Apigenin analogues as SARS-CoV-2 main protease inhibitors: In-silico screening approach

Identification of anti-inflammatory and anti-cancer compounds targeting the NF-κB-NLRP3 inflammasome pathway from a phytochemical library of the Sideritis genus

ETHNOBOTANICAL RELEVANCE

For centuries, the aerial parts of Sideritis species have been known for their medicinal properties as herbal teas. Although the antioxidant and anti-inflammatory properties of the genus have been widely documented, the underlying mechanisms are yet to be sufficiently clarified.

AIM OF THE STUDY

We investigated the anti-inflammatory and anticancer activities of phytochemicals of the Sideritis genus.

MATERIAL AND METHODS

Through literature mining, a chemical library containing 657 components of the Sideritis genus was formed. We studied these compounds for binding to NLRP3 and NF-κB proteins in silico by virtual drug screening and molecular docking, and in vitro by microscale thermophoresis (MST). Liquid chromatography-high-resolution mass spectrometry analysis (LC-HRMS) was performed in the Sideritis extracts. One of the identified compounds, verbascoside, was investigated for its cytotoxic activity by mining a panel of 49 tumor cell lines in the data repository of the National Cancer Institute (NCI, USA).

RESULTS

Virtual screening and molecular docking results highlighted two compounds targeting both proteins of interest, i.e., verbascoside (acteoside) and apigenin 7,4'-bis(trans-p-coumarate), as both had lowest binding energies of less than -10 kcal/mol. Using MST, we then verified that both compounds bound to the target proteins. Verbascoside bound to NLRP3 and NF-κB with Kd values of 0.67 ± 0.18 μM and 0.01 ± 0.08 μM, while apigenin 7,4'-bis(trans-p-coumarate) had Kd values of 4.60 ± 1.66 μM and 0.27 ± 0.75 μM, respectively. Verbascoside was abundant in the Sideritis extracts, according to LC-HRMS analysis. Since inflammation is strongly related to carcinogenesis, we investigated the anticancer activity of verbascoside in the second part of this study. We investigated the activity of verbascoside in 49 tumor cell lines of the NCI. Comparing its activity with 81 standard anticancer drugs revealed numerous interactions with DNA-damaging agents (alkylators, topoisomerase I/II inhibitors, antimetabolites), indicating that verbascoside may also affect the DNA of tumor cells. We further investigated the involvement of verbascoside in several main drug resistance mechanisms, i.e., ABC transporters, oncogenes, tumor suppressors, cellular proliferation rates, and other parameters. Except for the correlation to the mutational status of NRAS, no other significant relationships were found, indicating that verbascoside is not involved in most of the common drug resistance mechanisms. Two-dimensional cluster analysis-based heatmap generation of a proteomic profile from 40 out of 3171 proteins revealed a significant correlation between the expression of these proteins in 49 tumor cell lines, and the cellular response to verbascoside. This indicates that the presence of these proteins is a determinant for sensitivity or resistance to this natural product.

CONCLUSION

The database established here represents a valuable resource for the screening of bioactivites of the Sideritis genus. The experimental validation of the anti-inflammatory and cytotoxic activities of selected compounds proved that virtual drug screening and molecular docking are suitable tools for the identification of putative drug candidates. Verbascoside was among the top 10 compounds binding to two key anti-inflammatory proteins, NLRP3 and NF-kB. Additionally, data from the NCI indicate that verbascoside is not linked to main drug resistance mechanisms.

High-throughput screening identification of apigenin that reverses the colistin resistance of mcr-1-positive pathogens

The plasmid-mediated gene mcr-1 that makes bacteria resistant to the antibiotic colistin is spreading quickly, which means that colistin is no longer working well to treat Gram-negative bacterial infections. Herein, we utilized a computer-aided high-throughput screening drugs method to identify the natural product apigenin, a potential mcr-protein inhibitor, which effectively enhanced the antimicrobial activity of colistin. Several assays, including a checkerboard minimum inhibitory concentration assay, a time-kill assay, the combined disk test, molecular simulation dynamics, and animal infection models assay, were conducted to verify whether apigenin enhanced the ability of colistin to fight Gram-negative bacterial infections. The results showed that apigenin improved the antimicrobial activity of colistin against multidrug-resistant Enterobacteriaceae infection. Moreover, apigenin not only did not increase the toxic effect of colistin but also had the ability to effectively inhibit the frequency of bacterial resistance mutations to colistin. Studies clearly elucidated that apigenin could interfere with the thermal stability of the protein by binding to the mcr-1 protein. Additionally, the combination of apigenin and colistin could exert multiple effects, including disrupting bacterial membranes, the generation of bacterial nitric oxide and reactive oxygen species, as well as inhibiting bacterial adenosine triphosphate production. Furthermore, the addition of apigenin was able to significantly inhibit colistin-stimulated high expression levels of the bacterial mcr-1 gene. Finally, apigenin exhibited a characteristic anti-inflammatory effect while enhancing the antimicrobial activity of colistin against mcr-1-positive Escherichia coli (E. coli) infected animals. In conclusion, as a potential lead compound, apigenin is promising in combination with colistin in the future treatment of mcr-1-positive E. coli infections.IMPORTANCEThis study found that apigenin was able to inhibit the activity of the mcr-1 protein using a high-throughput virtual screening method. Apigenin effectively enhanced the antimicrobial activity of colistin against multidrug-resistant Enterobacteriaceae, including mcr-1-positive strains, in vitro and in vivo. This study will provide new options and strategies for the future treatment of multidrug-resistant pathogen infections.

COVID-19-Associated Sepsis: Potential Role of Phytochemicals as Functional Foods and Nutraceuticals

The acute manifestations of coronavirus disease 2019 (COVID-19) exhibit the hallmarks of sepsis-associated complications that reflect multiple organ failure. The inflammatory cytokine storm accompanied by an imbalance in the pro-inflammatory and anti-inflammatory host response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection leads to severe and critical septic shock. The sepsis signature in severely afflicted COVID-19 patients includes cellular reprogramming and organ dysfunction that leads to high mortality rates, emphasizing the importance of improved clinical care and advanced therapeutic interventions for sepsis associated with COVID-19. Phytochemicals of functional foods and nutraceutical importance have an incredible impact on the healthcare system, which includes the prevention and/or treatment of chronic diseases. Hence, in the present review, we aim to explore the pathogenesis of sepsis associated with COVID-19 that disrupts the physiological homeostasis of the body, resulting in severe organ damage. Furthermore, we have summarized the diverse pharmacological properties of some potent phytochemicals, which can be used as functional foods as well as nutraceuticals against sepsis-associated complications of SARS-CoV-2 infection. The phytochemicals explored in this article include quercetin, curcumin, luteolin, apigenin, resveratrol, and naringenin, which are the major phytoconstituents of our daily food intake. We have compiled the findings from various studies, including clinical trials in humans, to explore more into the therapeutic potential of each phytochemical against sepsis and COVID-19, which highlights their possible importance in sepsis-associated COVID-19 pathogenesis. We conclude that our review will open a new research avenue for exploring phytochemical-derived therapeutic agents for preventing or treating the life-threatening complications of sepsis associated with COVID-19.

Metabolites profiling and cheminformatics bioprospection of selected medicinal plants against the main protease and RNA-dependent RNA polymerase of SARS-CoV-2

Despite the existence of some vaccines, SARS-CoV-2 (S-2) infections persist for various reasons relating to vaccine reluctance, rapid mutation rate, and an absence of specific treatments targeted to the infection. Due to their availability, low cost and low toxicity, research into potentially repurposing phytometabolites as therapeutic alternatives has gained attention. Therefore, this study explored the antiviral potential of metabolites of some medicinal plants [Spondias mombin, Macaranga barteri and Dicerocaryum eriocarpum (Sesame plant)] identified using liquid chromatography-mass spectrometry (LCMS) as possible inhibitory agents against the S-2 main protease (S-2 MP) and RNA-dependent RNA polymerase (RP) using computational approaches. Molecular docking was used to identify the compounds with the best affinities for the selected therapeutics targets. Afterwards, compounds with poor physicochemical characteristics, pharmacokinetics, and drug-likeness were screened out. The top-ranked compounds were further subjected to a 120-ns molecular dynamics (MD) simulation. Only quercetin 3-O-rhamnoside (-48.77 kcal/mol) had higher binding free energy than the reference standard (zafirlukast) (-44.99 kcal/mol) against S-2 MP. Conversely, all the top-ranked compounds (ellagic acid hexoside, spiraeoside, apigenin-4'-glucoside and chrysoeriol 7-glucuronide) except gnetin L (-24.24 kcal/mol) had higher binding free energy (-55.19 kcal/mol, -52.75 kcal/mol, -47.22 kcal/mol and -43.35 kcal/mol) respectively, against S-2 RP relative to the reference standard (-34.79 kcal/mol). The MD simulations study further revealed that the investigated inhibitors are thermodynamically stable and form structurally compatible complexes that impede the regular operation of the respective S-2 therapeutic targets. Although, these S-2 therapeutic candidates are promising, further in vitro and in vivo evaluation is required and highly recommended.Communicated by Ramaswamy H. Sarma.

The Antiviral Potential of Perilla frutescens: Advances and Perspectives

Viruses pose a significant threat to human health, causing widespread diseases and impacting the global economy. Perilla frutescens, a traditional medicine and food homologous plant, is well known for its antiviral properties. This systematic review examines the antiviral potential of Perilla frutescens, including its antiviral activity, chemical structure and pharmacological parameters. Utilizing bioinformatics analysis, we revealed the correlation between Perilla frutescens and antiviral activity, identified overlaps between Perilla frutescens target genes and virus-related genes, and explored related signaling pathways. Moreover, a classified summary of the active components of Perilla frutescens, focusing on compounds associated with antiviral activity, provides important clues for optimizing the antiviral drug development of Perilla frutescens. Our findings indicate that Perilla frutescens showed a strong antiviral effect, and its active ingredients can effectively inhibit the replication and spread of a variety of viruses in this review. The antiviral mechanisms of Perilla frutescens may involve several pathways, including enhanced immune function, modulation of inflammatory responses, and inhibition of key enzyme activities such as viral replicase. These results underscore the potential antiviral application of Perilla frutescens as a natural plant and provide important implications for the development of new antiviral drugs.

Pistacia vera L. as natural source against antimicrobial and antiviral resistance

Increased global research is focused on the development of novel therapeutics to combat antimicrobial and antiviral resistance. Pistachio nuts represent a good source of protein, fiber, monounsaturated fatty acids, minerals, vitamins, and phytochemicals (carotenoids, phenolic acids, flavonoids and anthocyanins). The phytochemicals found in pistachios are structurally diverse compounds with antimicrobial and antiviral potential, demonstrated as individual compounds, extracts and complexed into nanoparticles. Synergistic effects have also been reported in combination with existing drugs. Here we report an overview of the antimicrobial and antiviral potential of pistachio nuts: studies show that Gram-positive bacterial strains, such as Staphylococcus aureus, are the most susceptible amongst bacteria, whereas antiviral effect has been reported against herpes simplex virus 1 (HSV-1). Amongst the known pistachio compounds, zeaxanthin has been shown to affect both HSV-1 attachment penetration of human cells and viral DNA synthesis. These data suggest that pistachio extracts and derivatives could be used for the topical treatment of S. aureus skin infections and ocular herpes infections.

Flavonoids derived from medicinal plants as a COVID-19 treatment

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19 disease. Through its viral spike (S) protein, the virus enters and infects epithelial cells by utilizing angiotensin-converting enzyme 2 as a host cell's receptor protein. The COVID-19 pandemic had a profound impact on global public health and economies. Although various effective vaccinations and medications are now available to prevent and treat COVID-19, natural compounds derived from medicinal plants, particularly flavonoids, demonstrated therapeutic potential to treat COVID-19 disease. Flavonoids exhibit dual antiviral mechanisms: direct interference with viral invasion and inhibition of replication. Specifically, they target key viral molecules, particularly viral proteases, involved in infection. These compounds showcase significant immunomodulatory and anti-inflammatory properties, effectively inhibiting various inflammatory cytokines. Additionally, emerging evidence supports the potential of flavonoids to mitigate the progression of COVID-19 in individuals with obesity by positively influencing lipid metabolism. This review aims to elucidate the molecular structure of SARS-CoV-2 and the underlying mechanism of action of flavonoids on the virus. This study evaluates the potential anti-SARS-CoV-2 properties exhibited by flavonoid compounds, with a specific interest in their structure and mechanisms of action, as therapeutic applications for the prevention and treatment of COVID-19. Nevertheless, a significant portion of existing knowledge is based on theoretical frameworks and findings derived from in vitro investigations. Further research is required to better assess the effectiveness of flavonoids in combating SARS-CoV-2, with a particular emphasis on in vivo and clinical investigations.

Emerging Therapeutic Potential of Polyphenols from Geranium sanguineum L. in Viral Infections, Including SARS-CoV-2

The existing literature supports the anti-inflammatory, antioxidant, and antiviral capacities of the polyphenol extracts derived from Geranium sanguineum L. These extracts exhibit potential in hindering viral replication by inhibiting enzymes like DNA polymerase and reverse transcriptase. The antiviral properties of G. sanguineum L. seem to complement its immunomodulatory effects, contributing to infection resolution. While preclinical studies on G. sanguineum L. suggest its potential effectiveness against COVID-19, there is still a lack of clinical evidence. Therefore, the polyphenols extracted from this herb warrant further investigation as a potential alternative for preventing and treating COVID-19 infections.

Antiviral Flavonoids: A Natural Scaffold with Prospects as Phytomedicines against SARS-CoV2

Flavonoids are vital candidates to fight against a wide range of pathogenic microbial infections. Due to their therapeutic potential, many flavonoids from the herbs of traditional medicine systems are now being evaluated as lead compounds to develop potential antimicrobial hits. The emergence of SARS-CoV-2 caused one of the deadliest pandemics that has ever been known to mankind. To date, more than 600 million confirmed cases of SARS-CoV2 infection have been reported worldwide. Situations are worse due to the unavailability of therapeutics to combat the viral disease. Thus, there is an urgent need to develop drugs against SARS-CoV2 and its emerging variants. Here, we have carried out a detailed mechanistic analysis of the antiviral efficacy of flavonoids in terms of their potential targets and structural feature required for exerting their antiviral activity. A catalog of various promising flavonoid compounds has been shown to elicit inhibitory effects against SARS-CoV and MERS-CoV proteases. However, they act in the high-micromolar regime. Thus a proper leadoptimization against the various proteases of SARS-CoV2 can lead to high-affinity SARS-CoV2 protease inhibitors. To enable lead optimization, a quantitative structure-activity relationship (QSAR) analysis has been developed for the flavonoids that have shown antiviral activity against viral proteases of SARS-CoV and MERS-CoV. High sequence similarities between coronavirus proteases enable the applicability of the developed QSAR to SARS-CoV2 proteases inhibitor screening. The detailed mechanistic analysis of the antiviral flavonoids and the developed QSAR models is a step forward toward the development of flavonoid-based therapeutics or supplements to fight against COVID-19.

Conventional Understanding of SARS-CoV-2 Mpro and Common Strategies for Developing Its Inhibitors

The Coronavirus Disease 2019 (COVID-19) pandemic has brought a widespread influence on the world, especially in the face of sudden coronavirus infections, and there is still an urgent need for specific small molecule therapies to cope with possible future pandemics. The pathogen responsible for this pandemic is Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and understanding its structure and lifecycle is beneficial for designing specific drugs of treatment for COVID-19. The main protease (Mpro ) which has conservative and specific advantages is essential for viral replication and transcription. It is regarded as one of the most potential targets for anti-SARS-CoV-2 drug development. This review introduces the popular knowledge of SARS-CoV-2 Mpro in drug development and lists a series of design principles and relevant activities of advanced Mpro inhibitors, hoping to provide some new directions and ideas for researchers.

The Therapeutic Potential of Natural Dietary Flavonoids against SARS-CoV-2 Infection

The exploration of non-toxic and cost-effective dietary components, such as epigallocatechin 3-gallate and myricetin, for health improvement and disease treatment has recently attracted substantial research attention. The recent COVID-19 pandemic has provided a unique opportunity for the investigation and identification of dietary components capable of treating viral infections, as well as gathering the evidence needed to address the major challenges presented by public health emergencies. Dietary components hold great potential as a starting point for further drug development for the treatment and prevention of SARS-CoV-2 infection owing to their good safety, broad-spectrum antiviral activities, and multi-organ protective capacity. Here, we review current knowledge of the characteristics-chemical composition, bioactive properties, and putative mechanisms of action-of natural bioactive dietary flavonoids with the potential for targeting SARS-CoV-2 and its variants. Notably, we present promising strategies (combination therapy, lead optimization, and drug delivery) to overcome the inherent deficiencies of natural dietary flavonoids, such as limited bioavailability and poor stability.

Plausibility of natural immunomodulators in the treatment of COVID-19-A comprehensive analysis and future recommendations

The COVID-19 pandemic has inflicted millions of deaths worldwide. Despite the availability of several vaccines and some special drugs approved for emergency use to prevent or treat this disease still, there is a huge concern regarding their effectiveness, adverse effects, and most importantly, their efficacy against the new variants. A cascade of immune-inflammatory responses is involved with the pathogenesis and severe complications with COVID-19. People with dysfunctional and compromised immune systems display severe complications, including acute respiratory distress syndrome, sepsis, multiple organ failure etc., when they get infected with the SARS-CoV-2 virus. Plant-derived natural immune-suppressant compounds, such as resveratrol, quercetin, curcumin, berberine, luteolin, etc., have been reported to inhibit pro-inflammatory cytokines and chemokines. Therefore, natural products with immunomodulatory and anti-inflammatory potential could be plausible targets to treat this contagious disease. This review aims to delineate the clinical trials status and outcomes of natural compounds with immunomodulatory potential in COVID-19 patients along with the outcomes of their in-vivo studies. In clinical trials several natural immunomodulators resulted in significant improvement of COVID-19 patients by diminishing COVID-19 symptoms such as fever, cough, sore throat, and breathlessness. Most importantly, they reduced the duration of hospitalization and the need for supplemental oxygen therapy, improved clinical outcomes in patients with COVID-19, especially weakness, and eliminated acute lung injury and acute respiratory distress syndrome. This paper also discusses many potent natural immunomodulators yet to undergo clinical trials. In-vivo studies with natural immunomodulators demonstrated reduction of a wide range of proinflammatory cytokines. Natural immunomodulators that were found effective, safe, and well tolerated in small-scale clinical trials are warranted to undergo large-scale trials to be used as drugs to treat COVID-19 infections. Alongside, compounds yet to test clinically must undergo clinical trials to find their effectiveness and safety in the treatment of COVID-19 patients.

Graphene oxide and flavonoids as potential inhibitors of the spike protein of SARS-CoV-2 variants and interaction between ligands: a parallel study of molecular docking and DFT

Nanocarriers allow the connection between biomolecules and other structures to enhance the treatment efficacy, through the biomolecule's properties to an existing drug, or to allow a better and specific delivery. Apigenin and orientin are biomolecules with excellent therapeutic properties that are proposed in the fight against COVID-19. Besides that, graphene oxide is a nanomaterial that exhibits antiviral activity and is used as a nanocarrier of several drugs. We evaluated in this work, through molecular docking, the binding affinity between these structures to the receptor-binding domain of spike protein of two coronavirus variants, Delta and Omicron. The results indicate that all the structures exhibit affinity with the two protein targets, with binding affinity values of -11.88 to -6.65 kcal/mol for the Delta variant and values of -9.58 to -13.20 kcal/mol for the Omicron variant, which is a successful value as found in the literature as a potential inhibitor of SARS-CoV-2 infection. Also, through first-principles calculations based on Density Functional Theory, the interaction of graphene oxide with the biomolecules apigenin and orientin occurred. The results exhibit weak binding energy, which indicates that physical adsorption occurs, with better results when the biomolecule is set in parallel to the nanomaterial due to attractive π-π staking. These results are conducive to the development of a nanocarrier.

Phytochemicals, Biological Activities, Molecular Mechanisms, and Future Prospects of Plantago asiatica L

Plantago asiatica L. has been used as a vegetable and nutritious food in Asia for thousands of years. According to recent phytochemical and pharmacological research, the active compositions of the plant contribute to various health benefits, such as antioxidant, anti-inflammatory, antibacterial, antiviral, and anticancer. This article reviews the 87 components of the plant and their structures, as well as their biological activities and molecular research progress, in detail. This review provides valuable reference material for further study, production, and application of P. asiatica, as well as its components in functional foods and therapeutic agents.

Efficient Synthesis and In Vitro Hypoglycemic Activity of Rare Apigenin Glycosylation Derivatives

Apigenin is a natural flavonoid with significant biological activity, but poor solubility in water and low bioavailability limits its use in the food and pharmaceutical industries. In this paper, apigenin-7-O-β-(6″-O)-d-glucoside (AG) and apigenin-7-O-β-(6″-O-succinyl)-d-glucoside (SAG), rare apigenin glycosyl and succinyl derivatives formed by the organic solvent-tolerant bacteria Bacillus licheniformis WNJ02 were used in a 10.0% DMSO (v/v) system. The water solubility of SAG was 174 times that of apigenin, which solved the application problem. In the biotransformation reaction, the conversion rate of apigenin (1.0 g/L) was 100% at 24 h, and the yield of SAG was 94.2%. Molecular docking showed that the hypoglycemic activity of apigenin, apigenin-7-glucosides (AG), and SAG was mediated by binding with amino acids of α-glucosidase. The molecular docking results were verified by an in vitro anti-α-glucosidase assay and glucose consumption assay of active compounds. SAG had significant anti-α-glucosidase activity, with an IC₅₀ of 0.485 mM and enhanced glucose consumption in HepG2 cells, which make it an excellent α-glucosidase inhibitor.

Phytochemicals in the Prevention and Treatment of SARS-CoV-2-Clinical Evidence

The first case of SARS-CoV-2 infection was reported in December 2019. Due to the rapid spread of the disease and the lack of adequate therapy, the use of plants that have a long history in the treatment of viral infections has often been considered. The aim of this paper is to provide a brief review of the literature on the use of phytochemicals during the new pandemic. An extensive search of published works was performed through platforms Google Scholar, PubMed, Science Direct, Web of Science and Clinicaltrials.gov. Numerous preclinical studies on the use of phytochemicals (quercetin, curcumin, baicalin, kaempferol, resveratrol, glycyrrhizin, lycorine, colchicine) against SARS-CoV-2 have shown that these components can be effective in the prevention and treatment of this infection. Clinical research has proven that the use of black cumin and green propolis as well as quercetin has positive effects. As for other phytochemicals, in addition to preclinical testing which has already been carried out, it would be necessary to conduct clinical tests in order to assert their effectiveness. For those phytochemicals whose clinical efficacy has been proven, it would be necessary to conduct research on a larger number of patients, so that the conclusions are more representative.

In silico evidence of antiviral activity against SARS-CoV-2 main protease of oligosaccharides from Porphyridium sp

The coronavirus pandemic (COVID-19) has created an urgent need to develop effective strategies for prevention and treatment. In this context, therapies against protease M^pro, a conserved viral target, would be essential to contain the spread of the virus and reduce mortality. Using combined techniques of structure modelling, in silico docking and pharmacokinetics prediction, many compounds from algae were tested for their ability to inhibit the SARS-CoV-2 main protease and compared to the recent recognized drug Paxlovid. The screening of 27 algal molecules including 15 oligosaccharides derived from sulfated and non-sulphated polysaccharides, eight pigments and four poly unsaturated fatty acids showed high affinities to interact with the protein active site. Best candidates showing high docking scores in comparison with the reference molecule were sulfated tri-, tetra- and penta-saccharides from Porphyridium sp. exopolysaccharides (SEP). Structural and energetic analyses over 100 ns MD simulation demonstrated high SEP fragments-M^pro complex stability. Pharmacokinetics predictions revealed the prospects of the identified molecules as potential drug candidates.

Synergistic deciphering of bioenergy production and electron transport characteristics to screen traditional Chinese medicine (TCM) for COVID-19 drug development

Background

Traditional Chinese medicine (TCM) has been used as an "immune booster” for disease prevention and clinical treatment since ancient China. However, many studies were focused on the organic herbal extract rather than aqueous herbal extract (AHE; decoction). Due to the COVID-19 pandemics, this study tended to decipher phytochemical contents in the decoction of herbs and derived bioactivities (e.g., anti-oxidant and anti-inflammatory properties). As prior works revealed, the efficacy of Parkinson's medicines and antiviral flavonoid herbs was strongly governed by their bioenergy-stimulating proficiency.

Methods

Herbal extracts were prepared by using a traditional Chinese decoction pot. After filtration and evaporation, crude extracts were used to prepare sample solutions for various bioassays. The phytochemical content and bioactivities of AHEs were determined via ELISA microplate reader. Microbial fuel cells (MFCs) were used as a novel platform to evaluate bioenergy contents with electron-transfer characteristics for antiviral drug development.

Significant findings

Regarding 18 TCM herbal extracts for the prevention of SARS and H1N1 influenza, comparison on total polyphenol, flavonoid, condensed tannins and polysaccharides were conducted. Moreover, considerable total flavonoid contents were detected for 11 herb extracts. These AEHs were not only rich in phytonutrient contents but also plentiful in anti-oxidant and anti-inflammatory activities. Herbs with high polyphenol content had higher antioxidant activity. Forsythia suspensa extract expressed the highest inhibition against nitric oxide production for anti-inflammation. MFC bioenergy-stimulating studies also revealed that top ranking COVID-19 efficacious herbs were both bioenergy driven and electron mediated. That is, electron transfer-controlled bioenergy extraction was significant to antiviral characteristics for anti-COVID-19 drug development.

Peptide candidates for the development of therapeutics and vaccines against β-coronavirus infection

Betacoronaviruses (β-CoVs) have caused major viral outbreaks in the last two decades in the world. The mutation and recombination abilities in β-CoVs resulted in zoonotic diseases in humans. Proteins responsible for viral attachment and replication are highly conserved in β-CoVs. These conserved proteins have been extensively studied as targets for preventing infection and the spread of β-CoVs. Peptides are among the most promising candidates for developing vaccines and therapeutics against viral pathogens. The immunostimulatory and viral inhibitory potential of natural and synthetic peptides has been extensively studied since the SARS-CoV outbreak. Food-derived peptides demonstrating high antiviral activity can be used to develop effective therapeutics against β-CoVs. Specificity, tolerability, and customizability of peptides can be explored to develop potent drugs against β-CoVs. However, the proteolytic susceptibility and low bioavailability of peptides pose challenges for the development of therapeutics. This review illustrates the potential role of peptides in eliciting an adaptive immune response and inhibiting different stages of the β-CoV life cycle. Further, the challenges and future directions associated with developing peptide-based therapeutics and vaccines against existing and future β-CoV pathogens have been discussed.