Tomatidine, a natural steroidal alkaloid shows antiviral activity towards chikungunya virus in vitro

Review on toxicology and activity of tomato glycoalkaloids in immature tomatoes

Owing to the lack of selection and limited intelligence in mechanical picking, some immature tomatoes that contain alkaloids are thrown away. Tomatine alkaloids are steroidal alkaloids naturally present in Solanaceae plants, which are distributed in small amounts in immature tomato fruits and decrease as the fruits ripen. Tomato glycoalkaloids are harmful to human health. However, in small quantities, there is some evidence that these compounds might be beneficial, as other non-antioxidant bioactivities. This article considers recent research on the biological effects of tomato glycoalkaloids in immature tomatoes, providing reference value for the potential development of these compounds.

Untargeted metabolomics for lifestyle biomarker discovery in human hair

There is a risk of crimes remaining unsolved when no matching DNA profiles or fingermarks are found. If this is the case, forensic investigations are faced with a significant shortage of evidence and information regarding the unknown perpetrator and/or victim as well as any missing persons. However, a rather commonly found biological trace encountered at crime scenes is human hair. As hair acts as a biochemical reservoir, it may contain valuable information regarding one's characteristics and habits. This study aimed to build an analytical method capable of determining a marker set of relevant metabolites in hair, eventually building up a profile of its donor. To find potential markers, an untargeted metabolomics approach was developed to select and identify statistically significant features. For that purpose, a total of 68 hair samples were collected at several hairdresser shops in varying neighbourhoods. Compound extraction was achieved via methanolic incubation overnight and analysis performed using a high-resolution mass spectrometry (HRMS) Orbitrap Q Exactive Focus. The acquired data was uploaded and statistically evaluated using two free online software/libraries, where a total of eight compounds have given a match on both tools. Their presumptive identity was confirmed using reference standards and consequently added to a dynamic target donor profiling list. These results show the potential of using untargeted metabolomics for the search for lifestyle biomarkers capable of differentiating individuals. Such tools are of paramount importance in a forensic setting with little or no evidence available and no clear tactical leads.

Antiherpetic Activity of a Root Exudate from Solanum lycopersicum

The rise of drug resistance to antivirals poses a significant global concern for public health; therefore, there is a pressing need to identify novel compounds that can effectively counteract strains resistant to current antiviral treatments. In light of this, researchers have been exploring new approaches, including the investigation of natural compounds as alternative sources for developing potent antiviral therapies. Thus, this work aimed to evaluate the antiviral properties of the organic-soluble fraction of a root exudate derived from the tomato plant Solanum lycopersicum in the context of herpesvirus infections. Our findings demonstrated that a root exudate from Solanum lycopersicum exhibits remarkable efficacy against prominent members of the family Herpesviridae, specifically herpes simplex virus type 1 (HSV-1) (EC50 25.57 µg/mL, SI > 15.64) and human cytomegalovirus (HCMV) (EC50 9.17 µg/mL, SI 32.28) by inhibiting a molecular event during the herpesvirus replication phase. Moreover, the phytochemical fingerprint of the Solanum lycopersicum root exudate was characterized through mass spectrometry. Overall, these data have unveiled a novel natural product with antiherpetic activity, presenting a promising and valuable alternative to existing drugs.

In Vitro Analyses of the Multifocal Effects of Natural Alkaloids Berberine, Matrine, and Tabersonine against the O'nyong-nyong Arthritogenic Alphavirus Infection and Inflammation

O'nyong-nyong virus (ONNV) is a member of the reemerging arthritogenic alphaviruses that cause chronic debilitating polyarthralgia and/or polyarthritis via their tropism for the musculoskeletal system. Thus, the discovery of dual antiviral and anti-inflammatory drugs is a great challenge in this field. We investigated the effects of the common plant-derived alkaloids berberine (isoquinoline), matrine (quinolizidine), and tabersonine (indole) at a non-toxic concentration (10 μM) on a human fibroblast cell line (HS633T) infected by ONNV (MOI 1). Using qRT-PCR analyses, we measured the RNA levels of the gene coding for the viral proteins and for the host cell immune factors. These alkaloids demonstrated multifocal effects by the inhibition of viral replication, as well as the regulation of the type-I interferon antiviral signaling pathway and the inflammatory mediators and pathways. Berberine and tabersonine proved to be the more valuable compounds. The results supported the proposal that these common alkaloids may be useful scaffolds for drug discovery against arthritogenic alphavirus infection.

Biofilm stimulating activity of solanidine and Solasodine in Pseudomonas aeruginosa

BACKGROUND

Biofilm formation has reported as an important virulence associated properties of Pseudomonas aeruginosa that is regulated by quorum-sensing associated genes. Biofilm and quorum-sensing interfering properties of steroidal alkaloids, Solanidine and Solasodine were investigated in the present study.

RESULTS

Biofilm formation capacity and relative expression level of five studied genes(lasI, lasR, rhlI, rhlR and algD) were significantly increased dose-dependently after treatment with sub-inhibitory concentrations (32 and 512 µg/ml) of the both Solanidine and Solasodine. Biofilm formation capacity was more stimulated in weak biofilm formers(9 iaolates) in comparison to the strong biofilm producers(11 isolates). The lasI gene was the most induced QS-associated gene among five investigated genes.

CONCLUSION

Biofilm inducing properties of the plants alkaloids and probably medicines derived from them has to be considered for revision of therapeutic guidelines. Investigating the biofilm stimulating properties of corticosteroids and other medicines that comes from plant alkaloids also strongly proposed.

The Therapeutic Value of Solanum Steroidal (Glyco)Alkaloids: A 10-Year Comprehensive Review

Steroidal (glycol)alkaloids S(G)As are secondary metabolites made of a nitrogen-containing steroidal skeleton linked to a (poly)saccharide, naturally occurring in the members of the Solanaceae and Liliaceae plant families. The genus Solanum is familiar to all of us as a food source (tomato, potato, eggplant), but a few populations have also made it part of their ethnobotany for their medicinal properties. The recent development of the isolation, purification and analysis techniques have shed light on the structural diversity among the SGAs family, thus attracting scientists to investigate their various pharmacological properties. This review aims to overview the recent literature (2012-2022) on the pharmacological benefits displayed by the SGAs family. Over 17 different potential therapeutic applications (antibiotic, antiviral, anti-inflammatory, etc.) were reported over the past ten years, and this unique review analyzes each pharmacological effect independently without discrimination of either the SGA's chemical identity or their sources. A strong emphasis is placed on the discovery of their biological targets and the subsequent cellular mechanisms, discussing in vitro to in vivo biological data. The therapeutic value and the challenges of the solanum steroidal glycoalkaloid family is debated to provide new insights for future research towards clinical development.

Ethyl palmitate, an anti-chikungunya virus principle from Sauropus androgynus, a medicinal plant used to alleviate fever in ethnomedicine

ETHNOPHARMACOLOGICAL RELEVANCE

Sauropus androgynus is a medicinal shrub used for the treatment of fever in ethnomedical traditions in various Southeast Asian countries.

AIM OF THE STUDY

This study was aimed to identify antiviral principles from S. androgynus against Chikungunya virus (CHIKV), a major mosquito-borne pathogen that re-emerged in the last decade, and to unravel their mechanism of action.

MATERIALS AND METHODS

Hydroalcoholic extract of S. androgynus leaves was screened for anti-CHIKV activity using cytopathic effect (CPE) reduction assay. The extract was subjected to activity guided isolation and the resultant pure molecule was characterized by GC-MS, Co-GC and Co-HPTLC. The isolated molecule was further evaluated for its effect by plaque reduction assay, Western blot and immunofluorescence assays. In silico docking with CHIKV envelope proteins and molecular dynamics simulation (MD) analyses were used to elucidate its possible mechanism of action.

RESULTS

S. androgynus hydroalcoholic extract showed promising anti-CHIKV activity and its active component, obtained by activity guided isolation, was identified as ethyl palmitate (EP), a fatty acid ester. At 1 μg/mL, EP led to 100% inhibition of CPE and a significant 3 log₁₀ reduction in CHIKV replication in Vero cells at 48 h post-infection. EP was highly potent with an EC₅₀ of 0.0019 μg/mL (0.0068 μM) and a very high selectivity index. EP treatment significantly reduced viral protein expression, and time of addition studies revealed that it acts at the stage of viral entry. A strong binding to the viral envelope protein E1 homotrimer during entry, thus preventing viral fusion, was identified as a possible mechanism by which EP imparts its antiviral effect.

CONCLUSIONS

S. androgynus contains EP as a potent antiviral principle against CHIKV. This justifies the use of the plant against febrile infections, possibly caused by viruses, in various ethnomedical systems. Our results also prompt more studies on fatty acids and their derivatives against viral diseases.

Alkaloids as potential antivirals. A comprehensive review

Alkaloids are a diverse group of natural phytochemicals. These phytochemicals in plants provide them protection against pests, and herbivorous organisms and also control their development. Numerous of these alkaloids have a variety of biological effects, and some have even been developed into medications with different medicinal properties. This review aims to provide a broad overview of the numerous naturally occurring alkaloids (isolated from both terrestrial and aquatic species) along with synthetically produced alkaloid compounds having prominent antiviral properties. Previous reviews on this subject have focused on the biological actions of both natural and synthetic alkaloids, but they have not gone into comprehensive detail about their antiviral properties. We reviewed here several antiviral alkaloids that have been described in the literature in different investigational environments i.e. (in-vivo, in-ovo, in-vitro, and in-silico), and found that these alkaloid compounds have significant antiviral properties against several infectious viruses. These alkaloids repressed and targeted various important stages of viral infection at non-toxic doses while some of the alkaloids reported here also exhibited comparable inhibitory activities to commercially used drugs. Overall, these anti-viral effects of alkaloids point to a high degree of specificity, implying that they could serve as effective and safe antiviral medicines if further pursued in medicinal and pharmacological investigations.

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.

Anti-Alphaviral Alkaloids: Focus on Some Isoquinolines, Indoles and Quinolizidines

The discovery and the development of safe and efficient therapeutics against arthritogenic alphaviruses (e.g., chikungunya virus) remain a continuous challenge. Alkaloids are structurally diverse and naturally occurring compounds in plants, with a wide range of biological activities including beneficial effects against prominent pathogenic viruses and inflammation. In this short review, we discuss the effects of some alkaloids of three biologically relevant structural classes (isoquinolines, indoles and quinolizidines). Based on various experimental models (viral infections and chronic diseases), we highlight the immunomodulatory effects of these alkaloids. The data established the capacity of these alkaloids to interfere in host antiviral and inflammatory responses through key components (antiviral interferon response, ROS production, inflammatory signaling pathways and pro- and anti-inflammatory cytokines production) also involved in alphavirus infection and resulting inflammation. Thus, these data may provide a convincing perspective of research for the use of alkaloids as immunomodulators against arthritogenic alphavirus infection and induced inflammation.

Natural therapeutics against SARS CoV2: the potentiality and challenges

The incidence of the COVID-19 pandemic completely reoriented global socio-economic parameters and human civilization have experienced the worst situation in the recent past. The rapid mutation rates in viruses have continuously been creating emerging variants of concerns (VOCs) which devastated different parts of the world with subsequent waves of infection. Although, series of antiviral drugs and vaccines were formulated but cent percent effectiveness of these drugs is still awaited. Many of these drugs have different side effects which necessitate proper trial before release. Plants are the storehouse of antimicrobial metabolites which have also long been utilized as traditional medicines against different viral infections. Although, proper mechanism of action of these traditional medicines are unknown, they may be a potential source of effective anti-COVID drug for future implications. Advanced bioinformatic applications have opened up a new arena in predicting these repurposed drugs as a potential COVID mitigator. The present review summarizes brief accounts of the corona virus with their possible entry mechanism. This study also tries to classify different possible anti COVID-19 plant-derived metabolites based on their probable mode of action. This review will surely provide useful information on repurposed drugs to combat COVID-19 in this critical situation.

Potential Antiviral Action of Alkaloids

Viral infections and outbreaks have become a major concern and are one of the main causes of morbidity and mortality worldwide. The development of successful antiviral therapeutics and vaccines remains a daunting challenge. The discovery of novel antiviral agents is a public health emergency, and extraordinary efforts are underway globally to identify safe and effective treatments for different viral diseases. Alkaloids are natural phytochemicals known for their biological activities, many of which have been intensively studied for their broad-spectrum of antiviral activities against different DNA and RNA viruses. The purpose of this review was to summarize the evidence supporting the efficacy of the antiviral activity of plant alkaloids at half-maximum effective concentration (EC₅₀) or half-maximum inhibitory concentration (IC₅₀) below 10 μM and describe the molecular sites most often targeted by natural alkaloids acting against different virus families. This review highlights that considering the devastating effects of virus pandemics on humans, plants, and animals, the development of high efficiency and low-toxicity antiviral drugs targeting these viruses need to be developed. Furthermore, it summarizes the current research status of alkaloids as the source of antiviral drug development, their structural characteristics, and antiviral targets. Overall, the influence of alkaloids at the molecular level suggests a high degree of specificity which means they could serve as potent and safe antiviral agents waiting for evaluation and exploitation.

HSBP1 Is a Novel Interactor of FIP200 and ATG13 That Promotes Autophagy Initiation and Picornavirus Replication

ATG13 and FIP200 are two subunits of the ULK kinase complex, a key regulatory component of the autophagy machinery. We have previously found that the FIP200-ATG13 subcomplex controls picornavirus replication outside its role in the ULK kinase complex and autophagy. Here, we characterized HSBP1, a very small cytoplasmic coiled-coil protein, as a novel interactor of FIP200 and ATG13 that binds these two proteins via FIP200. HSBP1 is a novel pro-picornaviral host factor since its knockdown or knockout, inhibits the replication of various picornaviruses. The anti-picornaviral function of the FIP200-ATG13 subcomplex was abolished when HSBP1 was depleted, inferring that this subcomplex negatively regulates HSBP1’s pro-picornaviral function during infections. HSBP1depletion also reduces the stability of ULK kinase complex subunits, resulting in an impairment in autophagy induction. Altogether, our data show that HSBP1 interaction with FIP200-ATG13-containing complexes is involved in the regulation of different cellular pathways.

The steroidal alkaloids α-tomatine and tomatidine: Panorama of their mode of action and pharmacological properties

The steroidal glycoalkaloid α-tomatine (αTM) and its aglycone tomatidine (TD) are abundant in the skin of unripe green tomato and present in tomato leaves and flowers. They mainly serve as defensive agents to protect the plant against infections by insects, bacteria, parasites, viruses, and fungi. In addition, the two products display a range of pharmacological properties potentially useful to treat various human diseases. We have analyzed all known pharmacological activities of αTM and TD, and the corresponding molecular targets and pathways impacted by these two steroidal alkaloids. In experimental models, αTM displays anticancer effects, particularly strong against androgen-independent prostate cancer, as well as robust antifungal effects. αTM is a potent cholesterol binder, useful as a vaccine adjuvant to improve delivery of protein antigens or therapeutic oligonucleotides. TD is a much less cytotoxic compound, able to restrict the spread of certain viruses (such as dengue, chikungunya and porcine epidemic diarrhea viruses) and to provide cardio and neuro-protective effects toward human cells. Both αTM and TD exhibit marked anti-inflammatory activities. They proceed through multiple signaling pathways and protein targets, including the sterol C24 methyltransferase Erg6 and vitamin D receptor, both directly targeted by TD. αTM is a powerful regulator of the NFkB/ERK signaling pathway implicated in various diseases. Collectively, the analysis shed light on the multitargeted action of αTM/TD and their usefulness as chemo-preventive or chemotherapeutic agents. A novel medicinal application for αTM is proposed.

Tomatidine reduces Chikungunya virus progeny release by controlling viral protein expression

Tomatidine, a natural steroidal alkaloid from unripe green tomatoes has been shown to exhibit many health benefits. We recently provided in vitro evidence that tomatidine reduces the infectivity of Dengue virus (DENV) and Chikungunya virus (CHIKV), two medically important arthropod-borne human infections for which no treatment options are available. We observed a potent antiviral effect with EC50 values of 0.82 μM for DENV-2 and 1.3 μM for CHIKV-LR. In this study, we investigated how tomatidine controls CHIKV infectivity. Using mass spectrometry, we identified that tomatidine induces the expression of p62, CD98, metallothionein and thioredoxin-related transmembrane protein 2 in Huh7 cells. The hits p62 and CD98 were validated, yet subsequent analysis revealed that they are not responsible for the observed antiviral effect. In parallel, we sought to identify at which step of the virus replication cycle tomatidine controls virus infectivity. A strong antiviral effect was seen when in vitro transcribed CHIKV RNA was transfected into Huh7 cells treated with tomatidine, thereby excluding a role for tomatidine during CHIKV cell entry. Subsequent determination of the number of intracellular viral RNA copies and viral protein expression levels during natural infection revealed that tomatidine reduces the RNA copy number and viral protein expression levels in infected cells. Once cells are infected, tomatidine is not able to interfere with active RNA replication yet it can reduce viral protein expression. Collectively, the results delineate that tomatidine controls viral protein expression to exert its antiviral activity. Lastly, sequential passaging of CHIKV in presence of tomatidine did not lead to viral resistance. Collectively, these results further emphasize the potential of tomatidine as an antiviral treatment towards CHIKV infection.

Chikungunya fever is a debilitating disease caused by the mosquito-borne Chikungunya virus. Over the past two decades the geographical spread of the virus and its mosquito vector has drastically increased thereby causing millions of infections. To date there is no antiviral drug and no vaccine available to treat/prevent Chikungunya virus infection. We recently showed that the natural steroidal alkaloid tomatidine has potent antiviral activity towards Chikungunya virus at submicromolar concentrations. In this study we dissected how tomatidine reduces the production of Chikungunya virus particles. We show that tomatidine lowers viral protein expression and we hypothesize that the effect of tomatidine on viral protein translation hampers the production of progeny viral RNA copies / number of infected cells thereby leading to a reduced production of secreted virus particles. Also, we show that Chikungunya virus does not readily become resistant to tomatidine. Collectively, we deciphered the mechanism by which tomatidine exerts antiviral activity to Chikungunya virus and our results strengthen the potential of tomatidine as an antiviral treatment strategy towards Chikungunya virus.

Concise Large-Scale Synthesis of Tomatidine, A Potent Antibiotic Natural Product

Tomatidine has recently generated a lot of interest amongst the pharmacology, medicine, and biology fields of study, especially for its newfound activity as an antibiotic agent capable of targeting multiple strains of bacteria. In the light of its low natural abundance and high cost, an efficient and scalable multi-gram synthesis of tomatidine has been developed. This synthesis uses a Suzuki-Miyaura-type coupling reaction as a key step to graft an enantiopure F-ring side chain to the steroidal scaffold of the natural product, which was accessible from low-cost and commercially available diosgenin. A Lewis acid-mediated spiroketal opening followed by an azide substitution and reduction sequence is employed to generate the spiroaminoketal motif of the natural product. Overall, this synthesis produced 5.2 g in a single pass in 15 total steps and 15.2% yield using a methodology that is atom economical, scalable, and requires no flash chromatography purifications.

Tomatidine and Patchouli Alcohol as Inhibitors of SARS-CoV-2 Enzymes (3CLpro, PLpro and NSP15) by Molecular Docking and Molecular Dynamics Simulations

Considering the current dramatic and fatal situation due to the high spreading of SARS-CoV-2 infection, there is an urgent unmet medical need to identify novel and effective approaches for prevention and treatment of Coronavirus disease (COVID 19) by re-evaluating and repurposing of known drugs. For this, tomatidine and patchouli alcohol have been selected as potential drugs for combating the virus. The hit compounds were subsequently docked into the active site and molecular docking analyses revealed that both drugs can bind the active site of SARS-CoV-2 3CLpro, PLpro, NSP15, COX-2 and PLA2 targets with a number of important binding interactions. To further validate the interactions of promising compound tomatidine, Molecular dynamics study of 100 ns was carried out towards 3CLpro, NSP15 and COX-2. This indicated that the protein-ligand complex was stable throughout the simulation period, and minimal backbone fluctuations have ensued in the system. Post dynamic MM-GBSA analysis of molecular dynamics data showed promising mean binding free energy 47.4633 ± 9.28, 51.8064 ± 8.91 and 54.8918 ± 7.55 kcal/mol, respectively. Likewise, in silico ADMET studies of the selected ligands showed excellent pharmacokinetic properties with good absorption, bioavailability and devoid of toxicity. Therefore, patchouli alcohol and especially, tomatidine may provide prospect treatment options against SARS-CoV-2 infection by potentially inhibiting virus duplication though more research is guaranteed and secured.

Antimicrobial properties of tomato leaves, stems, and fruit and their relationship to chemical composition

BACKGROUND

We previously reported that the tomato glycoalkaloid tomatine inhibited the growth of Trichomonas vaginalis strain G3, Tritrichomonas foetus strain D1, and Tritrichomonas foetus-like strain C1 that cause disease in humans and farm and domesticated animals. The increasing prevalence of antibiotic resistance requires development of new tools to enhance or replace medicinal antibiotics.

METHODS

Wild tomato plants were harvested and divided into leaves, stems, and fruit of different colors: green, yellow, and red. Samples were freeze dried and ground with a handheld mill. The resulting powders were evaluated for their potential anti-microbial effects on protozoan parasites, bacteria, and fungi. A concentration of 0.02% (w/v) was used for the inhibition of protozoan parasites. A high concentration of 10% (w/v) solution was tested for bacteria and fungi as an initial screen to evaluate potential anti-microbial activity and results using this high concentration limits its clinical relevance.

RESULTS

Natural powders derived from various parts of tomato plants were all effective in inhibiting the growth of the three trichomonads to varying degrees. Test samples from leaves, stems, and immature 'green' tomato peels and fruit, all containing tomatine, were more effective as an inhibitor of the D1 strain than those prepared from yellow and red tomato peels which lack tomatine. Chlorogenic acid and quercetin glycosides were present in all parts of the plant and fruit, while caffeic acid was only found in the fruit peels. Any correlation between plant components and inhibition of the G3 and C1 strains was not apparent, although all the powders were variably effective. Tomato leaf was the most effective powder in all strains, and was also the highest in tomatine. S. enterica showed a minor susceptibility while B. cereus and C. albicans fungi both showed a significant growth inhibition with some of the test powders. The powders inhibited growth of the pathogens without affecting beneficial lactobacilli found in the normal flora of the vagina.

CONCLUSIONS

The results suggest that powders prepared from tomato leaves, stems, and green tomato peels and to a lesser extent from peels from yellow and red tomatoes offer potential multiple health benefits against infections caused by pathogenic protozoa, bacteria, and fungi, without affecting beneficial lactobacilli that also reside in the normal flora of the vagina.

Inhibitors of Venezuelan Equine Encephalitis Virus Identified Based on Host Interaction Partners of Viral Non-Structural Protein 3

Venezuelan equine encephalitis virus (VEEV) is a new world alphavirus and a category B select agent. Currently, no FDA-approved vaccines or therapeutics are available to treat VEEV exposure and resultant disease manifestations. The C-terminus of the VEEV non-structural protein 3 (nsP3) facilitates cell-specific and virus-specific host factor binding preferences among alphaviruses, thereby providing targets of interest when designing novel antiviral therapeutics. In this study, we utilized an overexpression construct encoding HA-tagged nsP3 to identify host proteins that interact with VEEV nsP3 by mass spectrometry. Bioinformatic analyses of the putative interactors identified 42 small molecules with the potential to inhibit the host interaction targets, and thus potentially inhibit VEEV. Three inhibitors, tomatidine, citalopram HBr, and Z-VEID-FMK, reduced replication of both the TC-83 strain and the Trinidad donkey (TrD) strain of VEEV by at least 10-fold in astrocytoma, astroglial, and microglial cells. Further, these inhibitors reduced replication of the related New World (NW) alphavirus Eastern equine encephalitis virus (EEEV) in multiple cell types, thus demonstrating broad-spectrum antiviral activity. Time-course assays revealed all three inhibitors reduced both infectious particle production and positive-sense RNA levels post-infection. Further evaluation of the putative host targets for the three inhibitors revealed an interaction of VEEV nsP3 with TFAP2A, but not eIF2S2. Mechanistic studies utilizing siRNA knockdowns demonstrated that eIF2S2, but not TFAP2A, supports both efficient TC-83 replication and genomic RNA synthesis, but not subgenomic RNA translation. Overall, this work reveals the composition of the VEEV nsP3 proteome and the potential to identify host-based, broad spectrum therapeutic approaches to treat new world alphavirus infections.

Resveratrol and Pterostilbene Inhibit SARS-CoV-2 Replication in Air-Liquid Interface Cultured Human Primary Bronchial Epithelial Cells

The current COVID-19 pandemic is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has an enormous impact on human health and economy. In search for therapeutic options, researchers have proposed resveratrol, a food supplement with known antiviral, anti-inflammatory, and antioxidant properties as an advantageous antiviral therapy for SARS-CoV-2 infection. Here, we provide evidence that both resveratrol and its metabolically more stable structural analog, pterostilbene, exhibit potent antiviral properties against SARS-CoV-2 in vitro. First, we show that resveratrol and pterostilbene antiviral activity in African green monkey kidney cells. Both compounds actively inhibit virus replication within infected cells as reduced virus progeny production was observed when the compound was added at post-inoculation conditions. Without replenishment of the compound, antiviral activity was observed up to roughly five rounds of replication, demonstrating the long-lasting effect of these compounds. Second, as the upper respiratory tract represents the initial site of SARS-CoV-2 replication, we also assessed antiviral activity in air-liquid interface (ALI) cultured human primary bronchial epithelial cells, isolated from healthy volunteers. Resveratrol and pterostilbene showed a strong antiviral effect in these cells up to 48 h post-infection. Collectively, our data indicate that resveratrol and pterostilbene are promising antiviral compounds to inhibit SARS-CoV-2 infection. Because these results represent laboratory findings in cells, we advocate evaluation of these compounds in clinical trials before statements are made whether these drugs are advantageous for COVID-19 treatment.

In silico analysis of echinocandins binding to the main proteases of coronaviruses PEDV (3CLpro) and SARS-CoV-2 (Mpro)

The porcine epidemic diarrhea virus (PEDV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are two highly pathogenic viruses causing tremendous damages to the swine and human populations, respectively. Vaccines are available to prevent contamination and to limit dissemination of these two coronaviruses, but efficient and widely affordable treatments are needed. Recently, four natural products targeting the 3C-like protease (3CLpro) of PEDV and inhibiting replication of the virus in vitro have been identified: tomatidine, epigallocatechin-3-gallate, buddlejasaponin IVb and pneumocandin B0. We have evaluated the interaction of these compounds with 3CLpro of PEDV and with the structurally similar main protease (Mpro) of SARS-CoV-2. The molecular docking analysis indicated that the echinocandin-type lipopeptide pneumocandin B0 can generate much more stable complexes with both proteases compared to tomatidine. The empirical energy of interaction (ΔE) calculated with pneumocandin B0 bound to Mpro is extremely high, comparable to that measured with known antiviral drugs. Pneumocandin B0 and its analogue capsofungin appeared a little less adapted to interact with 3CLpro compared to Mpro. In contrast, the antifungal drug micafungin bearing an unfused tricyclic side chain, emerges as a better ligand of 3CLpro of PEDV compared to Mpro of SARS-CoV-2, based on our calculations. Collectively, the analysis underlines the benefit of echinocandin-type antifungal drugs as potential inhibitors of PEDV and SARS-CoV-2 main proteases. These clinically important antifungal natural products deserve further studies as antiviral agents.

Irinotecan (CPT-11) Canonical Anti-Cancer Drug Can also Modulate Antiviral and Pro-Inflammatory Responses of Primary Human Synovial Fibroblasts

Alphaviruses are a group of arboviruses that generate chronic inflammatory rheumatisms in humans. Currently, no approved vaccines or antiviral therapies are available to prevent or treat alphavirus-induced diseases. The aim of this study was to evaluate the repositioning of the anti-cancer molecule irinotecan as a potential modulator of the antiviral and inflammatory responses of primary human synovial fibroblasts (HSF), the main stromal cells of the joint synovium. HSF were exposed to O’nyong-nyong virus (ONNV) and polyinosinic-polycytidylic acid (PIC) to mimic, respectively, acute and chronic infectious settings. The cytokine IL-1β was used as a major pro-inflammatory cytokine to stimulate HSF. Quantitative RT-PCR analysis revealed that irinotecan at 15 µM was able to amplify the antiviral response (i.e., interferon-stimulated gene expression) of HSF exposed to PIC and reduce the expression of pro-inflammatory genes (CXCL8, IL-6 and COX-2) upon IL-1β treatment. These results were associated with the regulation of the expression of several genes, including those encoding for STAT1, STAT2, p53 and NF-κB. Irinotecan did not modulate these responses in both untreated cells and cells stimulated with ONNV. This suggests that this drug could be therapeutically useful for the treatment of chronic and severe (rather than acute) arthritis due to viruses.

Screening and pharmacodynamic evaluation of the antirespiratory syncytial virus activity of steroidal pyridine compounds in vitro and in vivo

Respiratory syncytial virus (RSV) causes serious lower respiratory tract infections and there are currently no safer or more effective drugs available. It is important to find novel medications for RSV infection. A series of steroidal pyridines were synthesized for screening and evaluation of their antiviral activity and investigation of their antiviral mechanism of action. Compound 3l had the highest antiviral activity, with a half-maximal effective concentration (EC50 ) of 3.13 μM. Compound 3l was explored for its effects in vitro on RSV 2 h before infection (pretreatment), at the time of infection (competition), and 2 h after infection (postinfection). Toll-like receptor (TLR)-3, retinoic acid-inducible gene (RIG)-I, interleukin (IL)-6, and interferon (IFN)-β were suppressed at the cellular level. Mouse lung tissue was subjected to hematoxylin and eosin (HE) staining and immunohistochemistry, which showed that RSV antigen and M gene expression could be reduced by compound 3l. Decreased expression of TLR-3, RIG-I, IL-6, IFN-β, and IL-10 was also found in vivo. The results indicated that compound 3l exerted its antiviral effects mainly through inhibition of viral replication and downregulation of inflammatory factors.

Identification of phytochemicals as potential therapeutic agents that binds to Nsp15 protein target of coronavirus (SARS-CoV-2) that are capable of inhibiting virus replication

BACKGROUND

Coronavirus disease 2019 (COVID-19) playing havoc across the globe caused 585,727 deaths and 13,616,593 confirmed cases so far as per World Health Organization data released till 17th July 2020. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV- 2) is responsible for causing this pandemic across different continents. It is not only impacting the world economy but also quarantined millions of people in their homes or hospitals.

PURPOSE

At present, there is no Food and Drug Administration-approved drug or vaccine available to treat this disease. Still, people are trying various pre-existing medicines that are known to have anti-viral or anti-parasitic effects. In view of this, the present study aimed to study the binding potential of various phytochemicals present in multiple natural plant extract as a secondary metabolite to non-structural protein 15 (Nsp15) protein, a drug target known to play a crucial role in virulence of coronavirus.

METHOD

Nsp15 protein was selected because it shows 89% similarity to the other SARS-CoV, which caused the earlier outbreak. The assumption is that inhibition of Nsp15 slowdowns the viral replication. Phytochemicals are selected as these are present in various plant parts (seed, flower, roots, etc.), which are used in different food cuisines in different geographical regions across the globe. The molecular docking approach was performed using two different software, i.e., Autodock, and Swissdock, to study the interaction of various phytochemicals with Nsp15 protein. Hydroxychloroquine is used as a positive control as it is used by medical professionals showing some positive effects in dealing with coronavirus.

RESULTS

The present study demonstrated the binding potential of approximately 50 phytochemicals with Nsp15 and capable of inhibiting the viral replication, although in vitro and in vivo tests are required to confirm these findings.

CONCLUSIONS

In conclusion, the present study successfully demonstrated the binding of phytochemicals such as sarsasapogenin, ursonic acid, curcumin, ajmalicine, novobiocin, silymarin and aranotin, piperine, gingerol, rosmarinic acid, and alpha terpinyl acetate to Nsp15 viral protein and they might play a key role in inhibiting SARS-CoV-2 replication.

Therapeutic Potentials of Antiviral Plants Used in Traditional African Medicine With COVID-19 in Focus: A Nigerian Perspective

The coronavirus disease 2019 (COVID-19) pandemic is caused by an infectious novel strain of coronavirus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which was earlier referred to as 2019-nCoV. The respiratory disease is the most consequential global public health crisis of the 21st century whose level of negative impact increasingly experienced globally has not been recorded since World War II. Up till now, there has been no specific globally authorized antiviral drug, vaccines, supplement or herbal remedy available for the treatment of this lethal disease except preventive measures, supportive care and non-specific treatment options adopted in different countries via divergent approaches to halt the pandemic. However, many of these interventions have been documented to show some level of success particularly the Traditional Chinese Medicine while there is paucity of well reported studies on the impact of the widely embraced Traditional African Medicines (TAM) adopted so far for the prevention, management and treatment of COVID-19. We carried out a detailed review of publicly available data, information and claims on the potentials of indigenous plants used in Sub-Saharan Africa as antiviral remedies with potentials for the prevention and management of COVID-19. In this review, we have provided a holistic report on evidence-based antiviral and promising anti-SARS-CoV-2 properties of African medicinal plants based on in silico evidence, in vitro assays and in vivo experiments alongside the available data on their mechanistic pharmacology. In addition, we have unveiled knowledge gaps, provided an update on the effort of African Scientific community toward demystifying the dreadful SARS-CoV-2 micro-enemy of man and have documented popular anti-COVID-19 herbal claims emanating from the continent for the management of COVID-19 while the risk potentials of herb-drug interaction of antiviral phytomedicines when used in combination with orthodox drugs have also been highlighted. This review exercise may lend enough credence to the potential value of African medicinal plants as possible leads in anti-COVID-19 drug discovery through research and development.

Phytochemicals from Plant Foods as Potential Source of Antiviral Agents: An Overview

To date, the leading causes of mortality and morbidity worldwide include viral infections, such as Ebola, influenza virus, acquired immunodeficiency syndrome (AIDS), severe acute respiratory syndrome (SARS) and recently COVID-19 disease, caused by the SARS-CoV-2 virus. Currently, we can count on a narrow range of antiviral drugs, especially older generation ones like ribavirin and interferon which are effective against viruses in vitro but can often be ineffective in patients. In addition to these, we have antiviral agents for the treatment of herpes virus, influenza virus, HIV and hepatitis virus. Recently, drugs used in the past especially against ebolavirus, such as remdesivir and favipiravir, have been considered for the treatment of COVID-19 disease. However, even if these drugs represent important tools against viral diseases, they are certainly not sufficient to defend us from the multitude of viruses present in the environment. This represents a huge problem, especially considering the unprecedented global threat due to the advancement of COVID-19, which represents a potential risk to the health and life of millions of people. The demand, therefore, for new and effective antiviral drugs is very high. This review focuses on three fundamental points: (1) presents the main threats to human health, reviewing the most widespread viral diseases in the world, thus describing the scenario caused by the disease in question each time and evaluating the specific therapeutic remedies currently available. (2) It comprehensively describes main phytochemical classes, in particular from plant foods, with proven antiviral activities, the viruses potentially treated with the described phytochemicals. (3) Consideration of the various applications of drug delivery systems in order to improve the bioavailability of these compounds or extracts. A PRISMA flow diagram was used for the inclusion of the works. Taking into consideration the recent dramatic events caused by COVID-19 pandemic, the cry of alarm that denounces critical need for new antiviral drugs is extremely strong. For these reasons, a continuous systematic exploration of plant foods and their phytochemicals is necessary for the development of new antiviral agents capable of saving lives and improving their well-being.

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.

An Account of Immune Senescence in the Clinical Pathophysiology of COVID-19 Infection in Aging

Worldwide COVID-19 infection poses an enormous risk to public health and an alarming global socioeconomic burden. The impact of the COVID-19 pandemic on individuals with underlying health conditions as well as on the elderly population is extensive and effective strategies are needed to understand the mechanism behind it. Cellular senescence defines as an irreversible cell cycle arrest due to DNA damage leading to accumulation of senescent cells in the elderly population and may result in worsening of COVID-19 mediated increased mortality. However, whether this variation in senescence levels, in different aged populations, translation to COVID-19 infection is unknown. The spike protein of SARS-CoV-2 has been recently identified to be responsible for inducing pathogenic signals, although a clear understanding of how the host receptor interacts with SARS-CoV-2 protein and mediates the immune responses is not clear. In this review, we address the epidemiology of SARS-CoV-2 and the cellular senescence responding immune response to pathogenic SARS-CoV-2. We provide a prospective summary of what to expect and how to brace the possible immunological strategy to protect against COVID-19 infection. The review majorly explores an underline mechanism of how senescent cells trigger a hyperimmune inflammatory response and cause high mortality in aging people could serve as a potential aid to alleviate the treatment for elderly battling COVID-19 infection.

Combination With Tomatidine Improves the Potency of Posaconazole Against Trypanosoma cruzi

Azoles such as posaconazole (Posa) are highly potent against Trypanosoma cruzi. However, when tested in chronic Chagas disease patients, a high rate of relapse after Posa treatment was observed. It appears that inhibition of T. cruzi cytochrome CYP51, the target of azoles, does not deliver sterile cure in monotherapy. Looking for suitable combination partners of azoles, we have selected a set of inhibitors of sterol and sphingolipid biosynthetic enzymes. A small-scale phenotypic screening was conducted in vitro against the proliferative forms of T. cruzi, extracellular epimastigotes and intracellular amastigotes. Against the intracellular, clinically relevant forms, four out of 15 tested compounds presented higher or equal activity as benznidazole (Bz), with EC₅₀ values ≤2.2 μM. Ro48-8071, an inhibitor of lanosterol synthase (ERG7), and the steroidal alkaloid tomatidine (TH), an inhibitor of C-24 sterol methyltransferase (ERG6), exhibited the highest potency and selectivity indices (SI = 12 and 115, respectively). Both were directed to combinatory assays using fixed-ratio protocols with Posa, Bz, and fexinidazole. The combination of TH with Posa displayed a synergistic profile against amastigotes, with a mean ΣFICI value of 0.2. In vivo assays using an acute mouse model of T. cruzi infection demonstrated lack of antiparasitic activity of TH alone in doses ranging from 0.5 to 5 mg/kg. As observed in vitro, the best combo proportion in vivo was the ratio 3 TH:1 Posa. The combination of Posa at 1.25 mpk plus TH at 3.75 mpk displayed suppression of peak parasitemia of 80% and a survival rate of 60% in the acute infection model, as compared to 20% survival for Posa at 1.25 mpk alone and 40% for Posa at 10 mpk alone. These initial results indicate a potential for the combination of posaconazole with tomatidine against T. cruzi.

Amino acid-derived defense metabolites from plants: A potential source to facilitate novel antimicrobial development

For millennia, humanity has relied on plants for its medicines, and modern pharmacology continues to reexamine and mine plant metabolites for novel compounds and to guide improvements in biological activity, bioavailability, and chemical stability. The critical problem of antibiotic resistance and increasing exposure to viral and parasitic diseases has spurred renewed interest into drug treatments for infectious diseases. In this context, an urgent revival of natural product discovery is globally underway with special attention directed toward the numerous and chemically diverse plant defensive compounds such as phytoalexins and phytoanticipins that combat herbivores, microbial pathogens, or competing plants. Moreover, advancements in “omics,” chemistry, and heterologous expression systems have facilitated the purification and characterization of plant metabolites and the identification of possible therapeutic targets. In this review, we describe several important amino acid–derived classes of plant defensive compounds, including antimicrobial peptides (e.g., defensins, thionins, and knottins), alkaloids, nonproteogenic amino acids, and phenylpropanoids as potential drug leads, examining their mechanisms of action, therapeutic targets, and structure–function relationships. Given their potent antibacterial, antifungal, antiparasitic, and antiviral properties, which can be superior to existing drugs, phytoalexins and phytoanticipins are an excellent resource to facilitate the rational design and development of antimicrobial drugs.

Modulation of Autophagy: A Novel "Rejuvenation" Strategy for the Aging Liver

Aging is a natural life process which leads to a gradual decline of essential physiological processes. For the liver, it leads to alterations in histomorphology (steatosis and fibrosis) and function (protein synthesis and energy generation) and affects central hepatocellular processes (autophagy, mitochondrial respiration, and hepatocyte proliferation). These alterations do not only impair the metabolic capacity of the liver but also represent important factors in the pathogenesis of malignant liver disease. Autophagy is a recycling process for eukaryotic cells to degrade dysfunctional intracellular components and to reuse the basic substances. It plays a crucial role in maintaining cell homeostasis and in resisting environmental stress. Emerging evidence shows that modulating autophagy seems to be effective in improving the age-related alterations of the liver. However, autophagy is a double-edged sword for the aged liver. Upregulating autophagy alleviates hepatic steatosis and ROS-induced cellular stress and promotes hepatocyte proliferation but may aggravate hepatic fibrosis. Therefore, a well-balanced autophagy modulation strategy might be suitable to alleviate age-related liver dysfunction. Conclusion. Modulation of autophagy is a promising strategy for "rejuvenation" of the aged liver. Detailed knowledge regarding the most devastating processes in the individual patient is needed to effectively counteract aging of the liver without causing obvious harm.

Antiviral Compounds for Blocking Arboviral Transmission in Mosquitoes

Mosquito-borne arthropod-borne viruses (arboviruses) such as the dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) are important human pathogens that are responsible for significant global morbidity and mortality. The recent emergence and re-emergence of mosquito-borne viral diseases (MBVDs) highlight the urgent need for safe and effective vaccines, therapeutics, and vector-control approaches to prevent MBVD outbreaks. In nature, arboviruses circulate between vertebrate hosts and arthropod vectors; therefore, disrupting the virus lifecycle in mosquitoes is a major approach for combating MBVDs. Several strategies were proposed to render mosquitoes that are refractory to arboviral infection, for example, those involving the generation of genetically modified mosquitoes or infection with the symbiotic bacterium Wolbachia. Due to the recent development of high-throughput screening methods, an increasing number of drugs with inhibitory effects on mosquito-borne arboviruses in mammalian cells were identified. These antivirals are useful resources that can impede the circulation of arboviruses between arthropods and humans by either rendering viruses more vulnerable in humans or suppressing viral infection by reducing the expression of host factors in mosquitoes. In this review, we summarize recent advances in small-molecule antiarboviral drugs in mammalian and mosquito cells, and discuss how to use these antivirals to block the transmission of MBVDs.

Small-Molecule Inhibitors of Chikungunya Virus: Mechanisms of Action and Antiviral Drug Resistance

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that has spread to more than 60 countries worldwide. CHIKV infection leads to a febrile illness known as chikungunya fever (CHIKF), which is characterized by long-lasting and debilitating joint and muscle pain. CHIKV can cause large-scale epidemics with high attack rates, which substantiates the need for development of effective therapeutics suitable for outbreak containment. In this review, we highlight the different strategies used for developing CHIKV small-molecule inhibitors, ranging from high-throughput cell-based screening to in silico screens and enzymatic assays with purified viral proteins.

Chikungunya virus (CHIKV) is a mosquito-transmitted alphavirus that has spread to more than 60 countries worldwide. CHIKV infection leads to a febrile illness known as chikungunya fever (CHIKF), which is characterized by long-lasting and debilitating joint and muscle pain. CHIKV can cause large-scale epidemics with high attack rates, which substantiates the need for development of effective therapeutics suitable for outbreak containment. In this review, we highlight the different strategies used for developing CHIKV small-molecule inhibitors, ranging from high-throughput cell-based screening to in silico screens and enzymatic assays with purified viral proteins. We further discuss the current status of the most promising molecules, including in vitro and in vivo findings. In particular, we focus on describing host and/or viral targets, mode of action, and mechanisms of antiviral drug resistance and associated mutations. Knowledge of the key molecular determinants of drug resistance will aid selection of the most promising antiviral agent(s) for clinical use. For these reasons, we also summarize the available information about drug-resistant phenotypes in Aedes mosquito vectors. From this review, it is evident that more of the active molecules need to be evaluated in preclinical and clinical models to address the current lack of antiviral treatment for CHIKF.

Tomatidine inhibits porcine epidemic diarrhea virus replication by targeting 3CL protease

Porcine epidemic diarrhea virus (PEDV) causes lethal diarrhea in suckling piglets, leading to severe economic losses worldwide. There is an urgent need to find new therapeutic methods to prevent and control PEDV. Not only is there a shortage of commercial anti-PEDV drugs, but available commercial vaccines fail to protect against highly virulent PEDV variants. We screened an FDA-approved library of 911 natural products and found that tomatidine, a steroidal alkaloid extracted from the skin and leaves of tomatoes, demonstrates significant inhibition of PEDV replication in Vero and IPEC-J2 cells in vitro. Molecular docking and molecular dynamics analysis predicted interactions between tomatidine and the active pocket of PEDV 3CL protease, which were confirmed by fluorescence spectroscopy and isothermal titration calorimetry (ITC). The inhibiting effect of tomatidine on 3CL protease was determined using cleavage visualization and FRET assay. Tomatidine-mediated blocking of 3CL protease activity in PEDV-infected cells was examined by western blot detection of the viral polyprotein in PEDV-infected cells. It indicates that tomatidine inhibits PEDV replication mainly by targeting 3CL protease. In addition, tomatidine also has antiviral activity against transmissible gastroenteritis virus (TGEV), porcine reproductive and respiratory syndrome virus (PRRSV), encephalo myocarditis virus (EMCV) and seneca virus A (SVA) in vitro. These results may be helpful in developing a new prophylactic and therapeutic strategy against PEDV and other swine disease infections.

In silico analysis of selected alkaloids against main protease (Mpro) of SARS-CoV-2

In the present situation, COVID-19 has become the global health concern due to its high contagious nature. It initially appeared in December 2019 in Wuhan, China and now affected more than 190 countries. As of now preventive measures are the sole solution to stop this disease for further transmission from person to person transmissions as there is no effective treatment or vaccine available to date. Research and development of new molecule is a laborious process; therefore, drug repurposing can be an alternative solution that involves the identification of potential compounds from the already available data. Alkaloids are potential source of therapeutic agents which might be able to treat novel COVID-19. Therefore, in the present study, twenty potential alkaloid molecules that possess antiviral activity against different viral diseases have taken into consideration and scrutinized using Lipinski's rule. Then out of twenty compounds seventeen were further selected for docking study. Docking study was performed using Autodock software and the best four molecule which provides maximum negative binding energy was selected for further analysis. Two alkaloids namely thalimonine and sophaline D showed potential activity to inhibit the M^pro but to confirm the claim further in-vitro studies are required.

Recent advances in antiviral drug development towards dengue virus

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