Bioactive Natural Antivirals: An Updated Review of the Available Plants and Isolated Molecules

Oreoch-1: A broad-spectrum virus and host-targeting peptide against animal infections

In recent decades, the global rise of viral emerging infectious diseases has posed a substantial threat to both human and animal health worldwide. The rapid spread and accumulation of mutations into viruses, and the limited availability of antiviral drugs and vaccines, stress the urgent need for alternative therapeutic strategies. Antimicrobial peptides (AMPs) derived from natural sources present a promising avenue due to their specificity and effectiveness against a broad spectrum of pathogens. The present study focuses on investigating the antiviral potential of oreochromicin-1 (oreoch-1), a fish-derived AMP obtained from Nile tilapia, against a wide panel of animal viruses including canine distemper virus (CDV), Schmallenberg virus (SBV), caprine herpesvirus 1 (CpHV-1), and bovine herpesvirus 1 (BoHV-1). Oreoch-1 exhibited a strong antiviral effect, demonstrating an inhibition of infection at concentrations in the micromolar range. The mechanism of action involves the interference with viral entry into host cells and a direct interaction between oreoch-1 and the viral envelope. In addition, we observed that the peptide could also interact with the cell during the CDV infection. These findings not only highlight the efficacy of oreoch-1 in inhibiting viral infection but also emphasize the potential of fish-derived peptides, specifically oreoch-1, as effective antiviral agents against viral infections affecting animals, whose potential to spill into humans is high. This research contributes valuable insights to the ongoing quest for novel antiviral drugs with the potential to mitigate the impact of infectious diseases on a global scale.

Alsayegh A, Ahmad FA, Akhtar MS, Alavudeen SS, Bantun F, Wahab S, Ahmed A, Ali M, Elbendary EY, Raposo A, Kambal N, H. Abdelrahman M. Ganoderma lucidum: Insight into antimicrobial and antioxidant properties with development of secondary metabolites

Ganoderma lucidum is a versatile mushroom. Polysaccharides and triterpenoids are the major bioactive compounds and have been used as traditional medicinal mushrooms since ancient times. They are currently used as nutraceuticals and functional foods. G. lucidum extracts and their bioactive compounds have been used as an alternative to antioxidants and antimicrobial agents. Secondary metabolites with many medicinal properties make it a possible substitute that could be applied as immunomodulatory, anticancer, antimicrobial, anti-oxidant, anti-inflammatory, and anti-diabetic. The miraculous properties of secondary metabolites fascinate researchers for their development and production. Recent studies have paid close attention to the different physical, genetic, biochemical, and nutritional parameters that potentiate the production of secondary metabolites. This review is an effort to collect biologically active constituents from G. lucidum that reveal potential actions against diseases with the latest improvement in a novel technique to get maximum production of secondary metabolites. Studies are going ahead to determine the efficacy of numerous compounds and assess the valuable properties achieved by G. lucidum in favor of antimicrobial and antioxidant outcomes.

Discovery and Structural Optimization of 1,2,3,4-Tetrahydro-β-carbolines as Novel Reactive Oxygen Species Inducers for Controlling Intractable Plant Bacterial Diseases

Nowadays, reactive oxygen species (ROS) have been acknowledged as promising bactericidal targets against pesticide-resistant bacteria. Herein, to further excavate more excellent ROS inducers, simple 1,2,3,4-tetrahydro-β-carboline derivatives containing a 3-aminopropanamide moiety were prepared and assessed for their antibacterial potency. Notably, three promising compounds displayed significant antibacterial potency. Compound I₂₉ exhibits excellent in vitro bioactivity, with an EC₅₀ value of 5.73 μg/mL, and admirable in vivo activities (protective activity of 55.74% and curative activity of 65.50%) toward Xanthomonas oryzae pv. oryzae. Compound I₁₆ has good activity in vitro, with an EC₅₀ of 3.43 μg/mL, and outstanding bioactivities in vivo (protective activity of 92.50% and curative activity of 59.68%) against Xanthomonas axonopodis pv. citri. Compound I₆ shows excellent in vitro bioactivity (EC₅₀ = 2.86 μg/mL) and significant protective activity (94.02%) for preventing Pseudomonas syringae pv. actinidiae. Antibacterial mechanism investigations indicate that these compounds disrupt the balance of the redox system to kill bacteria. These simple 1,2,3,4-tetrahydro-β-carboline derivatives are promising leads to the discovery of bactericidal agents.

The bioprospecting potential of Clusia fluminensis Planch. & Triana: a scoping review

Many biological activities are described for the Clusiaceae family. Clusia fluminensis, a species from Brazilian flora, is mainly employed for ornamental purposes. This review aimed to depict the current knowledge of C. fluminensis from a bioprospecting standpoint. "Clusia fluminensis" search term was applied in Scopus, Web of Science, PubMed and Bireme databases according to PRISMA-ScR statement. Selected papers on Phytochemistry or Bioactivity followed hand searching procedures. Bioactivity preclinical studies considered in vitro or in vivo biological systems, treated with plant extracts or isolated compounds. The outcomes were compared with standard or no treatment control groups. Critical appraisal of individual trials considered completeness in the research fields. Our results showed that 81% of the selected papers presented high level of completeness, 69% revealed phytochemical parameters and 31% biological applications of plant extracts and isolated compounds. Polyisoprenylated benzophenones, terpenoids, sterols and phenolic compounds were identified. Antiviral, insecticidal and snake antivenom activities were reported. In conclusion, the phytochemical data reinforce the reported activities. Potential applications in personal care, nutritional supplementation and pharmaceutical, food, chemical or textile industries were also identified. Toxicological and phytochemical complementary studies may be required.

Plant ingredients in Thai food: a well-rounded diet for natural bioactive associated with medicinal properties

Background

Seeking cures for chronic inflammation-associated diseases and infectious diseases caused by critical human pathogens is challenging and time-consuming. Even as the research community searches for novel bioactive agents, consuming a healthy diet with functional ability might be an effective way to delay and prevent the progression of severe health conditions. Many plant ingredients in Thai food are considered medicinal, and these vegetables, herbs, and spices collectively possess multiple biological and pharmacological activities, such as anti-inflammatory, antimicrobial, antidiabetic, antipyretic, anticancer, hepatoprotective, and cardioprotective effects.

Methodology

In this review, the selected edible plants are unspecific to Thai food, but our unique blend of recipes and preparation techniques make traditional Thai food healthy and functional. We searched three electronic databases: PUBMED, Science Direct, and Google Scholar, using the specific keywords "Plant name" followed by "Anti-inflammatory" or "Antibacterial" or "Antiviral" and focusing on articles published between 2017 and 2021.

Results

Our selection of 69 edible and medicinal plant species (33 families) is the most comprehensive compilation of Thai food sources demonstrating biological activities to date. Focusing on articles published between 2017 and 2021, we identified a total of 245 scientific articles that have reported main compounds, traditional uses, and pharmacological and biological activities from plant parts of the selected species.

Conclusions

Evidence indicates that the selected plants contain bioactive compounds responsible for anti-inflammatory, antibacterial, and antiviral properties, suggesting these plants as potential sources for bioactive agents and suitable for consumption for health benefits.

HSV: The scout and assault for digestive system tumors

More than 25% of all malignant tumors are digestive system tumors (DSTs), which mostly include esophageal cancer, gastric cancer, pancreatic cancer, liver cancer, gallbladder cancer and cholangiocarcinoma, and colorectal cancer. DSTs have emerged as one of the prominent reasons of morbidity and death in many nations and areas around the world, posing a serious threat to human life and health. General treatments such as radiotherapy, chemotherapy, and surgical resection can poorly cure the patients and have a bad prognosis. A type of immunotherapy known as oncolytic virus therapy, have recently shown extraordinary anti-tumor effectiveness. One of the viruses that has been the subject of the greatest research in this field, the herpes simplex virus (HSV), has shown excellent potential in DSTs. With a discussion of HSV-1 based on recent studies, we outline the therapeutic effects of HSV on a number of DSTs in this review. Additionally, the critical function of HSV in the detection of cancers is discussed, and some HSV future possibilities are shown.

A comprehensive review on pharmacologic agents, immunotherapies and supportive therapeutics for COVID-19

The emergence of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected many countries throughout the world. As urgency is a necessity, most efforts have focused on identifying small molecule drugs that can be repurposed for use as anti-SARS-CoV-2 agents. Although several drug candidates have been identified using in silico method and in vitro studies, most of these drugs require the support of in vivo data before they can be considered for clinical trials. Several drugs are considered promising therapeutic agents for COVID-19. In addition to the direct-acting antiviral drugs, supportive therapies including traditional Chinese medicine, immunotherapies, immunomodulators, and nutritional therapy could contribute a major role in treating COVID-19 patients. Some of these drugs have already been included in the treatment guidelines, recommendations, and standard operating procedures. In this article, we comprehensively review the approved and potential therapeutic drugs, immune cells-based therapies, immunomodulatory agents/drugs, herbs and plant metabolites, nutritional and dietary for COVID-19.

Tackling the Future Pandemics: Broad-Spectrum Antiviral Agents (BSAAs) Based on A-Type Proanthocyanidins

A-type proanthocyanidins (PAC-As) are plant-derived natural polyphenols that occur as oligomers or polymers of flavan-3-ol monomers, such as (+)-catechin and (-)-epicatechin, connected through an unusual double A linkage. PAC-As are present in leaves, seeds, flowers, bark, and fruits of many plants, and are thought to exert protective natural roles against microbial pathogens, insects, and herbivores. Consequently, when tested in isolation, PAC-As have shown several biological effects, through antioxidant, antibacterial, immunomodulatory, and antiviral activities. PAC-As have been observed in fact to inhibit replication of many different human viruses, and both enveloped and non-enveloped DNA and RNA viruses proved sensible to their inhibitory effect. Mechanistic studies revealed that PAC-As cause reduction of infectivity of viral particles they come in contact with, as a result of their propensity to interact with virion surface capsid proteins or envelope glycoproteins essential for viral attachment and entry. As viral infections and new virus outbreaks are a major public health concern, development of effective Broad-Spectrum Antiviral Agents (BSAAs) that can be rapidly deployable even against future emerging viruses is an urgent priority. This review summarizes the antiviral activities and mechanism of action of PAC-As, and their potential to be deployed as BSAAs against present and future viral infections.

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.

Screening of Phytoconstituents from Traditional Plants against SARSCoV- 2 using Molecular Docking Approach

Background:

The emergence of COVID-19 as a fatal viral disease encourages researchers to develop effective and efficient therapeutic agents. The intervention of in silico studies has led to revolutionary changes in the conventional method of testing the bioactivity of plant constituents.

Objective:

The current study deals with the investigation of some traditional immunomodulators of plant origin to combat this ailment.

Materials and Methods:

A total of 151 phytomolecules of 12 immunomodulatory plants were evaluated for their inhibitory action against the main protease (PDB ID: 7D1M) and NSP15 endoribonuclease (PDB ID: 6WLC) by structure-based virtual screening. In addition, the promising molecules with ligand efficiency of more than -0.3(kcal/mol)/heavy atoms were further predicted for pharmacokinetic properties and druggability using the SwissADME web server, and their toxicity was also evaluated using Protox-II.

Result:

Myricetin-3-O-arabinofuranoside of cranberry plant was found to be the most potential candidate against both enzymes: main protease (–14.2 kcal/mol) and NSP15 endoribonuclease (–12.2 kcal/mol).

Conclusion:

The promising outcomes of the current study may be implemented in future drug development against coronavirus. The findings also help in the development of lead candidates of plant origin with a better ADMET profile in the future.

Honokiol and Alpha-Mangostin Inhibit Mayaro Virus Replication through Different Mechanisms

Mayaro virus (MAYV) is an emerging arbovirus with an increasing circulation across the Americas. In the present study, we evaluated the potential antiviral activity of the following natural compounds against MAYV and other arboviruses: Sanguinarine, (R)-Shikonin, Fisetin, Honokiol, Tanshinone IIA, and α-Mangostin. Sanguinarine and Shikonin showed significant cytotoxicity, whereas Fisetin, Honokiol, Tanshinone IIA, and α-Mangostin were well tolerated in all the cell lines tested. Honokiol and α-Mangostin treatment protected Vero-E6 cells against MAYV-induced damage and resulted in a dose-dependent reduction in viral progeny yields for each of the MAYV strains and human cell lines assessed. These compounds also reduced MAYV viral RNA replication in HeLa cells. In addition, Honokiol and α-Mangostin disrupted MAYV infection at different stages of the virus life cycle. Moreover, Honokiol and α-Mangostin decreased Una, Chikungunya, and Zika viral titers and downmodulated the expression of E1 and nsP1 viral proteins from MAYV, Una, and Chikungunya. Finally, in Honokiol- and α-Mangostin-treated HeLa cells, we observed an upregulation in the expression of type I interferon and specific interferon-stimulated genes, including IFNα, IFNβ, MxA, ISG15, OAS2, MDA-5, TNFα, and IL-1β, which may promote an antiviral cellular state. Our results indicate that Honokiol and α-Mangostin present potential broad-spectrum activity against different arboviruses through different mechanisms.

Inhibitory activity of aqueous extracts of tea compositions, individual ingredients for their preparation and some plants against replication of Herpes simplex virus type 2 <i>in vitro</i>

Aim. In vitro analysis of the inhibitory activity of aqueous extracts of tea compositions, plant raw materials and as well as plants from different families against replication of Herpes simplex virus type 2.

Material and Methods. The viral strain MS of HSV‐2 was passivated on Vero cell culture. Antiviral (inhibitory) activity of aqueous extracts was studied in vitro according to the classical scheme of neutralization (inactivation) of the virus.

Results. For comparison we used control samples of aqueous extracts of Chaga mushroom (Inonotus obliquus) and grass of Alchemilla vulgaris L. with EC50 equal to 21.36±3.92 and 39.67±8.75 µg/ml (for dry raw materials) versus 103  PFU/ml HSV‐2. As a result the prevailing activity (from 15.25±3.92 to 1.71±0.54 µg/ml) was identified for extracts of tea compositions based on black and green tea, as well as individual ingredients for their composition – black tea, leaves of Mentha piperita L.,  flowers  of  Lavandula  angustifolia  Mill. and  clove  spices  (Syzygium aromaticum L.). Extracts obtained from plants that are not part of tea compositions of interest are fermented leaves of Epilobium angustifolium L. (Onagraceae) and grass of two species Euphorbia (E. pilosa L. and E. esula  L.,  Euphorbiaceae)  with  inhibitory  activity  at  concentrations  of 10.675±1.96; 2.29±0.57 and 1.71±0.54 µg/ml, respectively.

Conclusion. The results presented can become the basis for the search for individual biologically active substances of plant origin that inhibit HSV‐2 replication as well as for the development of effective medicines in the form of tea beverages and/or formulations for topical use to reduce relapses of chronic herpes.

Glycyrrhizic Acid Derivatives Bearing Amino Acid Residues in the Carbohydrate Part as Dengue Virus E Protein Inhibitors: Synthesis and Antiviral Activity

Dengue virus (DENV) is one of the most geographically distributed mosquito-borne flaviviruses, like Japanese encephalitis virus (JEV), and Zika virus (ZIKV). In this study, a library of the known and novel Glycyrrhizic acid (GL) derivatives bearing amino acid residues or their methyl/ethyl esters in the carbohydrate part were synthesized and studied as DENV inhibitors in vitro using the cytopathic effect (CPE), viral infectivity and virus yield assays with DENV1 and DENV-2 in Vero E6 and A549 cells. Among the GL conjugates tested, compound hits GL-D-ValOMe 3, GL-TyrOMe 6, GL-PheOEt 11, and GL-LysOMe 21 were discovered to have better antiviral activity than GL, with IC50 values ranging from <0.1 to 5.98 μM on the in vitro infectivity of DENV1 and DENV2 in Vero E6 and A549 cells. Compound hits 3, 6, 11, and 21 had a concentration-dependent inhibition on the virus yield in Vero E6, in which GL-D-ValOMe 3 and GL-PheOEt 11 were the most active inhibitors of DENV2 yield. Meanwhile, the time-of-addition assay indicated that conjugates GL-D-ValOMe 3 and GL-PheOEt 11 exhibited a substantial decrease in the DENV2 attachment stage. Subsequently, chimeric single-round infectious particles (SRIPs) of DENV2 C-prM-E protein/JEV replicon and DENV2 prM-E/ZIKV replicon were utilized for the DENV envelope I protein-mediated attachment assay. GL conjugates 3 and 11 significantly reduced the attachment of chimeric DENV2 C-prM-E/JEV and DENV2 prM-E/ZIKV SRIPs onto Vero E6 cells in a concentration-dependent manner but did not impede the attachment of wild-type JEV CprME/JEV and ZIKV prM-E/ZIKV SRIPs, indicating the inhibition of Compounds 3 and 11 on DENV2 E-mediated attachment. Molecular docking data revealed that Compounds 3 and 11 have hydrophobic interactions within a hydrophobic pocket among the interfaces of Domains I, II, and the stem region of the DENV2 envelope (E) protein. These results displayed that Compounds 3 and 11 were the lead compounds targeting the DENV E protein. Altogether, our findings provide new insights into the structure−activity relationship of GL derivatives conjugated with amino acid residues and can be the new fundamental basis for the search and development of novel flavivirus inhibitors based on natural compounds.

Role of Diet and Nutrients in SARS-CoV-2 Infection: Incidence on Oxidative Stress, Inflammatory Status and Viral Production

Coronavirus illness (COVID-19) is an infectious pathology generated by intense severe respiratory syndrome coronavirus 2 (SARS-CoV-2). This infectious disease has emerged in 2019. The COVID-19-associated pandemic has considerably affected the way of life and the economy in the world. It is consequently crucial to find solutions allowing remedying or alleviating the effects of this infectious disease. Natural products have been in perpetual application from immemorial time given that they are attested to be efficient towards several illnesses without major side effects. Various studies have shown that plant extracts or purified molecules have a promising inhibiting impact towards coronavirus. In addition, it is substantial to understand the characteristics, susceptibility and impact of diet on patients infected with COVID-19. In this review, we recapitulate the influence of extracts or pure molecules from medicinal plants on COVID-19. We approach the possibilities of plant treatment/co-treatment and feeding applied to COVID-19. We also show coronavirus susceptibility and complications associated with nutrient deficiencies and then discuss the major food groups efficient on COVID-19 pathogenesis. Then, we covered emerging technologies using plant-based SARS-CoV-2 vaccine. We conclude by giving nutrient and plants curative therapy recommendations which are of potential interest in the COVID-19 infection and could pave the way for pharmacological treatments or co-treatments of COVID-19.

Antiviral Activities of Officinaloside C against Herpes Simplex Virus-1

The iridoid compounds in traditional Chinese medicine play a prominent role in their antiviral effects. We previously reported the anti-inflammatory effect of new iridoids from the aerial parts of Morinda officinalis. Nevertheless, several open questions remain to explore the other biological functions of these new iridoid compounds. Herpes simplex virus-1 (HSV-1) is one of the most prevalent pathogens in human beings worldwide and due to limited therapies, mainly with the guanosine analog aciclovir (ACV) and other analogs, the search for new drugs with different modes of action and low toxicity becomes particularly urgent for public health. This study aimed to explore the anti-HSV-1 effects of iridoids from the aerial parts of Morinda officinalis. The dried aerial parts of Morinda officinalis were extracted with 95% ethanol and systematic separation and purification were then carried out by modern column chromatography methods such as silica gel column, RP-ODS column, Sephadex LH-20 gel column, and semi-preparative liquid phase, and the structure of these compounds were identified through the physical and chemical properties and a variety of spectral techniques. The obtained seven new iridoid compounds were screened for antiviral activity on HSV-1 through CCK8 and the cytopathic effect, and then the plaque reduction assay, the anti-fluorescence reporter virus strain replication, and RT-qPCR experiments were carried out to further evaluate the antiviral effect. Seven new iridoid compounds (officinaloside A-G) were identified from the aerial parts of Morinda officinalis, and officinaloside C showed anti-HSV-1 activity. Further functional experiments confirmed that officinaloside C has a significant inhibiting effect on HSV-1 virus plaque formation, viral gene, and protein expression, and fluorescent virus replication. Our findings suggest that officinaloside C has significant inhibitory effects on viral plaque formation, genome replication, and viral protein expression of HSV-1 which implies that officinaloside C exhibits viral activity and may be a promising treatment for HSV-1 infection.

Seven classes of antiviral agents

The viral epidemics and pandemics have stimulated the development of known and the discovery of novel antiviral agents. About a hundred mono- and combination antiviral drugs have been already approved, whereas thousands are in development. Here, we briefly reviewed 7 classes of antiviral agents: neutralizing antibodies, neutralizing recombinant soluble human receptors, antiviral CRISPR/Cas systems, interferons, antiviral peptides, antiviral nucleic acid polymers, and antiviral small molecules. Interferons and some small molecules alone or in combinations possess broad-spectrum antiviral activity, which could be beneficial for treatment of emerging and re-emerging viral infections.

Phytochemical Profile and Biological Activities of the Extracts from Two Oenanthe Species (O. aquatica and O. silaifolia)

This study presents the evaluation of biological activities and chemical profiling of Oenanthe aquatica (L.) Poir. and Oenanthe silaifolia M. Bieb. The phytochemical profile, antioxidant, enzyme inhibitory, cytotoxic and antiviral activities of the methanolic and aqueous extracts were investigated. The aqueous extract of O. aquatica possessing the highest content of phenolics (60.85 mg gallic acid equivalent/g extract), also exhibited the strongest radical scavenging potential against 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (79.46 and 148.66 mg Trolox equivalent/g extract, respectively), the highest reducing ability (207.59 and 107.27 mg Trolox equivalent/g extract, for cupric reducing antioxidant capacity and ferric reducing antioxidant activity, respectively), metal chelating potential (33.91 mg ethylenediaminetetraacetic acid equivalent/g extract) and total antioxidant ability (1.60 mmol Trolox equivalent/g extract). Liquid chromatography-electrospray ionization-quadrupole time-of-flight-mass spectrometry (LC-ESI-QTOF-MS/MS) permitted tentative identification of compounds from simple organic acids, phenolic acids, coumarins, flavonoids and their glycosides in O. aquatica and O. silaifolia extracts. The methanolic extract of O. aquatica substantially depressed acetylcholinesterase (3.67 mg galantamine equivalent/g extract), tyrosinase (126.66 mg kojic acid equivalent/g extract), and α-amylase (0.83 mmol acarbose equivalent/g extract) enzymes. The methanolic extract of O. silaifolia showed highest enzymatic inhibitory property against butyrylcholinesterase, and its aqueous extract depressed α-glucosidase activity (0.26 mmol acarbose equivalent/g extract). All tested extracts exerted selective toxicity towards cancer cell lines, and the highest anticancer potential was found for O. aquatica aqueous extract on FaDu and HeLa cells with CC₅₀ of 57.36 and 47.16 µg/mL, respectively. Significant antiviral activity against HSV-1 (HHV-1) was found for both aqueous extracts in concentrations of 1000 µg/mL, which inhibited the HSV-1 cytopathic effect (CPE) in virus infected VERO cells and reduced the virus infective titer by more than 3 log (logCCID₅₀/mL). This study has produced critical scientific data on O. aquatica and O. silaifolia, which are potential contenders for the development of novel phyto-pharmaceuticals.

Screening of a Small Molecule Compound Library Identifies Toosendanin as an Inhibitor Against Bunyavirus and SARS-CoV-2

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne virus causing serious infectious disease with a high case-fatality of up to 50% in severe cases. Currently, no effective drug has been approved for the treatment of SFTSV infection. Here, we performed a high-throughput screening of a natural extracts library for compounds with activities against SFTSV infection. Three hit compounds, notoginsenoside Ft1, punicalin, and toosendanin were identified for displaying high anti-SFTSV efficacy, in which, toosendanin showed the highest inhibition potency. Mechanistic investigation indicated that toosendanin inhibited SFTSV infection at the step of virus internalization. The anti-viral effect of toosendanin against SFTSV was further verified in mouse infection models, and the treatment with toosendanin significantly reduced viral load and histopathological changes in vivo. The antiviral activity of toosendanin was further expanded to another bunyavirus and the emerging SARS-CoV-2. This study revealed a broad anti-viral effect of toosendanin and indicated its potential to be developed as an anti-viral drug for clinical use.

Demystifying therapeutic potential of medicinal plants against chikungunya virus

Viral infections are posing a great threat to humanity for the last few years. Among these, Chikungunya which is a mosquito-borne viral infection has produced enormous epidemics around the world after been rebounded. Although this infection shows a low mortality rate, patients suffer from fever, arthralgia, and maculopapular rashes, which reduce the quality of life for several weeks to years. The currently available treatments only provide symptomatic relief based on analgesics, antipyretics, and anti-inflammatory drugs which are nonspecific without satisfactory results. Medicinal plants are a widely accepted source of new molecules for the treatment of infectious diseases including viral infections. The scientific reports, primarily focusing on the anti-chikungunya activity of plant extracts, natural origin pure compounds, and their synthetic analog published from 2011 to 2021, were selected from PubMed, Google Scholar, and Scopus by using related keywords like anti-chikungunya plants, natural antivirals for Chikungunya. The present review decodes scientific reports on medicinal plants against chikungunya virus (CHIKV) infection and demystifies the potential phytoconstituents which reveals that the screening of flavonoids containing plants and phytochemicals showing efficacy against other arbovirus infections, may prove as a potential lead for drug development against CHIKV. The present article also outlines pathogenesis, clinical aspects, molecular virology, and diagnostic approaches of CHIKV infection.

In Vitro Anti-Epstein Barr Virus Activity of Olea europaea L. Leaf Extracts

Olea europaea L. var. sativa (OESA) preparations are widely used in traditional medicine in the Mediterranean region to prevent and treat different diseases. In this research, olive extracts derived from the leaves of the OESA tree have been screened for antioxidant activity by two methods: the DPPH free radical scavenging assay (DPPH) and the Ferric reducing antioxidant power (FRAP) assay. The DPPH assay showed that OESA possesses a stronger antioxidant activity (84%) at 1 mg/mL while the FRAP method showed a strong metal ion chelating activity (90%) at 1 mg/mL. The low IC₅₀ values, obtained by two different methods, implies that OESA has a noticeable effect on scavenging free radicals comparable to standards. During EBV infection, the free radicals increased triggering lipid oxidation. Therefore, the monitoring of the secondary lipid peroxidation products was done by measuring malonaldehyde (MDA) and conjugated dienes (DC). The simultaneous treatment of Raji cells with OESA and TPA, as an inductorof the lytic cycle, generated a significant decrease in MDA levels and DC (p < 0.05). Besides, Raji cells simultaneously exposed to TPA and OESA exhibited a percentage of EBV-positive fluorescence cells lower than TPA treated cells (**** p < 0.0001). This suggests that OESA treatment has a protective effect against EBV lytic cycle induction.

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

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

In Vitro Anti-HIV-1 Reverse Transcriptase and Integrase Properties of Punica granatum L. Leaves, Bark, and Peel Extracts and Their Main Compounds

In a search for natural compounds with anti-HIV-1 activity, we studied the effect of the ethanolic extract obtained from leaves, bark, and peels of Punica granatum L. for the inhibition of the HIV-1 reverse transcriptase (RT)-associated ribonuclease H (RNase H) and integrase (IN) LEDGF-dependent activities. The chemical analyses led to the detection of compounds belonging mainly to the phenolic and flavonoid chemical classes. Ellagic acid, flavones, and triterpenoid molecules were identified in leaves. The bark and peels were characterized by the presence of hydrolyzable tannins, such as punicalins and punicalagins, together with ellagic acid. Among the isolated compounds, the hydrolyzable tannins and ellagic acid showed a very high inhibition (IC50 values ranging from 0.12 to 1.4 µM and 0.065 to 0.09 µM of the RNase H and IN activities, respectively). Of the flavonoids, luteolin and apigenin were found to be able to inhibit RNase H and IN functions (IC50 values in the 3.7-22 μM range), whereas luteolin 7-O-glucoside showed selective activity for HIV-1 IN. In contrast, betulinic acid, ursolic acid, and oleanolic acid were selective for the HIV-1 RNase H activity. Our results strongly support the potential of non-edible P. granatum organs as a valuable source of anti-HIV-1 compounds.

Potential antiviral effects of some native Iranian medicinal plants extracts and fractions against influenza A virus

Background

Influenza A virus (IAV) infection is a continual threat to the health of animals and humans globally. Consumption of the conventional drugs has shown several side effects and drug resistance. This study was aimed to screen some Iranian medicinal plants extracts and their fractions against influenza A virus.

Methods

Glycyrrhiza glabra (rhizome), Myrtus  commonis (leaves), Melissa officinalis (leaves), Hypericum perforatum (aerial parts), Tilia platyphyllos (flower), Salix alba (bark), and Camellia sinensis (green and fermented leaves) were extracted with 80% methanol and fractionated with chloroform and methanol, respectively. The cytotoxicity of the compounds were determined by MTT colorimetric assay on MDCK cells. The effective concentrations (EC₅₀) of the compounds were calculated from the MTT results compared to the negative control with no significant effects on cell viability. The effects of EC₅₀ of the compounds on viral surface glycoproteins and viral titer were tested by HI and HA virological assays, respectively and compared with oseltamivir and amantadine. Preliminary phytochemical analysis were done for promising anti-IAV extracts and fractions.

Results

The most effective samples against IAV titer (P ≤ 0.05) were crude extracts of G. glabra, M. officinalis and S. alba; methanol fractions of M. communis and M. officinalis; and chloroform fractions of M. communis and C. sinensis (fermented) mostly in co- and pre-penetration combined treatments. The potential extracts and fractions were rich in flavonoids, tannins, steroids and triterpenoids.

Conclusion

The outcomes confirmed a scientific basis for anti-influenza A virus capacity of the extracts and fractions from the selected plants for the first time, and correlated their effects with their phytochemical constituents. It is worth focusing on elucidating pure compounds and identifying their mechanism(s) of action.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03423-x.

Use of medicinal plants for COVID-19 prevention and respiratory symptom treatment during the pandemic in Cusco, Peru: A cross-sectional survey

BACKGROUND

The burden of the COVID-19 pandemic in Peru has led to people seeking alternative treatments as preventives and treatment options such as medicinal plants. This study aimed to assess factors associated with the use of medicinal plants as preventive or treatment of respiratory symptom related to COVID-19 during the pandemic in Cusco, Peru.

METHOD

A web-based cross-sectional study was conducted on general public (20- to 70-year-old) from August 31 to September 20, 2020. Data were collected using a structured questionnaire via Google Forms, it consisted of an 11-item questionnaire that was developed and validated by expert judgment using Aiken's V (Aiken's V > 0.9). Both descriptive statistics and bivariate followed by multivariable logistic regression analyses were conducted to assess factors associated with the use of medicinal plants for COVID-19 prevention and respiratory symptom treatment during the pandemic. Prevalence ratios (PR) with 95% Confidence Interval (CI), and a P-value of 0.05 was used to determine statistical significance.

RESULTS

A total of 1,747 respondents participated in the study, 80.2% reported that they used medicinal plants as preventives, while 71% reported that they used them to treat respiratory symptoms. At least, 24% of respondents used medicinal plants when presenting with two or more respiratory symptoms, while at least 11% used plants for malaise. For treatment or prevention, the multivariate analysis showed that most respondents used eucalyptus (p < 0.001 for both), ginger (p < 0.022 for both), spiked pepper (p < 0.003 for both), garlic (p = 0.023 for prevention), and chamomile (p = 0.011 for treatment). The respondents with COVID-19 (p < 0.001), at older ages (p = 0.046), and with a family member or friend who had COVID-19 (p < 0.001) used more plants for prevention. However, the respondents with technical or higher education used less plants for treatment (p < 0.001).

CONCLUSION

There was a significant use of medicinal plants for both prevention and treatment, which was associated with several population characteristics and whether respondents had COVID-19.

Mode-Dependent Antiviral Activity of Medicinal Plant Extracts against the Mosquito-Borne Chikungunya Virus

The lack of specific treatment for chikungunya fever makes the need for anti-chikungunya virus agents more crucial. This study was conducted to evaluate 132 extracts obtained by sequential solvent extraction from 21 medicinal plants for cytopathic effect inhibitory activity using virus-infected Vero cells in two different sample introduction modes. Among the extracts, 42 extracts (31.8%) from 12 plants in the concurrent mode and three extracts (2.3%) from a plant in the non-concurrent mode displayed strong cytopathic effect inhibitory activity (cell viability ≥70%). Viral load quantification analysis unveiled that the extracts of Clinacanthus nutans (chloroform, ethyl acetate, and ethanol), Hydrocotyle sibthorpioides (ethanol), and Ocimum americanum (ethanol and methanol) hindered the release of viral progeny from the infected cells while the extracts of Ficus deltoidea (ethanol), Gynura bicolor (water), H. sibthorpioides (water), and O. americanum (chloroform and ethyl acetate) blocked the entry of virus into the cells. The extracts of Diodella sarmentosa (ethyl acetate), Diplazium esculentum (chloroform, ethyl acetate, and ethanol), and G. bicolor (ethanol) possessed virucidal effect and caused 5.41-log to 6.63-log reductions of viral load compared to the virus control. The results indicate that these medicinal plants are potential sources of anti-chikungunya virus agents that have varied modes of action.

Machine Learning in Discovery of New Antivirals and Optimization of Viral Infections Therapy

Nowadays, computational approaches play an important role in the design of new drug-like compounds and optimization of pharmacotherapeutic treatment of diseases. The emerging growth of viral infections, including those caused by the Human Immunodeficiency Virus (HIV), Ebola virus, recently detected coronavirus, and some others, leads to many newly infected people with a high risk of death or severe complications. A huge amount of chemical, biological, clinical data is at the disposal of the researchers. Therefore, there are many opportunities to find the relationships between the particular features of chemical data and the antiviral activity of biologically active compounds based on machine learning approaches. Biological and clinical data can also be used for building models to predict relationships between viral genotype and drug resistance, which might help determine the clinical outcome of treatment. In the current study, we consider machine-learning approaches in the antiviral research carried out during the past decade. We overview in detail the application of machine-learning methods for the design of new potential antiviral agents and vaccines, drug resistance prediction, and analysis of virus-host interactions. Our review also covers the perspectives of using the machine-learning approaches for antiviral research, including Dengue, Ebola viruses, Influenza A, Human Immunodeficiency Virus, coronaviruses, and some others.

Antiviral Cyanometabolites-A Review

Global processes, such as climate change, frequent and distant travelling and population growth, increase the risk of viral infection spread. Unfortunately, the number of effective and accessible medicines for the prevention and treatment of these infections is limited. Therefore, in recent years, efforts have been intensified to develop new antiviral medicines or vaccines. In this review article, the structure and activity of the most promising antiviral cyanobacterial products are presented. The antiviral cyanometabolites are mainly active against the human immunodeficiency virus (HIV) and other enveloped viruses such as herpes simplex virus (HSV), Ebola or the influenza viruses. The majority of the metabolites are classified as lectins, monomeric or dimeric proteins with unique amino acid sequences. They all show activity at the nanomolar range but differ in carbohydrate specificity and recognize a different epitope on high mannose oligosaccharides. The cyanobacterial lectins include cyanovirin-N (CV-N), scytovirin (SVN), microvirin (MVN), Microcystisviridis lectin (MVL), and Oscillatoria agardhii agglutinin (OAA). Cyanobacterial polysaccharides, peptides, and other metabolites also have potential to be used as antiviral drugs. The sulfated polysaccharide, calcium spirulan (CA-SP), inhibited infection by enveloped viruses, stimulated the immune system’s response, and showed antitumor activity. Microginins, the linear peptides, inhibit angiotensin-converting enzyme (ACE), therefore, their use in the treatment of COVID-19 patients with injury of the ACE2 expressing organs is considered. In addition, many cyanobacterial extracts were revealed to have antiviral activities, but the active agents have not been identified. This fact provides a good basis for further studies on the therapeutic potential of these microorganisms.

Demystifying therapeutic potential of medicinal plants against chikungunya virus

Viral infections are posing a great threat to humanity for the last few years. Among these, Chikungunya which is a mosquito-borne viral infection has produced enormous epidemics around the world after been rebounded. Although this infection shows a low mortality rate, patients suffer from fever, arthralgia, and maculopapular rashes, which reduce the quality of life for several weeks to years. The currently available treatments only provide symptomatic relief based on analgesics, antipyretics, and anti-inflammatory drugs which are nonspecific without satisfactory results. Medicinal plants are a widely accepted source of new molecules for the treatment of infectious diseases including viral infections. The scientific reports, primarily focusing on the anti-chikungunya activity of plant extracts, natural origin pure compounds, and their synthetic analog published from 2011 to 2021, were selected from PubMed, Google Scholar, and Scopus by using related keywords like anti-chikungunya plants, natural antivirals for Chikungunya. The present review decodes scientific reports on medicinal plants against chikungunya virus (CHIKV) infection and demystifies the potential phytoconstituents which reveals that the screening of flavonoids containing plants and phytochemicals showing efficacy against other arbovirus infections, may prove as a potential lead for drug development against CHIKV. The present article also outlines pathogenesis, clinical aspects, molecular virology, and diagnostic approaches of CHIKV infection.

Phytochemicals as Anti-Inflammatory Agents in Animal Models of Prevalent Inflammatory Diseases

Phytochemicals are known to have anti-inflammatory effects in vitro and in vivo, such as in inflammatory disease model systems. Inflammation is an essential immune response to exogenous stimuli such as infection and injury. Although inflammation is a necessary host-defense mechanism, chronic inflammation is associated with the continuous local or systemic release of inflammatory mediators, non-cytokine mediators, such as ROS and NO, and inflammatory cytokines are strongly implicated in the pathogenesis of various inflammatory disorders. Phytochemicals that exhibit anti-inflammatory mechanisms that reduce sustained inflammation could be therapeutic candidates for various inflammatory diseases. These phytochemicals act by modulating several main inflammatory signaling pathways, including NF-κB, MAPKs, STAT, and Nrf-2 signaling. Here, we discuss the characteristics of phytochemicals that possess anti-inflammatory activities in various chronic inflammatory diseases and review the molecular signaling pathways altered by these anti-inflammatory phytochemicals, with a focus on transcription factor pathways. Furthermore, to evaluate the phytochemicals as drug candidates, we translate the effective doses of phytochemicals in mice or rat disease models into the human-relevant equivalent and compare the human-relevant equivalent doses of several phytochemicals with current anti-inflammatory drugs doses used in different types of chronic inflammatory diseases.