Quercetin in the Prevention and Treatment of Coronavirus Infections: A Focus on SARS-CoV-2

Abstract

The COVID-19 outbreak seems to be the most dangerous challenge of the third millennium due to its highly contagious nature. Amongst natural molecules for COVID-19 treatment, the flavonoid molecule quercetin (QR) is currently considered one of the most promising. QR is an active agent against SARS and MERS due to its antimicrobial, antiviral, anti-inflammatory, antioxidant, and some other beneficial effects. QR may hold therapeutic potential against SARS-CoV-2 due to its inhibitory effects on several stages of the viral life cycle. In fact, QR inhibits viral entry, absorption, and penetration in the SARS-CoV virus, which might be at least partly explained by the ability of QR and its derivatives to inhibit 3-chymotrypsin-like protease (3CLpro) and papain-like protease (PLpro). QR is a potent immunomodulatory molecule due to its direct modulatory effects on several immune cells, cytokines, and other immune molecules. QR-based nanopreparations possess enhanced bioavailability and solubility in water. In this review, we discuss the prospects for the application of QR as a preventive and treatment agent for COVID-19. Given the multifactorial beneficial action of QR, it can be considered a very valid drug as a preventative, mitigating, and therapeutic agent of COVID-19 infection, especially in synergism with zinc, vitamins C, D, and E, and other polyphenols.

Green synthesis of multifunctional ZnO/chitosan nanocomposite film using wild Mentha pulegium extract for packaging applications

“…When cytokine storm hits, the afflicted victims die. A cytokine storm caused by a coronavirus can be prevented by several naturally occurring polyphenols, such as curcumin, apigenin, resveratrol, and kaempferol [70] , [71] , [72] , [73] , [74] . These findings suggest that edible antimicrobial coatings on fruits can help prevent virus transmission before infection, while also extending the shelf-life of polyphenolic fruits, which are vital for the recovery of COVID-19 patients.…”

Natural Compounds and Products from an Anti-Aging Perspective

“…Plant polyphenols are one of the most important categories of natural active principles with antioxidant effects, being increasingly used in skin antiaging therapy, having remarkable properties in combating the harmful effects of solar radiation and atmospheric pollutants, preventing and alleviating the symptoms of premature skin aging. Specifically, polyphenols are recognized for their antioxidant, anti-inflammatory, antibacterial, antiviral, antitumor, and anti-atherogenic action (against deposition on blood vessels) [ 116 , 117 ]. The main action of antioxidants is to prevent the formation of free radicals, fighting against aging processes.…”

Polyphenols in Metabolic Diseases

“…In another study, researchers reported that curcumin from turmeric and mustard plants is a source of a non-flavonoid polyphenol that can effectively suppress inflammatory mediators such as cyclooxygenase (COX) [ 47 , 48 , 49 ]. In addition to the PPs mentioned above, gingerol, caffeic acid, and quercetin can suppress severe inflammation [ 42 , 50 , 51 ]. Rodríguez-Ramiro et al reported that cocoa enriched with PPs and its bioactive properties could reduce severe inflammation effects such as intestinal inflammation and avoid associated cancer [ 52 ].…”