Polyphenols vs. Coronaviruses: How Far Has Research Moved Forward?

Phenolic compounds versus SARS-CoV-2: An update on the main findings against COVID-19

The COVID-19 pandemic caused by SARS-CoV-2 remains an international concern. Although there are drugs to fight it, new natural alternatives such as polyphenols are essential due to their antioxidant activity and high antiviral potential. In this context, this review reports the main findings on the effect of phenolic compounds (PCs) against SARS-CoV-2 virus. First, the proven activity of PCs against different human viruses is briefly detailed, which serves as a starting point to study their anti-COVID-19 potential. SARS-CoV-2 targets (its proteins) are defined. Findings from in silico, in vitro and in vivo studies of a wide variety of phenolic compounds are shown, emphasizing their mechanism of action, which is fundamental for drug design. Furthermore, clinical trials have demonstrated the effectiveness of PCs in the prevention and as a possible therapeutic management against COVID-19. The results were complemented with information on the influence of polyphenols in strengthening/modulating the immune system. It is recommended to investigate compounds such as vitamins, minerals, alkaloids, triterpenes and fatty acids, and their synergistic use with PCs, many of which have been successful against SARS-CoV-2. Based on findings on other viruses, synergistic evaluation of PCs with accepted drugs against COVID-19 is also suggested. Other recommendations and limitations are also shown, which is useful for professionals involved in the development of efficient, safe and low-cost therapeutic strategies based on plant matrices rich in PCs. To the authors' knowledge, this manuscript is the first to evaluate the relationship between the antiviral and immunomodulatory (including anti-inflammatory and antioxidant effects) activity of PCs and their underlying mechanisms in relation to the fight against COVID-19. It is also of interest for the general population to be informed about the importance of consuming foods rich in bioactive compounds for their health benefits.

Antimicrobial Biomaterial on Sutures, Bandages and Face Masks with Potential for Infection Control

Antimicrobial resistance (AMR) is a challenge for the survival of the human race. The steady rise of resistant microorganisms against the common antimicrobials results in increased morbidity and mortality rates. Iodine and a plethora of plant secondary metabolites inhibit microbial proliferation. Antiseptic iodophors and many phytochemicals are unaffected by AMR. Surgical site and wound infections can be prevented or treated by utilizing such compounds on sutures and bandages. Coating surgical face masks with these antimicrobials can reduce microbial infections and attenuate their burden on the environment by re-use. The facile combination of Aloe Vera Barbadensis Miller (AV), Trans-cinnamic acid (TCA) and Iodine (I₂) encapsulated in a polyvinylpyrrolidone (PVP) matrix seems a promising alternative to common antimicrobials. The AV-PVP-TCA-I₂ formulation was impregnated into sterile discs, medical gauze bandages, surgical sutures and face masks. Morphology, purity and composition were confirmed by several analytical methods. Antimicrobial activity of AV-PVP-TCA-I₂ was investigated by disc diffusion methods against ten microbial strains in comparison to gentamycin and nystatin. AV-PVP-TCA-I₂ showed excellent antifungal and strong to intermediate antibacterial activities against most of the selected pathogens, especially in bandages and face masks. The title compound has potential use for prevention or treatment of surgical site and wound infections. Coating disposable face masks with AV-PVP-TCA-I₂ may be a sustainable solution for their re-use and waste management.

Probing marine brown macroalgal phlorotannins as antiviral candidate against SARS-CoV-2: molecular docking and dynamics simulation approach

Abstract

Over the past year, owing to the emergent demand for the search for potential COVID-19 therapeutics, identifying alternative candidates from biological sources is one of the sustainable ways to reinforce the drug discovery process. Marine macroalgae have numerous advantages because of the richest availability of underexploited bioactive compounds. Polyphenolic compounds like phlorotannins obtained from brown macroalgae are reported as proven antiviral and immunostimulatory agents. Thus, the present study evaluated the possibility of phlorotannins as antagonists to the multiple target proteins essential for SARS-CoV-2 replication. Twenty different types of potent phlorotannins were targeted against druggable target proteins, viz., 3CLpro, RdRp, and Spro using AutoDock molecular docking, drug-likeness were assessed by ADMET profiling (QikProp module). Further, validated with 200 ns molecular dynamics (MD) simulation (Desmond module) for the top-ranked phlorotannins based on docking binding affinities. Among the twenty phlorotannins studied, eckol hexacetate, phlorofucofuroeckol, fucofuroeckol, and bifuhalol-hexacetate showed significant binding affinities across the selected targets. Besides, MD simulations highlighted Glu166, Gln189, Cys145, and Thr190 tetrad as potential interaction sites to inhibit 3CLpro's activity. Moreover, phlorotannins were confirmed to be druglike, with no major deviation observed in ADMET-profiling. Hence, phlorotannins could be therapeutic candidates against SARS-CoV-2. However, further investigations are needed to prove its efficacy as an antiviral agent. Conclusively, this study may envisage that the novel finding could notably impact the advancement of antiviral interventions for COVID-19 in the near future.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11030-022-10383-y.

Immunity-Boosting Natural Herbs to Combat COVID-19 Pandemic: A Narrative Review

Coronaviruses cause some severe forms of respiratory infections such as Severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and Coronavirus disease 2019 (Covid-19). These viruses cause diarrhea in pigs and cows and upper respiratory disease in chickens, while other symptoms may differ. In humans, a total of six coronaviruses have been identified HCoVs-NL63, HCoVs-OC43, HCoVs-229E, HCoVs-HKU1, MERS-CoV, and SARS-CoV. The world health organization (WHO) has done a great deal of hard work regarding combating the monstrous effects of this virus. So far, no specific antiviral drugs have been developed for the treatment of Covid-19. Therefore, the medicinal plants used for the previous epidemic outbreaks are getting attention for their potential treatment against the virus. It has been reported that 70 to 80% of people in developing countries depend on medicinal plants or phytomedicine compared to allopathic drugs for their primary healthcare. The south Asian subcontinents have used almost up to 25,000 formulations and extracts obtained from medicinal plants for treatment in folk medicine. The present review discusses an overview of the coronavirus, its immune responses, and some immunity-boosting herbs to combat Covid-19.

Promising Antiviral Activities of Natural Flavonoids against SARS-CoV-2 Targets: Systematic Review

The ongoing COVID-19 pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) became a globally leading public health concern over the past two years. Despite the development and administration of multiple vaccines, the mutation of newer strains and challenges to universal immunity has shifted the focus to the lack of efficacious drugs for therapeutic intervention for the disease. As with SARS-CoV, MERS-CoV, and other non-respiratory viruses, flavonoids present themselves as a promising therapeutic intervention given their success in silico, in vitro, in vivo, and more recently, in clinical studies. This review focuses on data from in vitro studies analyzing the effects of flavonoids on various key SARS-CoV-2 targets and presents an analysis of the structure-activity relationships for the same. From 27 primary papers, over 69 flavonoids were investigated for their activities against various SARS-CoV-2 targets, ranging from the promising 3C-like protease (3CLpro) to the less explored nucleocapsid (N) protein; the most promising were quercetin and myricetin derivatives, baicalein, baicalin, EGCG, and tannic acid. We further review promising in silico studies featuring activities of flavonoids against SARS-CoV-2 and list ongoing clinical studies involving the therapeutic potential of flavonoid-rich extracts in combination with synthetic drugs or other polyphenols and suggest prospects for the future of flavonoids against SARS-CoV-2.

Consumption of Phenolic-Rich Food and Dietary Supplements as a Key Tool in SARS-CoV-19 Infection

The first cases of COVID-19, which is caused by the SARS-CoV-2, were reported in December 2019. The vertiginous worldwide expansion of SARS-CoV-2 caused the collapse of health systems in several countries due to the high severity of the COVID-19. In addition to the vaccines, the search for active compounds capable of preventing and/or fighting the infection has been the main direction of research. Since the beginning of this pandemic, some evidence has highlighted the importance of a phenolic-rich diet as a strategy to reduce the progression of this disease, including the severity of the symptoms. Some of these compounds (e.g., curcumin, gallic acid or quercetin) already showed capacity to limit the infection of viruses by inhibiting entry into the cell through its binding to protein Spike, regulating the expression of angiotensin-converting enzyme 2, disrupting the replication in cells by inhibition of viral proteases, and/or suppressing and modulating the host's immune response. Therefore, this review intends to discuss the most recent findings on the potential of phenolics to prevent SARS-CoV-2.

Antimicrobial Properties of Lepidium sativum L. Facilitated Silver Nanoparticles

Antibiotic resistance toward commonly used medicinal drugs is a dangerously growing threat to our existence. Plants are naturally equipped with a spectrum of biomolecules and metabolites with important biological activities. These natural compounds constitute a treasure in the fight against multidrug-resistant microorganisms. The development of plant-based antimicrobials through green synthesis may deliver alternatives to common drugs. Lepidium sativum L. (LS) is widely available throughout the world as a fast-growing herb known as garden cress. LS seed oil is interesting due to its antimicrobial, antioxidant, and anti-inflammatory activities. Nanotechnology offers a plethora of applications in the health sector. Silver nanoparticles (AgNP) are used due to their antimicrobial properties. We combined LS and AgNP to prevent microbial resistance through plant-based synergistic mechanisms within the nanomaterial. AgNP were prepared by a facile one-pot synthesis through plant-biomolecules-induced reduction of silver nitrate via a green method. The phytochemicals in the aqueous LS extract act as reducing, capping, and stabilizing agents of AgNP. The composition of the LS-AgNP biohybrids was confirmed by analytical methods. Antimicrobial testing against 10 reference strains of pathogens exhibited excellent to intermediate antimicrobial activity. The bio-nanohybrid LS-AgNP has potential uses as a broad-spectrum microbicide, disinfectant, and wound care product.

Antiviral Effects of Polyphenols from Marine Algae

The disease-preventive and medicinal properties of plant polyphenolic compounds have long been known. As active ingredients, they are used to prevent and treat many noncommunicable diseases. In recent decades, marine macroalgae have attracted the attention of biotechnologists and pharmacologists as a promising and almost inexhaustible source of polyphenols. This heterogeneous group of compounds contains many biopolymers with unique structure and biological properties that exhibit high anti-infective activity. In the present review, the authors focus on the antiviral potential of polyphenolic compounds (phlorotannins) from marine algae and consider the mechanisms of their action as well as other biological properties of these compounds that have effects on the progress and outcome of viral infections. Effective nutraceuticals, to be potentially developed on the basis of algal polyphenols, can also be used in the complex therapy of viral diseases. It is necessary to extend in vivo studies on laboratory animals, which subsequently will allow proceeding to clinical tests. Polyphenolic compounds have a great potential as active ingredients to be used for the creation of new antiviral pharmaceutical substances.