Chloroquine analogs as antimalarial candidates with potent in vitro and in vivo activity

The Nociceptive and Inflammatory Responses Induced by the Ehrlich Solid Tumor Are Changed in Mice Healed of Plasmodium berghei Strain ANKA Infection after Chloroquine Treatment

Comorbidities that involve infectious and noninfectious diseases, such as malaria and cancer, have been described. Cancer and malaria induce changes in the nociceptive and inflammatory responses through similar pathophysiological mechanisms. However, it is unclear whether malaria and antimalarial treatment can change the inflammatory and nociceptive responses induced by solid cancer. Therefore, the present study experimentally evaluated the effect of infection by Plasmodium berghei strain ANKA and chloroquine treatment on the nociceptive and inflammatory responses induced by the solid Ehrlich tumor in male BALB/c mice. On the 1st experimental day, mice were infected with Plasmodium berghei and injected with tumor cells in the left hind paw. From the 7th to the 9th experimental day, mice were treated daily with chloroquine. The parasitemia was evaluated on the 7th and 10th days after infection. On the 11th experimental day, mice were evaluated on the von Frey filament test, the hot plate test, and the paw volume test. At the end of the experimental tests on the 11th day, the peripheral blood of all mice was collected for dosing of IL-1β and TNF-α. The blood parasitemia significantly increased from the 7th to the 10th day. The chloroquine treatment significantly decreased the parasitemia on the 10th day. The presence of the tumor did not significantly change the parasitemia on the 7th and 10th days in mice treated and nontreated with chloroquine. On the 11th day, the mechanical and thermal nociceptive responses significantly increased in mice with tumors. The treatment with antimalarial significantly reduced the mechanical nociceptive response induced by tumors. The hyperalgesia induced by tumors did not change with malaria. The mechanical and thermal hyperalgesia induced by the tumor was significantly reduced in mice treated and healed from malaria. On the 11th day, the volume of the paw injected by the tumor was significantly increased. The mice treated with chloroquine, infected with malaria, or healed of malaria showed reduced paw edema induced by the tumor. Mice with tumors did not show a change in IL-β and TNF-α serum levels. Mice with tumors showed a significant increase in serum levels of IL-1β but not TNF-α when treated with chloroquine, infected with malaria, or healed of malaria. In conclusion, the results show that malaria infection and chloroquine treatment can influence, in synergic form, the nociceptive and inflammatory responses induced by the solid tumor. Moreover, the mechanical antinociception, the thermal hyperalgesia, and the antiedema effect observed in mice treated with chloroquine and healed from malaria can be related to the increase in the serum level of IL-1β.

New anti-SARS-CoV-2 aminoadamantane compounds as antiviral candidates for the treatment of COVID-19

Here, the antiviral activity of aminoadamantane derivatives were evaluated against SARS-CoV-2. The compounds exhibited low cytotoxicity to Vero, HEK293 and CALU-3 cells up to a concentration of 1,000 µM. The inhibitory concentration (IC50) of aminoadamantane was 39.71 µM in Vero CCL-81 cells and the derivatives showed significantly lower IC50 values, especially for compounds 3F4 (0.32 µM), 3F5 (0.44 µM) and 3E10 (1.28 µM). Additionally, derivatives 3F5 and 3E10 statistically reduced the fluorescence intensity of SARS-CoV-2 protein S from Vero cells at 10 µM. Transmission microscopy confirmed the antiviral activity of the compounds, which reduced cytopathic effects induced by the virus, such as vacuolization, cytoplasmic projections, and the presence of myelin figures derived from cellular activation in the face of infection. Additionally, it was possible to observe a reduction of viral particles adhered to the cell membrane and inside several viral factories, especially after treatment with 3F4. Moreover, although docking analysis showed favorable interactions in the catalytic site of Cathepsin L, the enzymatic activity of this enzyme was not inhibited significantly in vitro. The new derivatives displayed lower predicted toxicities than aminoadamantane, which was observed for either rat or mouse models. Lastly, in vivo antiviral assays of aminoadamantane derivatives in BALB/cJ mice after challenge with the mouse-adapted strain of SARS-CoV-2, corroborated the robust antiviral activity of 3F4 derivative, which was higher than aminoadamantane and its other derivatives. Therefore, aminoadamantane derivatives show potential broad-spectrum antiviral activity, which may contribute to COVID-19 treatment in the face of emerging and re-emerging SARS-CoV-2 variants of concern.

Inhibitory effects on bovine babesial infection by iron chelator, 1-(N-acetyl-6-aminohexyl)- 3-hydroxy-2-methylpyridin-4-one (CM1), and antimalarial drugs

BACKGROUND

Babesiosis is an infectious disease caused by protozoa of the apicomplexan phylum, genus Babesia. It is a malaria-like parasitic disease that can be transmitted via tick bites. The apicomplexan phylum of eukaryotic microbial parasites has had detrimental impacts on human and veterinary medicine. There are only a few drugs currently available to treat this disease; however, parasitic strains that are resistant to these commercial drugs are increasing in numbers. Plasmodium and Babesia are closely related as they share similar biological features including mechanisms for host cell invasion and metabolism. Therefore, antimalarial drugs may be useful in the treatment of Babesia infections. In addition to antimalarials, iron chelators also inhibit parasite growth. In this study, we aimed to evaluate the in vitro inhibitory efficacy of iron chelator and different antimalarials in the treatment of Babesia bovis.

METHODS

Cytotoxicity of antimalarial drugs; pyrimethamine, artefenomel, chloroquine, primaquine, dihydroarthemisinine, and the iron chelator, 1-(N-acetyl-6-aminohexyl)- 3-hydroxy-2 methylpyridin-4-one (CM1), were evaluated against Madin Darby Bovine Kidney (MDBK) cells and compared to diminazene aceturate, which is the currently available drug for animal babesiosis using an MTT solution. Afterwards, an evaluation of the in vitro growth-inhibitory effects of antimalarial drug concentrations was performed and monitored using a flow cytometer. Half maximal inhibitory concentrations (IC50) of each antimalarial and iron chelator were determined and compared to the antibabesial drug, diminazine aceturate, by interpolation using a curve-fitting technique. Subsequently, the effect of the drug combination was assessed by constructing an isobologram. Values of the sum of fractional inhibitions at 50% inhibition were then estimated.

RESULTS

Results indicate that all drugs tested could safely inhibit babesia parasite growth, as high as 2500 μM were non-toxic to mammalian cells. Although no drugs inhibited B. bovis more effectively than diminazine aceturate in this experiment, in vitro growth inhibition results with IC50 values of pyrimethamine 6.25 ± 2.59 μM, artefenomel 2.56 ± 0.67 μM, chloroquine 2.14 ± 0.76 μM, primaquine 22.61 ± 6.72 μM, dihydroarthemisinine 4.65 ± 0.22 μM, 1-(N-acetyl-6-aminohexyl)- 3-hydroxy-2 methylpyridin-4-one (CM1) 9.73 ± 1.90 μM, and diminazine aceturate 0.42 ± 0.01 μM, confirm that all drugs could inhibit B. bovis and could be used as alternative treatments for bovine babesial infection. Furthermore, the efficacy of a combination of the iron chelator, CM1, in combination with artefenomel dihydroarthemisinin or chloroquine, and artefenomel in combination with the iron chelator, CM1, dihydroarthemisinin or chloroquine, exhibited synergism against B. bovis in vitro.

CONCLUSION

Our evaluation of the inhibitory efficacy of the iron chelator CM1, antimalarial drugs, and a combination of these drugs against B. bovis could be potentially useful in the development and discovery of a novel drug for the treatment of B. bovis in the future.

Development of diphenylmethylpiperazine hybrids of chloroquinoline and triazolopyrimidine using Petasis reaction as new cysteine proteases inhibitors for malaria therapeutics

Malaria is a widespread infectious disease, causing nearly 247 million cases in 2021. The absence of a broadly effective vaccine and rapidly decreasing effectiveness of most of the currently used antimalarials are the major challenges to malaria eradication efforts. To design and develop novel antimalarials, we synthesized a series of 4,7-dichloroquinoline and methyltriazolopyrimidine analogues using a multi-component Petasis reaction. The synthesized molecules (11-31) were screened for in-vitro antimalarial activity against drug-sensitive and drug-resistant strains of Plasmodium falciparum with an IC₅₀ value of 0.53 μM. The selected compounds were screened to evaluate in-vitro and in-silico enzyme inhibition efficacy against two cysteine proteases, PfFP2 and PfFP3. The compounds 15 and 17 inhibited PfFP2 with an IC₅₀ = 3.5 and 4.8 μM, respectively and PfFP3 with an IC₅₀ = 4.9 and 4.7 μM, respectively. Compounds 15 and 17 were found equipotent against the Pf3D7 strain with an IC₅₀ value of 0.74 μM, whereas both were displayed IC₅₀ values of 1.05 μM and 1.24 μM for the PfW2 strain, respectively. Investigation of effect of compounds on parasite development demonstrated that compounds were able to arrest the growth of the parasites at trophozoite stage. The selected compounds were screened for in-vitro cytotoxicity against mammalian lines and human red-blood-cell (RBC), which demonstrated no significant cytotoxicity associated with the molecules. In addition, in silico ADME prediction and physiochemical properties supported the drug-likeness of the synthesized molecules. Thus, the results highlighted the diphenylmethylpiperazine group cast on 4,7-dichloroquinoline and methyltriazolopyrimidine using Petasis reaction may serve as models for the development of new antimalarial agents.

New Iron Twist to Chloroquine─Upgrading Antimalarials with Immunomodulatory and Antimicrobial Features

Herein, upgraded chloroquine (CQ) derivatives capable of overcoming Plasmodium resistance and, at the same time, suppressing excessive immune response and risk of concurrent bacteremia were developed. Twelve new ferrocene-CQ hybrids tethered with a small azathia heterocycle (1,3-thiazolidin-4-one, 1,3-thiazinan-4-one, or 5-methyl-1,3-thiazolidin-4-one) were synthesized and fully characterized. All hybrids were evaluated for their in vitro antiplasmodial, antimicrobial, and immunomodulatory activities. Additional assays were performed on selected hybrids to gain insights into their mode of action. Although only hybrid 4a was more potent than the parent drug toward CQ-resistant Dd2 Plasmodium falciparum strain, several other hybrids (such as 6b, 6c, and 6d) manifested substantially improved antimicrobial and immunomodulatory properties. Interesting structure-activity relationship data were obtained, hinting at future research for the development of new multitarget chemotherapies for malaria and other infectious diseases complicated by drug resistance, bacterial co-infection, and immune-driven pathology issues.

Fighting Plasmodium chloroquine resistance with acetylenic chloroquine analogues

Malaria is among the tropical diseases that cause the most deaths in Africa. Around 500,000 malaria deaths are reported yearly among African children under the age of five. Chloroquine (CQ) is a low-cost antimalarial used worldwide for the treatment of Plasmodium vivax malaria. Due to resistance mechanisms, CQ is no longer effective against most malaria cases caused by P. falciparum. The World Health Organization recommends artemisinin combination therapies for P. falciparum malaria, but resistance is emerging in Southeast Asia and some parts of Africa. Therefore, new medicines for treating malaria are urgently needed. Previously, our group identified the 4-aminoquinoline DAQ, a CQ analog containing an acetylenic bond in its side chain, which overcomes CQ resistance in K1 P. falciparum strains. In this work, the antiplasmodial profile, drug-like properties, and pharmacokinetics of DAQ were further investigated. DAQ showed no cross-resistance against standard CQ-resistant strains (e.g., Dd2, IPC 4912, RF12) nor against P. falciparum and P. vivax isolates from patients in the Brazilian Amazon. Using drug pressure assays, DAQ showed a low propensity to generate resistance. DAQ showed considerable solubility but low metabolic stability. The main metabolite was identified as a mono N-deethylated derivative (DAQ_M), which also showed significant inhibitory activity against CQ-resistant P. falciparum strains. Our findings indicated that the presence of a triple bond in CQ-analogues may represent a low-cost opportunity to overcome known mechanisms of resistance in the malaria parasite.

Mayaro Virus: The State-of-the-Art for Antiviral Drug Development

Mayaro virus is an emerging arbovirus that causes nonspecific febrile illness or arthralgia syndromes similar to the Chikungunya virus, a virus closely related from the Togaviridae family. MAYV outbreaks occur more frequently in the northern and central-western states of Brazil; however, in recent years, virus circulation has been spreading to other regions. Due to the undifferentiated initial clinical symptoms between MAYV and other endemic pathogenic arboviruses with geographic overlapping, identification of patients infected by MAYV might be underreported. Additionally, the lack of specific prophylactic approaches or antiviral drugs limits the pharmacological management of patients to treat symptoms like pain and inflammation, as is the case with most pathogenic alphaviruses. In this context, this review aims to present the state-of-the-art regarding the screening and development of compounds/molecules which may present anti-MAYV activity and infection inhibition.

Synthesis, in silico docking studies, and antiplasmodial activity of hybrid molecules bearing 7-substituted 4-aminoquinoline moiety and cinnamic acid derivatives

This paper reports a series of nine hybrid compounds of 7-substituted 4-aminoquinoline and cinnamic acid as antiplasmodial agents. ¹ H NMR and ¹³ C NMR spectroscopic analysis and mass spectrometry studies were used to confirm the structures. The synthesized compounds were moderately active, with IC₅₀ values ranging from 1.8 to 16 µM against the Pf3D7 chloroquine-sensitive strain in vitro. Compound C11 was shown to be the most potent in this investigation, with an IC₅₀ value of 1.8 µM. Molecular docking studies revealed that compounds C14 and C17, with binding energies ( Δ G 0 ) of -7.19 and -7.72 kcal/mol and inhibition constants (K_i ) of 5.36 and 2.20 µM, respectively, were the best inhibitor candidates. The results of the Frontier molecular orbitals revealed that compounds possessed a small HOMO-LUMO energy gap. The HOMO-LUMO energy distributions indicated that the cinnamic acid regions favored the LUMO distribution, while the quinoline regions favored the HOMO energy. The investigation of absorption, distribution, metabolism, excretion, and toxicity based on in silico ADME tools predicted that the compounds have a good drug-like character.

Title: A Comprehensive Review on Classifying Fast-acting and Slow-acting Antimalarial Agents Based on Time of Action and Target Organelle of Plasmodium sp

The clinical resistance towards malarial parasites has rendered many antimalarials ineffective, likely due to a lack of understanding of time of action and stage specificity of all life stages. Therefore, to tackle this problem a more incisive comprehensive analysis of the fast and slow-acting profile of antimalarial agents relating to parasite time-kill kinetics and the target organelle on the progression of blood-stage parasites was carried out. It is evident from numerous findings that drugs targeting food vacuole, nuclear components, and endoplasmic reticulum mainly exhibit a fast-killing phenotype within 24h affecting first-cycle activity. Whereas drugs targeting mitochondria, apicoplast, microtubules, parasite invasion and egress exhibit a largely slow-killing phenotype within 96-120h, affecting second-cycle activity with few exemptions as moderately fast-killing. It is essential to understand the susceptibility of drugs on rings, trophozoites, schizonts, merozoites, and the appearance of organelle at each stage of 48h intraerythrocytic parasite cycle. Therefore, these parameters may facilitate the paradigm for understanding the timing of antimalarials action in deciphering its precise mechanism linked with time. Thus, classifying drugs based on the time of killing may promote designing new combination regimens against varied strains of P. falciparum and evaluating potential clinical resistance.

Dual Quinoline-Hybrid Compounds with Antimalarial Activity Against Plasmodium falciparum Parasites

Although we have at our disposal relatively low-cost drugs that can be prescribed for the treatment of malaria, the prevalence of resistant strains of the causative parasite has required the...

Artemisinin and Derivatives-Based Hybrid Compounds: Promising Therapeutics for the Treatment of Cancer and Malaria

Cancer and malaria are major health conditions around the world despite many strategies and therapeutics available for their treatment. The most used strategy for the treatment of these diseases is the administration of therapeutic drugs, which suffer from several shortcomings. Some of the pharmacological limitations associated with these drugs are multi-drug resistance, drug toxicity, poor biocompatibility and bioavailability, and poor water solubility. The currently ongoing preclinical studies have demonstrated that combination therapy is a potent approach that can overcome some of the aforementioned limitations. Artemisinin and its derivatives have been reported to exhibit potent efficacy as anticancer and antimalarial agents. This review reports hybrid compounds containing artemisinin scaffolds and their derivatives with promising therapeutic effects for the treatment of cancer and malaria.

A methanol extract and N,N-dimethyltryptamine from Psychotria viridis Ruiz & Pav. inhibit Zika virus infection in vitro

Zika virus (ZIKV) is a public health problem due to its association with serious fetal and neurological complications and the lack of antiviral agents and licensed vaccines against this virus. Surveillance studies have alerted about the potential occurrence of a new South American epidemic episode due to the recent circulation of an African ZIKV strain detected in Brazil. Therefore, it is essential to discover antiviral agents, including natural substances, that are capable of neutralizing the action of ZIKV. Several Psychotria species have antimicrobial and anti-inflammatory properties. Thus, a methanol extract and dimethyltryptamine from Psychotria viridis were evaluated for their ability to inhibit ZIKV infection in vitro by measuring the effective concentration that protects 50% of cells and investigating their possible mechanisms of action. The tested samples showed antiviral activity against ZIKV. The extract showed virucidal activity, affecting viral and non-cellular elements, inactivating the virus before infection or when it becomes extracellular after the second cycle of infection. It was also observed that both extract and dimethyltryptamine could inhibit the virus at intracellular stages of the viral cycle. In addition to dimethyltryptamine, it is believed that other compounds also contribute to the promising virucidal effect observed for the methanol extract. To our knowledge, this is the first report of the activity of a methanolic extract and dimethyltryptamine from Psychotria viridis against cellular ZIKV infection. These two samples, extracted from natural sources, are potential candidates for use as antiviral drugs to inhibit ZIKV infections.

Coronavirus and its terrifying inning around the globe: The pharmaceutical cares at the main frontline

A novel coronavirus (2019-nCoV) is an acute life-threatening disease, emerged in China, which imposed a potentially immense toll in terms of public health emergency due to high infection rate and has a devastating economic impact that attracts the world's attention. After that, on January 30, 2020, it was officially declared as a global pandemic by World Health Organization (WHO). The International Committee on Taxonomy of Viruses (ICTV) recognized it as a Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) and the disease named Coronavirus Disease-19 (COVID-19). Several studies have been ameliorated the active role of COVID-19 transmission, etiology, pathogenicity, and mortality rate as serious impact on human life. The symptoms of this disease may include fever, fatigue, cough and some peoples are severely prone to gastrointestinal infection. The elderly and seriously affected peoples are likely concerned with serious outcomes. In this review, we mainly aimed to provide a benchmark summary of the silent characteristics and findings of some candidates for antiviral drugs and immunotherapies such as plasma therapy, cytokine therapy, antibodies, intravenous immunoglobulin, and pharmaceutical health concerns that are related to this disease.

Use of nanotechnology in combating coronavirus

Recent COVID-19 pandemic situation caused due to the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) affected global health as well as economics. There is global attention on prevention, diagnosis as well as treatment of COVID-19 infection which would help in easing the current situation. The use of nanotechnology and nanomedicine has been considered to be promising due to its excellent potential in managing various medical issues such as viruses which is a major threat. Nanoparticles have shown great potential in various biomedical applications and can prove to be of great use in antiviral therapy, especially over other conventional antiviral agents. This review focusses on the pathophysiology of SARS-CoV-2 and the progression of the COVID-19 disease followed by currently available treatments for the same. Use of nanotechnology has been elaborated by exploiting various nanoparticles like metal and metal oxide nanoparticles, carbon-based nanoparticles, quantum dots, polymeric nanoparticles as well as lipid-based nanoparticles along with its mechanism of action against viruses which can prove to be beneficial in COVID-19 therapeutics. However, it needs to be considered that use of these nanotechnology-based approaches in COVID-19 therapeutics only aids the human immunity in fighting the infection. The main function is performed by the immune system in combatting any infection.

COVID-19 and SARS-CoV-2 Variants: Current Challenges and Health Concern

The ongoing coronavirus disease 2019 (COVID-19) outbreak in Wuhan, China, was triggered and unfolded quickly throughout the globe by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The new virus, transmitted primarily through inhalation or contact with infected droplets, seems very contagious and pathogenic, with an incubation period varying from 2 to 14 days. The epidemic is an ongoing public health problem that challenges the present global health system. A worldwide social and economic stress has been observed. The transitional source of origin and its transport to humans is unknown, but speedy human transportation has been accepted extensively. The typical clinical symptoms of COVID-19 are almost like colds. With case fatality rates varying from 2 to 3 percent, a small number of patients may experience serious health problems or even die. To date, there is a limited number of antiviral agents or vaccines for the treatment of COVID-19. The occurrence and pathogenicity of COVID-19 infection are outlined and comparatively analyzed, given the outbreak's urgency. The recent developments in diagnostics, treatment, and marketed vaccine are discussed to deal with this viral outbreak. Now the scientist is concerned about the appearance of several variants over the globe and the efficacy of the vaccine against these variants. There is a need for consistent monitoring of the virus epidemiology and surveillance of the ongoing variant and related disease severity.

A review on COVID-19 for medical students

It has not been very long since the SARS-CoV 2002 and MERS-CoV 2012 epidemics. Yet again, nature has introduced SARS-CoV-2, also known as COVID-19, a highly virulent strain of the coronavirus that has its origin in the city of Wuhan, Hubei Province, China. Primarily, a zoonotic infection, the virus probably found its way to humans through infected wild bats sold in the Wuhan local market. What makes the virus virulent, is its ability to infect multiple people at once through single index case. This has led to inability to contain the virus with ease posing a significant threat to national and international health-care resources and economies. The objective of this review is to highlight the key features of the novel CoV-19 infection as per existing data for better understanding of the disease.

Chloroquine Analogs: An Overview of Natural and Synthetic Quinolines as Broad Spectrum Antiviral Agents

SARS-CoV-2, a positive single-stranded RNA enveloped coronavirus, currently poses a global health threat. Drugs with quinoline scaffolds have been studied to repurpose their useful broad-spectrum properties into treating various diseases, including viruses. Preliminary studies on the quinoline medications, chloroquine and hydroxychloroquine, against SARS-CoV-2, have shown to be a potential area of interest for drug development due to their ability to prevent viral entry, act as anti-inflammatory modulators, and inhibit key enzymes allowing reduced viral infectivity. In addition to Chloroquine and Hydroxychloroquine, we discussed analogs of the drugs to understand the quinoline scaffold's potential antiviral mechanisms. The heterocyclic scaffold of quinoline can be modified in many ways, primarily through the modification of its substituents. We studied these different synthetic derivatives to understand properties that could enhance its antiviral specificity thoroughly. Chloroquine and its analogs can act on various stages of the viral life cycle, pre and post entry. In this study, we reviewed chloroquine and its synthetic and natural analogs for their antiviral properties in a variety of viruses. Furthermore, we reviewed the compound's potential abilities to attenuate symptoms associated with viral infections. Natural compounds that share scaffolding to chloroquine can act as antivirals or attenuate symptoms through the stimulation of the host immune system or reduction of oxidative stress. Furthermore, we discuss perspectives of the drug's repurposing due to its ability to inhibit the beta-hematin formation and to be a Zinc Ionophore.

Therapeutic Development in COVID-19

Since the outbreak of coronavirus disease 2019 (COVID-19) caused by the SARS-CoV-2, the disease has spread rapidly worldwide and developed into a global pandemic, causing a significant impact on the global health system and economic development. Scientists have been racing to find effective drugs and vaccines for the treatment and prevention of COVID-19. However, due to the diversity of clinical manifestations caused by COVID-19, no standard antiviral regimen beyond supportive therapy has been established. Ongoing clinical trials are underway to evaluate the efficacy of drugs that primarily act on the viral replication cycle or enhanced immunity of patients. This chapter will summarize the currently used antiviral and adjuvant therapies in clinical practice and provide a theoretical basis for the future treatment of COVID-19.

Repositioning of Antiparasitic Drugs for Tumor Treatment

Drug repositioning is a strategy for identifying new antitumor drugs; this strategy allows existing and approved clinical drugs to be innovatively repurposed to treat tumors. Based on the similarities between parasitic diseases and cancer, recent studies aimed to investigate the efficacy of existing antiparasitic drugs in cancer. In this review, we selected two antihelminthic drugs (macrolides and benzimidazoles) and two antiprotozoal drugs (artemisinin and its derivatives, and quinolines) and summarized the research progresses made to date on the role of these drugs in cancer. Overall, these drugs regulate tumor growth via multiple targets, pathways, and modes of action. These antiparasitic drugs are good candidates for comprehensive, in-depth analyses of tumor occurrence and development. In-depth studies may improve the current tumor diagnoses and treatment regimens. However, for clinical application, current investigations are still insufficient, warranting more comprehensive analyses.

Prevention and treatment of COVID-19: Focus on interferons, chloroquine/hydroxychloroquine, azithromycin, and vaccine

The ongoing pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has drawn the attention of researchers and clinicians from several disciplines and sectors who are trying to find durable solutions both at preventive and treatment levels. To date, there is no approved effective treatment or vaccine available to control the coronavirus disease-2019 (COVID-19). The preliminary in vitro studies on viral infection models showed potential antiviral activities of type I and III interferons (IFNs), chloroquine (CQ)/hydroxychloroquine (HCQ), and azithromycin (AZM); however, the clinical studies on COVID-19 patients treated with CQ/HCQ and AZM led to controversies in different regions due to their adverse side effects, as well as their combined treatment could prolong the QT interval. Interestingly, the treatment with type I IFNs showed encouraging results. Moreover, the different preliminary reports of COVID-19 candidate vaccines showcase promising results by inducing the production of a high level of neutralizing antibodies (NAbs) and specific T cell-mediated immune response in almost all participants. The present review aims to summarize and analyze the recent progress evidence concerning the use of IFNs, CQ/HCQ, and AZM for the treatment of COVID-19. The available data on immunization options to prevent the COVID-19 are also analyzed with the aim to present the promising options which could be investigated in future for sustainable control of the pandemic.

Theoretical Insights into the Anti-SARS-CoV-2 Activity of Chloroquine and Its Analogs and In Silico Screening of Main Protease Inhibitors

Corona virus disease (COVID-19) is a dangerous disease rapidly spreading all over the world today. Currently there are no treatment options for it. Drug repurposing studies explored the potency of antimalarial drugs, chloroquine and hydroxychloroquine, against SARS-CoV-2 virus. These drugs can inhibit the viral protease, called chymotrypsin-like cysteine protease, also known as Main protease (3CLpro); hence, we studied the binding efficiencies of 4-aminoquinoline and 8-aminoquinoline analogs of chloroquine. Six compounds furnished better binding energies than chloroquine and hydroxychloroquine. The interactions with the active site residues especially with Cys145 and His41, which are involved in catalytic diad for proteolysis, make these compounds potent main protease inhibitors. A regression model correlating binding energy and the molecular descriptors for chloroquine analogs was generated with R2 = 0.9039 and Q2 = 0.8848. This model was used to screen new analogs of primaquine and molecules from the Asinex compound library. The docking and regression analysis showed these analogs to be more potent inhibitors of 3CLpro than hydroxychloroquine and primaquine. The molecular dynamic simulations of the hits were carried out to determine the binding stabilities. Finally, we propose four compounds that show drug likeness toward SARS-CoV-2 that can be further validated through in vitro and in vivo studies.

Designing spike protein (S-Protein) based multi-epitope peptide vaccine against SARS COVID-19 by immunoinformatics

The outbreak of COVID-19 was originated from China, responsible for Several Acute Respiratory Syndrome (SARS). Scientists are forced to develop vaccine and effective drugs to control COVID-19 infection. To develop effective vaccine for SARS - COVID 19, immunoinformatics and computational approaches could helps to design successful vaccine against this biggest danger for humanity. Here we used various in - silico approaches to designed vaccine against COVID-19. To develop vaccine, we target S- protein, expressed on the virus surface plays important role in COVID-19 infection. We identified 12 B-cell, 9 T-helper and 20 Cytotoxic T-cell epitope based on criteria of selection. The predicted epitopes were link simultaneously with GPGPG & AAY linkers. The β-defensin was used as adjuvant, linked with selected epitope by using EAAAK linker. For vaccine construct justification we analysed its immunogenicity, allergenicity and physiochemical properties. Our study revealed that vaccine was non toxic, immunogenic and antigenic in nature and covers 98.6% of world population, important for vaccine effectively. In- silico cloning was used to analyse its expression in vector. Molecular docking was performed to study the interaction of construct with TLR (TLR3, TLR4, and TLR9) molecules. The immune simulation was conducted and conformed that our vaccine constructs can induces both acquired and humoral immunity effectively against COVID-19 at very low concentration, but along with bioinformatics study we need to conduct experiment in laboratory to validate its safety and effectiveness.

Antiviral effect of silymarin against Zika virus in vitro

Zika virus (ZIKV) epidemic and its association with severe neurological syndromes have raised worldwide concern. Despite the great clinical relevance of this infection, no vaccine or specific treatment is available and the search for antiviral compounds against ZIKV is extremely necessary. Several natural compounds, such as silymarin, exhibit antioxidant, hepatoprotective, and antiviral properties; however, the antiviral potential of this compound remains partially investigated. Therefore, the objective of this study was to evaluate in vitro the antiviral activity of silymarin against ZIKV infection. Global antiviral activity, dose-dependent, plaque reduction, and time-of-drug-addition assays were used to determine the anti-ZIKV activity of silymarin. Additionally, to start characterizing the mechanisms of action we determined whether silymarin could have a virucidal effect and inhibit viral adsorption and penetration stages. Regarding its global antiviral activity, silymarin showed significant inhibition of ZIKV infection, protecting cells infected with EC₅₀ equal to 34.17μg/mL, with a selectivity index greater than 17 and 4x greater than that of the positive control (ribavirin). Its greatest efficiency was achieved at 125μg/mL, whose cell viability did not differ from the control without infection and treatment. Furthermore, treatment with silymarin reduced viral load by up to two logs (> 90%) concerning viral control, when evaluating virucidal activity and the precocious times of infection. Thus, our results set to show the promising anti-ZIKV activity of silymarin, which does not seem to have a single inhibition mechanism, acting at different times of infection, and still has the advantage of silymarin be a phytotherapy already available on the market.

SARS-COV-2 (COVID-19): Cellular and biochemical properties and pharmacological insights into new therapeutic developments

COVID‐19 caused by SARS‐COV‐2 first appeared in the Wuhan City of China and began to spread rapidly among people. Rapid progression of the outbreak has led to a major global public health problem of a potentially fatal disease. On January 30, 2020, WHO declared the pandemic as the sixth public health emergency of the world. Upon this, the whole country has started to take the necessary precautions. The new coronavirus uses membrane‐bound angiotensin‐converting enzyme 2 (ACE2) to enter into the cells, such as SARS‐CoV, and mostly affects the respiratory tract. Symptoms of COVID‐19 patients include fever (93%), fatigue (70%), cough (70%), anorexia (40%) and dyspnoea (34.5%). The elderly and people with underlying chronic diseases are more susceptible to infection and higher mortality. Currently, a large number of drugs and vaccines studies are ongoing. In this review, we discussed the virology, epidemiological data, the replication of the virus, and its relationship with cardiovascular diseases on COVID‐19 pandemics, treatment and vaccines. Thereby, this study aims to neatly present scientific data in light of many regarding literature that can be a clue for readers who research this disease prevention and treatment.

Chloroquine against malaria, cancers and viral diseases

Quinoline (QN) derivatives are often used for the prophylaxis and treatment of malaria. Chloroquine (CQ), a protonated, weakly basic drug, exerts its antimalarial effect mainly by increasing pH and accumulating in the food vacuole of the parasites. Repurposing CQ is an emerging strategy for new indications. Given the inhibition of autophagy and its immunomodulatory action, CQ shows positive efficacy against cancer and viral diseases, including Coronavirus 2019 (COVID-19). Here, we review the underlying mechanisms behind the antimalarial, anticancer and antiviral effects of CQ. We also discuss the clinical evidence for the use of CQ and hydroxychloroquine (HCQ) against COVID-19.

Update of the current knowledge on genetics, evolution, immunopathogenesis, and transmission for coronavirus disease 19 (COVID-19)

In December 2019, an acute respiratory disease caused by novel species of coronavirus (SARS-CoV-2), emerged in China and has spread throughout the world. On 11th March 2020, the World Health Organization (WHO) officially declared coronavirus disease 19 (COVID-19) a pandemic, severe coronavirus-mediated human disease. Based on genomic and phylogenetic studies, SARS-CoV-2 might originate from bat coronaviruses and infects humans directly or through intermediate zoonotic hosts. However, the exact origin or the host intermediate remains unknown. Genetically, SARS-CoV-2 is similar to several existing coronaviruses, particularly SARS-CoV, but differs by silent and non-silent mutations. The virus uses different transmission routes and targets cells and tissues with angiotensin-converting enzyme 2 (ACE2) protein, which makes it contagious. COVID-19 shares both the main clinical features and excessive/dysregulated cell responses with the two previous Middle East respiratory syndrome coronavirus (MERS) and severe acute respiratory syndrome coronavirus (SARS) epidemics. In this review, we provide an update of the current knowledge on the COVID-19 pandemic. Gaining a deeper understanding of SARS-CoV-2 structure, transmission routes, and molecular responses, will assist in the prevention and control of COVID-19 outbreaks in the future.

Developing a holistic contingency plan: Challenges and dilemmas for cancer patients during the COVID-19

During the first quarter of 2020 the world is experiencing a pandemic of Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2), a novel beta coronavirus that is responsible for the 2019 novel coronavirus disease (COVID-19). The COVID-19 pandemic revealed that healthcare systems around the world were not prepared to deal with either the direct effects of the pandemic or with the indirect effects that are imposed on the health of patients with chronic disorders such as cancer patients. Some challenges and dilemmas currently faced during the pandemic include the management of cancer patients during the treatment and follow-up phases, the assessment of the safety of treatments currently used for the management of SARS-CoV-2 for use in cancer patients, the development of psychoeducation and emotional support for cancer patients and the safe conduct of clinical trials involving participation of cancer patients. Evidence from the literature supports the need for the urgent development of a holistic contingency plan which will include clear guidelines for the protection and comprehensive care of cancer patients. The implementation of such a plan is expected to have many beneficial effects by mainly minimizing the increased morbidity and mortality of cancer patients that could result as an adverse consequence of the COVID-19 or future pandemics.

COVID-19: Transmission, prevention, and potential therapeutic opportunities

The novel coronavirus disease (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), remains a global challenge. Despite intense research efforts worldwide, an effective vaccine and viable treatment options have eluded investigators. Therefore, infection prevention, early viral detection and identification of successful treatment protocols provide the best approach in controlling disease spread. In this review, current therapeutic options, preventive methods and transmission routes of COVID-19 are discussed.

Antiviral Potential of Nanoparticles-Can Nanoparticles Fight Against Coronaviruses?

Infectious diseases account for more than 20% of global mortality and viruses are responsible for about one-third of these deaths. Highly infectious viral diseases such as severe acute respiratory (SARS), Middle East respiratory syndrome (MERS) and coronavirus disease (COVID-19) are emerging more frequently and their worldwide spread poses a serious threat to human health and the global economy. The current COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). As of 27 July 2020, SARS-CoV-2 has infected over 16 million people and led to the death of more than 652,434 individuals as on 27 July 2020 while also causing significant economic losses. To date, there are no vaccines or specific antiviral drugs to prevent or treat COVID-19. Hence, it is necessary to accelerate the development of antiviral drugs and vaccines to help mitigate this pandemic. Non-Conventional antiviral agents must also be considered and exploited. In this regard, nanoparticles can be used as antiviral agents for the treatment of various viral infections. The use of nanoparticles provides an interesting opportunity for the development of novel antiviral therapies with a low probability of developing drug resistance compared to conventional chemical-based antiviral therapies. In this review, we first discuss viral mechanisms of entry into host cells and then we detail the major and important types of nanomaterials that could be used as antiviral agents. These nanomaterials include silver, gold, quantum dots, organic nanoparticles, liposomes, dendrimers and polymers. Further, we consider antiviral mechanisms, the effects of nanoparticles on coronaviruses and therapeutic approaches of nanoparticles. Finally, we provide our perspective on the future of nanoparticles in the fight against viral infections.

Therapeutic Strategies in the Development of Anti-viral Drugs and Vaccines Against SARS-CoV-2 Infection

The whole world is currently facing a pandemic of an infectious disease known as novel coronavirus disease-2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) . This outbreak emerged unexpectedly and imposed a potential threat to humans, associated with the social and economic burden on the individual and federal governments. COVID-19, which initially started in Wuhan City of China and then spread to the whole world, has been declared a Public Health Emergency of International Concern. The continuous increase in the number of confirmed cases leads to high mortality across the world. Growing evidence indicates that the mortality rate is very predominant in elderly people and those with preexisting health conditions. However, the potential pathogenesis of SARS-CoV-2 infection in humans is still unknown. The dysregulated/exuberant immune response may have substantially contributed to the SARS-CoV-2-mediated pathology. Nevertheless, there is no clinically approved drug/vaccine currently available that can restrict its pathogenesis. However, several drugs are currently shown to provide some therapeutic benefits for COVID-19 patients, including antiviral drugs that might have a significant role in restricting the current pandemic of COVID-19. In this article, we highlighted the pharmacological treatment strategies for COVID-19 and purposed the therapeutic targets for the development of vaccines or anti-viral drug molecules against SARS-CoV-2 infection in humans.

Antivirals Against Coronaviruses: Candidate Drugs for SARS-CoV-2 Treatment?

Coronaviruses (CoVs) are a group of viruses from the family Coronaviridae that can infect humans and animals, causing mild to severe diseases. The ongoing pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) represents a global threat, urging the development of new therapeutic strategies. Here we present a selection of relevant compounds that have been described from 2005 until now as having in vitro and/or in vivo antiviral activities against human and/or animal CoVs. We also present compounds that have reached clinical trials as well as further discussing the potentiality of other molecules for application in (re)emergent CoVs outbreaks. Finally, through rationalization of the data presented herein, we wish to encourage further research encompassing these compounds as potential SARS-CoV-2 drug candidates.

In Vitro Data of Current Therapies for SARS-CoV-2

BACKGROUND

In December 2019, a new coronavirus, named Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), emerged from China, causing pneumonia outbreaks first in the Wuhan region and then spread worldwide. Due to a lack of efficient and specific treatments and the need to contain the epidemic, drug repurposing appears to be the most efficient tool to find a therapeutic solution.

OBJECTIVES

The aim of this study was to summarize in vitro data of current agents used for the management of SARS-CoV-2 all over the world.

METHODS

A literature search of articles from January 2000 until April 2020 was performed using MEDLINE, EMBASE and the Cochrane Library to assess in vitro data of current or putative therapies for SARS-CoV-2.

RESULTS

Although in vitro studies are scarce, data regarding chloroquine, hydroxychloroquine, remdesivir, nitazoxanide, teicoplanin, ivermectin, lopinavir, homoharringtonine, and emetine seem promising.

CONCLUSION

Scientists all over the world should work together and increase their efforts in order to find feasible and efficient solutions against this new global viral threat.

Overview of Immune Response During SARS-CoV-2 Infection: Lessons From the Past

After the 1918 flu pandemic, the world is again facing a similar situation. However, the advancement in medical science has made it possible to identify that the novel infectious agent is from the coronavirus family. Rapid genome sequencing by various groups helped in identifying the structure and function of the virus, its immunogenicity in diverse populations, and potential preventive measures. Coronavirus attacks the respiratory system, causing pneumonia and lymphopenia in infected individuals. Viral components like spike and nucleocapsid proteins trigger an immune response in the host to eliminate the virus. These viral antigens can be either recognized by the B cells or presented by MHC complexes to the T cells, resulting in antibody production, increased cytokine secretion, and cytolytic activity in the acute phase of infection. Genetic polymorphism in MHC enables it to present some of the T cell epitopes very well over the other MHC alleles. The association of MHC alleles and its downregulated expression has been correlated with disease severity against influenza and coronaviruses. Studies have reported that infected individuals can, after recovery, induce strong protective responses by generating a memory T-cell pool against SARS-CoV and MERS-CoV. These memory T cells were not persistent in the long term and, upon reactivation, caused local damage due to cross-reactivity. So far, the reports suggest that SARS-CoV-2, which is highly contagious, shows related symptoms in three different stages and develops an exhaustive T-cell pool at higher loads of viral infection. As there are no specific treatments available for this novel coronavirus, numerous small molecular drugs that are being used for the treatment of diseases like SARS, MERS, HIV, ebola, malaria, and tuberculosis are being given to COVID-19 patients, and clinical trials for many such drugs have already begun. A classical immunotherapy of convalescent plasma transfusion from recovered patients has also been initiated for the neutralization of viremia in terminally ill COVID-19 patients. Due to the limitations of plasma transfusion, researchers are now focusing on developing neutralizing antibodies against virus particles along with immuno-modulation of cytokines like IL-6, Type I interferons (IFNs), and TNF-α that could help in combating the infection. This review highlights the similarities of the coronaviruses that caused SARS and MERS to the novel SARS-CoV-2 in relation to their pathogenicity and immunogenicity and also focuses on various treatment strategies that could be employed for curing COVID-19.

Potential new treatment strategies for COVID-19: is there a role for bromhexine as add-on therapy?

Of huge importance now is to provide a fast, cost-effective, safe, and immediately available pharmaceutical solution to curb the rapid global spread of SARS-CoV-2. Recent publications on SARS-CoV-2 have brought attention to the possible benefit of chloroquine in the treatment of patients infected by SARS-CoV-2. Whether chloroquine can treat SARS-CoV-2 alone and also work as a prophylactic is doubtful. An effective prophylactic medication to prevent viral entry has to contain, at least, either a protease inhibitor or a competitive virus ACE2-binding inhibitor. Using bromhexine at a dosage that selectively inhibits TMPRSS2 and, in so doing, inhibits TMPRSS2-specific viral entry is likely to be effective against SARS-CoV-2. We propose the use of bromhexine as a prophylactic and treatment. We encourage the scientific community to assess bromhexine clinically as a prophylactic and curative treatment. If proven to be effective, this would allow a rapid, accessible, and cost-effective application worldwide.

Antimicrobial and antiproliferative activity studies of some new quinoline-3-carbaldehyde hydrazone derivatives

In this study, a total of 22 piece quinoline-3-carbaldehyde hydrazone derivative compounds were designed and synthesized, 2 of which were not original, their antimicrobial activities were determined with microdilution method and their in vitro cytotoxic effect was investigated in MCF-7 and A549 cells by MTT assay. When the activity results are examined, although the antimicrobial effects of quinoline derivatives, in general, are weaker than standard drugs; 3q5 and 3q6 against MRSA showed promising activity with MIC:16 µg/ml compared to reference drugs. Compounds generally showed weaker cytotoxic activity on the A549 and MCF-7 cell line. 3q12, 3q17 and 3q22 at 100 µM reduced cell viability to 59.28%, 76.24% and 72.92% on A549 cells, respectively. Compound 3q6, one of the most effective compounds against MRSA, formed a 2.10 Å long hydrogen bond between the quinoline nitrogen and ARG132 in the DNA topoisomerase IV active site (PDB: 3FV5). Theoretical ADME profiles of all compounds comply with Lipinski and other limiting rules. In addition, MEP analysis of 3q6, geometric optimization and molecular reactivity analysis were calculated with the 6-311G (d,p) base set DFT/B3LYP theory, and ΔE = E_LUMO-E_HOMO, which is a measure of the stable structure of the molecule, was calculated as 0.13377 for 3q6 and had the most stable electronic structure among all compounds.

Novel therapeutic approaches for treatment of COVID-19

To date, there is no licensed treatment or approved vaccine to combat the coronavirus disease of 2019 (COVID-19), and the number of new cases and mortality multiplies every day. Therefore, it is essential to develop an effective treatment strategy to control the virus spread and prevent the disease. Here, we summarized the therapeutic approaches that are used to treat this infection. Although it seems that antiviral drugs are effective in improving clinical manifestation, there is no definite treatment protocol. Lymphocytopenia, excessive inflammation, and cytokine storm followed by acute respiratory distress syndrome are still unsolved issues causing the severity of this disease. Therefore, immune response modulation and inflammation management can be considered as an essential step. There is no doubt that more studies are required to clarify immunopathogenesis and immune response; however, new therapeutic approaches including mesenchymal stromal cell and immune cell therapy showed inspiring results.

Light as a potential treatment for pandemic coronavirus infections: A perspective

The recent outbreak of COVID-19, which continues to ravage communities with high death tolls and untold psychosocial and catastrophic economic consequences, is a vivid reminder of nature's capacity to defy contemporary healthcare. The pandemic calls for rapid mobilization of every potential clinical tool, including phototherapy—one of the most effective treatments used to reduce the impact of the 1918 “Spanish influenza” pandemic. This paper cites several studies showing that phototherapy has immense potential to reduce the impact of coronavirus diseases, and offers suggested ways that the healthcare industry can integrate modern light technologies in the fight against COVID-19 and other infections. The evidence shows that violet/blue (400–470 nm) light is antimicrobial against numerous bacteria, and that it accounts for Niels Ryberg Finsen's Nobel-winning treatment of tuberculosis. Further evidence shows that blue light inactivates several viruses, including the common flu coronavirus, and that in experimental animals, red and near infrared light reduce respiratory disorders, similar to those complications associated with coronavirus infection. Moreover, in patients, red light has been shown to alleviate chronic obstructive lung disease and bronchial asthma. These findings call for urgent efforts to further explore the clinical value of light, and not wait for another pandemic to serve as a reminder. The ubiquity of inexpensive light emitting lasers and light emitting diodes (LEDs), makes it relatively easy to develop safe low-cost light-based devices with the potential to reduce infections, sanitize equipment, hospital facilities, emergency care vehicles, homes, and the general environment as pilot studies have shown.

The origin, transmission and clinical therapies on coronavirus disease 2019 (COVID-19) outbreak - an update on the status

An acute respiratory disease, caused by a novel coronavirus (SARS-CoV-2, previously known as 2019-nCoV), the coronavirus disease 2019 (COVID-19) has spread throughout China and received worldwide attention. On 30 January 2020, World Health Organization (WHO) officially declared the COVID-19 epidemic as a public health emergency of international concern. The emergence of SARS-CoV-2, since the severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002 and Middle East respiratory syndrome coronavirus (MERS-CoV) in 2012, marked the third introduction of a highly pathogenic and large-scale epidemic coronavirus into the human population in the twenty-first century. As of 1 March 2020, a total of 87,137 confirmed cases globally, 79,968 confirmed in China and 7169 outside of China, with 2977 deaths (3.4%) had been reported by WHO. Meanwhile, several independent research groups have identified that SARS-CoV-2 belongs to β-coronavirus, with highly identical genome to bat coronavirus, pointing to bat as the natural host. The novel coronavirus uses the same receptor, angiotensin-converting enzyme 2 (ACE2) as that for SARS-CoV, and mainly spreads through the respiratory tract. Importantly, increasingly evidence showed sustained human-to-human transmission, along with many exported cases across the globe. The clinical symptoms of COVID-19 patients include fever, cough, fatigue and a small population of patients appeared gastrointestinal infection symptoms. The elderly and people with underlying diseases are susceptible to infection and prone to serious outcomes, which may be associated with acute respiratory distress syndrome (ARDS) and cytokine storm. Currently, there are few specific antiviral strategies, but several potent candidates of antivirals and repurposed drugs are under urgent investigation. In this review, we summarized the latest research progress of the epidemiology, pathogenesis, and clinical characteristics of COVID-19, and discussed the current treatment and scientific advancements to combat the epidemic novel coronavirus.

A Review on Onychine and its Analogs: Synthesis and Biological Activity

BACKGROUND

Onychine is a 4-azafluorenone alkaloid isolated from the Annonaceae family, in low concentrations. Onychine and its analogs exhibit a wide range of pharmacological activities such as antifungal, antibacterial, anticancer, and antimalarial. Because of the high bioactivity of some 4-azafluorenone derivatives, several synthetic methods have been developed for their procurement.

OBJECTIVE

Considering the importance of these alkaloids, we aim to present the main synthetic approaches to onychines and its derivatives and the biological activity of some 4-azafluorenones.

METHODS

The most prominent methodologies for the synthesis of onychines were reviewed.

RESULTS

In this work, we cover many synthetic approaches for the synthesis of onychine and 4-azafluorenone derivatives including intramolecular cyclizations, multicomponent reactions, microwave-assisted multicomponent reactions, Diels-alder reactions, among others. Moreover, we also review the biological activity of 4-azafluorenones.

CONCLUSION

4-azafluorenones have risen as prominent structures in medicinal chemistry; however, most of the time, access to new derivatives involves toxic catalysts, harsh reaction conditions, and long-step procedures. Therefore, the development of new synthetic routes with more operational simplicity, simple purification procedure, good yields, and low environmental impact, is desirable.

Virucidal activity of proanthocyanidin against Mayaro virus

Mayaro virus (MAYV) is a sublethal arbovirus transmitted by mosquitoes with possible installation of an urban cycle in the Americas. Its infection causes disabling arthralgia, and still, there is no vaccine or treatment to it. We recently investigated nearly 600 compounds by molecular docking and identified epicatechin as a potent antiviral against MAYV. The root extract of Maytenus imbricata showed anti-MAYV activity and two isolated compounds from this plant were also evaluated in vitro. Proanthocyanidin (PAC), a dimer containing epicatechin, showed an effective concentration for 50% of the cells infected by MAYV (EC₅₀) of 37.9 ± 2.4 μM and a selectivity index (SI) above 40. PAC showed significant virucidal activity, inhibiting 100% of the virus proliferation (7 log units), and caused moderate effect during adsorption and virus internalization stage. However, PAC was unable to block the infection when only the cells were pretreated. It was observed a reduction in virus yields when adding PAC at different moments after infection. The set of results indicates that PAC binds to viral and non-cellular elements and may inactivate the MAYV. The inactivation occurs before infection or when the virus reaches the extracellular environment from the 2nd cycle of infection that could block its progression cell-to-cell or to tissues not yet infected.