Plant as a Source of Natural Antiviral Agents

An Overview on Rumex dentatus L.: Its Functions as a Source of Nutrient and Health-Promoting Plant

Rumex dentatus L. (Polygonaceae), also known as toothed dock or Aegean dock, is a medicinal plant with a high culinary value in addition to being used as an ethnomedicinal plant. This review focuses on the botanical, nutritional, phytochemical, and pharmacological activities of R. dentatus, as well as the future prospects for systematic investigations into these areas. R. dentatus has been subjected to scientific evaluation, which has confirmed its traditional uses and demonstrated a wide range of biological and pharmacological potentials, including antioxidant, anticancer, antifungal, antibacterial, anti-inflammatory, and other biological properties. Phytochemical analyses showed the presence of anthraquinones, chromones, flavonoids, and essential oils. As a result of this current review, the medicinal significance of R. dentatus has been confirmed, and future research on its unexplored aspects, such as the identification of pharmacologically active chemical constituents and related mechanisms and safety, may be stimulated, with the goal of developing it into a drug.

Potential Antiviral Action of Alkaloids

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

Combination of natural antivirals and potent immune invigorators: A natural remedy to combat COVID-19

The flare‐up in severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) that emerged in December 2019 in Wuhan, China, and spread expeditiously worldwide has become a health challenge globally. The rapid transmission, absence of anti‐SARS‐CoV‐2 drugs, and inexistence of vaccine are further exacerbating the situation. Several drugs, including chloroquine, remdesivir, and favipiravir, are presently undergoing clinical investigation to further scrutinize their effectiveness and validity in the management of COVID‐19. Natural products (NPs) in general, and plants constituents specifically, are unique sources for various effective and novel drugs. Immunostimulants, including vitamins, iron, zinc, chrysin, caffeic acid, and gallic acid, act as potent weapons against COVID‐19 by reinvigorating the defensive mechanisms of the immune system. Immunity boosters prevent COVID‐19 by stimulating the proliferation of T‐cells, B‐cells, and neutrophils, neutralizing the free radicals, inhibiting the immunosuppressive agents, and promoting cytokine production. Presently, antiviral therapy includes several lead compounds, such as baicalin, glycyrrhizin, theaflavin, and herbacetin, all of which seem to act against SARS‐CoV‐2 via particular targets, such as blocking virus entry, attachment to host cell receptor, inhibiting viral replication, and assembly and release.

Natural product remedies for COVID-19: A focus on safety

Infection by the novel coronavirus SARS-CoV-2 causing the coronavirus disease (COVID-19), is currently a global pandemic with more than two million deaths to date. Though a number of vaccines have recently been approved against the virus, availability remains a big challenge, and also acceptance by most people has become a big debate. This review discusses possible/proposed natural product remedies and some major conventional treatment options used to manage the infection and, safety concerns on the use of unproven or unapproved health products against COVID-19. An extensive literature review indicated that the influx of unproven and unapproved health products in the global market are on the rise, leading to various forms of self- medication. To this effect, there have been warnings by the United States Food and Drug Administration and the World Health Organisation against the use of such products. Conventional drugs such as remdesivir, chloroquine/hydroxychloroquine and dexamethasone are the major proposed drugs that are currently undergoing clinical trials for the management of this disease. Efforts are being made globally in the search for possible therapeutics which may be the best way to eradicating this disease. Some countries have approved the use of natural products in the management of COVID-19, despite little or no clinical evidence on their efficacy and safety. Natural products may hold a great potential in the fight against COVID-19 but without detailed clinical trials, their potency against the virus and their safe use cannot be established. To attain this goal, extensive research followed by clinical studies are needed. Collaborative efforts between researchers, clinicians, governments and traditional medicinal practitioners in the search and development of safe and effective therapeutics from natural products for the treatment of COVID-19 could be a potential option.

Candidate Anti-COVID-19 Medicinal Plants from Ethiopia: A Review of Plants Traditionally Used to Treat Viral Diseases

BACKGROUND

Emerging viral infections are among the major global public health concerns. The pandemic COVID-19 is a contagious respiratory and vascular disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). There are no medicines that can treat SARS-CoV-2 except the vaccines. Therefore, searching for plant-originated therapeutics for the treatment of COVID-19 is required. Consequently, reviewing medicinal plants used to treat different viral infections is mandatory. This review article aims to review the ethnobotanical knowledge of medicinal plants traditionally used to treat different viral diseases by the Ethiopian people and suggests those plants as candidates to fight COVID-19.

METHODS

Articles written in English were searched from online public databases using searching terms like "Traditional Medicine," "Ethnobotanical study," "Active components," "Antiviral activities," and "Ethiopia." Ethnobotanical data were analyzed using the Excel statistical software program.

RESULT

From the 46 articles reviewed, a total of 111 plant species were claimed to treat viral infections. Fifty-six (50.4%) of the plant species had reported to have antiviral active components that are promising to treat COVID-19. Lycorine, gingerol shogaol, resveratrol, rhoifolin, oleanolic acid, kaempferol, rosmarinic acid, almond oil, ursolic acid, hederagenin, nigellidine, α-hederin, apigenin, nobiletin, tangeretin, chalcone, hesperidin, epigallocatechin gallate, allicin, diallyl trisulfide, ajoene, aloenin, artemisinin, glucobrassicin, curcumin, piperine, flavonoids, anthraquinone, hydroxychloroquine, and jensenone were some of them.

CONCLUSION

The Ethiopian traditional knowledge applies a lot of medicinal plants to treat different viral infections. Reports of the chemical components of many of them confirm that they can be promising to fight COVID-19.

Positive Therapeutic Role of Selected Foods and Plant on Ailments with a Trend Towards COVID-19: A Review

Each day since December 2019, increasing numbers of cases of the novel coronavirus 2019 (COVID-19) infection are being detected as it spreads throughout all continents of the world except Antarctica. The virus is transmitted through contact with an infected environment or person, and the symptoms include fever, cough, and difficulty breathing. The healthcare systems of many countries are overwhelmed due to limited therapeutic options and the absence of an approved vaccine. Due to its poor healthcare systems, Africa may be the worst hit continent if other therapeutic alternatives are not explored. This review explores the source and origin of the COVID-19 infection, and alternative therapeutic options derived from available and cheap medicinal foods and plants that have been shown to alleviate similar infections. The results demonstrate the inhibitory activities of selected food crops and plants against human viruses similar to the novel COVID-19.

Therapeutic opportunities of edible antiviral plants for COVID-19

The pandemic of Serious Acute Respiratory Syndrome Corona Virus-2 (SARS-CoV-2) that produces corona virus disease (COVID-19) has challenged the entire mankind by rapidly spreading globally in 210 countries affecting over 25 million people and about 1 million deaths worldwide. It continues to spread, afflicting the health system globally. So far there is no remedy for the ailment and the available antiviral regimens have been unsatisfactory for the clinical outcomes and the mode of treatment has been mainly supportive for the prevention of COVID-19-induced morbidity and mortality. From the time immortal the traditional plant-based ethno-medicines have provided the leads for the treatment of infectious diseases. Phytopharmaceuticals have provided potential and less toxic antiviral drugs as compared to conventional modern therapeutics which are associated with severe toxicities. The ethnopharmacological knowledge about plants has provided food supplements and nutraceuticals as a promise for prevention and treatment of the current pandemic. In this review article, we have attempted to comprehend the information about the edible medicinal plant materials with potential antiviral activity specifically against RNA virus which additionally possess property to improve immunity along with external and internal respiration and exhibit anti-inflammatory properties for the prevention and treatment of the disease. This will open an arena for the development of novel nutraceutical herbal formulations as an alternative therapy that can be used for the prevention and treatment of COVID-19.

Development of nanoparticle-delivery systems for antiviral agents: A review

The COVID-19 pandemic has resulted in unprecedented increases in sickness, death, economic disruption, and social disturbances globally. However, the virus (SARS-CoV-2) that caused this pandemic is only one of many viruses threatening public health. Consequently, it is important to have effective means of preventing viral transmission and reducing its devastating effects on human and animal health. Although many antivirals are already available, their efficacy is often limited because of factors such as poor solubility, low permeability, poor bioavailability, un-targeted release, adverse side effects, and antiviral resistance. Many of these problems can be overcome using advanced antiviral delivery systems constructed using nanotechnology principles. These delivery systems consist of antivirals loaded into nanoparticles, which may be fabricated from either synthetic or natural materials. Nevertheless, there is increasing emphasis on the development of antiviral delivery systems from natural substances, such as lipids, phospholipids, surfactants, proteins, and polysaccharides, due to health and environmental issues. The composition, morphology, dimensions, and interfacial characteristics of nanoparticles can be manipulated to improve the handling, stability, and potency of antivirals. This article outlines the major classes of antivirals, summarizes the challenges currently limiting their efficacy, and highlights how nanoparticles can be used to overcome these challenges. Recent studies on the application of antiviral nanoparticle-based delivery systems are reviewed and future directions are described.

ADMET profile and virtual screening of plant and microbial natural metabolites as SARS-CoV-2 S1 glycoprotein receptor binding domain and main protease inhibitors

In an attempt to search for selective inhibitors against the SARS-CoV-2 which caused devastating of lives and livelihoods across the globe, 415 natural metabolites isolated from several plants, fungi and bacteria, belonging to different classes, were investigated. The drug metabolism and safety profiles were computed in silico and the results showed seven compounds namely fusaric acid, jasmonic acid, jasmonic acid methyl ester, putaminoxin, putaminoxin B and D, and stagonolide K were predicted to having considerable absorption, metabolism, distribution and excretion parameters (ADME) and safety indices. Molecular docking against the receptor binding domain (RBD) of spike glycoprotein (S1) and the main protease (Mpro) exposed the compounds having better binding affinity to main protease as compared to the S1 receptor binding domain. The docking results were compared to an antiviral drug penciclovir reportedly of clinical significance in treating the SARS-CoV-2 infected patients. The results demonstrated the test compounds jasmonic acid, putaminoxins B and D bound to the HIS-CYS catalytic dyad as well as to other residues within the MPro active site with much greater affinity than penciclovir. The findings of the study suggest that these compounds could be explored as potential SARS-CoV-2 inhibitors, and could further be combined with the experimental investigations to develop effective therapeutics to deal with the present pandemic.

A systematic review on phytochemicals for the treatment of dengue

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

Review of Phytochemical Compounds as Antiviral Agents Against Arboviruses from the Genera Flavivirus and Alphavirus

Arboviruses are a diverse group of viruses that are among the major causes of emerging infectious diseases. Arboviruses from the genera flavivirus and alphavirus are the most important human arboviruses from a public health perspective. During recent decades, these viruses have been responsible for millions of infections and deaths around the world. Over the past few years, several investigations have been carried out to identify antiviral agents to treat these arbovirus infections. The use of synthetic antiviral compounds is often unsatisfactory since they may raise the risk of viral mutation; they are costly and possess either side effects or toxicity. One attractive strategy is the use of plants as promising sources of novel antiviral compounds that present significant inhibitory effects on these viruses. In this review, we describe advances in the exploitation of compounds and extracts from natural sources that target the vital proteins and enzymes involved in arbovirus replication.

Antiviral and healing potential of Sambucus nigra extracts

Nowadays, the application of alternative methods instead of clinical treatment creates a new possibility to prevent the development of diseases. Medicinal plants such as Sambucus nigra have been well known due to their extraordinary properties. The similarity to synthetic substances makes it potentially dependable; however, a high concentration of cyanogenic glycosides may exert detrimental consequences. It has been documented that Sambucus nigra extracts are used against both human and animal viruses, like influenza A and B viruses, human immunodeficiency virus (HIV), dengue virus (DENV-2), human herpesvirus type 1 (HSV-1) and human coronavirus NL63 (HCoV-NL63). Such reports are notably valuable especially considering the widespread usage of commercial drugs, which could be ineffective. This review provides insight on recent research on the health properties of plant Sambucus nigra as an antiviral medication that may help propose new therapy.

In Vitro Data of Current Therapies for SARS-CoV-2

BACKGROUND

In December 2019, a new coronavirus, named Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), emerged from China, causing pneumonia outbreaks first in the Wuhan region and then spread worldwide. Due to a lack of efficient and specific treatments and the need to contain the epidemic, drug repurposing appears to be the most efficient tool to find a therapeutic solution.

OBJECTIVES

The aim of this study was to summarize in vitro data of current agents used for the management of SARS-CoV-2 all over the world.

METHODS

A literature search of articles from January 2000 until April 2020 was performed using MEDLINE, EMBASE and the Cochrane Library to assess in vitro data of current or putative therapies for SARS-CoV-2.

RESULTS

Although in vitro studies are scarce, data regarding chloroquine, hydroxychloroquine, remdesivir, nitazoxanide, teicoplanin, ivermectin, lopinavir, homoharringtonine, and emetine seem promising.

CONCLUSION

Scientists all over the world should work together and increase their efforts in order to find feasible and efficient solutions against this new global viral threat.

Association between ABO blood/rhesus grouping and hepatitis B and C: a case-control study

During past decades, a connection between hepatitis and the host ABO/Rh blood groups has been always under dispute, with no appropriately designed study yet. This study aimed to investigate possible association between ABO blood/Rh groups with both hepatitis B and C. In this case-control setting, 200 healthy individuals (controls), 200 patients with chronic Hepatitis-B infection (HB) and 200 patients with chronic Hepatitis-C infection (HC) were recruited from 2010 to 2013 in Tabriz Sina Hospital. ABO blood and Rh grouping was performed and the results were compared between the case and control groups. Both pair of the control and HB groups and the control and HC groups were matched for their subjects' age and sex. In the control group, 178 subjects (89%) were Rh+ and 22 subjects (11%) were Rh-. In the HB group, there were 180 Rh+ (90%) and 20 Rh- (10%) patients. In the HC group there were 168 Rh+ (84%) and 32 Rh-negative (16%) patients. Both pair of the control and HB groups (p = 0.74), as well as the control and HC groups (p = 0.14) were comparable for the status of Rh. In the control group there were 84 (42%), 32 (16%), 66 (33%) and 18 (9%) subjects with A, B, O and AB blood groups, respectively. The corresponding figures were 84 (42%), 34 (17%), 58 (29%) and 24 (12%) for the HB patients; and 80 (40%), 29 (14.5%), 85 (42.5%) and 6 (3%) for the HC patients. Comparing between the control and HB groups showed no significant difference in terms of the frequency of ABO blood groups (p = 0.70). However, with comparing the control and HC groups, the rate of O blood group was significantly higher in the HC group and concomitantly, the rate of AB blood group was significantly higher in the control group (p = 0.04). Although, there is not a significant association between ABO blood groups and HB, this association is significant between certain ABO blood groups and HC.

Association between Human Leukocyte Antigen class-I and hepatitis C: the first report in Azeri patients

It has been suggested that host genetic diversity may be associated with Hepatitis C (HC). However, available data are tremendously heterogeneous due to the influence of ethnic and geographical differences. This study aimed to investigate possible association between certain Human Leukocyte Antigen (HLA) class-I alleles with HC in a group of Azeri patients for the first time in the literature. In a case-control study, 50 patients with confirmed HC (cases) and 50 healthy age- and sex-matched counterparts (controls) were evaluated in Tabriz Sina and Imam Reza Hospitals in a 2-year period of time (2011-2013). The investigated HLA alleles in the present study were: A2, A3, B35, B38, BW4, CW4 and CW7. The A2-positive cases were significantly more frequent in the case than in the control group (58 vs. 32%, p = 0.01, Odds Ratio (OR) = 2.9). Similar trend was documented for A3 (62 vs. 26%, p < 0.001, OR = 4.6), B35 (24 vs. 2%, p = 0.001, OR = 15.5) and BW4 (78 vs. 46%, p = 0.001, OR = 4.2). In contrast, the rate of B38-positive (34 vs. 8%, p = 0.001, OR = 0.2) and CW7-positive (38 vs. 14%, p = 0.01, OR = 0.3) cases was significantly higher in the hepatitis-C-negative subjects. There was no significant difference in terms of the rate of CW4-positivity between the two groups (20% in the cases vs. 34% in the controls, p = 0.12, OR = 0.5). This study showed that there are significant associations between certain HLA-I alleles with hepatitis C in Azeri patients. While some alleles make the host prone to the disease, others may have a protective role in this regard.

Polygonum cuspidatum and its active components inhibit replication of the influenza virus through toll-like receptor 9-induced interferon beta expression

Influenza virus infection is a global public health issue. The effectiveness of antiviral therapies for influenza has been limited by the emergence of drug-resistant viral strains. Therefore, there is an urgent need to identify novel antiviral therapies. Here we tested the effects of 300 traditional Chinese medicines on the replication of various influenza virus strains in a lung cell line, A549, using an influenza-specific luciferase reporter assay. Of the traditional medicines tested, Polygonum cuspidatum (PC) and its active components, resveratrol and emodin, were found to attenuate influenza viral replication in A549 cells. Furthermore, they preferentially inhibited the replication of influenza A virus, including clinical strains isolated in 2009 and 2011 in Taiwan and the laboratory strain A/WSN/33 (H1N1). In addition to inhibiting the expression of hemagglutinin and neuraminidase, PC, emodin, and resveratrol also increased the expression of interferon beta (IFN-β) through Toll-like receptor 9 (TLR9). Moreover, the anti-viral activity of IFN-β or resveratrol was reduced when the A549 cells were treated with neutralizing anti-IFN-β antibodies or a TLR9 inhibitor, suggesting that IFN-β likely acts synergistically with resveratrol to inhibit H1N1 replication. This potential antiviral mechanism, involving direct inhibition of virus replication and simultaneous activation of the host immune response, has not been previously described for a single antiviral molecule. In conclusion, our data support the use of PC, resveratrol or emodin for inhibiting influenza virus replication directly and via TLR-9–induced IFN-β production.

The study of antinociceptive effect of hydroalcoholic extract of Teucrium oliverianum (a plant used in southern Iranian traditional medicine) in rat by formalin test

Antinociceptive and anti-inflammatory activities of hydroalcoholic extract of Teucrium Oliverianum were investigated by formalin test model. This study was conducted in on the male Wistar rats, weighting 150-180 g. The animals were divided into seven groups (n = 7) and received 200, 400, 600 and 800 mg kg(-1) of hydroalcoholic extract of teucrium oliverianum intraperitoneally, respectively. Negative control group received normal saline (5 mL kg(-1)) and the positive control groups received 2.5 mg kg(-1) morphine and 300 mg kg(-1) aspirin, intraperitoneally respectively. The results showed that all doses of extract have significant analgesic effect (p < 0.05) in all studies times in comparison with negative control. The best result achieved with 600 mg kg(-1) of extract. The result revealed that the analgesic effect of the extract (600 mg kg(-1)) \was less than aspirin (300 mg kg(-1)) on the second phase of pain and less than morphine (2.5 mg kg(-1)) in both phases of the pain, more than aspirin in first phase of pain. One group of animals was treated with naloxone (1 mg kg(-1), i.p.) and suitable dose of extract (600 mg kg(-1), i.p.). Also, Naloxone inhibited analgesic effect of alcoholic extract of Teucrium Oliverianum. It can be concluded that the alcoholic extract of Teucrium oliverianum may exert its effect through opioid receptors, stimulating GABAergic system or promotes the release of endogenous opipeptides or decreasing free radicals.

Phytochemical screening and in vitro amylase inhibitory effect of the leaves of Breynia retusa

This study was proposed based on the folklore claim and on the scarcity of scientific evidence from the literature for the medicinal uses of Breynia retusa. The aim of the present study was to analyse the phytochemical constituents of the leaves of B. retusa. The fractions obtained by successive fractionation using solvents of varying polarity were studied for the presence of primary and secondary metabolites and the total phenolic content of the different fractions were determined by HPLC. The results of the study support the traditional acclaim of the therapeutic uses of B. retusa. The potential of B. retusa to inhibit alpha-amylase, a prime enzyme involved in carbohydrate metabolism was analysed and it was observed that the ethyl acetate and methanolic extract of the leaves of B. retusa possessed in vitro amylase inhibitory activity.