Antiviral effect of compounds derived from the seeds of Mammea americana and Tabernaemontana cymosa on Dengue and Chikungunya virus infections

An update review on monoterpene indole alkaloids and biological activities of Tabernaemontana species occurring in Brazil

ETHNOPHARMACOLOGICAL RELEVANCE

The Tabernaemontana genus belongs to the Apocynaceae family of which 30 species are found in Brazil. Some Tabernaemontana species are used by Brazilian indigenous people and other communities, or are listed in the Yanomami Pharmacopeia. Ethnopharmacological data include use(s) for muscle problems, depressed sternum, back pain, abscess, indigestion, eye irritation, earache, itching, vaginal discharge, as an aid for older people who are slow and forgetful, mosquito and snake bites, infection by the human botfly larvae, calmative, and fever. Obviously, many of these uses are attributed to the alkaloids found in Tabernaemontana species.

AIM OF THE REVIEW

The aim is to gather information on Tabernaemontana species occurring in Brazil, as sources of monoterpene indole alkaloids (MIAs). In addition, we aim to collect reported experimental demonstrations of their biological activity, which may provide the foundation for further studies, including phytochemistry, the development of medicinal agents, and validation of phytopreparations.

MATERIAL AND METHODS

The Brazilian Flora 2020 database was used as source for Tabernamontana species occurring in Brazil. The literature review on these species was collected from Web of Science, Scopus, PubMed, and Scifinder. The keywords included names and synonyms of Tabernaemontana species found in Brazil, which were validated by the Word Flora Online Plant List.

RESULTS

A literature survey covering the time frame from 1960 until June 2023 resulted in 121 MIAs, including 48 not yet reported in the last review published in 2016. Some alkaloid extracts, fractions, and isolated alkaloids present evidenced biological activity, such as anticancer, anti-inflammatory, antinociceptive, antimicrobial, antiparasitic, antiviral, and against snake venoms, among others. Notably, ethnopharmacological based information has been the basis of some reports on Tabernaemontana species.

CONCLUSIONS

Our literature survey shows that Tabernaemontana species present bioactive MIAs, such as voacamine and affinisine, demonstrating significant cytotoxicity activity against several tumoral cell lines. Those compounds can be considered promising candidates in the search for new anticancer drugs. However, the Amazonian plant biome is increasingly damaged, which may lead to the extinction of biological diversity. This threat may also affect Tabernaemontana species, which have scarcely been investigated regarding the potential of their phytochemicals for the development of new drugs.

Searching possible SARS-CoV-2 main protease inhibitors in constituents from herbal medicines using in silico studies

The largest threat to civilization since the Second World War is the spread of the new coronavirus disease (COVID-19). Therefore, there is an urgent need for innovative therapeutic medicines to treat COVID-19. Reusing bio-actives is a workable and efficient strategy in the battle against new epidemics because the process of developing new drugs is time-consuming. This research aimed to identify which herbal remedies had the highest affinity for the receptor and assess a variety of them for potential targets to suppress the SARS-CoV-2 Mpro. The use of AutoDock Vina for structure-based virtual screening was done first due to the importance of protein interactions in the development of drugs. Molecular docking was used in the comparative study to assess 89 different chemicals from medicinal herbs. To anticipate their effectiveness against the primary protease of SARS-CoV-2, more analysis was done on the ADMET profile, drug-likeness, and Lipinski's rule of five. The next step involved three replicas of 100 ns-long molecular dynamics simulations on the potential candidates, which were preceded by calculations of the binding free energy of MM-GBSA. The outcomes showed that Achyrodimer A, Cinchonain Ib, Symphonone F, and Lupeol acetate all performed well and had the highest 6LU7 binding affinities. Using RMSD, RMSF, and protein-ligand interactions, the stability of the protein-ligand complex was assessed. The studies indicate that bioactive substances obtained from herbal medicines may function as a COVID-19 therapeutic agent, necessitating additional wet lab research to confirm their therapeutic potential, efficacy, and pharmacological capacity against the condition.Communicated by Ramaswamy H. Sarma.

Medicinal Plants against Viral Infections: A Review of Metabolomics Evidence for the Antiviral Properties and Potentials in Plant Sources

Most plants have developed unique mechanisms to cope with harsh environmental conditions to compensate for their lack of mobility. A key part of their coping mechanisms is the synthesis of secondary metabolites. In addition to their role in plants' defense against pathogens, they also possess therapeutic properties against diseases, and their use by humans predates written history. Viruses are a unique class of submicroscopic agents, incapable of independent existence outside a living host. Pathogenic viruses continue to pose a significant threat to global health, leading to innumerable fatalities on a yearly basis. The use of medicinal plants as a natural source of antiviral agents has been widely reported in literature in the past decades. Metabolomics is a powerful research tool for the identification of plant metabolites with antiviral potentials. It can be used to isolate compounds with antiviral capacities in plants and study the biosynthetic pathways involved in viral disease progression. This review discusses the use of medicinal plants as antiviral agents, with a special focus on the metabolomics evidence supporting their efficacy. Suggestions are made for the optimization of various metabolomics methods of characterizing the bioactive compounds in plants and subsequently understanding the mechanisms of their operation.

Role of phytocompounds as the potential anti-viral agent: an overview

Viral diseases are the most notorious infective agent(s) causing morbidity and mortality in every nook and corner for ages; viruses are active in host cells, and specific anti-virus medicines' developments remain uncanny. In this century of the biological era, human viruses act predominantly as versatile spreaders. The infection of the present COVID-19 virus is up in the air; blithely, the integument of medicinal chemistry approaches, particularly bioactive derived phytocompounds could be helpful to control those human viruses, recognized in the last 100 years. Indeed, natural products are being used for various therapeutic purposes. The major bioactive phytocompounds are chemically containing coumarin, thiosulfonate, steroid, polysaccharide, tannin, lignin, proanthocyanidin, terpene, quinone, saponin, flavonoid, alkaloid, and polyphenol, that are documented for inhibitory action against several viral infections. Mostly, about 20-30% of plants from tropical or temperate regions are known to have some antiviral activity. This comprehensive analysis of bioactive-derived phytocompounds would represent a significant impact and might be helpful for antiviral research and the current state of viral treatments.

Ethnopharmacological Potential of Phytochemicals and Phytogenic Products against Human RNA Viral Diseases as Preventive Therapeutics

RNA viruses have been the most destructive due to their transmissibility and lack of control measures. Developments of vaccines for RNA viruses are very tough or almost impossible as viruses are highly mutable. For the last few decades, most of the epidemic and pandemic viral diseases have wreaked huge devastation with innumerable fatalities. To combat this threat to mankind, plant-derived novel antiviral products may contribute as reliable alternatives. They are assumed to be nontoxic, less hazardous, and safe compounds that have been in uses in the beginning of human civilization. In this growing COVID-19 pandemic, the present review amalgamates and depicts the role of various plant products in curing viral diseases in humans.

In Silico Study of Coumarins: Wedelolactone as a Potential Inhibitor of the Spike Protein of the SARS-CoV-2 Variants

Despite the rigorous global efforts to control SARS-CoV-2 transmission, it continues to pose a serious threat to humans with the frequent emergence of new variants. Thus, robust therapeutics to combat the virus are a desperate need. The SARS-CoV-2 spike (S) protein is an important target protein as it mediates the entry of the virus inside the host cells, which is initiated by the binding of the receptor-binding domain (RBD) to its cognate receptor, angiotensin-converting enzyme 2 (ACE-2). Herein, the inhibition potential of several naturally occurring coumarins was investigated against the spike proteins of SARS-CoV-2 variants using computational approaches. Molecular docking studies revealed 26 coumarins with better binding energies than the reference ligands, molnupiravir and ceftazidime, against the S-RBD of the omicron variant. The top 10 best-docked coumarins were further analyzed to understand their binding interactions against the spike proteins of other variants (wild-type, Alpha, Beta, Gamma, and Delta), and these studies also demonstrated decent binding energies. Physicochemical, QSAR, and pharmacokinetics analyses of the coumarins revealed wedelolactone as the best inhibitor of the spike protein with ideal Lipinski’s drug-likeness and optimal ADMET properties. Furthermore, coarse-grained molecular dynamics (MD) simulation studies of spike protein-wedelolactone complexes validated the stable binding of wedelolactone in the respective binding pockets. As an outcome, wedelolactone could be utilized to develop a potent drug candidate against COVID-19 by blocking the viral entry into the host cell.

Plants extracts from Cameroon pharmacopeia strongly inhibit the Chikungunya virus infection by targeting entry and replication steps

ETHNOPHARMACOLOGICAL RELEVANCE

Cameroon is one of the sub-Saharan African countries affected by Chikungunya virus (CHIKV). With the absence of approved treatment, this disease represents globally a major public health concern. Several plants are traditionally used in Cameroon for the treatment of virus induced fever and arthralgia. But to date there is no study that validate the efficacy of these plants for the treatment of Chikungunya virus infection.

AIM OF THE STUDY

This study aims to explore the inhition effect, mechanism of action of plant extracts against Chikungunya virus.

MATERIAL AND METHODS

An ethnobotanical survey conducted in some regions of Cameroon, led to the identification of nine medicinal plants used in traditional medicine for the healing of fever-related diseases and arthritis. Crude hydro-ethanolic extracts of each plant were prepared by maceration and their effects against CHIKV infection were investigated. CHIKV S27 strain was used to infection in Vero cell line. The antiviral activities were determined by plaque assay and/or RT-PCR targeting E1 envelope gene of CHIKV. Dose-response studies of the active plants were also determined by flow cytometry and Western blot.

RESULTS

Four extracts, Entada africana Guill et Pers. (E4), Entandrophragma cylindricum Sprague (EI), Khaya grandifoliola C. D.C. Sapindales (E2) and Macaranga hurifolia Beille (E6) showed antiviral activity with the half-maximal inhibitory concentration of 8.29; 8.14; 12.81 and 26.89 μg/mL respectively. All extracts were nontoxic up to the concentration of 100 μg/μL. Entandrophragma cylindricum Sprague (EI), Khaya grandifoliola C. D.C. Sapindales (E2), and Entada africana Guill et Pers. (E4) showed strong inhibition on the entry step of viral infection. At the same time, only Entandrophragma cylindricum Sprague (EI) inhibited the viral titer significantly in replication and intercellular assembly steps. Four plant extracts namely Entandrophragma cylindricum Sprague (EI), Macaranga hurifolia Beille (E6), Phragmentera capitata (Sprengel) Balle (E12), and Detarium microcarpum (E13) were effective against egression step.

CONCLUSIONS

Together, the results of this study showed anti-chikungunya activities of Entandrophragma cylindricum Sprague (EI) and Macaranga hurifolia Beille (E6), with therapeutics perspectives and can be promising sources of the development of anti-CHIKV molecule in future.

Contemporary exploitation of natural products for arthropod-borne pathogen transmission-blocking interventions

An integrated approach to innovatively counter the transmission of various arthropod-borne diseases to humans would benefit from strategies that sustainably limit onward passage of infective life cycle stages of pathogens and parasites to the insect vectors and vice versa. Aiming to accelerate the impetus towards a disease-free world amid the challenges posed by climate change, discovery, mindful exploitation and integration of active natural products in design of pathogen transmission-blocking interventions is of high priority. Herein, we provide a review of natural compounds endowed with blockade potential against transmissible forms of human pathogens reported in the last 2 decades from 2000 to 2021. Finally, we propose various translational strategies that can exploit these pathogen transmission-blocking natural products into design of novel and sustainable disease control interventions. In summary, tapping these compounds will potentially aid in integrated combat mission to reduce disease transmission trends.

Therapeutic Potential of Medicinal Plants against Dengue Infection: A Mechanistic Viewpoint

Dengue is a tropical disease caused by the Dengue virus (DENV), a positive-sense, single stranded RNA virus of the family Flaviviridae, which is transmitted by Aedes mosquitoes. The occurrence of dengue has grown dramatically around the globe in recent decades, and it is rapidly becoming a global burden. Furthermore, all four DENV serotypes cocirculate and create a problematic hyperendemic situation. Characteristic symptoms range from being asymptomatic, dengue fever to life-threatening complications such as hemorrhagic fever and shock. Apart from the inherent virulence of the virus strain, a dysregulated host immune response makes the condition worse. Currently, there is no highly recommended vaccine or therapeutic agent against dengue. With the advent of virus strains resistant to antiviral agents, there is a constant need for new therapies to be developed. Since time immemorial, human civilization has utilized plants in traditional medicine to treat various diseases, including infectious viral diseases. With the advancement in molecular biology, cell biology techniques, and bioinformatics, recent studies have tried to provide scientific evidence and determine the mechanism of anti-dengue activity of various plant extracts and plant-derived agents. The current Review consolidates the studies on the last 20 years of in vitro and in vivo experiments on the ethnomedicinal plants used against the dengue virus. Several active phytoconstituents like quercetin, castanospermine, α-mangostin, schisandrin-A, hirsutin have been found to be promising to inhibition of all the four DENV serotypes. However, novel therapeutics need to be reassessed in relevant cells using high-throughput techniques. Further, in vivo dose optimization for the immunomodulatory and antiviral activity should be examined on a vast sample size. Such a Review should help take the knowledge forward, validate it, and use medicinal plants in different combinations targeting multiple stages of virus infection for more effective multipronged therapy against dengue infection.

In Vitro and In Silico Antistaphylococcal Activity of Indole Alkaloids Isolated from Tabernaemontana cymosa Jacq (Apocynaceae)

The species of the genus Tabernaemontana have a long tradition of use in different pathologies of infectious origins; the antibacterial, antifungal, and antiviral effects related to the control of the pathologies where the species of this genus are used, have been attributed to the indole monoterpene alkaloids, mainly those of the iboga type. There are more than 1000 alkaloids isolated from different species of Tabernaemontana and other genera of the Apocynaceae family, several of which lack studies related to antibacterial activity. In the present study, four monoterpene indole alkaloids were isolated from the seeds of the species Tabernaemontana cymosa Jacq, namely voacangine (1), voacangine-7-hydroxyindolenine (2), 3-oxovoacangine (3), and rupicoline (4), which were tested in an in vitro antibacterial activity study against the bacteria S. aureus, sensitive and resistant to methicillin, and classified by the World Health Organization as critical for the investigation of new antibiotics. Of the four alkaloids tested, only voacangine was active against S. aureus, with an MIC of 50 µg/mL. In addition, an in silico study was carried out between the four isolated alkaloids and some proteins of this bacterium, finding that voacangine also showed binding to proteins involved in cell wall synthesis, mainly PBP2 and PBP2a.

Anti-Zika Virus Activity of Plant Extracts Containing Polyphenols and Triterpenes on Vero CCL-81 and Human Neuroblastoma SH-SY5Y Cells

Zika virus (ZIKV) infection is a global threat associated to neurological disorders in adults and microcephaly in children born to infected mothers. No vaccine or drug is available against ZIKV. We herein report the anti-ZIKV activity of 36 plant extracts containing polyphenols and/or triterpenes. ZIKV-infected Vero CCL-81 cells were treated with samples at non-cytotoxic concentrations, determined by MTT and LDH assays. One third of the extracts elicited concentration-dependent anti-ZIKV effect, with viral loads reduction from 0.4 to 3.8 log units. The 12 active extracts were tested on ZIKV-infected SH-SY5Y cells and significant reductions of viral loads (in log units) were induced by Maytenus ilicifolia (4.5 log), Terminalia phaeocarpa (3.7 log), Maytenus rigida (1.7 log) and Echinodorus grandiflorus (1.7 log) extracts. Median cytotoxic concentration (CC₅₀ ) of these extracts in Vero cells were higher than in SH-SY5Y lineage. M. ilicifolia (IC₅₀ =16.8±10.3 μg/mL, SI=3.4) and T. phaeocarpa (IC₅₀ =22.0±6.8 μg/mL, SI=4.8) were the most active extracts. UPLC-ESI-MS/MS analysis of M. ilicifolia extract led to the identification of 7 triterpenes, of which lupeol and a mixture of friedelin/friedelinol showed no activity against ZIKV. The composition of T. phaeocarpa extract comprises phenolic acids, ellagitannins and flavonoids, as recently reported by us. In conclusion, the anti-ZIKV activity of 12 plant extracts is here described for the first time and polyphenols and triterpenes were identified as the probable bioactive constituents of T. phaeocarpa and M. ilicifolia, respectively.

Mammea B/BA Isolated From the Seeds of Mammea americana L. (Calophyllaceae) is a Potent Inhibitor of Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus remains a pathogen of high concern in public health programs worldwide due to antibiotic resistance and emergence of highly virulent strains. Many phytochemicals have demonstrated activity against S. aureus and other Gram-positive bacteria, but the minimum inhibitory concentration (MIC) values comparable to commonly used antibiotics are needed. In the present study, bio-guided fractionation of the ethanol extract of seeds of Mammea americana L. (Calophyllaceae) throughout the antibacterial activity, against S. aureus strains that are sensitive and resistant to methicillin, led to the isolation of four coumarins identified as mammea B/BA, mammea B/BC, mammea A/AA cyclo D and mammea A/AA cyclo F, and a mixture of mammea B/BA cyclo F plus mammea B/BD cyclo F. The extract inhibited the growth of S. aureus with MIC values of 2–4 μg/ml and Mammea B/BA (MaBBA) presented MIC values in a range between 0.5 and 1.0 μg/ml in six methicillin-sensitive strains and eight methicillin-resistant strains evaluated. We consider MaBBA the most potent of all mammea coumarins reported to date, according to the literature review carried out at the time of writing of this article. Toxicity assessment in vivo against the nematode Caenorhabditis elegans and in vitro against human fibroblasts of the extract and the compound MaBBA indicated that both had low toxicity.

Pharmacological perspectives and molecular mechanisms of coumarin derivatives against virus disease

Infections caused by viruses are one of the foremost causes of morbidity and mortality in the world. Although a number of antiviral drugs are currently used for treatment of various kinds of viral infection diseases, there is still no available therapeutic agent for most of the viruses in clinical practice. Coumarin is a chemical compound which is found naturally in a variety of plants, it can also be synthetically produced possessing diverse biological effects. More recently, reports have highlighted the potential role of coumarin derivatives as antiviral agents. This review outlines the advances in coumarin-based compounds against various viruses including human immunodeficiency virus, hepatitis virus, herpes simplex virus, Chikungunya virus and Enterovirus 71, as well as the structure activity relationship and the possible mechanism of action of the most potent coumarin derivatives.

A systematic literature review of clinical trials and therapeutic applications of ibogaine

BACKGROUND

Iboga and its primary alkaloids, ibogaine and noribogaine, have been of interest to researchers and practitioners, mainly due to their putative efficacy in treating substance use disorders (SUDs). For many SUDs, still no effective pharmacotherapies exist. Distinct psychoactive and somatic effects of the iboga alkaloids set them apart from classic hallucinogens like LSD, mescaline, and psilocybin.

AIMS

The study team performed this systematic review focusing on clinical data and therapeutic interventions involving ibogaine and noribogaine.

METHODS

The team conducted a search for all publications up to December 7, 2020, using PubMed and Embase following PRISMA guidelines.

RESULTS

In total, we identified 743 records. In this review, we consider 24 studies, which included 705 individuals receiving ibogaine or noribogaine. This review includes two randomized, double-blind, controlled clinical trials, one double-blind controlled clinical trial, 17 open-label studies or case series (including observational or retrospective studies), three case reports, and one retrospective survey. The published data suggest that ibogaine is an effective therapeutic intervention within the context of SUDs, reducing withdrawal symptoms and craving. Data also point toward a beneficial impact on depressive and trauma-related psychological symptoms. However, studies have reported severe medical complications and deaths, which seem to be associated with neuro- and cardiotoxic effects of ibogaine. Two of these fatalities were described in the 24 studies included in this review.

CONCLUSION

Treatment of SUDs and persisting comorbidities requires innovative treatment approaches. Rapid-onset therapies such as the application of ibogaine may offer novel treatment opportunities for specific individuals. Rigorous study designs within medical settings are necessary to warrant safe application, monitoring, and, possibly, medical intervention.

A Preliminary Investigation on the Antiviral Activities of the Philippine Marshmint (Mentha arvensis) Leaf Extracts against Dengue Virus Serotype 2 In Vitro

In this study, we investigated the antiviral activity of lyophilized crude leaf extracts of the Philippine marshmint (Mentha arvensis L., commonly called yerba buena) against DENV-2 in vitro. The plant specimen was authenticated by DNA barcoding analysis using standard primers for amplification of rbcL, matK, ITS1, ITS2 and trnH-psbA. Aqueous, methanol and ethanol leaf extracts were prepared, and lyophilized prior to testing for its cytotoxicity and antiviral activities. All extracts presented cytotoxic activities against Vero cells in a dose-dependent manner. Half maximal cytotoxicity concentration (CC50) was calculated at 2,889.60 µg/mL for the aqueous extract, 1,928.62 µg/mL for the methanol extract, and 3,380.30 µg/mL for the ethanol extract. Antiviral activities assessed by plaque reduction assay revealed reduced DENV-2 viral infectivity, with the ethanol extract observed to have the strongest activity decreasing plaque numbers by 62% relative to the control. The methanol extract was observed to be most effective when added before infection causing 72% reduction in plaque numbers, whereas none of the extracts inhibited plaque formation by more than 40% when added after infection. DENV-2 NS1 antigen production was significantly reduced by the methanol extract, while viral RNA levels were also decreased as determined by real time RT-PCR. Phytochemical analysis revealed the presence of flavonoids, phenolics, tannins, proteins, reducing sugars and saponins. Our preliminary results are promising, however, it should be interpreted with caution as further studies are needed to establish its potential therapeutic application against dengue infection.

Lupeol acetate isolated from Chrysophyllum cainito L. fruit as a template for the synthesis of N-alkyl-arylsulfonamide derivatives and their synergistic effects with metronidazole against Trichomonas vaginalis

Pentacyclic triterpenes are found in a great variety of natural products and constitute an organic template for the development of new derivative compounds with therapeutic applications. In the present work, lupeol acetate isolated from Chrysophyllum cainito L. fruit was used as a template for the synthesis of novel N-alkyl-arylsulfonamide derivatives, and their synergistic effects with metronidazole against strains of Trichomonas vaginalis were tested. A library of 18 derivatives was synthesized. Ten compounds exhibited an IC₅₀ < 100 μM against a metronidazole-sensitive strain of T. vaginalis. Only seven of these compounds (12, 15, 18-22) also showed activity against metronidazole-resistant strains. The compounds 20 (N-cyclohexyl-p-chlorobenzenesulfonamidolupeol acetate) and 22 (N-cyclohexyl-p-nitrobenzenesulfonamidolupeol acetate) exhibited a similar IC₅₀ against both susceptible and resistant T. vaginalis strains and enhanced the efficacy of metronidazole in a partial and total synergistic way, respectively. These data provided evidence of the trichomonicidal effect of N-alkyl-arylsulfonamide derivatives of lupeol acetate, representing highly promising novel antiparasitic agents.

Production, Transmission, Pathogenesis, and Control of Dengue Virus: A Literature-Based Undivided Perspective

Dengue remains one of the most serious and widespread mosquito-borne viral infections in human beings, with serious health problems or even death. About 50 to 100 million people are newly infected annually, with almost 2.5 billion people living at risk and resulting in 20,000 deaths. Dengue virus infection is especially transmitted through bites of Aedes mosquitos, hugely spread in tropical and subtropical environments, mostly found in urban and semiurban areas. Unfortunately, there is no particular therapeutic approach, but prevention, adequate consciousness, detection at earlier stage of viral infection, and appropriate medical care can lower the fatality rates. This review offers a comprehensive view of production, transmission, pathogenesis, and control measures of the dengue virus and its vectors.

Plant-Based Natural Products and Extracts: Potential Source to Develop New Antiviral Drug Candidates

Viral infections are among the most complex medical problems and have been a major threat to the economy and global health. Several epidemics and pandemics have occurred due to viruses, which has led to a significant increase in mortality and morbidity rates. Natural products have always been an inspiration and source for new drug development because of their various uses. Among all-natural sources, plant sources are the most dominant for the discovery of new therapeutic agents due to their chemical and structural diversity. Despite the traditional use and potential source for drug development, natural products have gained little attention from large pharmaceutical industries. Several plant extracts and isolated compounds have been extensively studied and explored for antiviral properties against different strains of viruses. In this review, we have compiled antiviral plant extracts and natural products isolated from plants reported since 2015.

Indole alkaloids inhibit zika and chikungunya virus infection in different cell lines

BACKGROUND

In recent years, an increase in the occurrence of illnesses caused by two clinically- important arboviruses has been reported: Zika virus (ZIKV) and Chikungunya virus (CHIKV). There is no licensed antiviral treatment for either of the two abovementioned viruses. Bearing in mind that the antiviral effect of indole alkaloids has been reported for other arboviral models, the present study proposed to evaluate the antiviral in vitro and in silico effects of four indole alkaloids on infections by these two viruses in different cell lines.

METHODS

The antiviral effects of voacangine (VOAC), voacangine-7-hydroxyindolenine (VOAC-OH), rupicoline and 3-oxo voacangine (OXO-VOAC) were evaluated in Vero, U937 and A549 cells using different experimental strategies (Pre, Trans, Post and combined treatment). Viral infection was quantified by different methodologies, including infectious viral particles by plating, viral genome by RT-qPCR, and viral protein by cell ELISA. Moreover, molecular docking was used to evaluate the possible interactions between structural and nonstructural viral proteins and the compounds. The results obtained from the antiviral strategies for each experimental condition were compared in all cases with the untreated controls. Statistically significant differences were identified using a parametric Student's t-test. In all cases, p values below 0.05 (p < 0.05) were considered statistically significant.

RESULTS

In the pre-treatment strategy in Vero cells, VOAC and VOAC-OH inhibited both viral models and OXO-VOAC inhibited only ZIKV; in U937 cells infected with CHIKV/Col, only VOAC-OH inhibited infection, but none of the compounds had activity in A549 cells; in U937 cells and A549 cells infected with ZIKV/Col, the three compounds that were effective in Vero cells also had antiviral activity. In the trans-treatment strategy, only VOAC-OH was virucidal against ZIKV/Col. In the post-treatment strategy, only rupicoline was effective in the CHIKV/Col model in Vero and A549 cells, whereas VOAC and VOAC-OH inhibited ZIKV infection in all three cell lines. In the combined strategy, VOAC, VOAC-OH and rupicoline inhibited CHIKV/Col and ZIKV/Col, but only rupicoline improved the antiviral effect of ZIKV/Col-infected cultures with respect to the individual strategies. Molecular docking showed that all the compounds had favorable binding energies with the structural proteins E2 and NSP2 (CHIKV) and E and NS5 (ZIKV).

CONCLUSIONS

The present study demonstrates that indole alkaloids are promising antiviral drugs in the process of ZIKV and CHIKV infection; however, the mechanisms of action evaluated in this study would indicate that the effect is different in each viral model and, in turn, dependent on the cell line.

Phytoconstituents as Lead Compounds for Anti-Dengue Drug Discovery

Dengue is an arthropod-borne viral disease common in subtropical and tropical regions. The widespread use of traditional medicines in these regions for dengue fever (DF) has encouraged researchers to explore the therapeutic effect of herbs and their phytochemicals in dengue infection. Phytochemicals such as quercetin, baicalein, luteolin, oxindole alkaloids, celastrol and geraniin have shown significant inhibition of dengue virus in vitro. Many phytoconstituents have better selectivity index supporting their safety profile for future development. However, in vivo studies supporting therapeutic potency for these active phytoconstituents are limited. There is a need for studies translating anti-dengue profile of active phytoconstituents to find successful anti-dengue compounds.

The Antiviral and Virucidal Activities of Voacangine and Structural Analogs Extracted from Tabernaemontana cymosa Depend on the Dengue Virus Strain

Currently, no specific licensed antiviral exists for treating the illness caused by dengue virus (DENV). Therefore, the search for compounds of natural origin with antiviral activity is an important area of research. In the present study, three compounds were isolated and identified from seeds of Tabernaemontana cymosa plants. The in vitro antiviral effect of those compounds and voacangine against different DENV strains was assessed using different experimental approaches: compounds added before the infection (Pre), at the same time with the virus (Trans), after the infection (Post) or compounds present in all moments of the experiment (Pre-Trans-Post, Combined treatment). In silico studies (docking and molecular dynamics) were also performed to explain the possible antiviral mechanisms. The identified compounds were three structural analogs of voacangine (voacangine-7-hydroxyindolenine, rupicoline and 3-oxo-voacangine). In the Pre-treatment, only voacangine-7-hydroxyindolenine and rupicoline inhibited the infection caused by the DENV-2/NG strain (16.4% and 29.6% infection, respectively). In the Trans-treatment approach, voacangine, voacangine-7-hydroxyindolenine and rupicoline inhibited the infection in both DENV-2/NG (11.2%, 80.4% and 75.7% infection, respectively) and DENV-2/16681 infection models (73.7%, 74.0% and 75.3% infection, respectively). The latter strain was also inhibited by 3-oxo-voacangine (82.8% infection). Moreover, voacangine (most effective virucidal agent) was also effective against one strain of DENV-1 (DENV-1/WestPac/74) and against the third strain of DENV-2 (DENV-2/S16803) (48.5% and 32.4% infection, respectively). Conversely, no inhibition was observed in the post-treatment approach. The last approach (combined) showed that voacangine, voacangine-7-hydroxyindolenine and rupicoline inhibited over 90% of infections (3.5%, 6.9% and 3.5% infection, respectively) of both strains (DENV-2/NG and DENV-2/16681). The free energy of binding obtained with an in silico approach was favorable for the E protein and compounds, which ranged between −5.1 and −6.3 kcal/mol. Finally, the complex formed between DENV-2 E protein and the best virucidal compound was stable for 50 ns. Our results show that the antiviral effect of indole alkaloids derived from T. cymose depends on the serotype and the virus strain.

Molecular Human Targets of Bioactive Alkaloid-Type Compounds from Tabernaemontana cymose Jacq

Alkaloids are a group of secondary metabolites that have been widely studied for the discovery of new drugs due to their properties on the central nervous system and their anti-inflammatory, antioxidant and anti-cancer activities. Molecular docking was performed for 10 indole alkaloids identified in the ethanol extract of Tabernaemontana cymosa Jacq. with 951 human targets involved in different diseases. The results were analyzed through the KEGG and STRING databases, finding the most relevant physiological associations for alkaloids. The molecule 5-oxocoronaridine proved to be the most active molecule against human proteins (binding energy affinity average = −9.2 kcal/mol) and the analysis of the interactions between the affected proteins pointed to the PI3K/ Akt/mTOR signaling pathway as the main target. The above indicates that indole alkaloids from T. cymosa constitute a promising source for the search and development of new treatments against different types of cancer.

Potent phytochemicals against COVID-19 infection from phyto-materials used as antivirals in complementary medicines: a review

Background

Following the outbreak of the COVID-19 pandemic, there was a surge of research activity to find methods/drugs to treat it. There has been drug-repurposing research focusing on traditional medicines. Concomitantly, many researchers tried to find in silico evidence for traditional medicines. There is a great increase in article publication to commensurate the new-found research interests. This situation inspired the authors to have a comprehensive understanding of the multitude of publications related to the COVID-19 pandemic with a wish to get promising drug leads.

Main body

This review article has been conceived and made as a hybrid of the review of the selected papers advertised recently and produced in the interest of the COVID-19 situation, and in silico work done by the authors. The outcome of the present review underscores a recommendation for thorough MDS analyses of the promising drug leads. The inclusion of in silico work as an addition to the review was motivated by a recently published article of Toelzer and colleagues. The in silico investigation of free fatty acids is novel to the field and it buttresses the further MDS analysis of drug leads for managing the COVID-19 pandemic.

Conclusion

The review performed threw light on the need for MDS analyses to be considered together with the application of other in silico methods of prediction of pharmacologic properties directing towards the sites of drug-receptor regulation. Also, the present analysis would help formulate new recipes for complementary medicines.

In Vitro and In Silico Anti-Arboviral Activities of Dihalogenated Phenolic Derivates of L-Tyrosine

Despite the serious public health problem represented by the diseases caused by dengue (DENV), Zika (ZIKV) and chikungunya (CHIKV) viruses, there are still no specific licensed antivirals available for their treatment. Here, we examined the potential anti-arbovirus activity of ten di-halogenated compounds derived from L-tyrosine with modifications in amine and carboxyl groups. The activity of compounds on VERO cell line infection and the possible mechanism of action of the most promising compounds were evaluated. Finally, molecular docking between the compounds and viral and cellular proteins was evaluated in silico with Autodock Vina®, and the molecular dynamic with Gromacs®. Only two compounds (TDC-2M-ME and TDB-2M-ME) inhibited both ZIKV and CHIKV. Within the possible mechanism, in CHIKV, the two compounds decreased the number of genome copies and in the pre-treatment strategy the infectious viral particles. In the ZIKV model, only TDB-2M-ME inhibited the viral protein and demonstrate a virucidal effect. Moreover, in the U937 cell line infected with CHIKV, both compounds inhibited the viral protein and TDB-2M-ME inhibited the viral genome too. Finally, the in silico results showed a favorable binding energy between the compounds and the helicases of both viral models, the NSP3 of CHIKV and cellular proteins DDC and β2 adrenoreceptor.

In silico approach of secondary metabolites from Brazilian herbal medicines to search for potential drugs against SARS-CoV-2

The new severe acute respiratory syndrome coronavirus (SARS‐CoV‐2) recently emerged as a worrying pandemic, with many confirmed cases and deaths globally. Therefore, there is a clear need for identifying effective therapeutic options and a review of secondary metabolites related to Brazilian herbal medicines was performed as a strategy for the discovery of new antiviral agents. To confirm this potential, an in silico screening of the identified compounds identified was also evaluated. The review was performed by the PubMed database and the selected natural compounds were subjected to in silico analysis such as QSAR, molecular docking and ADMET. 497 secondary metabolites were identified from 23 species. The in silico assays indicated 19 potential anti‐SARS‐CoV‐2 compounds, being triterpenes and phenolic compounds. The indicated compounds showed a high affinity with proteins considered as the main molecular targets against SARS‐CoV‐2 and parameters indicated low toxicity. In addition to Brazilian medicinal plants, these compounds can be found in other species and they can be a base for the synthesis of other anti‐COVID‐19 drugs. Therefore, this review is important to conduct researches that address the emerging need for drugs in COVID‐19 treatment.

Major Bioactive Alkaloids and Biological Activities of Tabernaemontana Species (Apocynaceae)

Several species belonging to the genus Tabernaemontana have been well researched and utilized for their wide-ranging biological activities. A few of the most prominent species include Tabernaemontana divaricata, Tabernaemontana catharinensis, Tabernaemontana crassa, and Tabernaemontana elegans. These species and many others within the genus often display pharmacological importance, which is habitually related to their chemical constituents. The secondary metabolites within the genus have demonstrated huge medicinal potential for the treatment of infections, pain, injuries, and various diseases. Regardless of the indispensable reports and properties displayed by Tabernaemontana spp., there remains a wide variety of plants that are yet to be considered or examined. Thus, an additional inclusive study on species within this genus is essential. The current review aimed to extensively analyze, collate, and describe an updated report of the current literature related to the major alkaloidal components and biological activities of species within the genus Tabernaemontana.

A systematic review on phytochemicals for the treatment of dengue

Dengue fever is prevalent in subtopic regions, producing mortality and morbidity worldwide, which have been of major concern to different governments and World Health Organization. The search of new anti-dengue agents from phytochemicals was assumed to be highly emergent in past. The phytochemicals have been used in wide distribution of vector ailments such as malaria. The demand of the phytochemicals is based on the medicines which are mostly considered to be safer, less harmful than synthetic drugs and nontoxic. This review mentions majorly about the phytochemicals potentially inhibiting dengue fever around the world. The phytochemicals have been isolated from different species, have potential for the treatment of dengue. Different crude extracts and essential oils obtained from different species showed a broad activity against different phytochemicals. The current studies showed that natural products represent a rich source of medicines toward the dengue fever. Furthermore, ethnobotanical surveys and laboratory investigation established identified natural plants species in the development of drug discovery to control the dengue fever.

Antivirals against Chikungunya Virus: Is the Solution in Nature?

The worldwide outbreaks of the chikungunya virus (CHIKV) in the last years demonstrated the need for studies to screen antivirals against CHIKV. The virus was first isolated in Tanzania in 1952 and was responsible for outbreaks in Africa and Southwest Asia in subsequent years. Between 2007 and 2014, some cases were documented in Europe and America. The infection is associated with low rates of death; however, it can progress to a chronic disease characterized by severe arthralgias in infected patients. This infection is also associated with Guillain–Barré syndrome. There is no specific antivirus against CHIKV. Treatment of infected patients is palliative and based on analgesics and non-steroidal anti-inflammatory drugs to reduce arthralgias. Several natural molecules have been described as antiviruses against viruses such as dengue, yellow fever, hepatitis C, and influenza. This review aims to summarize the natural compounds that have demonstrated antiviral activity against chikungunya virus in vitro.

Coumarin: An emerging antiviral agent

Viral infections are responsible for many illnesses, and recent outbreaks have raised public health concerns. Despite the availability of many antiviral drugs, they are often unsuccessful due to the generation of viral mutants and less effective against their target virus. Identifying novel antiviral drugs is therefore of critical importance and natural products are an excellent source for such discoveries. Coumarin is one such natural compound that is a potential drug candidate owing to its properties of stability, solubility, and low toxicity. There are numerous evidences showing its inhibitory role against infection of various viruses such as HIV, Influenza, Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16). The mechanisms involve either inhibition of proteins essential for viral entry, replication and infection or regulation of cellular pathways such as Akt-Mtor (mammalian target of rapamycin), NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells), and anti-oxidative pathway including NrF-2 (The nuclear factor erythroid 2 (NFE2)-related factor 2). This review summarizes the present state of understanding with a focus on coumarin's antiviral effect and their possible molecular mechanisms against Influenza virus, HIV, Hepatitis virus, Dengue virus and Chikungunya virus.

In vitro and in silico anti-dengue activity of compounds obtained from Psidium guajava through bioprospecting

BACKGROUND

For decades, bioprospecting has proven to be useful for the identification of compounds with pharmacological potential. Considering the great diversity of Colombian plants and the serious worldwide public health problem of dengue-a disease caused by the dengue virus (DENV)-in the present study, we evaluated the anti-DENV effects of 12 ethanolic extracts derived from plants collected in the Colombian Caribbean coast, and 5 fractions and 5 compounds derived from Psidium guajava.

METHODS

The cytotoxicity and antiviral effect of 12 ethanolic extracts derived from plants collected in the Colombian Caribbean coast was evaluated in epithelial VERO cells. Five fractions were obtained by open column chromatography from the ethanolic extract with the highest selectivity index (SI) (derived from P. guajava, SI: 128.2). From the fraction with the highest selectivity (Pg-YP-I-22C, SI: 35.5), five compounds were identified by one- and two-dimensional nuclear magnetic resonance spectroscopy. The antiviral effect in vitro of the fractions and compounds was evaluated by different experimental strategies (Pre- and post-treatment) using non-toxic concentrations calculated by MTT method. The DENV inhibition was evaluated by plate focus assay. The results were analyzed by means of statistical analysis using Student's t-test. Finally the antiviral effect in Silico was evaluated by molecular docking.

RESULTS

In vitro evaluation of these compounds showed that three of them (gallic acid, quercetin, and catechin) were promising antivirals as they inhibit the production of infectious viral particles via different experimental strategies, with the best antiviral being catechin (100% inhibition with a pre-treatment strategy and 91.8% with a post-treatment strategy). When testing the interactions of these compounds with the viral envelope protein in silico by docking, only naringin and hesperidin had better scores than the theoretical threshold of - 7.0 kcal/mol (- 8.0 kcal/mol and - 8.2 kcal/mol, respectively). All ligands tested except gallic acid showed higher affinity to the NS5 protein than the theoretical threshold.

CONCLUSION

Even though bioprospecting has recently been replaced by more targeted tools for identifying compounds with pharmacological potential, our results show it is still useful for this purpose. Additionally, combining in vitro and in silico evaluations allowed us to identify promising antivirals as well as their possible mechanisms of action.

Recent update on anti-dengue drug discovery

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

Tomatidine, a novel antiviral compound towards dengue virus

Dengue is the most common arboviral disease worldwide with 96 million symptomatic cases annually. Despite its major impact on global human health and huge economic burden there is no antiviral drug available to treat the disease. The first tetravalent dengue virus vaccine was licensed in 2015 for individuals aged 9 to 45, however, most cases are reported in infants and young children. This, together with the limited efficacy of the vaccine to dengue virus (DENV) serotype 2, stresses the need to continue the search for compounds with antiviral activity to DENV. In this report, we describe tomatidine as a novel compound with potent antiviral properties towards all DENV serotypes and the related Zika virus. The strongest effect was observed for DENV-2 with an EC50 and EC90 value of 0.82 and 1.61 μM, respectively, following infection of Huh7 cells at multiplicity of infection of 1. The selectivity index is 97.7. Time-of-drug-addition experiments revealed that tomatidine inhibits virus particle production when added pre, during and up to 12 h post-infection. Subsequent experiments show that tomatidine predominantly acts at a step after virus-cell binding and membrane fusion but prior to the secretion of progeny virions. Tomatidine was found to control the expression of the cellular protein activating transcription factor 4 (ATF4), yet, this protein is not solely responsible for the observed antiviral effect. Here, we propose tomatidine as a candidate for the treatment of dengue given its potent antiviral activity.

Prediction of binding potential of natural leads against the prioritized drug targets of chikungunya and dengue viruses by computational screening

The current study aimed to assess the binding potential of herbal lead molecules against the prioritized molecular targets of chikungunya virus (CHIKV) and dengue virus (DENV) by computational virtual screening and suggests a novel therapeutic intervention. Based on the metabolic pathway analysis and virulent functions, the non-structural and envelop proteins present in CHIKV and DENV were identified as putative drug targets. The structures of the protein not available in their native forms were computationally predicted by homology modeling. The lead compounds from 43 herbal sources were screened and their drug likeliness and pharmacokinetics properties were computationally predicted. The binding potential of selected phytoligands against the prioritized drug targets were analyzed by molecular docking studies. This study revealed that Kaempferol (3,5,7-trihydroxy-2-(4-hydroxyphenyl)chromen-4-one) and Chymopain (disodium;4,5-dihydroxybenzene-1,3-disulfonate), natural flavonols present in Carica papaya and Gossypetin (3, 5, 7, 8, 3', 4'-hexahydroxyflavone), a natural flavonoid available in Hibiscus sabdariffa were demonstrated promising good binding potential with minimum binding energy (kcal/mol) and maximum stabilizing interactions to the putative drug targets of CHIKV and DENV. The selected lead molecules demonstrated ideal drug likeliness, ADMET (adsorption, distribution, excretion, metabolism and toxicity) features required for the drug development. The molecular docking studies suggested that the presence of these compounds probably responsible for the antiviral properties of Carica papaya, which was traditionally known as therapeutic remedy for dengue viral infections. This study provides profound insight for the experimental validation of the applied approach and industrial scale-up of the suggested herbal lead molecules as promising lead candidates against CHIKV and DENV infections.

Role of mitogen-activated protein kinase signaling in the pathogenesis of dengue virus infection

Dengue virus (DENV) infection is a disease that is endemic to many parts of the world, and its increasing prevalence ranks it among the diseases considered to be a significant threat to public health. The clinical manifestations of DENV infection range from mild dengue fever (DF) to more severe dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Increased proinflammatory cytokines and vascular permeability, both of which cause organ injury, are the hallmarks of severe dengue disease. Signs of liver injury were observed in studies using hepatic cell lines, mouse models, and autopsy specimens from DENV-infected patients, and these signs substantiated the effects of inflammatory responses and hepatic cell apoptosis. Mitogen-activated protein kinases (MAPK) are involved in inflammatory responses and cellular stress during viral infections. The roles of MAPK signaling in DENV infection were reviewed, and published data indicate MAPK signaling to be involved in inflammatory responses and hepatic cell apoptosis in both in vitro cultures and in vivo models. Modulation of MAPK signaling ameliorates the inflammatory responses and hepatic cell apoptosis in DENV infection. This accumulation of published data relative to the role of MAPK signaling in inflammatory responses and cell apoptosis in DENV infection is elucidatory, and may help to accelerate the development of novel or repositioned therapies to treat this unpredictable and often debilitating disease.

Co-circulation and simultaneous co-infection of dengue, chikungunya, and zika viruses in patients with febrile syndrome at the Colombian-Venezuelan border

BACKGROUND

In Colombia, the dengue virus (DENV) has been endemic for decades, and with the recent entry of the chikungunya virus (CHIKV) (2014) and the Zika virus (ZIKV) (2015), health systems are overloaded because the diagnosis of these three diseases is based on clinical symptoms, and the three diseases share a symptomatology of febrile syndrome. Thus, the objective of this study was to use molecular methods to identify their co-circulation as well as the prevalence of co-infections, in a cohort of patients at the Colombian-Venezuelan border.

METHODS

A total of 157 serum samples from patients with febrile syndrome consistent with DENV were collected after informed consent and processed for the identification of DENV (conventional PCR and real-time PCR), CHIKV (conventional PCR), and ZIKV (real-time PCR). DENV-positive samples were serotyped, and some of those positive for DENV and CHIKV were sequenced.

RESULTS

Eighty-two patients were positive for one or more viruses: 33 (21.02%) for DENV, 47 (29.94%) for CHIKV, and 29 (18.47%) for ZIKV. The mean age range of the infected population was statistically higher in the patients infected with ZIKV (29.72 years) than in those infected with DENV or CHIKV (21.09 years). Both co-circulation and co-infection of these three viruses was found. The prevalence of DENV/CHIKV, DENV/ZIKV, and CHIKV/ZIKV co-infection was 7.64%, 6.37%, and 5.10%, with attack rates of 14.90, 12.42, and 9.93 cases per 100,000 inhabitants, respectively. Furthermore, three patients were found to be co-infected with all three viruses (prevalence of 1.91%), with an attack rate of 4.96 cases per 100,000 inhabitants.

CONCLUSION

Our results demonstrate the simultaneous co-circulation of DENV, CHIKV, ZIKV and their co-infections at the Colombian-Venezuelan border. Moreover, it is necessary to improve the differential diagnosis in patients with acute febrile syndrome and to study the possible consequences of this epidemiological overview of the clinical outcomes of these diseases in endemic regions.

Vaccine and Therapeutic Options To Control Chikungunya Virus

Beginning in 2004, chikungunya virus (CHIKV) went from an endemic pathogen limited to Africa and Asia that caused periodic outbreaks to a global pathogen. Given that outbreaks caused by CHIKV have continued and expanded, serious consideration must be given to identifying potential options for vaccines and therapeutics. Currently, there are no licensed products in this realm, and control relies completely on the use of personal protective measures and integrated vector control, which are only minimally effective. Therefore, it is prudent to urgently examine further possibilities for control. Vaccines have been shown to be highly effective against vector-borne diseases. However, as CHIKV is known to rapidly spread and generate high attack rates, therapeutics would also be highly valuable. Several candidates are currently being developed; this review describes the multiple options under consideration for future development and assesses their relative advantages and disadvantages.

Advances in Developing Therapies to Combat Zika Virus: Current Knowledge and Future Perspectives

Zika virus (ZIKV) remained largely quiescent for nearly six decades after its first appearance in 1947. ZIKV reappeared after 2007, resulting in a declaration of an international "public health emergency" in 2016 by the World Health Organization (WHO). Until this time, ZIKV was considered to induce only mild illness, but it has now been established as the cause of severe clinical manifestations, including fetal anomalies, neurological problems, and autoimmune disorders. Infection during pregnancy can cause congenital brain abnormalities, including microcephaly and neurological degeneration, and in other cases, Guillain-Barré syndrome, making infections with ZIKV a substantial public health concern. Genomic and molecular investigations are underway to investigate ZIKV pathology and its recent enhanced pathogenicity, as well as to design safe and potent vaccines, drugs, and therapeutics. This review describes progress in the design and development of various anti-ZIKV therapeutics, including drugs targeting virus entry into cells and the helicase protein, nucleosides, inhibitors of NS3 protein, small molecules, methyltransferase inhibitors, interferons, repurposed drugs, drugs designed with the aid of computers, neutralizing antibodies, convalescent serum, antibodies that limit antibody-dependent enhancement, and herbal medicines. Additionally, covalent inhibitors of viral protein expression and anti-Toll-like receptor molecules are discussed. To counter ZIKV-associated disease, we need to make rapid progress in developing novel therapies that work effectually to inhibit ZIKV.