Antiviral activity of silymarin against Mayaro virus and protective effect in virus-induced oxidative stress

Current challenges in the discovery of treatments against Mayaro fever

INTRODUCTION

Mayaro fever is an emerging viral disease that manifests as an acute febrile illness. The disease is self-limiting, however joint pain can persist for months leading to chronic arthralgia. There is no specific treatment available, which ultimately leads to socioeconomic losses in populations at risk as well as strains to the public health systems.

AREAS COVERED

We reviewed the candidate treatments proposed for Mayaro virus (MAYV) infection and disease, including antiviral compounds targeting viral or host mechanisms, and pathways involved in disease development and pathogenicity. We assessed compound screening technologies and experimental infection models used in these studies and indicated the advantages and limitations of available technologies and intended therapeutic strategies.

EXPERT OPINION

Although several compounds have been suggested as candidate treatments against MAYV infection, notably those with antiviral activity, most compounds were assessed only in vitro. Compounds rarely progress toin vivo or preclinical studies, and such difficulty may be associated with limited experimental models. MAYV biology is largely inferred from related alphaviruses and reflected by few studies focusing on target proteins or mechanisms of action for MAYV. Therapeutic strategies targeting pathogenic inflammatory responses have shown potential against MAYV-induced disease in vivo, which might reduce long-term sequelae.

Metabolic profiling of milk thistle different organs using UPLC-TQD-MS/MS coupled to multivariate analysis in relation to their selective antiviral potential

INTRODUCTION

Silybum marianum commonly known as milk thistle is one of the most imperative medicinal plants due to its remarkable pharmacological activities. Lately, the antiviral activities of S. marianum extract have been studied and it showed effectiveness against many viruses.

OBJECTIVE

Although most previous studies were concerned mainly with silymarin content of the fruit, the present study provides comprehensive comparative evaluation of S. marianum different organs' chemical profiles using UPLC-MS/MS coupled to chemometrics to unravel potentially selective antiviral compounds against human coronavirus (HCoV-229E).

METHODOLOGY

UPLC-ESI-TQD-MS/MS analysis was utilized to establish metabolic fingerprints for S. marianum organs namely fruits, roots, stems and seeds. Multivariate analysis, using OPLS-DA and HCA-heat map was applied to explore the main discriminatory phytoconstituents between organs. Selective virucidal activity of organs extracts against coronavirus (HCoV-229E) was evaluated for the first time using cytopathic effect (CPE) inhibition assay. Correlation coefficient analysis was implemented for detection of potential constituents having virucidal activity.

RESULTS

UPLC-MS/MS analysis resulted in 87 identified metabolites belonging to different classes. OPLS-DA revealed in-between class discrimination between milk thistle organs proving their significantly different metabolic profiles. The results of CPE assay showed that all tested organ samples exhibited dose dependent inhibitory activity in nanomolar range. Correlation analysis disclosed that caffeic acid-O-hexoside, gadoleic and linolenic acids were the most potentially selective antiviral phytoconstituents.

CONCLUSION

This study valorizes the importance of different S. marianum organs as wealthy sources of selective and effective antiviral candidates. This approach can be extended to unravel potentially active constituents from complex plant matrices.

Silybin mitigates chronic Avermectin exposure-induced intestinal damage and growth inhibition in carp

Avermectins, as a new type of environmental pollutant, have received significant attention in recent years. Previous research has shown that acute exposure to avermectins can induce oxidative stress and inflammation in non-target fish species, such as carp. Flavonoid lignans, particularly Silybin, have demonstrated promising biological activities, including regulation of non-alcoholic fatty liver and cerebral ischemia-reperfusion injury. This study aims to investigate the impact of dietary supplementation with Silybin on the intestinal damage in carp caused by chronic exposure to avermectins and to improve the health status and production of carp in aquaculture. Silybin was used as a dietary supplement by adding it to the experimental feed, and an animal experimental model was utilized to assess its effects on oxidative stress, inflammation, and cell apoptosis in carp intestine. Additionally, intestinal barrier integrity, digestive capacity, and fish growth were evaluated. The results indicated that dietary supplementation with Silybin effectively alleviated the oxidative stress induced by chronic exposure to avermectins in carp intestine. Furthermore, Silybin improved intestinal barrier integrity and digestive capacity by modulating the Nrf2/Keap1 pathway. This study demonstrates that dietary supplementation with Silybin can effectively mitigate the intestinal damage caused by chronic exposure to avermectins in carp, providing a sustainable solution for the aquaculture industry to enhance the overall health and production of cultured fish. The research expands our understanding of avermectin environmental pollution and offers a potential remediation approach.

Protective role of flavonoids quercetin and silymarin in the viral-associated inflammatory bowel disease: an updated review

Inflammatory bowel disease (IBD) is a chronic recurrent inflammation of the gastrointestinal tract (GIT). IBD patients are susceptible to various infections such as viral infections due to the long-term consumption of immunosuppressive drugs and biologics. The antiviral and IBD protective traits of flavonoids have not been entirely investigated. This study objective included an overview of the protective role of flavonoids quercetin and silymarin in viral-associated IBD. Several viral agents such as cytomegalovirus (CMV), Epstein-Barr virus (EBV), varicella zoster virus (VZV) and enteric viruses can be reactivated and thus develop or exacerbate the IBD conditions or eventually facilitate the disease remission. Flavonoids such as quercetin and silymarin are non-toxic and safe bioactive compounds with remarkable anti-oxidant, anti-inflammatory and anti-viral effects. Mechanisms of anti-inflammatory and antiviral effects of silymarin and quercetin mainly include immune modulation and inhibition of caspase enzymes, viral binding and replication, RNA synthesis, viral proteases and viral assembly. In the nutraceutical sector, natural flavonoids low bioavailability and solubility necessitate the application of delivery systems to enhance their efficacy. This review study provided an updated understanding of the protective role of quercetin and silymarin against viral-associated IBD.

An update on the development of antiviral against Mayaro virus: from molecules to potential viral targets

Mayaro virus (MAYV), first isolated in 1954 in Trinidad and Tobago islands, is the causative agent of Mayaro fever, a disease characterized by fever, rashes, headaches, myalgia, and arthralgia. The infection can progress to a chronic condition in over 50% of cases, with persistent arthralgia, which can lead to the disability of the infected individuals. MAYV is mainly transmitted through the bite of the female Haemagogus spp. mosquito genus. However, studies demonstrate that Aedes aegypti is also a vector, contributing to the spread of MAYV beyond endemic areas, given the vast geographical distribution of the mosquito. Besides, the similarity of antigenic sites with other Alphavirus complicates the diagnoses of MAYV, contributing to underreporting of the disease. Nowadays, there are no antiviral drugs available to treat infected patients, being the clinical management based on analgesics and non-steroidal anti-inflammatory drugs. In this context, this review aims to summarize compounds that have demonstrated antiviral activity against MAYV in vitro, as well as discuss the potentiality of viral proteins as targets for the development of antiviral drugs against MAYV. Finally, through rationalization of the data presented herein, we wish to encourage further research encompassing these compounds as potential anti-MAYV drug candidates.

Phytochemical Profiles and Biological Studies of Selected Botanical Dietary Supplements Used in the United States

Based on their current wide bioavailability, botanical dietary supplements have become an important component of the United States healthcare system, although most of these products have limited scientific evidence for their use. The most recent American Botanical Council Market Report estimated for 2020 a 17.3% increase in sales of these products when compared to 2019, for a total sales volume of $11,261 billion. The use of botanical dietary supplements products in the United States is guided by the Dietary Supplement Health and Education Act (DSHEA) from 1994, enacted by the U.S. Congress with the aim of providing more information to consumers and to facilitate access to a larger number of botanical dietary supplements available on the market than previously. Botanical dietary supplements may be formulated for and use only using crude plant samples (e.g., plant parts such as the bark, leaves, or roots) that can be processed by grinding into a dried powder. Plant parts can also be extracted with hot water to form an "herbal tea." Other preparations of botanical dietary supplements include capsules, essential oils, gummies, powders, tablets, and tinctures. Overall, botanical dietary supplements contain bioactive secondary metabolites with diverse chemotypes that typically are found at low concentration levels. These bioactive constituents usually occur in combination with inactive molecules that may induce synergy and potentiation of the effects observed when botanical dietary supplements are taken in their different forms. Most of the botanical dietary supplements available on the U.S. market have been used previously as herbal remedies or as part of traditional medicine systems from around the world. Their prior use in these systems also provides a certain level of assurance in regard to lower toxicity levels. This chapter will focus on the importance and diversity of the chemical features of bioactive secondary metabolites found in botanical dietary supplements that are responsible for their applications. Many of the active principles of botanical dietary substances are phenolics and isoprenoids, but glycosides and some alkaloids are also present. Biological studies on the active constituents of selected botanical dietary supplements will be discussed. Thus, the present chapter should be of interest for both members of the natural products scientific community, who may be performing development studies of the products available, as well as for healthcare professionals who are directly involved in the analysis of botanical interactions and evaluation of the suitability of botanical dietary supplements for human consumption.

Anti-Mayaro virus activity of a hydroethanolic extract from Fridericia chica (Bonpl.) L. G. Lohmann leaves

ETHNOPHARMACOLOGICAL RELEVANCE

Mayaro fever is a neglected tropical disease. The region of the most significant circulation of the Mayaro virus (MAYV) is the Amazon rainforest, situated in remote areas that are difficult to access and where medicine is scarce. Thus, the regional population uses plants as an alternative for the treatment of various diseases. Fridericia chica is an endemic plant of tropical regions used in traditional medicine to treat fever, malaise, inflammation, and infectious diseases such as hepatitis B. However, its antiviral activity is poorly understood.

AIM OF THE STUDY

This study aimed to investigate the anti-MAYV activity of the hydroethanolic extract of the leaves of Fridericia chica (HEFc) in mammalian cells and its possible mechanism of action.

MATERIALS AND METHODS

The antiviral activity of HEFc was studied using Vero cell lines against MAYV. The cytotoxicity and antiviral activity of the extract were evaluated by the 3-(4, 5- dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay. The overall antiviral activity was confirmed by the plaque forming units (PFU) method. Then, the effects of HEFc on MAYV multiplication kinetics, virus adsorption, penetration, and post-penetration, and its virucidal activity were determined in Vero cells using standard experimental procedures.

RESULTS

HEFc exerted a effect against viral infection in Vero cells at a non-cytotoxic concentration, and no virion was detected in the supernatant in a dose-dependent and selective manner. HEFc inhibited MAYV in the early and late stages of the viral multiplication cycle. The extract showed significant virucidal activity at low concentrations and did not affect adsorption or viral internalization stages. In addition, HEFc reduced virions at all post-infection times investigated.

CONCLUSIONS

HEFc has good antiviral activity against MAYV, acting directly on the viral particles. This plant extract possesses an excellent and promising potential for developing effective herbal antiviral drugs.

In vitro inhibition of SARS-CoV-2 Infection by dry algae powders

Chlorella spp., Spirulina spp., and fucoidan dry powders, are commercialized as food supplements and are considered safe for human consumption. Their broad-spectrum antiviral properties have been studied, however, their effect against SARS-CoV-2 remains unknown. We investigated the potential antiviral activity of three algae powders: Chlorella vulgaris, Arthrospira maxima (Spirulina) and fucoidan purified from marine brown algae Sargassum spp. against SARS-CoV-2 infection in vitro. Vero cells were incubated with 70 μg/ml of each algae powder and either 50 or 100 TCID₅₀/ml of SARS-CoV-2, in two types of experiments (pretreatment and simultaneous) and comparing two kinds of solvents (DMEM and DMSO). Chlorella vulgaris powder, inhibited SARS-CoV-2 infection in all assays; viral RNA was significantly reduced in supernatants at 24, 48, 72, and 96 h post-infection, the highest difference in viral load (8000-fold) was observed after 96 h. Arthrospira maxima powder inhibited SARS-CoV-2 infection using 50 TCID₅₀/ml for both experimental schemes, but protection percent was lower when viral inoculum was increase to 100 TCID₅₀/ml; viral RNA decreased 48 h after infection, reaching a 250-fold difference at 72 h. Fucoidan powder partially inhibited SARS-CoV-2 infection since no CPE was observed in 62.5% of trated cultures in DMEM, but the antiviral activity was increased to 100% of protection when DMSO was used as solvent. All the algae samples showed high antiviral activity against SARS-CoV-2 with a SI above of 18. These results suggest that all three algae samples are potential therapeutic candidates for the treatment of COVID-19.

The favorable impacts of silibinin polyphenols as adjunctive therapy in reducing the complications of COVID-19: A review of research evidence and underlying mechanisms

The proceeding pandemic of coronavirus disease 2019 is the latest global challenge. Like most other infectious diseases, inflammation, oxidative stress, and immune system dysfunctions play a pivotal role in the pathogenesis of COVID-19. Furthermore, the quest of finding a potential pharmaceutical therapy for preventing and treating COVID-19 is still ongoing. Silymarin, a mixture of flavonolignans extracted from the milk thistle, has exhibited numerous therapeutic benefits. We reviewed the beneficial effects of silymarin on oxidative stress, inflammation, and the immune system, as primary factors involved in the pathogenesis of COVID-19. We searched PubMed/Medline, Web of Science, Scopus, and Science Direct databases up to April 2022 using the relevant keywords. In summary, the current review indicates that silymarin might exert therapeutic effects against COVID-19 by improving the antioxidant system, attenuating inflammatory response and respiratory distress, and enhancing immune system function. Silymarin can also bind to target proteins of SARS-CoV-2, including main protease, spike glycoprotein, and RNA-dependent RNA-polymerase, leading to the inhibition of viral replication. Although multiple lines of evidence suggest the possible promising impacts of silymarin in COVID-19, further clinical trials are encouraged.

Mechanistic Insights into the Pharmacological Significance of Silymarin

Medicinal plants are considered the reservoir of diverse therapeutic agents and have been traditionally employed worldwide to heal various ailments for several decades. Silymarin is a plant-derived mixture of polyphenolic flavonoids originating from the fruits and akenes of Silybum marianum and contains three flavonolignans, silibinins (silybins), silychristin and silydianin, along with taxifolin. Silybins are the major constituents in silymarin with almost 70–80% abundance and are accountable for most of the observed therapeutic activity. Silymarin has also been acknowledged from the ancient period and is utilized in European and Asian systems of traditional medicine for treating various liver disorders. The contemporary literature reveals that silymarin is employed significantly as a neuroprotective, hepatoprotective, cardioprotective, antioxidant, anti-cancer, anti-diabetic, anti-viral, anti-hypertensive, immunomodulator, anti-inflammatory, photoprotective and detoxification agent by targeting various cellular and molecular pathways, including MAPK, mTOR, β-catenin and Akt, different receptors and growth factors, as well as inhibiting numerous enzymes and the gene expression of several apoptotic proteins and inflammatory cytokines. Therefore, the current review aims to recapitulate and update the existing knowledge regarding the pharmacological potential of silymarin as evidenced by vast cellular, animal, and clinical studies, with a particular emphasis on its mechanisms of action.

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.

Inhibitory effect of tanshinone IIA, resveratrol and silibinin on enterovirus 68 production through inhibiting ATM and DNA-PK pathway

BACKGROUND

Human enterovirus 68 (EV68) is a primary etiological agent for respiratory illnesses, while no effective drug has yet used in clinics largely because the pathogenesis of EV68 is not clear. DNA damage response (DDR) responds to cellular DNA breaks and is also involved in viral replication. Three DDR pathways includes ataxia telangiectasia mutated (ATM), ATM and Rad3-related (ATR), and DNA-dependent protein kinase (DNA-PK). Natural products proved to be an excellent source for the discovery and isolation of novel antivirals. Among them, tanshinone IIA, resveratrol, silibinin, rutin and quercetin are reported to target DDR, therefore their roles in anti-EV68 are investigated in this study.

PURPOSE

This study investigated the anti-EV68 ability of various natural compounds related to DDR.

STUDY DESIGN AND METHODS

The methods include cell counting, flow cytometry, western blot, Immunofluorescence staining, comet assays, quantitative real-time RT PCR and short interfering RNAs (siRNAs) for analysis of cell number, cell cycle, protein expression, protein location, DNA damage, mRNA level and knock down target gene, respectively.

RESULTS

EV68 infection induced DDR. Down-regulation or inhibition of ATM or DNA-PK lowered DDR in EV68-infected cells and mitigated viral protein expression, however, down-regulation or inhibition of ATR unexpectedly up-regulated DDR, and promoted viral protein expression. Meanwhile tanshinone IIA, resveratrol, and silibinin inhibited ATM and/or DNA-PK activation and decreased viral proliferation, while rutin and quercetin inhibited ATR activation and promoted viral production. The role of them in ATM, DNA-PK and ATR activation was consistent with previous reports.

CONCLUSION

Tanshinone IIA, resveratrol and silibinin inhibited EV68 proliferation through inhibiting ATM and/or DNA-PK activation, and they were effective anti-EV68 candidates.

Obesity Exacerbates Coxsackievirus Infection via Lipid-Induced Mitochondrial Reactive Oxygen Species Generation

Coxsackievirus B3 (CVB3) infection causes acute pancreatitis and myocarditis. However, its pathophysiological mechanism is unclear. Here, we investigated how lipid metabolism is associated with exacerbation of CVB3 pathology using high-fat diet (HFD)-induced obese mice. Mice were intraperitoneally inoculated with 1×10⁶ pfu/mouse of CVB3 after being fed a control or HFD to induce obesity. Mice were treated with mitoquinone (MitoQ) to reduce the level of mitochondrial ROS (mtROS). In obese mice, lipotoxicity of white adipose tissue-induced inflammation caused increased replication of CVB3 and mortality. The coxsackievirus adenovirus receptor increased under obese conditions, facilitating CVB3 replication in vitro. However, lipid-treated cells with receptor-specific inhibitors did not reduce CVB3 replication. In addition, lipid treatment increased mitochondria-derived vesicle formation and the number of multivesicular bodies. Alternatively, we found that inhibition of lipid-induced mtROS decreased viral replication. Notably, HFD-fed mice were more susceptible to CVB3-induced mortality in association with increased levels of CVB3 replication in adipose tissue, which was ameliorated by administration of the mtROS inhibitor, MitoQ. These results suggest that mtROS inhibitors can be used as potential treatments for CVB3 infection.

Role of Silymarin in Cancer Treatment: Facts, Hypotheses, and Questions

The flavonoid silymarin extracted from the seeds of Sylibum marianum is a mixture of 6 flavolignan isomers. The 3 more important isomers are silybin (or silibinin), silydianin, and silychristin. Silybin is functionally the most active of these compounds. This group of flavonoids has been extensively studied and they have been used as hepato-protective substances for the mushroom Amanita phalloides intoxication and mainly chronic liver diseases such as alcoholic cirrhosis and nonalcoholic fatty liver. Hepatitis C progression is not, or slightly, modified by silymarin. Recently, it has also been proposed for SARS COVID-19 infection therapy. The biochemical and molecular mechanisms of action of these substances in cancer are subjects of ongoing research. Paradoxically, many of its identified actions such as antioxidant, promoter of ribosomal synthesis, and mitochondrial membrane stabilization, may seem protumoral at first sight, however, silymarin compounds have clear anticancer effects. Some of them are: decreasing migration through multiple targeting, decreasing hypoxia inducible factor-1α expression, inducing apoptosis in some malignant cells, and inhibiting promitotic signaling among others. Interestingly, the antitumoral activity of silymarin compounds is limited to malignant cells while the nonmalignant cells seem not to be affected. Furthermore, there is a long history of silymarin use in human diseases without toxicity after prolonged administration. The ample distribution and easy accessibility to milk thistle-the source of silymarin compounds, its over the counter availability, the fact that it is a weed, some controversial issues regarding bioavailability, and being a nutraceutical rather than a drug, has somehow led medical professionals to view its anticancer effects with skepticism. This is a fundamental reason why it never achieved bedside status in cancer treatment. However, in spite of all the antitumoral effects, silymarin actually has dual effects and in some cases such as pancreatic cancer it can promote stemness. This review deals with recent investigations to elucidate the molecular actions of this flavonoid in cancer, and to consider the possibility of repurposing it. Particular attention is dedicated to silymarin's dual role in cancer and to some controversies of its real effectiveness.

Antioxidant and antiviral activity of fullerol against Zika virus

Neglected for years, Zika virus (ZIKV) has become one of the most relevant arboviruses in current public health. The recent Zika fever epidemic in the Americas generated a worldwide alert due to the association with diseases such as Guillain-Barré syndrome and congenital syndromes. Among the pathogenesis of ZIKV, recent studies suggest that oxidative stress plays an important role during infection and that compounds capable of modulating oxidative stress are promising as therapeutics. Furthermore, so far there are no specific and efficient antiviral drug or vaccine available against ZIKV. Thus, fullerol was evaluated in the context of infection by ZIKV, since it is a carbon nanomaterial known for its potent antioxidant action. In this study, fullerol did not alter cell viability at the concentrations tested, proving to be inert, beyond to presenting high antioxidant power at low concentrations. ZIKV infection of human glioblastoma increased the production of reactive oxygen species by 60% and modulated the Nrf-2 pathway activity negatively. After treatment with fullerol, both conditions were restored to baseline levels. Additionally, fullerol was able to reduce viral production by up to 90%. Therefore, our results suggest that fullerol as a promising candidate in the control of ZIKV infections, presenting both antioxidant and antiviral action.

Favipiravir Inhibits Mayaro Virus Infection in Mice

Mayaro virus (MAYV) is an emergent alphavirus that causes MAYV fever. It is often associated with debilitating symptoms, particularly arthralgia and myalgia. MAYV infection is becoming a considerable health issue that, unfortunately, lacks a specific antiviral treatment. Favipiravir, a broad-spectrum antiviral drug, has recently been shown to exert anti-MAYV activity in vitro. In the present study, the potential of Favipiravir to inhibit MAYV replication in an in vivo model was evaluated. Immunocompetent mice were orally administrated 300 mg/kg/dose of Favipiravir at pre-, concurrent-, or post-MAYV infection. The results showed a significant reduction in infectious viral particles and viral RNA transcripts in the tissues and blood of the pre- and concurrently treated infected mice. A significant reduction in the presence of both viral RNA transcript and infectious viral particles in the tissue and blood of pre- and concurrently treated infected mice was observed. By contrast, Favipiravir treatment post-MAYV infection did not result in a reduction in viral replication. Interestingly, Favipiravir strongly decreased the blood levels of the liver disease markers aspartate- and alanine aminotransferase in the pre- and concurrently treated MAYV-infected mice. Taken together, these results suggest that Favipiravir is a potent antiviral drug when administered in a timely manner.

Recapitulation of Evidence of Phytochemical, Pharmacokinetic and Biomedical Application of Silybin

Silymarin is a standardized extract obtained from seeds of Silybum marianum (SM) belonging to the family Asteraceae. It is a flavonolignan complex and consists of various compounds like silybin A silybin B, isosilybin A, isosilybin B, silydianin, silychristin and isosilychristin. Silybin is the major active component present in 60-70% of the silymarin extract. It has been used traditionally for the treatment of various liver disorders like cirrhosis, jaundice, and hepatitis. Silymarin possesses antioxidant and anti-inflammatory properties and is responsible for its antitumor activity. Other than hepatoprotective effect SM also possesses renoprotective, anti-diabetic, neuroprotective, hypolipidemic, anti-atherosclerosis and cardioprotective effects. Rather antimicrobial property of silymarin was observed against specific microbes, fungi, and viruses. This manuscript covered recent preclinical and clinical evidence of specific components silybin, responsible for its efficacy and about clinical studies has been conducted so far, which proven it's safety and offers mild effect like nausea, diarrhea and bloating. This review specifically focused on recent updates on its active components therapeutic applications against complicated ailments not covered in earlier reports.

Review on oxidative stress relation on COVID-19: Biomolecular and bioanalytical approach

COVID-19 disease has put life of people in stress worldwide from many aspects. Since the virus has mutated in absolutely short period of time the challenge to find a suitable vaccine has become harder. Infection to COVID-19, especially at severe life threatening states is highly dependent on the strength of the host immune system. This system is partially dependent on the balance between oxidative stress and antioxidant. Besides, this virus still has unknown mechanism of action companied by a probable commune period. From another hand, some reactive oxygen species (ROS) levels can be helpful on the state determination of the disease. Thus it could be possible to use modern bioanalytical techniques for their detection and determination, which could indicate the disease state at the golden time window since they have the potential to show whether specific DNA, RNA, enzymes and proteins are affected. This also could be used as a preclude study or a reliable pathway to define the best optimized time of cure beside effective medical actions. Herein, some ROS and their relation with SARS-CoV-2 virus have been considered. In addition, modern bioelectroanalytical techniques on this approach from quantitative and qualitative points of view have been reviewed.

Evaluation of Antiviral Activity of Cyclic Ketones against Mayaro Virus

Mayaro virus (MAYV) is a neglected arthropod-borne virus found in the Americas. MAYV infection results in Mayaro fever, a non-lethal debilitating disease characterized by a strong inflammatory response affecting the joints and muscles. MAYV was once considered endemic to forested areas in Brazil but has managed to adapt and spread to urban regions using new vectors, such as Aedes aegypti, and has the potential to cause serious epidemics in the future. Currently, there are no vaccines or specific treatments against MAYV. In this study, the antiviral activity of a series of synthetic cyclic ketones were evaluated for the first time against MAYV. Twenty-four compounds were screened in a cell viability assay, and eight were selected for further evaluation. Effective concentration (EC₅₀) and selectivity index (SI) were calculated and compound 9-(5-(4-chlorophenyl]furan-2-yl)-3,6-dimethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2))-dione (9) (EC₅₀ = 21.5 µmol·L⁻¹, SI = 15.8) was selected for mechanism of action assays. The substance was able to reduce viral activity by approximately 70% in both pre-treatment and post-treatment assays.

Virucidal and antiviral activities of pomegranate (Punica granatum) extract against the mosquito-borne Mayaro virus

BACKGROUND

The arthropod-borne Mayaro virus (MAYV) causes "Mayaro fever," a disease of medical significance, primarily affecting individuals in permanent contact with forested areas in tropical South America. Recently, MAYV has attracted attention due to its likely urbanization. There are currently no licensed drugs against most mosquito-transmitted viruses. Punica granatum (pomegranate) fruits cultivated in Brazil have been subjected to phytochemical investigation for the identification and isolation of antiviral compounds. In the present study, we explored the antiviral activity of pomegranate extracts in Vero cells infected with Mayaro virus.

METHODS

The ethanol extract and punicalagin of pomegranate were extracted solely from the shell and purified by chromatographic fractionation, and were chemically identified using spectroscopic techniques. The cytotoxicity of the purified compounds was measured by the dye uptake assay, while their antiviral activity was evaluated by a virus yield inhibition assay.

RESULTS

Pomegranate ethanol extract (CC₅₀ = 588.9, IC₅₀ = 12.3) and a fraction containing punicalagin as major compound (CC₅₀ = 441.5, IC₅₀ = 28.2) were shown to have antiviral activity (SI 49 and 16, respectively) against Mayaro virus, an alphavirus. Immunofluorescence analysis showed the virucidal effect of pomegranate extract, and transmission electron microscopy (TEM) revealed damage in viral particles treated with this extract.

CONCLUSIONS

The P. granatum extract is a promising source of antiviral compounds against the alphavirus MAYV and represents an excellent candidate for future studies with other enveloped RNA viruses.

Hepatoprotective, antioxidant, anti-inflammatory, and antiviral activities of silymarin against mayaro virus infection

Infection caused by Mayaro virus (MAYV) is responsible for causing acute nonspecific fever, in which the majority of patients develop incapacitating and persistent arthritis/arthralgia. Mayaro fever is a neglected and underreported disease without treatment or vaccine, which has gained attention in recent years after the competence of Aedes aegypti to transmit MAYV was observed in the laboratory, coupled with the fact that cases are being increasingly reported outside of endemic forest areas, calling attention to the potential of an urban cycle arising in the near future. Thus, to mitigate the lack of information about the pathological aspects of MAYV, we previously described the involvement of oxidative stress in MAYV infection in cultured cells and in a non-lethal mouse model. Additionally, we showed that silymarin, a natural compound, attenuated MAYV-induced oxidative stress and inhibited MAYV replication in cells. The antioxidant and anti-MAYV effects prompted us to determine whether silymarin could also reduce oxidative stress and MAYV replication after infection in an immunocompetent animal model. We show that infected mice exhibited reduced weight gain, hepatomegaly, splenomegaly, anaemia, thrombocytopenia, leukopenia, increased liver transaminases, increased pro-inflammatory cytokines and liver inflammation, increased oxidative damage biomarkers, and reduced antioxidant enzyme activity. However, in animals infected and treated with silymarin, all these parameters were reversed or significantly improved, and the detection of viral load in the liver, spleen, brain, thigh muscle, and footpad was significantly reduced. This work reinforces the potent hepatoprotective, antioxidant, anti-inflammatory, and antiviral effects of silymarin against MAYV infection, demonstrating its potential against Mayaro fever disease.

Targeting Multiple Signal Transduction Pathways of SARS-CoV-2: Approaches to COVID-19 Therapeutic Candidates

Due to the complicated pathogenic pathways of coronavirus disease 2019 (COVID-19), related medicinal therapies have remained a clinical challenge. COVID-19 highlights the urgent need to develop mechanistic pathogenic pathways and effective agents for preventing/treating future epidemics. As a result, the destructive pathways of COVID-19 are in the line with clinical symptoms induced by severe acute coronary syndrome (SARS), including lung failure and pneumonia. Accordingly, revealing the exact signaling pathways, including inflammation, oxidative stress, apoptosis, and autophagy, as well as relative representative mediators such as tumor necrosis factor-α (TNF-α), nuclear factor erythroid 2-related factor 2 (Nrf2), Bax/caspases, and Beclin/LC3, respectively, will pave the road for combating COVID-19. Prevailing host factors and multiple steps of SARS-CoV-2 attachment/entry, replication, and assembly/release would be hopeful strategies against COVID-19. This is a comprehensive review of the destructive signaling pathways and host-pathogen interaction of SARS-CoV-2, as well as related therapeutic targets and treatment strategies, including potential natural products-based candidates.

Reactive oxygen species as potential antiviral targets

Reactive oxygen species (ROS) are by-products of cellular metabolism and can be either beneficial, at low levels, or deleterious, at high levels, to the cell. It is known that several viral infections can increase oxidative stress, which is mainly facilitated by viral-induced imbalances in the antioxidant defence mechanisms of the cell. While the exact role of ROS in certain viral infections (adenovirus and dengue virus) remains unknown, other viruses can use ROS for enhancement of pathogenesis (SARS coronavirus and rabies virus) or replication (rhinovirus, West Nile virus and vesicular stomatitis virus) or both (hepatitis C virus, human immunodeficiency virus and influenza virus). While several viral proteins (mainly for hepatitis C and human immunodeficiency virus) have been identified to play a role in ROS formation, most mediators of viral ROS modulation are yet to be elucidated. Treatment of viral infections, including hepatitis C virus, human immunodeficiency virus and influenza virus, with ROS inhibitors has shown a decrease in both pathogenesis and viral replication both in vitro and in animal models. Clinical studies indicating the potential for targeting ROS-producing pathways as possible broad-spectrum antiviral targets should be evaluated in randomized controlled trials.

Phytopharmaceuticals mediated Furin and TMPRSS2 receptor blocking: can it be a potential therapeutic option for Covid-19?

BACKGROUND

Currently, novel coronavirus disease (Covid-19) outbreak creates global panic across the continents, as people from almost all countries and territories have been affected by this highly contagious viral disease. The scenario is deteriorating due to lack of proper & specific target-oriented pharmacologically safe prophylactic agents or drugs, and or any effective vaccine. drug development is urgently required to back in the normalcy in the community and to combat this pandemic.

PURPOSE

Thus, we have proposed two novel drug targets, Furin and TMPRSS2, as Covid-19 treatment strategy. We have highlighted this target-oriented novel drug delivery strategy, based on their pathophysiological implication on SARS-CoV-2 infection, as evident from earlier SARS-CoV-1, MERS, and influenza virus infection via host cell entry, priming, fusion, and endocytosis. STUDY DESIGN &  METHODS: An earlier study suggested that Furin and TMPRSS2 knockout mice had reduced level of viral load and a lower degree of organ damage such as the lung. The present study thus highlights the promise of some selected novel and potential anti-viral Phytopharmaceutical that bind to Furin and TMPRSS2 as target.

RESULT

Few of them had shown promising anti-viral response in both preclinical and clinical study with acceptable therapeutic safety-index.

CONCLUSION

Hence, this strategy may limit life-threatening Covid-19 infection and its mortality rate through nano-suspension based intra-nasal or oral nebulizer spray, to treat mild to moderate SARS-COV-2 infection when Furin and TMPRSS2 receptor may initiate to express and activate for processing the virus to cause cellular infection by replication within the host cell and blocking of host-viral interaction.

Phyto-pharmacological perspective of Silymarin: A potential prophylactic or therapeutic agent for COVID-19, based on its promising immunomodulatory, anti-coagulant and anti-viral property

Coronavirus disease 2019 (COVID‐19) triggered by a new viral pathogen, named severe acute respiratory syndrome Coronavirus‐2 (SARS‐CoV‐2), is now a global health emergency. This debilitating viral pandemic not only paralyzed the normal daily life of the global community but also spread rapidly via global travel. To date there are no effective vaccines or specific treatments against this highly contagious virus; therefore, there is an urgent need to advocate novel prophylactic or therapeutic interventions for COVID‐19. This brief opinion critically discusses the potential of Silymarin, a flavonolignan with diverse pharmacological activity having antiinflammatory, antioxidant, antiplatelet, and antiviral properties, with versatile immune‐cytokine regulatory functions, that able to bind with transmembrane protease serine 2 (TMPRSS2) and induce endogenous antiviral cytokine interferon‐stimulated gene 15, for the management of COVID‐19. Silymarin inhibits the expression of host cell surface receptor TMPRSS2 with a docking binding energy corresponding to −1,350.61 kcal/mol and a full fitness score of −8.11. The binding affinity of silymarin with an impressive virtual score exhibits significant potential to interfere with SARS‐CoV‐2 replication. We propose in‐depth pre‐clinical and clinical review studies of silymarin for the development of anti‐COVID‐19 lead, based on its clinical manifestations of COVID‐19 and multifaceted bioactivities.

Repurposing Drugs for Mayaro Virus: Identification of EIDD-1931, Favipiravir and Suramin as Mayaro Virus Inhibitors

Despite the emerging threat of the Mayaro virus (MAYV) in Central and South-America, there are no licensed antivirals or vaccines available for this neglected mosquito-borne virus. Here, we optimized a robust antiviral assay based on the inhibition of the cytopathogenic effect that could be used for high-throughput screening to identify MAYV inhibitors. We first evaluated different cell lines and virus inputs to determine the best conditions for a reliable and reproducible antiviral assay. Next, we used this assay to evaluate a panel of antiviral compounds with known activity against other arboviruses. Only three drugs were identified as inhibitors of MAYV: β-D-N⁴-hydroxycytidine (EIDD-1931), favipiravir and suramin. The in vitro anti-MAYV activity of these antiviral compounds was further confirmed in a virus yield assay. These antivirals can therefore serve as reference compounds for future anti-MAYV compound testing. In addition, it is of interest to further explore the activity of EIDD-1931 and its orally bioavailable pro-drug molnupiravir in animal infection models to determine whether it offers promise for the treatment of MAYV infection.

Antiviral Drug Discovery and Development for Mayaro Fever - What do we have so far?

Tropical infectious diseases cause millions of deaths every year in developing countries, with about half of the world population living at risk. Mayaro virus (MAYV) is an emerging arbovirus that causes Mayaro fever, which is characterized by fever, headache, diarrhea, arthralgia, and rash. These symptoms can be clinically indistinguishable from other arboviruses, such as Dengue, Zika, and Chikungunya, which makes the diagnosis and treatment of the disease more difficult. Though, the Mayaro virus is a potential candidate to cause large-scale epidemics on the scale of ZIKV and CHIKV. Despite this, there is no licensed vaccine or antiviral for the treatment of Mayaro fever and most arboviruses, so the design and development of candidates for antiviral drugs are urgently needed. In this context, this mini-review aims to provide an overview of studies of anti-MAYV derivatives and highlight the importance of the discovery and development of promising drug candidates for Mayaro fever.

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.

Bombyx mori nucleopolyhedrovirus F-like protein Bm14 is a factor for viral-induced cytopathic effects via regulating oxidative phosphorylation and cellular ROS levels

Bombyx mori nucleopolyhedrovirus (BmNPV) is highly pathogenic to Bombyx mori, silkworm, which causes serious cytopathic effects (CPEs) during infection. However, the role of viral protein in the virus-induced CPEs remains unclear. Here, we discovered that BmNPV infection induced severe CPEs including titer-dependent cell floating and changes in cellular surface morphology. Further explorations revealed the involvement of F-like protein (Bm14), a viral envelope protein, in inducing cytotoxicity and detachment of adherent BmN cells, and its disruption significantly impaired the virus infection-mediated CPEs. Intriguingly, transcriptomic analysis identified the tight association of Bm14 deletion with the activation of cellular oxidative phosphorylation pathway, consistent with the elevated mitochondrial membrane potential (MMP) levels and ATP concentrations as well as reduced ROS levels. Collectively, our results characterized for the first time the novel role of Bm14 in accelerating viral-induced cytopathogenicity via suppressing the cellular oxidative phosphorylation levels and upregulating the ROS levels.

Health Benefits of Silybum marianum: Phytochemistry, Pharmacology, and Applications

Silybum marianum (SM), a well-known plant used as both a medicine and a food, has been widely used to treat various diseases, especially hepatic diseases. The seeds and fruits of SM contain a flavonolignan complex called silymarin, the active compounds of which include silybin, isosilybin, silychristin, dihydrosilybin, silydianin, and so on. In this review, we thoroughly summarize high-quality publications related to the pharmacological effects and underlying mechanisms of SM. SM has antimicrobial, anticancer, hepatoprotective, cardiovascular-protective, neuroprotective, skin-protective, antidiabetic, and other effects. Importantly, SM also counteracts the toxicities of antibiotics, metals, and pesticides. The diverse pharmacological activities of SM provide scientific evidence supporting its use in both humans and animals. Multiple signaling pathways associated with oxidative stress and inflammation are the common molecular targets of SM. Moreover, the flavonolignans of SM are potential agonists of PPARγ and ABCA1, PTP1B inhibitors, and metal chelators. At the end of the review, the potential and perspectives of SM are discussed, and these insights are expected to facilitate the application of SM and the discovery and development of new drugs. We conclude that SM is an interesting dietary medicine for health enhancement and drug discovery and warrants further investigation.

In-silico and biophysical investigation of biomolecular interaction between naringin and nsP2 of the chikungunya virus

Chikungunya virus; the pathogen for chikungunya febrile and arthritic disease, having 11.8 kb positive-sense RNA genome encodes polyproteins for structural and non-structural regions. The polyprotein (P1234) corresponding to the non-structural part from 5' end gets auto-cleaved by the action of nsP2 protease, which leads to the generation of individual functional enzymatic proteins like nsP4, nsP1, nsP2 and nsP3. Thus, nsP2 protein initiates viral replication. Targeting nsP2 to block virus replication has always been the foremost strategy to develop antivirals. Plant-based molecules are one of the top choices to develop as inhibitor due to their less toxicity and wide availability. Using a combination of receptor-based docking and MD simulations, we identified a flavanone glycoside- naringin, which binds to nsP2 protease at nM affinity. The biomolecular interaction between naringin and nsP2 was established through SPR. As discerned through FTIR and intrinsic fluorescence studies, upon binding with naringin, a global structural change in nsP2 occurs. This structural modulation in nsP2 due to binding of naringin is likely to interfere with the normal functioning of this enzyme during the viral life cycle. In conclusion, this report highlights the potential of naringin as an anti-viral agent against Chikungunya.

Anti-Zika virus activity and chemical characterization by ultra-high performance liquid chromatography (UPLC-DAD-UV-MS) of ethanol extracts in Tecoma species

Background

Plant species from the genus Tecoma are found in tropical and subtropical regions around the world. Some of them are grown as ornamental plants and others can be used as medicinal plants. In the present study, ethanolic extracts from trunks and leaves of Tecoma species were tested in vitro using assays against the Zika virus.

Methods

There was a total of 8 extracts obtained from different anatomical parts of three Tecoma species. The Tecoma castaneifolia, T. garrocha, T. stans var. angustata and T. stans var. stans were prepared by percolation with ethanol. The antiviral activity was assayed in vitro against the Zika virus by the MTT colorimetric method (n = 3). The UPLC-DAD-MS analysis of ethanolic extracts was performed from all the studied species. The biofractionation of T. stans var. stans trunk extract using different separation techniques led to the isolation of crenatoside compound.

Results

Ethanolic extract from Tecoma species leaves were more active against the Zika virus (EC₅₀ 149.90 to 61.25 μg/mL) when compared to the trunk extracts tested (EC₅₀ 131.0 to 66.79 μg/mL and two were not active). The ethyl acetate and aqueous fractions obtained from T. stans var. stans trunk were active against the Zika virus with EC₅₀ values of 149.90 and 78.98 μg/mL, respectively. Crenatoside is a phenylethanoid glycoside isolated from the ethyl acetate of T. stans var. stans trunk extract. This compound was tested and exhibited EC₅₀ 34.78 μM (21.64 μg/mL), thus demonstrating a better result than the original ethanolic extracts as well as others extracts of Tecoma species, and it was more active than the positive control, ribavirin (386.84 μM). Furthermore, its selectivity index was at least 2.5 times higher than the tested ethanolic extracts and 11.1 times more potent than ribavirin.

Conclusion

The Tecoma species demonstrated interesting in vitro activity against the Zika virus. The crenatoside, phenylethanoid glycoside that was for the first time isolated from Tecoma stans var. stans, exhibited a potent and relevant anti-Zika virus activity, being more active than ribavirin (positive control). The data show that crenatoside, was a promising compound with in vitro antiviral activity against the Zika virus.

Antiviral Natural Products for Arbovirus Infections

Over the course of the last 50 years, the emergence of several arboviruses have resulted in countless outbreaks globally. With a high proportion of infections occurring in tropical and subtropical regions where arthropods tend to be abundant, Asia in particular is a region that is heavily affected by arboviral diseases caused by dengue, Japanese encephalitis, West Nile, Zika, and chikungunya viruses. Major gaps in protection against the most significant emerging arboviruses remains as there are currently no antivirals available, and vaccines are only available for some. A potential source of antiviral compounds could be discovered in natural products—such as vegetables, fruits, flowers, herbal plants, marine organisms and microorganisms—from which various compounds have been documented to exhibit antiviral activities and are expected to have good tolerability and minimal side effects. Polyphenols and plant extracts have been extensively studied for their antiviral properties against arboviruses and have demonstrated promising results. With an abundance of natural products to screen for new antiviral compounds, it is highly optimistic that natural products will continue to play an important role in contributing to antiviral drug development and in reducing the global infection burden of arboviruses.

Antioxidant Potential of Antiviral Drug Umifenovir

Free radical reactions play an important role in biological functions of living systems. The balance between oxidants and antioxidants is necessary for the normal homeostasis of cells and organisms. Experimental works demonstrate the role of oxidative stress that is caused by influenza virus as well as the toxic effects of some antiviral drugs. Therefore, antiviral drugs should be characterized by its pro- and antioxidant activity, because it can affect its therapeutic efficiency. The aim of the study was to quantify the antioxidant capacity and propose the mechanism of the antioxidant effect of the antiviral drug Umifenovir (Arbidol®). The kinetic chemiluminescence with the 2,2'-azobis (2-amidinopropane) dihydrochloride + luminol system was used to quantify the antioxidant capacity of Umifenovir relative to the standard compound Trolox. With computer simulation, the reaction scheme and rate constants were proposed. The antioxidant capacity of 0.9 μM Umifenovir (maximum concentration of Umifenovir in blood after oral administration of 200 mg) was as high as 1.65 ± 0.18 μM of Trolox. Thus, the total antioxidant capacity of Umifenovir is comparable to the antioxidant capacity of Trolox. Unlike Trolox, Umifenovir reacts with free radicals in two stages. For Trolox, the free radical scavenging rate constant was k = 2000 nM-1 min.-1, for Umifenovir k1 = 300 nM-1min.-1, k2 = 4 nM-1min.-1. Slower kinetics of Umifenovir provides the prolonged antioxidant effect when compared to Trolox. This phenomenon can make a serious contribution to the compensation of oxidative stress that is caused by a viral disease and the therapeutic effect of the drug.

Antiviral activity of silymarin in comparison with baicalein against EV-A71

BACKGROUND

The hand, foot and mouth disease (HFMD) is a febrile and exanthematous childhood disease mainly caused by Enterovirus 71 (EV-A71). In severe HFMD, virulent EV-A71 strains can cause acute flaccid paralysis and cardiopulmonary edema leading to death. Currently, no FDA approved antiviral treatment or vaccine is available for EV-A71. Flavonoids such as silymarin and baicalein are known to possess in vitro antiviral properties against viruses. In this study, the cytotoxicity and antiviral activity of silymarin, baicalein and baicalin were investigated.

METHODS

The cytotoxic effects of three flavonoids towards rhabdomyosarcoma (RD) cells were first examined using cell proliferation MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] assay. Compounds found to be non-cytotoxic in RD cells were evaluated for their in vitro antiviral properties against the EV-A71 subgenotype B4 strain 41 (5865/SIN/000009) using antiviral assays. Viral infectivity was determined by reduction of the formation of plaques in RD cells. For the measurement of RNA copy number, the real time quantitative reverse transcription PCR (qRT-PCR) was used. The most potent compound was further evaluated to determine the mode of action of inhibition by time course, virus attachment and entry assays in Vero cells.

RESULTS

Silymarin was shown to exert direct extracellular virucidal effects against EV-A71 at 50% inhibitory concentration (IC₅₀) of 15.2 ± 3.53 μg/mL with SI of 10.53. Similarly, baicalein exhibited direct extracellular virucidal effects against EV-A71 at a higher IC₅₀ value of 30.88 ± 5.50 μg/mL with SI of 13.64. Besides virucidal activity, silymarin was shown to block both viral attachment and entry of EV-A71 to inhibit infection in Vero cells.

CONCLUSIONS

Silymarin has a stronger inhibition activity against EV-A71 in comparison to baicalein. It could serve as a promising antiviral drug to treat EV-A71 infections.

Curcumin inhibits alloxan-induced pancreatic islet cell damage via antioxidation and antiapoptosis

The present study elucidates the possible protective effects of curcumin on β-cells damaged by oxidative stress and its significance in controlling diabetes mellitus in in vitro experiments. Pancreatic islet (RIN-m5F) cells were treated with 25 mmol/L alloxan (AXN) to induce cell damage and the protective effects of curcumin were observed. The results showed that curcumin significantly promoted the cellular activity of AXN-treated RIN-m5F cells, decreased the ratio of apoptosis, downregulated the level of malondialdehyde, upregulated the levels of superoxide dismutase and reactive oxygen species, increased the expression of Bcl-2, cleaved caspase-3, and cleaved PARP1, and decreased the expression of Bax in AXN-treated cells. These results suggest that curcumin inhibits AXN-induced damage in RIN-m5F cells via antioxidative and antiapoptotic mechanisms.

Silymarin: not just another antioxidant

Silymarin (Silybum marianum; SM), popularly known as milk thistle, is an extract that has been used for many centuries to treat liver diseases. In recent years, several studies have shown that SM is not only just another antioxidant but also a multifunctional compound that exhibits several beneficial properties for use in the treatment and prevention of different types of pathologies and disorders. This review aims at demonstrating the main protective activities of SM in diseases, such as cancer, diabetes, hepatitis, non-alcoholic fatty liver disease, alcoholic liver disease, hepatitis C virus, hepatitis B virus, metabolic syndrome, depression, cardiovascular diseases and thalassemia, in addition to its photoprotective activity in in vitro tests and preclinical studies. Its main functions include antioxidant and anti-inflammatory effects, and it acts as modulator of signaling pathways. It has been suggested that SM presents great multifunctional potential and is capable of achieving promising results in different types of research. However, caution is still needed regarding its indiscriminate use in humans as there are only a few clinical studies relating to the adequate dose and the actual efficacy of this extract in different types of diseases.

Flavonoids as Antiviral Agents for Enterovirus A71 (EV-A71)

Flavonoids are natural biomolecules that are known to be effective antivirals. These biomolecules can act at different stages of viral infection, particularly at the molecular level to inhibit viral growth. Enterovirus A71 (EV-A71), a non-enveloped RNA virus, is one of the causative agents of hand, foot and mouth disease (HFMD), which is prevalent in Asia. Despite much effort, no clinically approved antiviral treatment is available for children suffering from HFMD. Flavonoids from plants serve as a vast reservoir of therapeutically active constituents that have been explored as potential antiviral candidates against RNA and DNA viruses. Here, we reviewed flavonoids as evidence-based natural sources of antivirals against non-picornaviruses and picornaviruses. The detailed molecular mechanisms involved in the inhibition of EV-A71 infections are discussed.

Antiviral drug discovery against arthritogenic alphaviruses: Tools and molecular targets

Alphaviruses are (mainly) arthropod-borne viruses that belong to the family of the Togaviridae. Based on the disease they cause, alphaviruses are divided into an arthritogenic and an encephalitic group. Arthritogenic alphaviruses such as the chikungunya virus (CHIKV), the Ross River virus (RRV) and the Mayaro virus (MAYV) have become a serious public health concern in recent years. Epidemics are associated with high morbidity and the infections cause in many patients debilitating joint pain that can persist for months to years. The recent (2013-2014) introduction of CHIKV in the Americas resulted in millions of infected persons. Massive outbreaks of CHIKV and other arthritogenic alphaviruses are likely to occur in the future. Despite the worldwide (re-)emergence of these viruses, there are no antivirals or vaccines available for the treatment or prevention of infections with alphaviruses. It is therefore of utmost importance to develop antiviral strategies against these viruses. We here review the possible molecular targets in the replication cycle of these viruses for the development of antivirals. In addition, we provide an overview of the currently available in vitro systems and mouse infection models that can be used to assess the potential antiviral effect against these viruses.

Mayaro Virus Induction of Oxidative Stress is Associated With Liver Pathology in a Non-Lethal Mouse Model

Mayaro virus (MAYV) causes Mayaro fever in humans, a self-limiting acute disease, with persistent arthralgia and arthritis. Although MAYV has a remerging potential, its pathogenic mechanisms remain unclear. Here, we characterized a model of MAYV infection in 3-4-week BALB/c mice. We investigated whether the liver acts as a site of viral replication and if the infection could cause histopathological alterations and an imbalance in redox homeostasis, culminating with oxidative stress. MAYV-infected mice revealed lower weight gain; however, the disease was self-resolving. High virus titre, neutralizing antibodies, and increased levels of aspartate and alanine aminotransferases were detected in the serum. Infectious viral particles were recovered in the liver of infected animals and the histological examination of liver tissues revealed significant increase in the inflammatory infiltrate. MAYV induced significant oxidative stress in the liver of infected animals, as well as a deregulation of enzymatic antioxidant components. Collectively, this is the first study to report that oxidative stress occurs in MAYV infection in vivo, and that it may be crucial in virus pathogenesis. Future studies are warranted to address the alternative therapeutic strategies for Mayaro fever, such as those based on antioxidant compounds.

Development of a rapid antiviral screening assay based on eGFP reporter virus of Mayaro virus

Mayaro virus (MAYV) is a neglected mosquito-borne alphavirus that causes illness similar to Chikungunya (CHIKV), Dengue (DENV) and Zika virus (ZIKV). Currently, there is no specific treatment or vaccine against MAYV infection. To develop an efficient antiviral screening assay for MAYV, we constructed the infectious clones of MAYV strain BeAr 20290 and its eGFP reporter virus. The reporter virus exhibited high replication capacity indistinguishable with the wild type MAYV, and was genetically stable within at least five rounds of passages in BHK-21 cell. The expression of eGFP correlated well with the viral replication. Using the known inhibitor ribavirin, we confirmed that the MAYV-eGFP reporter virus could be used for antiviral screening to identify the specific inhibitors against MAYV. Using the MAYV-eGFP based antiviral assay, we found that the compound 6-Azauridine which had antiviral activity against CHIKV and SFV, showed a significant inhibitory effect on MAYV replication.

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.

Antiviral Activities of Silymarin and Derivatives

Silymarin flavonolignans are well-known agents that typically possess antioxidative, anti-inflammatory, and hepatoprotective functions. Recent studies have also documented the antiviral activities of silymarin and its derivatives against several viruses, including the flaviviruses (hepatitis C virus and dengue virus), togaviruses (Chikungunya virus and Mayaro virus), influenza virus, human immunodeficiency virus, and hepatitis B virus. This review will describe some of the latest preclinical and clinical studies detailing the antiviral profiles of silymarin and its derivatives, and discuss their relevance for antiviral drug development.