Isoquercetin as an Anti-Covid-19 Medication: A Potential to Realize

Abstract

Isoquercetin and quercetin are secondary metabolites found in a variety of plants, including edible ones. Isoquercetin is a monoglycosylated derivative of quercetin. When ingested, isoquercetin accumulates more than quercetin in the intestinal mucosa where it is converted to quercetin; the latter is absorbed into enterocytes, transported to the liver, released in circulation, and distributed to tissues, mostly as metabolic conjugates. Physiologically, isoquercetin and quercetin exhibit antioxidant, anti-inflammatory, immuno-modulatory, and anticoagulant activities. Generally isoquercetin is less active than quercetin in vitro and ex vivo, whereas it is equally or more active in vivo, suggesting that it is primarily a more absorbable precursor to quercetin, providing more favorable pharmacokinetics to the latter. Isoquercetin, like quercetin, has shown broad-spectrum antiviral activities, significantly reducing cell infection by influenza, Zika, Ebola, dengue viruses among others. This ability, together with their other physiological properties and their safety profile, has led to the proposition that administration of these flavonols could prevent infection by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), or arrest the progression to severity and lethality of resulting coronavirus disease of 2019 (Covid-19). In silico screening of small molecules for binding affinity to proteins involved SARS-CoV-2 life cycle has repeatedly situated quercetin and isoquercetin near to top of the list of likely effectors. If experiments in cells and animals confirm these predictions, this will provide additional justifications for the conduct of clinical trials to evaluate the prophylactic and therapeutic efficacy of these flavonols in Covid-19.

Ultrasound-Assisted Extraction of Isoquercetin from Ephedra alata (Decne): Optimization Using Response Surface Methodology and In Vitro Bioactivities

“…Isoquercetin, a glycosidic form of quercetin, has been shown to possess antioxidant, neuroprotective, anti-inflammatory, and antidiabetic properties. Through activation of the Nrf2/ARE antioxidant signaling pathway, ISQ attenuates ethanol-induced hepatotoxicity, oxidative stress, and inflammatory responses [ 38 ]. By modulating nuclear factor B (NF-B), ISQ regulates nitric oxide synthase 2 (NO2) expression.…”

In silico and in vitro studies of potential inhibitors against Dengue viral protein NS5 Methyl Transferase from Ginseng and Notoginseng

“…Isoquercetin has been referred to as a broad-spectrum antiviral. 70 It was shown to inhibit Zika virus, Ebolavirus, Herpes Simplex virus, Varicella-Zoster virus and Human Cytomegalovirus. 70 Relating to Dengue virus, Isoquercitrin has been found to reduce in vitro activity of DENV NS2B-NS3 protease with IC 50 of 42–44 μM and inhibited NS5 RdRp activity with IC 50 of 9.5 μM.…”

Bridging the Chemical Profiles and Biological Effects of Spathodea campanulata Extracts: A New Contribution on the Road from Natural Treasure to Pharmacy Shelves

“…Another compound, isoquercetin, was shown to inhibit influenza virus replication, exert a synergistic effect when used with amantadine, and suppress the emergence of amantadine- or oseltamivir-resistant viruses in co-treatment with other antivirals [ 74 ]. Interestingly, isoquercetin was proven to possess broad-spectrum antiviral activity against herpesviruses (HHV-1, HHV-2, VZV, and HCMV (human cytomegalovirus)), Zika, dengue, and Ebola viruses [ 75 , 76 , 77 , 78 ]. There is also a report on the potential application of isoquercetin in the treatment and prevention of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection [ 76 ].…”

“…Interestingly, isoquercetin was proven to possess broad-spectrum antiviral activity against herpesviruses (HHV-1, HHV-2, VZV, and HCMV (human cytomegalovirus)), Zika, dengue, and Ebola viruses [ 75 , 76 , 77 , 78 ]. There is also a report on the potential application of isoquercetin in the treatment and prevention of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection [ 76 ].…”