Andrographolide and its fluorescent derivative inhibit the main proteases of 2019-nCoV and SARS-CoV through covalent linkage

Andrographolide inhibits porcine epidemic diarrhea virus by inhibiting the JAK2-STAT3 pathway and promoting apoptosis

Porcine epidemic diarrhea (PED) is an acute, virulent, and highly contagious disease caused by the porcine epidemic diarrhea virus (PEDV). The high mutation rate of PEDV makes it difficult to effectively control using traditional vaccines, emphasizing the need for novel anti-PEDV-specific drugs. Therefore, this study aimed to investigate the activity and mechanism of action of andrographolide (AND) against PEDV in vitro and in vivo. In vitro experiments showed that AND treatment significantly inhibited PEDV replication in a cell model. The mechanism is that AND treatment significantly suppressed PEDV-induced activation of the JAK2-STAT3 pathway, which promoted apoptosis and inhibited the proliferation of the virus. Moreover, PEDV-infected 3-day-old piglets were treated with AND, and clinical symptoms, intestinal morphology, and viral load were examined. In vivo experiments showed that AND treatment reduced clinical symptoms, ameliorated intestinal damage, and increased the survival rate of infected piglets by 16.7 %. Conclusively, this study contributes to the field of PEDV antiviral drug development and provides new directions for PED prevention and treatment.

Predictive Assessment of the Antiviral Properties of Imperata cylindrica against SARS-CoV-2

The omicron variant and its sublineages are highly contagious, and they still constitute a global source of concern despite vaccinations. Hospitalizations and mortality rates resulting from infections by these variants of concern are still common. The existing therapeutic alternatives have presented various setbacks such as low potency, poor pharmacokinetic profiles, and drug resistance. The need for alternative therapeutic options cannot be overemphasized. Plants and their phytochemicals present interesting characteristics that make them suitable candidates for the development of antiviral therapeutic agents. This study aimed to investigate the antiviral potential of Imperata cylindrica (I. cylindrica). Specifically, the objective of this study was to identify I. cylindrica phytochemicals that display inhibitory effects against SARS-CoV-2 main protease (Mpro), a highly conserved protein among coronaviruses. Molecular docking and in silico pharmacokinetic assays were used to assess 72 phytocompounds that are found in I. cylindrica as ligands and Mpro (6LU7) as the target. Only eight phytochemicals (bifendate, cylindrene, tabanone, siderin, 5-hydroxy-2-[2-(2-hydroxyphenyl)ethyl]-4H-1-benzopyran-4-one, maritimin, 5-methoxyflavone, and flavone) displayed high binding affinities with Mpro with docking scores ranging from -5.6 kcal/mol to -9.1 kcal/mol. The in silico pharmacokinetic and toxicological assays revealed that tabanone was the best and safest phytochemical for the development of an inhibitory agent against coronavirus main protease. Thus, the study served as a baseline for further in vitro and in vivo assessment of this phytochemical against Mpro of SARS-CoV-2 variants of concern to validate these in silico findings.

Covalent binding of withanolides to cysteines of protein targets

Withanolides represent an important category of natural products with a steroidal lactone core. Many of them contain an α,β-unsaturated carbonyl moiety with a high reactivity toward sulfhydryl groups, including protein cysteine thiols. Different withanolides endowed with marked antitumor and anti-inflammatory have been shown to form stable covalent complexes with exposed cysteines present in the active site of oncogenic kinases (BTK, IKKβ, Zap70), metabolism enzymes (Prdx-1/6, Pin1, PHGDH), transcription factors (Nrf2, NFκB, C/EBPβ) and other structural and signaling molecules (GFAP, β-tubulin, p97, Hsp90, vimentin, Mpro, IPO5, NEMO, …). The present review analyzed the covalent complexes formed through Michael addition alkylation reactions between six major withanolides (withaferin A, physalin A, withangulatin A, 4β-hydroxywithanolide E, withanone and tubocapsanolide A) and key cysteine residues of about 20 proteins and the resulting biological effects. The covalent conjugation of the α,β-unsaturated carbonyl system of withanolides with reactive protein thiols can occur with a large set of soluble and membrane proteins. It points to a general mechanism, well described with the leading natural product withaferin A, but likely valid for most withanolides harboring a reactive (electrophilic) enone moiety susceptible to react covalently with cysteinyl residues of proteins. The multiplicity of reactive proteins should be taken into account when studying the mechanism of action of new withanolides. Proteomic and network analyses shall be implemented to capture and compare the cysteine covalent-binding map for the major withanolides, so as to identify the protein targets at the origin of their activity and/or unwanted effects. Screening of the cysteinome will help understanding the mechanism of action and designing cysteine-reactive electrophilic drug candidates.

Computational Investigations to Identify Potent Natural Flavonoid Inhibitors of the Nonstructural Protein (NSP) 16/10 Complex Against Coronavirus

INTRODUCTION

Globally, the viral pandemic has spread rapidly, resulting in widespread infections. The coronavirus family (CoVs) is one of the various viral families capable of infecting mammals, causing diseases related to the gastrointestinal, neurological, and respiratory systems. Flavonoid compounds have been identified as potentially effective antiviral agents, specifically targeting the virus's nonstructural protein (NSP) 16/10. Flavonoids have also been shown to inhibit virus replication and viral attachment to host cells, making them a promising candidate for antiviral treatment. Further research is needed to understand the full potential of flavonoids as antiviral agents.

METHODOLOGY

This study investigated natural compounds derived from medicinal plants using in silico screening. In addition to assessing drug-likeness, pharmacokinetics, docking, molecular dynamics simulation, bioavailability assessment, and exploration of molecular targets, the screening process entailed analyses of molecular targets and bioavailability. The molecular properties and potential antiviral efficacy of these phytochemical candidates were determined by analyzing them as drug candidates. The results of the study showed that these compounds had potential antiviral activity and could be developed as therapeutic agents. Furthermore, the study showed that the compounds had good bioavailability, suggesting that they are suitable for use as therapeutic agents.

RESULT

An in silico method was used to identify flavonoid compounds for potent antiviral drug molecules against the coronavirus protein complex NSP16/10 protein. The NSP16/10 complex protein binding energy values were -6.14 for isoquercetin, -6.902 for narirutin, -6.052 for myricetin, -7.10 for hesperidin, -4.392 for silibinin, -3.997 for baicalein, -3.712 for taxifolin, and -3.321 for petunidin. Molecular dynamics simulations showed that isoquercetin, hesperidin, and narirutin flavonoids interacted with the COVID-19 virus protein complex NSP16/10 protease up to 100 nanoseconds.

Inhibitors of SARS-CoV-2 Main Protease (Mpro) as Anti-Coronavirus Agents

The main protease (Mpro) of SARS-CoV-2 is an essential enzyme that plays a critical part in the virus's life cycle, making it a significant target for developing antiviral drugs. The inhibition of SARS-CoV-2 Mpro has emerged as a promising approach for developing therapeutic agents to treat COVID-19. This review explores the structure of the Mpro protein and analyzes the progress made in understanding protein-ligand interactions of Mpro inhibitors. It focuses on binding kinetics, origin, and the chemical structure of these inhibitors. The review provides an in-depth analysis of recent clinical trials involving covalent and non-covalent inhibitors and emerging dual inhibitors targeting SARS-CoV-2 Mpro. By integrating findings from the literature and ongoing clinical trials, this review captures the current state of research into Mpro inhibitors, offering a comprehensive understanding of challenges and directions in their future development as anti-coronavirus agents. This information provides new insights and inspiration for medicinal chemists, paving the way for developing more effective Mpro inhibitors as novel COVID-19 therapies.

Andrographolide suppresses SARS-CoV-2 infection by downregulating ACE2 expression: A mechanistic study

Angiotensin-converting enzyme 2 (ACE2) is the receptor that enables SARS-CoV-2 to invade host cells. Previous studies have reported that reducing ACE2 expression may have an anti-SARS-CoV-2 effect. In this study, we constructed a pGL4.10-F2-ACE2 vector with double luciferase genes (firefly and Renilla luciferase) under the control of the ACE2 promoter and used it to screen compounds from Chinese traditional medicinal herbs (CTMHs) that can inhibit ACE2 transcription in human cells. We transfected HEK293T cells with pGL4.10-F2-ACE2 and treated them with CTMH compounds and then measured fluorescence to evaluate the indirect inhibition of ACE2 transcription. Out of 37 compounds tested, andrographolide demonstrated a dose-dependent inhibition of ACE2 transcription. We further confirmed by RT-qPCR and Western blot assays that andrographolide also reduced ACE2 expression in BEAS-2B cells in a dose-dependent manner. Moreover, pseudovirus infection assays in BEAS-2B cells demonstrated that andrographolide can inhibit SARS-CoV-2 infection in a dose-dependent manner. These results suggest that andrographolide has potential anti-SARS-CoV-2 activity and could be a candidate drug for COVID-19 prevention and treatment.

Nitrogen Sources Reprogram Carbon and Nitrogen Metabolism to Promote Andrographolide Biosynthesis in Andrographis paniculata (Burm.f.) Nees Seedlings

Carbon (C) and nitrogen (N) metabolisms participate in N source-regulated secondary metabolism in medicinal plants, but the specific mechanisms involved remain to be investigated. By using nitrate (NN), ammonium (AN), urea (UN), and glycine (GN), respectively, as sole N sources, we found that N sources remarkably affected the contents of diterpenoid lactone components along with C and N metabolisms reprograming in Andrographis paniculata, as compared to NN, the other three N sources raised the levels of 14-deoxyandrographolide, andrographolide, dehydroandrographolide (except UN), and neoandrographolide (except AN) with a prominent accumulation of farnesyl pyrophosphate (FPP). These N sources also raised the photosynthetic rate and the levels of fructose and/or sucrose but reduced the activities of phosphofructokinase (PFK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoenolpyruvate carboxylase (PEPC) and pyruvate dehydrogenase (PDH). Conversely, phosphoenolpyruvate carboxykinase (PEPCK) and malate enzyme (ME) activities were upregulated. Simultaneously, citrate, cis-aconitate and isocitrate levels declined, and N assimilation was inhibited. These results indicated that AN, UN and GN reduced the metabolic flow of carbohydrates from glycolysis into the TCA cycle and downstream N assimilation. Furthermore, they enhanced arginine and GABA metabolism, which increased C replenishment of the TCA cycle, and increased ethylene and salicylic acid (SA) levels. Thus, we proposed that the N sources reprogrammed C and N metabolism, attenuating the competition of N assimilation for C, and promoting the synthesis and accumulation of andrographolide through plant hormone signaling. To obtain a higher production of andrographolide in A. paniculata, AN fertilizer is recommended in its N management.

Isolation, Characterization, and Expression Analysis of NAC Transcription Factor from Andrographis paniculata (Burm. f.) Nees and Their Role in Andrographolide Production

Andrographis paniculata (Burm. f.) Nees is an important medicinal plant known for its bioactive compound andrographolide. NAC transcription factors (NAM, ATAF1/2, and CUC2) play a crucial role in secondary metabolite production, stress responses, and plant development through hormonal signaling. In this study, a putative partial transcript of three NAC family genes (ApNAC83, ApNAC21 22 and ApNAC02) was used to isolate full length genes using RACE. Bioinformatics analyses such as protein structure prediction, cis-acting regulatory elements, and gene ontology analysis were performed. Based on in silico predictions, the diterpenoid profiling of the plant's leaves (five-week-old) and the real-time PCR-based expression analysis of isolated NAC genes under abscisic acid (ABA) treatment were performed. Additionally, the expression analysis of isolated NAC genes under MeJA treatment and transient expression in Nicotiana tabacum was performed. Full-length sequences of three members of the NAC transcription factor family, ApNAC83 (1102 bp), ApNAC21 22 (996 bp), and ApNAC02 (1011 bp), were isolated and subjected to the promoter and gene ontology analysis, which indicated their role in transcriptional regulation, DNA binding, ABA-activated signaling, and stress management. It was observed that ABA treatment leads to a higher accumulation of andrographolide and 14-deoxyandrographolide content, along with the upregulation of ApNAC02 (9.6-fold) and the downregulation of ApNAC83 and ApNAC21 22 in the leaves. With methyl jasmonate treatment, ApNAC21 22 expression decreased, while ApNAC02 increased (1.9-fold), with no significant change being observed in ApNAC83. The transient expression of the isolated NAC genes in a heterologous system (Nicotiana benthamiana) demonstrated their functional transcriptional activity, leading to the upregulation of the NtHMGR gene, which is related to the terpene pathway in tobacco. The expression analysis and heterologous expression of ApNAC21 22 and ApNAC02 indicated their role in andrographolide biosynthesis.

Plant-derived compounds as potential leads for new drug development targeting COVID-19

COVID-19, which was first identified in 2019 in Wuhan, China, is a respiratory illness caused by a virus called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although some patients infected with COVID-19 can remain asymptomatic, most experience a range of symptoms that can be mild to severe. Common symptoms include fever, cough, shortness of breath, fatigue, loss of taste or smell and muscle aches. In severe cases, complications can arise including pneumonia, acute respiratory distress syndrome, organ failure and even death, particularly in older adults or individuals with underlying health conditions. Treatments for COVID-19 include remdesivir, which has been authorised for emergency use in some countries, and dexamethasone, a corticosteroid used to reduce inflammation in severe cases. Biological drugs including monoclonal antibodies, such as casirivimab and imdevimab, have also been authorised for emergency use in certain situations. While these treatments have improved the outcome for many patients, there is still an urgent need for new treatments. Medicinal plants have long served as a valuable source of new drug leads and may serve as a valuable resource in the development of COVID-19 treatments due to their broad-spectrum antiviral activity. To date, various medicinal plant extracts have been studied for their cellular and molecular interactions, with some demonstrating anti-SARS-CoV-2 activity in vitro. This review explores the evaluation and potential therapeutic applications of these plants against SARS-CoV-2. This review summarises the latest evidence on the activity of different plant extracts and their isolated bioactive compounds against SARS-CoV-2, with a focus on the application of plant-derived compounds in animal models and in human studies.

The Potential of Anti-coronavirus Plant Secondary Metabolites in COVID-19 Drug Discovery as an Alternative to Repurposed Drugs: A Review

In early 2020, a global pandemic was announced due to the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), known to cause COVID-19. Despite worldwide efforts, there are only limited options regarding antiviral drug treatments for COVID-19. Although vaccines are now available, issues such as declining efficacy against different SARS-CoV-2 variants and the aging of vaccine-induced immunity highlight the importance of finding more antiviral drugs as a second line of defense against the disease. Drug repurposing has been used to rapidly find COVID-19 therapeutic options. Due to the lack of clinical evidence for the therapeutic benefits and certain serious side effects of repurposed antivirals, the search for an antiviral drug against SARS-CoV-2 with fewer side effects continues. In recent years, numerous studies have included antiviral chemicals from a variety of plant species. A better knowledge of the possible antiviral natural products and their mechanism against SARS-CoV-2 will help to develop stronger and more targeted direct-acting antiviral agents. The aim of the present study was to compile the current data on potential plant metabolites that can be investigated in COVID-19 drug discovery and development. This review represents a collection of plant secondary metabolites and their mode of action against SARS-CoV and SARS-CoV-2.

Role of dietary supplements in the continuous battle against COVID-19

A sudden outbreak of the COVID-19 pandemic was a big blow to the world community on every level. Created by a novel coronavirus, SARS-CoV-2, which was previously unknown to the human immune system. The expert opinion almost immediately united on the fact that the most effective way of fighting the pandemic would be by building immunity artificially via a mass immunization program. However, it took about a year for the approval of the first vaccine against COVID-19. In the meantime, a big part of the general population started adapting nutritious diet plans and dietary supplements to boost natural immunity as a potential prophylactic strategy against SARS-CoV-2 infection. Whether they originate from mainstream medicine, such as synthetic supplements, or traditional herbal remedies in the form of single or poly-herbs, these supplements may comprise various components that exhibit immunomodulatory, anti-inflammatory, antioxidant, and antimicrobial characteristics. There is a substantial body of predictions and expert opinions suggesting that enhancing one's diet with dietary supplements containing additional nutrients and bioactive compounds like vitamins, minerals, amino acids, fatty acids, phytochemicals, and probiotics can enhance the immune system's ability to develop resistance against COVID-19, although none of them have any conclusive evidence nor officially recommended by World Health Organization (WHO). The current review critically acclaims the gap between public perception-based preference and real evidence-based study to weigh the actual benefit of dietary supplements in relation to COVID-19 prevention and management.

A novel film spray containing curcumin inhibits SARS-CoV-2 and influenza virus infection and enhances mucosal immunity

BACKGROUND

Infection by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and influenza virus is still a major worldwide health concern. Plants are a good source of bioactive compounds to be used as preventive measures for both inhibiting the virus binding and enhancing mucosal innate immunity. Curcumin has been shown to possess antiviral activity and modulate innate immunity. Therefore, the purpose of this study was to develop an oro-nasal film spray containing curcumin and determine its antiviral activity against SARS-CoV-2 and influenza virus infection, as well as its effects on mucosal innate immunity and inflammatory cytokines in vitro.

METHODS

The antiviral activity of the film spray against SARS-CoV-2, influenza A/H1N1, A/H3N2, and influenza B was assessed in vitro by plaque reduction assay. Cytotoxicity of the film spray to oral keratinocytes and nasal epithelial cells was assessed by MTT assay, and cytotoxicity to Vero and MDCK cells was assessed by an MTS-based cytotoxicity assay. Oral and nasal innate immune markers in response to the film spray were determined by ELISA and by a commercial Milliplex Map Kit, respectively.

RESULTS

Our data show that the film spray containing curcumin can inhibit both SARS-CoV-2 and influenza virus infections while maintaining cell viability. Results obtained among 4 viruses revealed that curcumin film spray demonstrated the highest inhibitory activity against SARS-CoV-2 with the lowest EC50 of 3.15 µg/ml and the highest SI value of 4.62, followed by influenza B (EC50 = 6.32 µg/ml, SI = 2.04), influenza A/H1N1 (EC50 = 7.24 µg/ml, SI = 1.78), and influenza A/H3N2 (EC50 > 12.5 µg/ml, SI < 1.03), respectively. Antimicrobial peptides LL-37 and HD-5, IL-6 and TNF-α produced by oral keratinocytes were significantly induced by the film spray, while hBD2 was significantly reduced.

CONCLUSION

Film spray containing curcumin possesses multiple actions against SARS-CoV-2 infection by inhibiting ACE-2 binding in target cells and enhancing mucosal innate immunity. The film spray can also inhibit influenza virus infection. Therefore, the curcumin film spray may be effective in preventing the viral infection of both SARS-CoV-2 and influenza.

Design, synthesis, and anti-cancer evaluation of C-14 arylcarbamate derivatives of andrographolide

In this study, we explored a concise and mild synthetic route to produce novel C-14 arylcarbamate derivatives of andrographolide, a known anti-inflammatory and anticancer natural product. Upon assessing their anti-cancer efficacy against pancreatic ductal adenocarcinoma (PDAC) cells, some derivatives showed stronger cytotoxicity against PANC-1 cells than andrographolide. In addition, we demonstrated one derivative, compound 3m, effectively reduced the expression of oncogenic p53 mutant proteins (p53R273H and p53R248W), proliferation, and migration in PDAC lines, PANC-1 and MIA PaCa-2. Accordingly, the novel derivative holds promise as an anti-cancer agent against pancreatic cancer. In summary, our study broadens the derivative library of andrographolide and develops an arylcarbamate derivative of andrographolide with promising anticancer activity against PDAC.

AG5 is a potent non-steroidal anti-inflammatory and immune regulator that preserves innate immunity

An archetypal anti-inflammatory compound against cytokine storm would inhibit it without suppressing the innate immune response. AG5, an anti-inflammatory compound, has been developed as synthetic derivative of andrographolide, which is highly absorbable and presents low toxicity. We found that the mechanism of action of AG5 is through the inhibition of caspase-1. Interestingly, we show with in vitro generated human monocyte derived dendritic cells that AG5 preserves innate immune response. AG5 minimizes inflammatory response in a mouse model of lipopolysaccharide (LPS)-induced lung injury and exhibits in vivo anti-inflammatory efficacy in the SARS-CoV-2-infected mouse model. AG5 opens up a new class of anti-inflammatories, since contrary to NSAIDs, AG5 is able to inhibit the cytokine storm, like dexamethasone, but, unlike corticosteroids, preserves adequately the innate immunity. This is critical at the early stages of any naïve infection, but particularly in SARS-CoV-2 infections. Furthermore, AG5 showed interesting antiviral activity against SARS-CoV-2 in humanized mice.

Structure and function of SARS-CoV and SARS-CoV-2 main proteases and their inhibition: A comprehensive review

Severe acute respiratory syndrome-associated coronavirus (SARS-CoV) identified in 2003 infected ∼8000 people in 26 countries with 800 deaths, which was soon contained and eradicated by syndromic surveillance and enhanced quarantine. A closely related coronavirus SARS-CoV-2, the causative agent of COVID-19 identified in 2019, has been dramatically more contagious and catastrophic. It has infected and caused various flu-like symptoms of billions of people in >200 countries, including >6 million people died of or with the virus. Despite the availability of several vaccines and antiviral drugs against SARS-CoV-2, finding new therapeutics is needed because of viral evolution and a possible emerging coronavirus in the future. The main protease (Mpro) of these coronaviruses plays important roles in their life cycle and is essential for the viral replication. This article represents a comprehensive review of the function, structure and inhibition of SARS-CoV and -CoV-2 Mpro, including structure-activity relationships, protein-inhibitor interactions and clinical trial status.

Andrographolide inhibits infectious bronchitis virus-induced apoptosis, pyroptosis, and inflammation

BACKGROUND

Avian infectious bronchitis virus (IBV), a coronavirus, causes a huge economic loss to the poultry industry. Andrographolide (APL) is a compound with a variety of pharmacological properties, including antiviral and anti-inflammatory effects. In this study, APL was evaluated for antiviral activity by its anti-apoptotic, anti-pyroptosis, and anti-inflammatory effects.

METHODS

The cytotoxicity of APL was determined by the MTT method. We investigated the therapeutic impact of APL on IBV through a plate assay. We explored that APL inhibited IBV-induced apoptosis, pyroptosis, and inflammation in HD11 cells by RT-qPCR and immunofluorescence. Also, it was verified in the clinical chicken embryo trial.

RESULTS

We found that APL down-regulated apoptosis-related genes Caspase-3, Caspase-8, Caspase-9, Bax, Bid, and Bak, down-regulated pyroptosis gene DFNA5, and down-regulated inflammation-related genes (NF-κB, NLRP3, iNOS, TNF-α, and IL-1β). In addition, APL reduced the reactive oxygen species (ROS) production in cells. Finally, clinical trials showed that APL inhibited IBV-induced apoptosis, pyroptosis, and inflammation, as well as reduced the mortality and malformation of chicken embryos.

CONCLUSIONS

In this study, we delved into the antiviral properties of APL in the context of chicken macrophage (HD11) infection with IBV. Our findings confirm that andrographolide effectively inhibits apoptosis, pyroptosis, and inflammation by IBV infection. Furthermore, this inhibition was verified on chicken embryos in vivo. This inhibition suggests a substantial potential for APL as a therapeutic agent to mitigate the harmful effects of IBV on host cells.

The Pathogenesis of COVID-19-Related Taste Disorder and Treatments

COVID-19, mainly manifested as acute respiratory distress syndrome, has afflicted millions of people worldwide since 2019. Taste dysfunction is a common early-stage symptom of COVID-19 infection that burdens patients for weeks or even permanently in some cases. Owing to its subjectivity and complexity, the mechanism of taste disorder is poorly studied. Previous studies have reported that the COVID-19 entry receptors are highly expressed in taste buds, thereby intensifying the cytocidal effect. Taste receptor cells are vulnerable to inflammation, and the COVID-19-induced cytokine storm causes secondary damage to taste function. Interferon and various proinflammatory cytokines can trigger cell apoptosis and disrupt the renewal of taste bud stem cells. This immune response can be further enhanced by the accumulation of Angiotensin II (Ang II) caused by an unbalanced local renin-angiotensin system (RAS) system. In addition, severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is neurotropic and can invade the brain through the olfactory bulb, affecting the nervous system. Other factors, such as host zinc deficiency, genetic susceptibility, sialic acid, and some neurotransmitters, also contribute to the pathogenesis process. Although several medical interventions have displayed effectiveness, only a few strategies exist for the treatment of postinfectious dysgeusia. Stem cell-based taste regeneration offers promise for long-term taste disorders. Clinical studies have demonstrated that stem cells can treat long COVID-19 through immune regulation. In dysgeusia, the differentiation of taste bud stem cells can be stimulated through exogenous epithelial-derived and neural-derived factors to regenerate taste buds. Tongue organoids are also emerging as functional taste buds, offering new insights into the study of taste regeneration. This review presents the current evidence of the pathogenesis of COVID-19-related dysgeusia, summarizes currently available treatments, and suggests future directions of taste regeneration therapy.

Identification of prospective covalent inhibitors for SARS-CoV-2 main protease using structure-based approach

The rapid global spread of SARS-CoV-2 has recently caused havoc and forced the world into a state of the pandemic causing respiratory, gastrointestinal, hepatic, and neurologic diseases. It persistently, through mutation, develops into new variants of the virus that have appeared over time. As main protease (Mpro) is involved in proteolysis of two overlapping polyproteins pp1a and pp1ab to produce 16 non-structural proteins having a paramount factor in the virus replication that have a cysteine-histidine catalytic dyad. A computational approach, guiding a covalent docking as it offers higher potency, long duration of action and decreased drug resistance advantages over the conventional docking of the ligands on a catalytic dyad, is applied for SARS-CoV-2 main protease (Mpro) in this manuscript to divulge better molecules. Mpro active site contains Cys145 residue which act as a nucleophile and can donate its electron to an electrophilic molecule by interacting covalently. Furthermore, the ligand-protein complexes are allowed to simulate their dynamic studies to look into their time-based interaction stability and also, a parallel study of ADME properties for the hit molecules is also performed. Important insights from the studies revealed that the interactions are persistent and molecules may be considered for further optimization in clinical investigation.Communicated by Ramaswamy H. Sarma.

COVID-19 Therapeutic Potential of Natural Products

Despite the fact that coronavirus disease 2019 (COVID-19) treatment and management are now considerably regulated, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is still one of the leading causes of death in 2022. The availability of COVID-19 vaccines, FDA-approved antivirals, and monoclonal antibodies in low-income countries still poses an issue to be addressed. Natural products, particularly traditional Chinese medicines (TCMs) and medicinal plant extracts (or their active component), have challenged the dominance of drug repurposing and synthetic compound libraries in COVID-19 therapeutics. Their abundant resources and excellent antiviral performance make natural products a relatively cheap and readily available alternative for COVID-19 therapeutics. Here, we deliberately review the anti-SARS-CoV-2 mechanisms of the natural products, their potency (pharmacological profiles), and application strategies for COVID-19 intervention. In light of their advantages, this review is intended to acknowledge the potential of natural products as COVID-19 therapeutic candidates.

Anti-Cancer Agent: The Labdane Diterpenoid-Andrographolide

In spite of the progress in treatment strategies, cancer remains a major cause of death worldwide. Therefore, the main challenge should be the early diagnosis of cancer and the design of an optimal therapeutic strategy to increase the patient's life expectancy as well as the continuation of the search for increasingly active and selective molecules for the treatment of different forms of cancer. In the recent decades, research in the field of natural compounds has increasingly shifted towards advanced and molecular level understandings, thus leading to the development of potent anti-cancer agents. Among them is the diterpene lactone andrographolide, isolated from Andrographis paniculata (Burm.f.) Wall. ex Nees that showed shows a plethora of biological activities, including not only anti-cancer activity, but also anti-inflammatory, anti-viral, anti-bacterial, neuroprotective, hepatoprotective, hypoglycemic, and immunomodulatory properties. Andrographolide has been shown to act as an anti-tumor drug by affecting specific molecular targets that play a part in the development and progression of several cancer types including breast, lung, colon, renal, and cervical cancer, as well as leukemia and hepatocarcinoma. This review comprehensively and systematically summarized the current research on the potential anti-cancer properties of andrographolide highlighting its mechanisms of action, pharmacokinetics, and potential side effects and discussing the future perspectives, challenges, and limitations of use.

Antiviral effects of phytochemicals against severe acute respiratory syndrome coronavirus 2 and their mechanisms of action: A review

The worldwide spreading of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has posed a serious threat to health, economic, environmental, and social aspects of human lives. Currently, there are no approved treatments that can effectively block the virus although several existing antimalarial and antiviral agents have been repurposed and allowed use during the pandemic under the emergency use authorization (EUA) status. This review gives an updated overview of the antiviral effects of phytochemicals including alkaloids, flavonoids, and terpenoids against the COVID-19 virus and their mechanisms of action. Search for natural lead molecules against SARS-CoV-2 has been focusing on virtual screening and in vitro studies on phytochemicals that have shown great promise against other coronaviruses such as SARS-CoV. Until now, there is limited data on in vivo investigations to examine the antiviral activity of plants in SARS-CoV-2-infected animal models and the studies were performed using crude extracts. Further experimental and preclinical investigations on the in vivo effects of phytochemicals have to be performed to provide sufficient efficacy and safety data before clinical studies can be performed to develop them into COVID-19 drugs. Phytochemicals are potential sources of new chemical leads for the development of safe and potent anti-SARS-CoV-2 agents.

J, Petermann O, Scapozza L, Orts J, Kirchmair J, Rabenau HF, Rollinger JM. Identification of Natural Products Inhibiting SARS-CoV-2 by Targeting Viral Proteases: A Combined in Silico and in Vitro Approach

In this study, an integrated in silico-in vitro approach was employed to discover natural products (NPs) active against SARS-CoV-2. The two SARS-CoV-2 viral proteases, i.e., main protease (Mpro) and papain-like protease (PLpro), were selected as targets for the in silico study. Virtual hits were obtained by docking more than 140,000 NPs and NP derivatives available in-house and from commercial sources, and 38 virtual hits were experimentally validated in vitro using two enzyme-based assays. Five inhibited the enzyme activity of SARS-CoV-2 Mpro by more than 60% at a concentration of 20 μM, and four of them with high potency (IC50 < 10 μM). These hit compounds were further evaluated for their antiviral activity against SARS-CoV-2 in Calu-3 cells. The results from the cell-based assay revealed three mulberry Diels-Alder-type adducts (MDAAs) from Morus alba with pronounced anti-SARS-CoV-2 activities. Sanggenons C (12), O (13), and G (15) showed IC50 values of 4.6, 8.0, and 7.6 μM and selectivity index values of 5.1, 3.1 and 6.5, respectively. The docking poses of MDAAs in SARS-CoV-2 Mpro proposed a butterfly-shaped binding conformation, which was supported by the results of saturation transfer difference NMR experiments and competitive 1H relaxation dispersion NMR spectroscopy.

Discovery of Natural Bisbenzylisoquinoline Analogs from the Library of Thai Traditional Plants as SARS-CoV-2 3CLPro Inhibitors: In Silico Molecular Docking, Molecular Dynamics, and In Vitro Enzymatic Activity

The emergence of SARS-CoV-2 in December 2019 has become a global issue due to the continuous upsurge in patients and the lack of drug efficacy for treatment. SARS-CoV-2 3CL^Pro is one of the most intriguing biomolecular targets among scientists worldwide for developing antiviral drugs due to its relevance in viral replication and transcription. Herein, we utilized computer-assisted drug screening to investigate 326 natural products from Thai traditional plants using structure-based virtual screening against SARS-CoV-2 3CL^Pro. Following the virtual screening, the top 15 compounds based on binding energy and their interactions with key amino acid Cys145 were obtained. Subsequently, they were further evaluated for protein-ligand complex stability via molecular dynamics simulation and binding free energy calculation using molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) approaches. Following drug-likeness and ADME/Tox assessments, seven bisbenzylisoquinolines were obtained, including neferine (3), liensinine (4), isoliensinine (5), dinklacorine (8), tiliacorinine (13), 2'-nortiliacorinine (14), and yanangcorinine (15). These compounds computationally showed a higher binding affinity than native N3 and GC-373 inhibitors and attained stable interactions on the active site of 3CL^pro during 100 ns in molecular dynamics (MD) simulation. Moreover, the in vitro enzymatic assay showed that most bisbenzylisoquinolines could experimentally inhibit SARS-CoV-2 3CL^Pro. To our delight, isoliensinine (5) isolated from Nelumbo nucifera demonstrated the highest inhibition of protease activity with the IC₅₀ value of 29.93 μM with low toxicity on Vero cells. Our findings suggested that bisbenzylisoquinoline scaffolds could be potentially used as an in vivo model for the development of effective anti-SARS-CoV-2 drugs.

Critical Review of Plant-Derived Compounds as Possible Inhibitors of SARS-CoV-2 Proteases: A Comparison with Experimentally Validated Molecules

Ever since coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, was declared a pandemic on March 11, 2020, by the WHO, a concerted effort has been made to find compounds capable of acting on the virus and preventing its replication. In this context, researchers have refocused part of their attention on certain natural compounds that have shown promising effects on the virus. Considering the importance of this topic in the current context, this study aimed to present a critical review and analysis of the main reports of plant-derived compounds as possible inhibitors of the two SARS-CoV-2 proteases: main protease (Mpro) and Papain-like protease (PLpro). From the search in the PubMed database, a total of 165 published articles were found that met the search patterns. A total of 590 unique molecules were identified from a total of 122 articles as potential protease inhibitors. At the same time, 114 molecules reported as natural products and with annotation of theoretical support and antiviral effects were extracted from the COVID-19 Help database. After combining the molecules extracted from articles and those obtained from the database, we identified 648 unique molecules predicted as potential inhibitors of Mpro and/or PLpro. According to our results, several of the predicted compounds with higher theoretical confidence are present in many plants used in traditional medicine and even food, such as flavonoids, carboxylic acids, phenolic acids, triterpenes, terpenes phytosterols, and triterpenoids. These are potential inhibitors of Mpro and PLpro. Although the predictions of several molecules against SARS-CoV-2 are promising, little experimental information was found regarding certain families of compounds. Only 45 out of the 648 unique molecules have experimental data validating them as inhibitors of Mpro or PLpro, with the most frequent scaffold present in these 45 compounds being the flavone. The novelty of this work lies in the analysis of the structural diversity of the chemical space among the molecules predicted as inhibitors of SARS-CoV-2 Mpro and PLpro proteases and the comparison to those molecules experimentally validated. This work emphasizes the need for experimental validation of certain families of compounds, preferentially combining classical enzymatic assays with interaction-based methods. Furthermore, we recommend checking the presence of Pan-Assay Interference Compounds (PAINS) and the presence of molecules previously reported as inhibitors of Mpro or PLpro to optimize resources and time in the discovery of new SARS-CoV-2 antivirals from plant-derived molecules.

Small molecules in the treatment of COVID-19

The outbreak of COVID-19 has become a global crisis, and brought severe disruptions to societies and economies. Until now, effective therapeutics against COVID-19 are in high demand. Along with our improved understanding of the structure, function, and pathogenic process of SARS-CoV-2, many small molecules with potential anti-COVID-19 effects have been developed. So far, several antiviral strategies were explored. Besides directly inhibition of viral proteins such as RdRp and Mpro, interference of host enzymes including ACE2 and proteases, and blocking relevant immunoregulatory pathways represented by JAK/STAT, BTK, NF-κB, and NLRP3 pathways, are regarded feasible in drug development. The development of small molecules to treat COVID-19 has been achieved by several strategies, including computer-aided lead compound design and screening, natural product discovery, drug repurposing, and combination therapy. Several small molecules representative by remdesivir and paxlovid have been proved or authorized emergency use in many countries. And many candidates have entered clinical-trial stage. Nevertheless, due to the epidemiological features and variability issues of SARS-CoV-2, it is necessary to continue exploring novel strategies against COVID-19. This review discusses the current findings in the development of small molecules for COVID-19 treatment. Moreover, their detailed mechanism of action, chemical structures, and preclinical and clinical efficacies are discussed.

Molecular Mechanism and Role of Japanese Encephalitis Virus Infection in Central Nervous System-Mediated Diseases

The Japanese encephalitis virus (JEV) is the most common cause of neurodegenerative disease in Southeast Asia and the Western Pacific region; approximately 1.15 billion people are at risk, and thousands suffer from permanent neurological disorders across Asian countries, with 10-15 thousand people dying each year. JEV crosses the blood-brain barrier (BBB) and forms a complex with receptors on the surface of neurons. GRP78, Src, TLR7, caveolin-1, and dopamine receptor D2 are involved in JEV binding and entry into the neurons, and these receptors also play a role in carcinogenic activity in cells. JEV binds to GRP78, a member of the HSP70 overexpressed on malignant cells to enter neurons, indicating a higher chance of JEV infection in cancer patients. However, JEV enters human brain microvascular endothelial cells via an endocytic pathway mediated by caveolae and the ezrin protein and also targets dopamine-rich areas for infection of the midbrain via altering dopamine levels. In addition, JEV complexed with CLEC5A receptor of macrophage cells is involved in the breakdown of the BBB and central nervous system (CNS) inflammation. CLEC5A-mediated infection is also responsible for the influx of cytokines into the CNS. In this review, we discuss the neuronal and macrophage surface receptors involved in neuronal death.

Neurological disorders of COVID-19: insights to applications of natural products from plants and microorganisms

In addition to the typical respiratory manifestations, various disorders including involvement of the nerve system have been detected in COVID-19 ranging from 22 to 36%. Although growing records are focusing on neurological aspects of COVID-19, the pathophysiological mechanisms and related therapeutic methods remain obscure. Considering the increased concerns of SARS-CoV-2 potential for more serious neuroinvasion conditions, the present review attempts to focus on the neuroprotective effects of natural compounds as the principle source of therapeutics inhibiting multiple steps of the SARS-CoV-2 infection cycle. The great majority of the natural products with anti-SARS-CoV-2 activity mainly inhibit the attachment, entry and gene expression rather than the replication, assembly, or release. Although microbial-derived natural products comprise 38.5% of the known natural products with neuroprotective effects following viral infection, the neuroprotective potential of the majority of microorganisms is still undiscovered. Among natural products, chrysin, huperzine A, ginsenoside Rg1, pterostilbene, and terrein have shown potent in vitro neuroprotective activity and can be promising for new or repurpose drugs for neurological complications of SARS-CoV-2.

The use of Andrographis paniculata and its effects on liver biochemistry of patients with gastrointestinal problems in Thailand during the COVID-19 pandemic: a cross sectional study

In the COVID-19 pandemic, healthcare facility supply and access are limited. There was an announcement promoting Andrographis paniculata (ADG) use for treatment of mild COVID-19 patients in Thailand, but misconception of taking for prevention might occur. Moreover, the effect of ADG on liver function test (LFT) has not been established. To study the ADG use and effect on LFT in patients with gastrointestinal (GI) problems, conducted a cross-sectional study including GI patients who voluntarily filled the ADG questionnaire in Aug-Sep 2021. LFT data at that visit and at the prior visit (if available) were obtained. The changes in LFT within the same person were analyzed and compared between patients with and without ADG consumption. During the study period, a total of 810 patients completed the survey, 168 patients (20.7%) took ADG within the past month. LFT data were available in 485 (59.9%) patients, the median alanine aminotransferase (ALT)  change compared with the prior visit was higher in the ADG vs control group (+ 2 vs 0, p = 0.029), and 44.5% had increased ALT (> 3 U/L) vs 32.2% in the ADG and control group, respectively (p = 0.018). Factors independently associated with an increased ALT, from a multivariable logistic regression, were ADG exposure (adjusted OR 1.62, p = 0.042), and patients with NAFLD who gained weight (adjusted OR 2.37, p = 0.046). In conclusion, one-fifth of GI patients recently took ADG, even it is not recommended for COVID-19 prevention. Those who took ADG are more likely to experience an increased ALT than who did not. The potential risk of ADG consumption on liver function should be further assessed.

Antiviral activity of medicinal plant-derived products against SARS-CoV-2

This review presents information from several studies that have demonstrated the antiviral activity of extracts (Andrographis paniculata, Artemisia annua, Artemisia afra, Cannabis sativa, Curcuma longa, Echinacea purpurea, Olea europaea, Piper nigrum, and Punica granatum) and phytocompounds derived from medicinal plants (artemisinins, glycyrrhizin, and phenolic compounds) against SARS-CoV-2. A brief background of the plant products studied, the methodology used to evaluate the antiviral activity, the main findings from the research, and the possible mechanisms of action are presented. These plant products have been shown to impede the adsorption of SARS-CoV-2 to the host cell, and prevent multiplication of the virus post its entry into the host cell. In addition to antiviral activity, the plant products have also been demonstrated to exert an immunomodulatory effect by controlling the excessive release of cytokines, which is commonly associated with SARS-CoV-2 infections.

Andrographolide, a natural anti-inflammatory agent: An Update

Botanicals have attracted much attention in the field of anti-inflammatory due to their good pharmacological activity and efficacy. Andrographis paniculata is a natural plant ingredient that is widely used around the world. Andrographolide is the main active ingredient derived from Andrographis paniculata, which has a good effect on the treatment of inflammatory diseases. This article reviews the application, anti-inflammatory mechanism and molecular targets of andrographolide in different inflammatory diseases, including respiratory, digestive, immune, nervous, cardiovascular, skeletal, and tumor system diseases. And describe its toxicity and explain its safety. Studies have shown that andrographolide can be used to treat inflammatory lesions of various systemic diseases. In particular, it acts on many inflammation-related signalling pathways. The future direction of andrographolide research is also introduced, as is the recent research that indicates its potential clinical application as an anti-inflammatory agent.

An Effective Platform for SARS-CoV-2 Prevention by Combining Neutralization and RNAi Technology

At present, the coronavirus disease 2019 (COVID-19) pandemic is a global health crisis. Scientists all over the globe are urgently looking forward to an effective solution to prevent the spread of the epidemic and avoid more casualties at an early date. In this study, we establish an effective platform for the prevention of SARS-CoV-2 by combining the neutralization strategy and RNAi technology. To protect normal cells from infection, the customized cells are constructed to stably express viral antigenic receptor ACE2 on the cell membrane. These modified cells are used as bait for inducing the viral entry. The transcription and replication activities of viral genome are intercepted subsequently by the intracellular shRNAs, which are complementary to the viral gene fragments. A pseudotyped virus reconstructed from the HIV lentivirus is utilized as a virus model, by which we validate the feasibility and effectiveness of our strategy in vitro. Our work establishes an initial model and lays the foundation for future prevention and treatment of various RNA viruses.

A comprehensive review on disposition kinetics and dosage of oral administration of Andrographis paniculata, an alternative herbal medicine, in co-treatment of coronavirus disease

Coronavirus disease 2019 (COVID-19) is a present global health crisis that is driving the investigation of alternative phytomedicines for antiviral purposes. The evidence suggests that Andrographis paniculata crude or extract is a promising candidate for treating symptoms of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This review aims to consolidate the available reports on the disposition kinetics of andrographolide, a main active component of A. paniculata. The second objective of this review is to summarize the available reports on an appropriate oral dosage for the use of andrographolide in upper respiratory tract infections (URTIs) and other viral infectious diseases. The data were collected from the literature on absorption, distribution, biotransformation, and excretion of andrographolide, and information was also obtained from scientific databases about the use of A. paniculata. The finding of this review on pharmacokinetics indicates that andrographolide is slightly absorbed into the blood circulation and exhibits poor oral bioavailability, whereas its distribution process is unrestricted. In the termination phase, andrographolide preferentially undergoes biotransformation partly through phase I hydroxylation and phase II conjugation, and it is then eliminated via the renal excretion and hepatobiliary system. The key summary of the recommended dosage for andrographolide in uncomplicated URTI treatment is 30 mg/day for children and 60 mg/day for adults. The dose for adult patients with pharyngotonsillitis could be increased to 180 mg/day, but not exceed 360 mg/day. Co-treatment with A. paniculata in concert with the standard supportive care for influenza reduced the severity of symptoms, shortened treatment duration, and decreased the risk of developing post-influenza complications. The recommended starting dose for use in patients with mild COVID-19 is 180 mg/day of andrographolide, based on the dose used in patients experiencing a URTI with inflammation. This review is not only applicable for evaluating the appropriate doses of andrographolide for antiviral treatments but also encourages future research evaluating the effectiveness of these recommended dosages during the COVID-19 pandemic.

Andrographolide and Deoxyandrographolide Inhibit Protease and IFN-Antagonist Activities of Foot-and-Mouth Disease Virus 3Cpro

Foot-and mouth-disease (FMD) caused by the FMD virus (FMDV) is highly contagious and negatively affects livestock worldwide. The control of the disease requires a combination of measures, including vaccination; however, there is no specific treatment available. Several studies have shown that plant-derived products with antiviral properties were effective on viral diseases. Herein, antiviral activities of andrographolide (AGL), deoxyandrographolide (DAG), and neoandrographolide (NEO) against FMDV serotype A were investigated using an in vitro cell-based assay. The results showed that AGL and DAG inhibited FMDV in BHK-21 cells. The inhibitory effects of AGL and DAG were evaluated by RT-qPCR and exhibited EC50 values of 52.18 ± 0.01 µM (SI = 2.23) and 36.47 ± 0.07 µM (SI = 9.22), respectively. The intracellular protease assay revealed that AGL and DAG inhibited FMDV 3Cpro with IC50 of 67.43 ± 0.81 and 25.58 ± 1.41 µM, respectively. Additionally, AGL and DAG significantly interfered with interferon (IFN) antagonist activity of the 3Cpro by derepressing interferon-stimulating gene (ISGs) expression. The molecular docking confirmed that the andrographolides preferentially interacted with the 3Cpro active site. However, NEO had no antiviral effect in any of the assays. Conclusively, AGL and DAG inhibited FMDV serotype A by interacting with the 3Cpro and hindered its protease and IFN antagonist activities.

A Comprehensive Review of Andrographis paniculata (Burm. f.) Nees and Its Constituents as Potential Lead Compounds for COVID-19 Drug Discovery

The COVID-19 pandemic has intensively disrupted global health, economics, and well-being. Andrographis paniculata (Burm. f.) Nees has been used as a complementary treatment for COVID-19 in several Asian countries. This review aimed to summarize the information available regarding A. paniculata and its constituents, to provide critical points relating to its pharmacological properties, safety, and efficacy, revealing its potential to serve as a source of lead compounds for COVID-19 drug discovery. A. paniculata and its active compounds possess favorable antiviral, anti-inflammatory, immunomodulatory, and antipyretic activities that could be beneficial for COVID-19 treatment. Interestingly, recent in silico and in vitro studies have revealed that the active ingredients in A. paniculata showed promising activities against 3CLpro and its virus-specific target protein, human hACE2 protein; they also inhibit infectious virion production. Moreover, existing publications regarding randomized controlled trials demonstrated that the use of A. paniculata alone or in combination was superior to the placebo in reducing the severity of upper respiratory tract infection (URTI) manifestations, especially as part of early treatment, without serious side effects. Taken together, its chemical and biological properties, especially its antiviral activities against SARS-CoV-2, clinical trials on URTI, and the safety of A. paniculata, as discussed in this review, support the argument that A. paniculata is a promising natural source for drug discovery regarding COVID-19 post-infectious treatment, rather than prophylaxis.

Virofree, an Herbal Medicine-Based Formula, Interrupts the Viral Infection of Delta and Omicron Variants of SARS-CoV-2

Coronavirus disease 2019 (COVID-19) remains a threat with the emergence of new variants, especially Delta and Omicron, without specific effective therapeutic drugs. The infection causes dysregulation of the immune system with a cytokine storm that eventually leads to fatal acute respiratory distress syndrome (ARDS) and further irreversible pulmonary fibrosis. Therefore, the promising way to inhibit infection is to disrupt the binding and fusion between the viral spike and the host ACE2 receptor. A transcriptome-based drug screening platform has been developed for COVID-19 to explore the possibility and potential of the long-established drugs or herbal medicines to reverse the unique genetic signature of COVID-19. In silico analysis showed that Virofree, an herbal medicine, reversed the genetic signature of COVID-19 and ARDS. Biochemical validations showed that Virofree could disrupt the binding of wild-type and Delta-variant spike proteins to ACE2 and its syncytial formation via cell-based pseudo-typed viral assays, as well as suppress binding between several variant recombinant spikes to ACE2, especially Delta and Omicron. Additionally, Virofree elevated miR-148b-5p levels, inhibited the main protease of SARS-CoV-2 (Mpro), and reduced LPS-induced TNF-α release. Virofree also prevented cellular iron accumulation leading to ferroptosis which occurs in SARS-CoV-2 patients. Furthermore, Virofree was able to reduce pulmonary fibrosis-related protein expression levels in vitro. In conclusion, Virofree was repurposed as a potential herbal medicine to combat COVID-19. This study highlights the inhibitory effect of Virofree on the entry of Delta and Omicron variants of SARS-CoV-2, which have not had any effective treatments during the emergence of the new variants spreading.

Andrographolide induces anti-SARS-CoV-2 response through host-directed mechanism: an in silico study

Aim: Considering the present alarming situation of COVID-19 pandemic, we concentrated on evaluating the efficacy of a novel natural antiviral drug-candidate andrographolide against SARS-CoV-2 through an in silico model of study. Materials & methods: Interaction of andrographolide against the major host molecules that are responsible for SARS-CoV-2 pathogenesis were determined using bio-computational tools, in other words, molecular docking, molecular dynamics simulation and pharmacodynamics–pharmacokinetics analysis. Result: Computational findings represent that andrographolide efficiently interacts with the major human–host-associated putative drug-targets of viral-entry points like furin (-10.54 kcal/mol), TMPRSS-2 (-9.50 kcal/mol), ACE2 (-8.99 kcal/mol) and Cathepsin L (-8.98 kcal/mol). Moreover, it also blocks the inflammatory regulators including TLR4-MD2 and IL-6, which promote virus-induced inflammation leading to cytokine storm in the host body. Conclusion: This work elucidates that, the candidature of andrographolide can be utilized as a potent natural agent for the therapeutic intervention of SARS-CoV-2 through host-directed treatment.

Maturation of the SARS-CoV-2 virus is regulated by dimerization of its main protease

SARS-CoV-2 main protease (M^pro) involved in COVID-19 is required for maturation of the virus and infection of host cells. The key question is how to block the activity of M^pro. By combining atomistic simulations with machine learning, we found that the enzyme regulates its own activity by a collective allosteric mechanism that involves dimerization and binding of a single substrate. At the core of the collective mechanism is the coupling between the catalytic site residues, H41 and C145, which direct the activity of M^pro dimer, and two salt bridges formed between R4 and E290 at the dimer interface. If these salt bridges are mutated, the activity of M^pro is blocked. The results suggest that dimerization of main proteases is a general mechanism to foster coronavirus proliferation, and propose a robust drug-based strategy that does not depend on the frequently mutating spike proteins at the viral envelope used to develop vaccines.

The NLRP3 Inflammasome Pathway: A Review of Mechanisms and Inhibitors for the Treatment of Inflammatory Diseases

The NLRP3 inflammasome is a multiprotein complex that plays a pivotal role in regulating the innate immune system and inflammatory signaling. Upon activation by PAMPs and DAMPs, NLRP3 oligomerizes and activates caspase-1 which initiates the processing and release of pro-inflammatory cytokines IL-1β and IL-18. NLRP3 is the most extensively studied inflammasome to date due to its array of activators and aberrant activation in several inflammatory diseases. Studies using small molecules and biologics targeting the NLRP3 inflammasome pathway have shown positive outcomes in treating various disease pathologies by blocking chronic inflammation. In this review, we discuss the recent advances in understanding the NLRP3 mechanism, its role in disease pathology, and provide a broad review of therapeutics discovered to target the NLRP3 pathway and their challenges.

Effect of herbal compounds on coronavirus; a systematic review and meta-analysis

BACKGROUND

The new coronavirus (COVID-19) has been transmitted exponentially. Numerous studies have been performed in recent years that have shown the inhibitory effect of plant extracts or plant-derived compounds on the coronavirus family. In this study, we want to use systematic review and meta-analysis to answer the question, which herbal compound has been more effective?

MAIN BODY

The present study is based on the guidelines for conducting meta-analyzes. An extensive search was conducted in the electronic database, and based on the inclusion and exclusion criteria, articles were selected and data screening was done. Quality control of articles was performed. Data analysis was carried out in STATA software.

CONCLUSION

Due to the variety of study methods, definitive conclusions are not possible. However, in this study, we attempted to gather all the available evidence on the effect of plant compounds on SARS-COV-2 to be used for the development and use of promising antiviral agents against this virus and other coronaviruses. Trypthantrin, Sambucus extract, S. cusia extract, Boceprevir and Indigole B, dioica agglutinin urtica had a good effect on reducing the virus titer. Also among the compounds that had the greatest effect on virus inhibition, Saikosaponins B2, SaikosaponinsD, SaikosaponinsA and Phillyrin, had an acceptable selectivity index greater than 10. Andrographolide showed the highest selectivity index on SARS-COV-2. Our study confirmed insufficient data to support alkaloid compounds against SARS-COV-2, and the small number of studies that used alkaloid compounds was a limitation. It is recommended to investigate the effect of more alkaloid compounds against Corona virus.

Molecular docking unveils the potential of andrographolide derivatives against COVID-19: an in silico approach

BACKGROUND

The recent severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection cause high mortality and there is an emergency need to develop a specific drug to treat the novel coronavirus disease, COVID-19. However, some natural and synthetic products with action against SARS-CoV-2 have been reported in recent research, there is no specific drug available for treating COVID-19. In the present study, molecular interaction analysis was performed for 16 semisynthetic andrographolides (AGP) against 5 SARS-CoV-2 enzymes main protease (Mpro, PDB: 6LU7), papain-like protease (PLpro, PDB: 6WUU), spike glycoprotein (S, PDB: 6VXX), NSP15 endoribonuclease (NSP15, PDB: 6VWW), and RNA-dependent RNA polymerase (RdRp, PDB: 6M71). Moreover, the compounds pharmacokinetic and toxic profiles were also analyzed using computational tools.

RESULTS

The protein-ligand docking score (kcal/mol) revealed that all the tested AGP derivatives showed a better binding affinity towards all the tested enzymes than hydroxychloroquine (HCQ). Meanwhile, all the tested AGP derivatives showed a better binding score with RdRp and S than remdesivir (REM). Interestingly, compounds 12, 14, and 15 showed a better binding affinity towards the all the tested enzyme than AGP, REM, and HCQ. AGP-16 had shown - 8.7 kcal/mol binding/docking score for Mpro, AGP-15 showed - 8.6 kcal/mol for NSP15, and AGP-10, 13, and 15 exhibited - 8.7, - 8.9, and - 8.7 kcal/mol, respectively, for S.

CONCLUSION

Overall results of the present study concluded that AGP derivatives 14 and 15 could be the best 'lead' candidate for the treatment against SARS-CoV-2 infection. However, molecular dynamic studies and pharmacological screenings are essential to developing AGP derivatives 14 and 15 as a drug against COVID-19.

Honeysuckle (Lonicera japonica) and Huangqi (Astragalus membranaceus) Suppress SARS-CoV-2 Entry and COVID-19 Related Cytokine Storm in Vitro

COVID-19 is threatening human health worldwide but no effective treatment currently exists for this disease. Current therapeutic strategies focus on the inhibition of viral replication or using anti-inflammatory/immunomodulatory compounds to improve host immunity, but not both. Traditional Chinese medicine (TCM) compounds could be promising candidates due to their safety and minimal toxicity. In this study, we have developed a novel in silico bioinformatics workflow that integrates multiple databases to predict the use of honeysuckle (Lonicera japonica) and Huangqi (Astragalus membranaceus) as potential anti-SARS-CoV-2 agents. Using extracts from honeysuckle and Huangqi, these two herbs upregulated a group of microRNAs including let-7a, miR-148b, and miR-146a, which are critical to reduce the pathogenesis of SARS-CoV-2. Moreover, these herbs suppressed pro-inflammatory cytokines including IL-6 or TNF-α, which were both identified in the cytokine storm of acute respiratory distress syndrome, a major cause of COVID-19 death. Furthermore, both herbs partially inhibited the fusion of SARS-CoV-2 spike protein-transfected BHK-21 cells with the human lung cancer cell line Calu-3 that was expressing ACE2 receptors. These herbs inhibited SARS-CoV-2 M^pro activity, thereby alleviating viral entry as well as replication. In conclusion, our findings demonstrate that honeysuckle and Huangqi have the potential to be used as an inhibitor of SARS-CoV-2 virus entry that warrants further in vivo analysis and functional assessment of miRNAs to confirm their clinical importance. This fast-screening platform can also be applied to other drug discovery studies for other infectious diseases.

Progress on SARS-CoV-2 3CLpro Inhibitors: Inspiration from SARS-CoV 3CLpro Peptidomimetics and Small-Molecule Anti-Inflammatory Compounds

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) currently poses a threat to human health. 3C-like proteinase (3CLpro) plays an important role in the viral life cycle. Hence, it is considered an attractive antiviral target protein. Whole-genome sequencing showed that the sequence homology between SARS-CoV-2 3CLpro and SARS-CoV 3CLpro is 96.08%, with high similarity in the substrate-binding region. Thus, assessing peptidomimetic inhibitors of SARS-CoV 3CLpro could accelerate the development of peptidomimetic inhibitors for SARS-CoV-2 3CLpro. Accordingly, we herein discuss progress on SARS-CoV-2 3CLpro peptidomimetic inhibitors. Inflammation plays a major role in the pathophysiological process of COVID-19. Small-molecule compounds targeting 3CLpro with both antiviral and anti-inflammatory effects are also briefly discussed in this paper.

Pharmacogenetics and Precision Medicine Approaches for the Improvement of COVID-19 Therapies

Many drugs are being administered to tackle coronavirus disease 2019 (COVID-19) pandemic situations without establishing clinical effectiveness or tailoring safety. A repurposing strategy might be more effective and successful if pharmacogenetic interventions are being considered in future clinical studies/trials. Although it is very unlikely that there are almost no pharmacogenetic data for COVID-19 drugs, however, from inferring the pharmacokinetic (PK)/pharmacodynamic(PD) properties and some pharmacogenetic evidence in other diseases/clinical conditions, it is highly likely that pharmacogenetic associations are also feasible in at least some COVID-19 drugs. We strongly mandate to undertake a pharmacogenetic assessment for at least these drug-gene pairs (atazanavir-UGT1A1, ABCB1, SLCO1B1, APOA5; efavirenz-CYP2B6; nevirapine-HLA, CYP2B6, ABCB1; lopinavir-SLCO1B3, ABCC2; ribavirin-SLC28A2; tocilizumab-FCGR3A; ivermectin-ABCB1; oseltamivir-CES1, ABCB1; clopidogrel-CYP2C19, ABCB1, warfarin-CYP2C9, VKORC1; non-steroidal anti-inflammatory drugs (NSAIDs)-CYP2C9) in COVID-19 patients for advancing precision medicine. Molecular docking and computational studies are promising to achieve new therapeutics against SARS-CoV-2 infection. The current situation in the discovery of anti-SARS-CoV-2 agents at four important targets from in silico studies has been described and summarized in this review. Although natural occurring compounds from different herbs against SARS-CoV-2 infection are favorable, however, accurate experimental investigation of these compounds is warranted to provide insightful information. Moreover, clinical considerations of drug-drug interactions (DDIs) and drug-herb interactions (DHIs) of the existing repurposed drugs along with pharmacogenetic (e.g., efavirenz and CYP2B6) and herbogenetic (e.g., andrographolide and CYP2C9) interventions, collectively called multifactorial drug-gene interactions (DGIs), may further accelerate the development of precision COVID-19 therapies in the real-world clinical settings.

Recent Development of Small Molecules for SARS-CoV-2 and the Opportunity for Fragment-Based Drug Discovery

Abstract:

The ongoing pandemic of Covid-19 caused by SARS-CoV-2 is a major threat to global public health, drawing attention to develop new therapeutics for treatment. Much research work is focused on identifying or repurposing new small molecules to serve as potential inhibitors by interacting with viral or host-cell molecular targets and understanding the nature of the virus in the host cells. Identifying small molecules as potent inhibitors at an early stage is advantageous to make a molecule with higher potency and then find a lead compound for the development of drug discovery. Small molecules can show their inhibition property by targeting either SARS-CoV-2 main protease (Mpro) enzyme, papain-like protease (PLpro) enzyme, or helicase (Hel), or blocking the spike (S) protein angiotensin-converting enzyme 2 (ACE2) receptor. A very recent outbreak of a new variant (B.1.617.2—termed as Delta variant) of SARS-CoV-2 worldwide posed a greater challenge as it is resistant to clinically undergoing vaccine trials. Thus, the development of new drug molecules is of potential interest to combat SARS-CoV-2 disease, and for that, fragment-based drug discovery (FBDD) approach could be one of the ways to bring out an effective solution. Two cysteine protease enzymes would be an attractive choice of target for fragment-based drug discovery to tune the molecular structure at an early stage with suitable functionality. In this short review, the recent development of small-molecule as inhibitors against Covid-19 are discussed and the opportunity for FBDD is envisioned optimistically to provide an outlook regarding Covid-19 that may pave the way in the direction of the Covid-19 drug development paradigm.

Andrographolide Derivatives Target the KEAP1/NRF2 Axis and Possess Potent Anti-SARS-CoV-2 Activity

Naturally occurring compounds represent a vast pool of pharmacologically active entities. One of such compounds is andrographolide, which is endowed with many beneficial properties, including the activity against severe acute respiratory syndrome coronavirus type 2 (SARS‐CoV‐2). To initiate a drug repurposing or hit optimization campaign, it is imperative to unravel the primary mechanism(s) of the antiviral action of andrographolide. Here, we showed by means of a reporter gene assay that andrographolide exerts its anti‐SARS‐CoV‐2 effects by inhibiting the interaction between Kelch‐like ECH‐associated protein 1 (KEAP1) and nuclear factor erythroid 2‐related factor 2 (NRF2) causing NRF2 upregulation. Moreover, we demonstrated that subtle structural modifications of andrographolide could lead to derivatives with stronger on‐target activities and improved physicochemical properties. Our results indicate that further optimization of this structural class is warranted to develop novel COVID‐19 therapies.

Discovery of Novel Andrographolide Derivatives as Antiviral Inhibitors against Human Enterovirus A71

Hand-foot-and-mouth disease (HFMD) caused by human enterovirus A71 (EV-A71) infection has been associated with severe neurological complications. With the lack of an internationally approved antiviral, coupled with a surge in outbreaks globally, EV-A71 has emerged as a neurotropic virus of high clinical importance. Andrographolide has many pharmacological effects including antiviral activity and its derivative, andrographolide sulfonate, has been used in China clinically to treat EV-A71 infections. This study sought to identify novel andrographolide derivatives as EV-A71 inhibitors and elucidate their antiviral mode of action. Using an immunofluorescence-based phenotypic screen, we identified novel EV-A71 inhibitors from a 344-compound library of andrographolide derivatives and validated them with viral plaque assays. Among these hits, ZAF-47, a quinolinoxy-andrographolide, was selected for downstream mechanistic studies. It was found that ZAF-47 acts on EV-A71 post-entry stages and inhibits EV-A71 protein expression. Subsequent luciferase studies confirm that ZAF-47 targets EV-A71 genome RNA replication specifically. Unsuccessful attempts in generating resistant mutants led us to believe a host factor is likely to be involved which coincide with the finding that ZAF-47 exhibits broad-spectrum antiviral activity against other enteroviruses (CV-A16, CV-A6, Echo7, CV-B5, CV-A24 and EV-D68). Furthermore, ZAF-46 and ZAF-47, hits from the screen, were derivatives of the same series containing quinolinoxy and olefin modifications, suggesting that an andrographolide scaffold mounted with these unique moieties could be a potential anti-EV-A71/HFMD strategy.

An insight into the pharmacological and analytical potential of Andrographolide

Andrographis paniculata is an annual medicinal herb from the family Acanthaceae. Andrographolide is generally considered an essential bioactive component of plant A. paniculata. Since ancient times, it has been widely recognized for its therapeutic qualities and has attracted the scientific and medical communities' attention. This review summarizes the molecular, clinical, and in vitro research of compound andrographolide and its mechanism of action. Andrographolide, when combined with other enhancing agents, offers a wide variety of health benefits. The therapeutic potential of andrographolide has been exemplified and exhibited by directly regulating genes and indirectly interacting with small molecules and different enzymes. This review compiles and consolidates the pharmacological action of andrographolide and its analogs and deciphers the gaps that have hindered its use in medicinal research.