Reappraisal of Dietary Phytochemicals for Coronavirus Infection: Focus on Hesperidin and Quercetin

Abstract

Food polyphenols constitute a large family of substances with beneficial properties in a large group of communicable and non-communicable diseases. These compounds support and improve the body’s defences against oxidative stress and are helpful in the prevention of pathologies related to metabolic syndrome. Furthermore, they exhibit anti-inflammatory, antiviral, and antimicrobial properties. This chapter draws attention to certain nutritional components such as hesperidin and quercetin, which are emerging as good candidates for a complementary beneficial effect in the case of diseases caused by viruses, including COVID-19. These nutraceuticals have a complex mechanism of action, which involves both cellular defence against oxidative stress and the modulation of inflammation, which although normally is a defence, repair and activation mechanism of the immune system, it can elude its controls and become a systemic and destructive pathology (cytokine storm, respiratory distress syndrome). Furthermore, recent in silico simulation tests suggest that both hesperidin and quercetin may interfere with SARS-CoV-2 by binding to cell receptors and the proteolytic enzymes involved in its replication. In addition to the inhibitory effects on the virus at cellular level, the two flavonoids can have indirect effects in respiratory infectious diseases as they prevent or improve metabolic and vascular comorbidities that can complicate the clinical course. This brief review focuses on biochemical and pharmacological mechanisms of action of polyphenols in the context of the revaluation of dietary approaches to the prevention and treatment of infectious diseases caused by viruses, with a special application to COVID-19.

Retrospective Study of Outcomes and Hospitalization Rates of Patients in Italy with a Confirmed Diagnosis of Early COVID-19 and Treated at Home Within 3 Days or After 3 Days of Symptom Onset with Prescribed and Non-Prescribed Treatments Between November 2020 and August 2021

“…Importantly, it has been shown that quercetin inhibits the coronavirus major protease [ 61 ] and NLRP3 inflammasome [ 62 ]. Furthermore, the flavonoids and vitamin C counteract oxidative stress, which is one of the major mechanisms of the direct cytotoxic effect of the virus [ 27 , 29 , 37 , 40 , 63 – 67 ] and of the activated NADPH oxidase of phagocytes involved in hyper-inflammatory syndromes [ 68 , 69 ].…”

A Review of the Potential Roles of Antioxidant and Anti-Inflammatory Pharmacological Approaches for the Management of Mild-to-Moderate Symptomatic COVID-19

“…3) [ 45 , 46 , 115 , 130 , 156 – 160 ], and the action of phagocytes activated NADPH oxidase ( Figure 1 , step no. 4) [ 161 , 162 ]. Finally, the known anti-inflammatory properties of indomethacin and aspirin may help prevent complications associated with excessive inflammatory and immune reactions ( Figure 1 , step no.…”

The Problem of Home Therapy during COVID-19 Pandemic in Italy: Government Guidelines versus Freedom of Cure?

“…In fact, when administered in high doses, this drug is metabolized with the formation of N-acetyl-p-benzoquinone imine (NAPQI), which in turn requires glutathione for hepatic catabolism, to the point that that the antidote for paracetamol intoxication is N-acetylcysteine. Glutathione is an indispensable element of cell metabolism and, in particular, of the defense against toxic oxygen derivatives (ROS) and thus cellular oxidative stress [ 35 – 38 ]. Furthermore, NAPQI metabolism in GSH deficiency leads to an accumulation of denatured proteins by alteration of their sulfhydryl residues.…”