Propolis,Bee Honey,and Their Components Protect against Coronavirus Disease 2019 (COVID-19): A Review of In Silico,In Vitro,and Clinical Studies

Despite the virulence and high fatality of coronavirus disease 2019 (COVID-19), no specific antiviral treatment exists until the current moment. Natural agents with immune-promoting potentials such as bee products are being explored as possible treatments. Bee honey and propolis are rich in bioactive compounds that express strong antimicrobial, bactericidal, antiviral, anti-inflammatory, immunomodulatory, and antioxidant activities. This review examined the literature for the anti-COVID-19 effects of bee honey and propolis, with the aim of optimizing the use of these handy products as prophylactic or adjuvant treatments for people infected with severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). Molecular simulations show that flavonoids in propolis and honey (e.g., rutin, naringin, caffeic acid phenyl ester, luteolin, and artepillin C) may inhibit viral spike fusion in host cells, viral-host interactions that trigger the cytokine storm, and viral replication. Similar to the potent antiviral drug remdesivir, rutin, propolis ethanolic extract, and propolis liposomes inhibited non-structural proteins of SARS-CoV-2 in vitro, and these compounds along with naringin inhibited SARS-CoV-2 infection in Vero E6 cells. Propolis extracts delivered by nanocarriers exhibit better antiviral effects against SARS-CoV-2 than ethanolic extracts. In line, hospitalized COVID-19 patients receiving green Brazilian propolis or a combination of honey and Nigella sativa exhibited earlier viral clearance, symptom recovery, discharge from the hospital as well as less mortality than counterparts receiving standard care alone. Thus, the use of bee products as an adjuvant treatment for COVID-19 may produce beneficial effects. Implications for treatment outcomes and issues to be considered in future studies are discussed.     

Targeting the RdRp of Emerging RNA Viruses: The Structure-Based Drug Design Challenge

The RNA-dependent RNA polymerase (RdRp) is an essential enzyme for the viral replication process, catalyzing the viral RNA synthesis using a metal ion-dependent mechanism. In recent years, RdRp has emerged as an optimal target for the development of antiviral drugs, as demonstrated by recent approvals of sofosbuvir and remdesivir against Hepatitis C virus (HCV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), respectively. In this work, we overview the main sequence and structural features of the RdRp of emerging RNA viruses such as Coronaviruses, Flaviviruses, and HCV, as well as inhibition strategies implemented so far. While analyzing the structural information available on the RdRp of emerging RNA viruses, we provide examples of success stories such as for HCV and SARS-CoV-2. In contrast, Flaviviruses’ story has raised attention about how the lack of structural details on catalytically-competent or ligand-bound RdRp strongly hampers the application of structure-based drug design, either in repurposing and conventional approaches.     

Curcumin Inhibits In Vitro SARS-CoV-2 Infection In Vero E6 Cells through Multiple Antiviral Mechanisms

Due to the scarcity of therapeutic approaches for COVID-19, we investigated the antiviral and anti-inflammatory properties of curcumin against SARS-CoV-2 using in vitro models. The cytotoxicity of curcumin was evaluated using MTT assay in Vero E6 cells. The antiviral activity of this compound against SARS-CoV-2 was evaluated using four treatment strategies (i. pre–post infection treatment, ii. co-treatment, iii. pre-infection, and iv. post-infection). The D614G strain and Delta variant of SARS-CoV-2 were used, and the viral titer was quantified by plaque assay. The anti-inflammatory effect was evaluated in peripheral blood mononuclear cells (PBMCs) using qPCR and ELISA. By pre–post infection treatment, Curcumin (10 µg/mL) exhibited antiviral effect of 99% and 99.8% against DG614 strain and Delta variant, respectively. Curcumin also inhibited D614G strain by pre-infection and post-infection treatment. In addition, curcumin showed a virucidal effect against D614G strain and Delta variant. Finally, the pro-inflammatory cytokines (IL-1β, IL-6, and IL-8) released by PBMCs triggered by SARS-CoV-2 were decreased after treatment with curcumin. Our results suggest that curcumin affects the SARS-CoV-2 replicative cycle and exhibits virucidal effect with a variant/strain independent antiviral effect and immune-modulatory properties. This is the first study that showed a combined (antiviral/anti-inflammatory) effect of curcumin during SARS-CoV-2 infection. However, additional studies are required to define its use as a treatment for the COVID-19.     

Electron Transfer Processes in the Reactivity of Nonsteroidal Anti-inflammatory Drugs in the Ground and Excited States

The nonsteroidal anti-inflammatory drugs (NSAID), naproxen, sulindac and indomethacin, were shown to donate electrons to nitro blue tetrazolium (NBT) when irradiated with UV light in deoxygenated aqueous buffer solution (pH 7.4, 30°C). The reaction was monitored spec-trophotometrically by the appearance of the diformazan reduction product from NBT. The electron transfer process facilitates the decomposition of the drugs. Naproxen in the presence of NBT is photodegraded principally to the alcohol (2-[1-hydroxyethyl]-6-methoxynaphthalene) at a rate approximately 20-fold faster than when irradiated alone in deoxygenated conditions. The photoproduct from naproxen also participates in the electron transfer to NBT but at a much slower rate than naproxen. Irradiation of sulindac or indomethacin in the presence of NBT caused the slow photoreduction of NBT to diformazan. In the absence of NBT, indomethacin and sulindac are essentially unreactive when irradiated in aqueous solution. The ability of a number of NSAID to act as electron donors in their ground state was studied by observing their oxidation by potassium peroxodisulfate in pH 7.0 phosphate buffer at 50°C. The HPLC analysis of the drug remaining showed that the 2-arylpropionic acid NSAID (naproxen, ibuprofen, ketoprofen and suprofen) reacted at a rate equivalent to the thermal decomposition of peroxodisulfate. The major products were the same as detected in the photooxidation of these drugs, resulting from decarboxylation and oxygen addition but also included a dimeric compound. On the other hand, the NSAID that do not contain the propionic acid substituent all reacted more slowly with peroxodisulfate, enabling specific reaction rate constants to be evaluated.     

Identification of SARS-CoV-2 Papain-like Protease (PLpro) Inhibitors Using Combined Computational Approach**

In the current pandemic, finding an effective drug to prevent or treat the infection is the highest priority. A rapid and safe approach to counteract COVID-19 is in silico drug repurposing. The SARS-CoV-2 PLpro promotes viral replication and modulates the host immune system, resulting in inhibition of the host antiviral innate immune response, and therefore is an attractive drug target. In this study, we used a combined in silico virtual screening for candidates for SARS-CoV-2 PLpro protease inhibitors. We used the Informational spectrum method applied for Small Molecules for searching the Drugbank database followed by molecular docking. After in silico screening of drug space, we identified 44 drugs as potential SARS-CoV-2 PLpro inhibitors that we propose for further experimental testing.     

Medicinal Plants,Phytochemicals, and Herbs to Combat Viral Pathogens Including SARS-CoV-2

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome corona virus-2 (SARS-CoV-2), is the most important health issue, internationally. With no specific and effective antiviral therapy for COVID-19, new or repurposed antiviral are urgently needed. Phytochemicals pose a ray of hope for human health during this pandemic, and a great deal of research is concentrated on it. Phytochemicals have been used as antiviral agents against several viruses since they could inhibit several viruses via different mechanisms of direct inhibition either at the viral entry point or the replication stages and via immunomodulation potentials. Recent evidence also suggests that some plants and its components have shown promising antiviral properties against SARS-CoV-2. This review summarizes certain phytochemical agents along with their mode of actions and potential antiviral activities against important viral pathogens. A special focus has been given on medicinal plants and their extracts as well as herbs which have shown promising results to combat SARS-CoV-2 infection and can be useful in treating patients with COVID-19 as alternatives for treatment under phytotherapy approaches during this devastating pandemic situation.     

Gold Metallodrugs to Target Coronavirus Proteins: Inhibitory Effects on the Spike-ACE2 Interaction and on PLpro Protease Activity by Auranofin and Gold Organometallics**

Gold complexes have a long tradition in medicine and for many examples antirheumatic, anticancer or anti-infective effects have been confirmed. Herein, we evaluated the lead compound Auranofin and five selected gold organometallics as inhibitors of two relevant drug targets of severe acute respiratory syndrome coronaviruses (SARS-CoV). The gold metallodrugs were effective inhibitors of the interaction of the SARS-CoV-2 spike protein with the angiotensin converting enzyme 2 (ACE2) host receptor and might thus interfere with the viral entry process. The gold metallodrugs were also efficient inhibitors of the papain-like protease (PLpro) of SARS-CoV-1 and SARS-CoV-2, which is a key enzyme in the viral replication. Regarding PLpro from SARS-CoV-2, the here reported inhibitors are among the very first experimentally confirmed examples with activity against this target enzyme. Importantly, the activity of the complexes against both PLpro enzymes correlated with the ability of the inhibitors to remove zinc ions from the labile zinc center of the enzyme. Taken together, the results of this pilot study suggest further evaluation of gold complexes as SARS-CoV antiviral drugs.     

Repurposing Cardiac Glycosides: Drugs for Heart Failure Surmounting Viruses

Drug repositioning is a successful approach in medicinal research. It significantly simplifies the long-term process of clinical drug evaluation, since the drug being tested has already been approved for another condition. One example of drug repositioning involves cardiac glycosides (CGs), which have, for a long time, been used in heart medicine. Moreover, it has been known for decades that CGs also have great potential in cancer treatment and, thus, many clinical trials now evaluate their anticancer potential. Interestingly, heart failure and cancer are not the only conditions for which CGs could be effectively used. In recent years, the antiviral potential of CGs has been extensively studied, and with the ongoing SARS-CoV-2 pandemic, this interest in CGs has increased even more. Therefore, here, we present CGs as potent and promising antiviral compounds, which can interfere with almost any steps of the viral life cycle, except for the viral attachment to a host cell. In this review article, we summarize the reported data on this hot topic and discuss the mechanisms of antiviral action of CGs, with reference to the particular viral life cycle phase they interfere with.     

Nanoemulsions: The rising star of antiviral therapeutics and nanodelivery system—current status and prospects

Nanoemulsions (NEs) of essential oil (EO) have significant potential to target microorganisms, especially viruses. They act as a vehicle for delivering antiviral drugs and vaccines. Narrowing of drug discovery pipeline and the emergence of new viral diseases, especially, coronavirus disease, have created a niche to use NEs for augmenting currently available therapeutic options. Published literature demonstrated that EOs have an inherent broad spectrum of activity across bacterial, fungal, and viral pathogens. The emulsification process significantly improved the efficacy of the active ingredients in the EOs. This article highlights the research findings and patent developments in the last 2 years especially, in EO antiviral activity, antiviral drug delivery, vaccine delivery, viral resistance development, and repurposing EO compounds against SARS-CoV-2.     

基于萘普生-芳基金属配合物的抗癌及抗炎性能

以萘普生(NPX)为前体, 分别与芳基钌(Ru)、 锇(Os)及铱(Ir)二聚体反应制备了3个单核配合物[Ru(η ⁶-p-cymene)(NPX-bpy)Cl]Cl(1), [Os(η ⁶-p-cymene)(NPX-bpy)Cl]Cl(2)和[Ir(η ⁵-Cp ^*)·(NPX-bpy)Cl]Cl(3). 利用元素分析、 电喷雾质谱和核磁共振波谱对3个配合物的组成和结构进行了表征, 并研究了其细胞毒性. 结果表明, 3个配合物对几种肿瘤细胞株均无毒性(IC₅₀>100 μmol/L), 仅配合物1对NB-4细胞有中等程度的毒性(IC₅₀=45.2 μmol/L), 且毒性大于配合物2和3, 这可能与配合物1在细胞核内具有更高的富集量有关. 此外, 3个配合物均可有效抑制COX-2的表达, 保留了萘普生的抗炎性质, 实现了金属配合物抗癌及抗炎的多功能化应用.     

Design of original bioactive formulations based on sugar-surfactant/non-steroidal anti-inflammatory catanionic self-assemblies: a new way of dermal drug delivery

A new kind of catanionic assembly was developed that associates a sugar-based surfactant with a non-steroidal anti-inflammatory drug (NSAID). Three different assemblies using indomethacin, ibuprofen and ketoprofen as NSAIDs were easily obtained in water by an acid-base reaction. These assemblies formed new amphiphilic entities because of electrostatic and hydrophobic effects in water and led to the spontaneous formation of vesicles. These catanionic vesicles were then tested as potential NSAID delivery systems for dermatological application. The anti-inflammatory activity was evaluated in vivo, and this study clearly showed an improved therapeutic effect for NSAIDs that were formulated as catanionic vesicles. These vesicles ensured a slower diffusion of the NSAID through the skin. This release probably increased the time of retention of the NSAID in the targeted strata of the skin. Thus, the present study suggests that this catanionic bioactive formulation could be a promising dermal delivery system for NSAIDs in the course of skin inflammation treatment.     

A COMPARATIVE STUDY OF THE PHOTOCHEMISTRY OF THE NON-STEROIDAL ANTI-INFLAMMATORY DRUGS, NAPROXEN, BENOXAPROFEN AND INDOMETHACIN

Abstract— The photochemical reactivity of the non-steroidal anti-inflammatory drugs, naproxen and indomethacin, has been studied and compared with benoxaprofen, a similar compound of known cutaneous phototoxicity. Although indomethacin shows some phosphorescence at 77 K, flash photolysis at room temperature revealed only a weak photoionization process, and no photochemical reactivity was detected in steady state photolysis. Naproxen has strong fluorescence and phosphorescence, and in laser flash photolysis showed photoionization and a triplet state species in approximately equal yield. Naproxen and benoxaprofen produced singlet oxygen with similar quantum yield, as deduced from the sensitized rates of photooxidation of 2,5-dimethylfuran. Naproxen underwent photodecarboxylation as detected by ESR-spin trap experiments with 2-methyl-2-nitrosopropane. The decarboxy-naproxen radical combined readily with oxygen in aerated solution, and l-(6-methoxy-2-napthyl)ethanol and 2-acetyl-6-methoxynaphthalene were formed as the oxidation products. In deaer-ated solution, the major product was 2-ethyI-6-methoxynaphthalene, with the alcohol also formed. In comparison, benoxaprofen also underwent decarboxylation, with much higher quantum yield, but the decarboxy-benoxaprofen radical did not add oxygen. This difference in photoreactivity between naproxen and benoxaprofen, together with the much lower molar absorptivity of naproxen are the significant factors in relating to the differences in reported levels of clinical photosensitivity responses.     

Improved anti-inflammatory properties for naproxen with cyclodextrin-grafted polysaccharides

Mannan and carboxymethylcellulose, previously activated by periodate oxidation, were grafted with mono-6-butylenediamino-6-deoxy-beta-cyclodextrin derivatives by reductive alkylation in the presence of sodium borohydride. The formation of supramolecular complexes between these polymers and Naproxen was confirmed by fluorescence spectroscopy. The solubility of the drug was 3.8-4.6 fold increased in the presence of the cyclodextrin-grafted polysaccharides. The in vivo anti-inflammatory property of Naproxen was 1.7 times higher after supramolecular association with beta-cyclodextrin-branched mannan.     

Virtual screening of approved drugs as potential SARS-CoV-2 main protease inhibitors

The global emergency caused by COVID-19 makes the discovery of drugs capable of inhibiting SARS-CoV-2 a priority, to reduce the mortality and morbidity of this disease. Repurposing approved drugs can provide therapeutic alternatives that promise rapid and ample coverage because they have a documented safety record, as well as infrastructure for large-scale production. The main protease of SARS-CoV-2 (Mpro) is an excellent therapeutic target because it is critical for viral replication; however, Mpro has a highly flexible active site that must be considered when performing computer-assisted drug discovery. In this work, potential inhibitors of the main protease (Mpro) of SARS-Cov-2 were identified through a docking-assisted virtual screening procedure. A total of 4384 drugs, all approved for human use, were screened against three conformers of Mpro. The ligands were further studied through molecular dynamics simulations and binding free energy analysis. A total of nine currently approved molecules are proposed as potential inhibitors of SARS-CoV-2. These molecules can be further tested to speed the development of therapeutics against COVID-19.     

Drug Repurposing for COVID-19: A Review and a Novel Strategy to Identify New Targets and Potential Drug Candidates

In December 2019, the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19) was first identified in the province of Wuhan, China. Since then, there have been over 400 million confirmed cases and 5.8 million deaths by COVID-19 reported worldwide. The urgent need for therapies against SARS-CoV-2 led researchers to use drug repurposing approaches. This strategy allows the reduction in risks, time, and costs associated with drug development. In many cases, a repurposed drug can enter directly to preclinical testing and clinical trials, thus accelerating the whole drug discovery process. In this work, we will give a general overview of the main developments in COVID-19 treatment, focusing on the contribution of the drug repurposing paradigm to find effective drugs against this disease. Finally, we will present our findings using a new drug repurposing strategy that identified 11 compounds that may be potentially effective against COVID-19. To our knowledge, seven of these drugs have never been tested against SARS-CoV-2 and are potential candidates for in vitro and in vivo studies to evaluate their effectiveness in COVID-19 treatment.     

Anti-SARS-CoV-2 Inhibitory Profile of New Quinoline Compounds in Cell Culture-Based Infection Models

The presently ongoing pandemic of human SARS-CoV-2 infections (COVID-19) presents an enormous challenge in surveillance, vaccine and antiviral drug development. Here we report the synthesis of new bioactive quinoline-morpholine hybrid compounds and their virological evaluation, which proves pronounced cell culture-based inhibitory profile against SARS-CoV-2. Thus, selected quinoline compounds may suggest specific hit-to-lead development.     

Synthesis and In Vitro Study of Antiviral Activity of Glycyrrhizin Nicotinate Derivatives against HIV-1 Pseudoviruses and SARS-CoV-2 Viruses

When developing drugs against SARS-CoV-2, it is important to consider the characteristics of patients with different co-morbidities. People infected with HIV-1 are a particularly vulnerable group, as they may be at a higher risk than the general population of contracting COVID-19 with clinical complications. For such patients, drugs with a broad spectrum of antiviral activity are of paramount importance. Glycyrrhizinic acid (Glyc) and its derivatives are promising biologically active compounds for the development of such broad-spectrum antiviral agents. In this work, derivatives of Glyc obtained by acylation with nicotinic acid were investigated. The resulting preparation, Glycyvir, is a multi-component mixture containing mainly mono-, di-, tri- and tetranicotinates. The composition of Glycyvir was characterized by HPLC-MS/MS and its toxicity assessed in cell culture. Antiviral activity against three strains of SARS-CoV-2 was tested in vitro on Vero E6 cells by MTT assay. Glycyvir was shown to inhibit SARS-CoV-2 replication in vitro (IC₅₀2–8 μM) with an antiviral activity comparable to the control drug Remdesivir. In addition, Glycyvir exhibited marked inhibitory activity against HIV pseudoviruses of subtypes B, A6 and the recombinant form CRF63_02A (IC₅₀ range 3.9–27.5 µM). The time-dependence of Glycyvir inhibitory activity on HIV pseudovirus infection of TZM-bl cells suggested that the compound interfered with virus entry into the target cell. Glycyvir is a promising candidate as an agent with low toxicity and a broad spectrum of antiviral action.     

Alterations in Skin Immune Response Throughout Chronic UVB Irradiation—Skin Cancer Development and Prevention by Naproxen

Skin exposure to UVB radiation has been reported to produce both a significant inflammatory response and marked immunosuppression. This work was aimed to evaluate whether the response of murine skin to an acute UVB dose was modified by pre-exposure to chronic UVB irradiation and by topical treatment with naproxen, a nonsteroidal anti-inflammatory drug. Moreover, the effect of naproxen on the incidence of UV-induced skin tumors was studied. Prostaglandin E₂ (PGE₂) and tumor necrosis factor alpha (TNF-α) levels were increased 96 h post-UVB in acutely irradiated animals and both mediators were modified by topical naproxen application—PGE₂ was decreased while TNF-α was increased. Such inflammatory response was suppressed when mice were chronically irradiated. Naproxen application on chronically irradiated mice reduced the incidence of tumor lesions. Taken together, our data suggest that chronic UVB irradiation generates an immunosuppressive state that prevents skin cells from responding normally to an acute irradiation challenge, thus impairing the protective effect of TNF-α against skin tumor development. Furthermore, reduction in the incidence of tumor lesions by naproxen may be due to its ability to increase TNF-α levels as well as to decrease PGE₂.