Possible Therapeutic Effects of Adjuvant Quercetin Supplementation Against Early-Stage COVID-19 Infection: A Prospective, Randomized, Controlled, and Open-Label Study

Abstract

Background: Quercetin, a well-known naturally occurring polyphenol, has recently been shown by molecular docking, in vitro and in vivo studies to be a possible anti-COVID-19 candidate. Quercetin has strong antioxidant, anti-inflammatory, immunomodulatory, and antiviral properties, and it is characterized by a very high safety profile, exerted in animals and in humans. Like most other polyphenols, quercetin shows a very low rate of oral absorption and its clinical use is considered by most of modest utility. Quercetin in a delivery-food grade system with sunflower phospholipids (Quercetin Phytosome ® , QP) increases its oral absorption up to 20-fold. Methods: In the present prospective, randomized, controlled, and open-label study, a daily dose of 1000 mg of QP was investigated for 30 days in 152 COVID-19 outpatients to disclose its adjuvant effect in treating the early symptoms and in preventing the severe outcomes of the disease. Results:The results revealed a reduction in frequency and length of hospitalization, in need of non-invasive oxygen therapy, in progression to intensive care units and in number of deaths. The results also confirmed the very high safety profile of quercetin and suggested possible anti-fatigue and pro-appetite properties. Conclusion: QP is a safe agent and in combination with standard care, when used in early stage of viral infection, could aid in improving the early symptoms and help in preventing the severity of COVID-19 disease. It is suggested that a double-blind, placebo-controlled study should be urgently carried out to confirm the results of our study.

Characterization of the Trans-Epithelial Transport of Green Tea (C. sinensis) Catechin Extracts with In Vitro Inhibitory Effect against the SARS-CoV-2 Papain-like Protease Activity

“…The other most abundant annotated flavonoids, i.e., kaempferol and quercetin, were not flawed or transported, probably due to their poor water solubility. Even if quercetin has potent antioxidant, anti-inflammatory, immunomodulatory, and antiviral properties and a very high safety profile, as with most other polyphenols, it shows a meager rate of oral absorption, and its clinical use is considered by most of modest utility [36].…”

TRP channels in COVID-19 disease: Potential targets for prevention and treatment

“…Several phytochemicals that interact with TRP channels were shown to be potential treatments for COVID-19 [ [121] , [122] , [123] , [124] , [125] , [126] , [127] , [128] , [129] , [130] , [131] , [132] , [133] , [134] , [135] , [136] , [137] , [138] , [139] , [140] , [141] , [142] ]. However, the implication of TRP channel in their mechanism of action had not been investigated yet.…”

“…In a prospective, randomized, controlled, and open-label study, a daily dose of 1000 mg of quercetin was given for 30 days to 152 COVID-19 outpatients to study its adjuvant effect in treating the early symptoms and in preventing the severe consequences of the disease. Quercetin was effective in improving COVID-19 early symptoms as well as preventing the severity of the disease [ 136 ].…”

“…Of note, broccoli capsules are considered potent agonists for Nrf2 and weak TRPA1 agonists [ 36 ]. In addition, open-labelled induced cough challenges were carried out in a COVID-19 patient using different treatments [ 136 ]. The results of this study suggested that there could be fast desensitization of TRPA1 and TRPV1 channels accompanied and a crosstalk with Nrf2 [ 136 ].…”

“…In addition, open-labelled induced cough challenges were carried out in a COVID-19 patient using different treatments [ 136 ]. The results of this study suggested that there could be fast desensitization of TRPA1 and TRPV1 channels accompanied and a crosstalk with Nrf2 [ 136 ]. In more detail, the study was performed using nutrients that have different agonistic activities for Nrf2, TRPA1 and TRPV1.…”