH-1 replication to approximately 70 %, while no effect was observed on virus entry. The antiviral activity of Fac4 was also observed on viral release, with almost 80 % of inhibition. No inhibitory effect was observed against genotype 3 replication. Fac4 was able to intercalate into dsRNA, however did not inhibit NS5B polymerase activity or translation driven by the HCV IRES. Although its mode of action is partly understood, Fac4 presents significant inhibition of HCV replication and can therefore be considered as a candidate for the development of a future anti-HCV treatment.

The Medicinal Chemistry of Dengue Virus

The dengue virus and related flaviviruses are an increasing global health threat. In this perspective, we comment on and review medicinal chemistry efforts aimed at the prevention or treatment of dengue infections. We include target-based approaches aimed at viral or host factors and results from phenotypic screenings in cellular assay systems for viral replication. This perspective is limited to the discussion of results that provide explicit chemistry or structure-activity relationship (SAR), or appear to be of particular interest to the medicinal chemist for other reasons. The discovery and development efforts discussed here may at least partially be extrapolated toward other emerging flaviviral infections, such as West Nile virus. Therefore, this perspective, although not aimed at flaviviruses in general, should also be able to provide an overview of the medicinal chemistry of these closely related infectious agents.