Quercetin: Antiviral Significance and Possible COVID-19 Integrative Considerations

Abstract

Quercetin, a naturally occurring dietary flavonoid, is well known to ameliorate chronic diseases and aging processes in humans, and its antiviral properties have been investigated in numerous studies. In silico and in vitro studies demonstrated that quercetin can interfere with various stages of the coronavirus entry and replication cycle such as PLpro, 3CLpro, and NTPase/helicase. Due to its pleiotropic activities and lack of systemic toxicity, quercetin and its derivatives may represent target compounds to be tested in future clinical trials to enrich the drug arsenal against coronavirus infections. There is evidence that quercetin in combination with, for example, vitamins C and D, may exert a synergistic antiviral action that may provide either an alternative or additional therapeutic/preventive option due to overlapping antiviral and immunomodulatory properties. This review summarizes the antiviral significance of quercetin and proposes a possible strategy for the effective utilization of natural polyphenols in our daily diet for the prevention of viral infection.

Rutin: A Potential Antiviral for Repurposing as a SARS-CoV-2 Main Protease (Mpro) Inhibitor

“…The antiviral activity of rutin, along with other flavonoids, has been reviewed in several publications. [104][105][106][107][108][109][110]…”

“…For patients with COVID-19, this may provide a dual benefit, both preventing overinflammation and restoring innate antiviral immunity. 123 Therefore, herbal medicines containing rutin and other flavonoids, such as quercetin, 107 diosmin, 181 and hesperidin 177 as major components might be meaningful for the treatment of SARS-CoV-2 infections. Since rutin is already present in FDA approved vitamin C supplements, it can be taken as a preventive medicine.…”

Lifestyle Adjustments in Long-COVID Management: Potential Benefits of Plant-Based Diets

“…It is exclusively found in plantfoods; thus, a plant-based eating pattern abundant in fruits, vegetables, and legumes enhances its intake and has been proposed as a promising approach for the prevention and treatment of anxiety and depression [53]. Although quercetin also possesses antiviral properties [64,65], it has not yet been tested in a clinical trial in patients suffering from COVID-19.…”

Plants and Natural Products with Activity against Various Types of Coronaviruses: A Review with Focus on SARS-CoV-2

“…This same extract further revealed competitive ACE inhibition with the substrate, N-[3-(2-furyl) acryloyl]-L-phenylalanylglycylglycine [ 26 ]. Agrawal and collegeus reported that quercetin can interfere with various stages of the coronavirus entry and replication cycle, such as PLpro, 3CLpro and nucleoside-triphosphatase (NTPase)/helicase, showing pleiotropic activities and lack of systemic toxicity [ 25 ]. Similarly, EGCG also inhibited ACE and blocked the AII binding to AT1R in vitro, showing the potential to control the symptoms of various diseases, especially those of a respiratory nature [ 108 ].…”