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0 0.25 0.5 0.75 1 1.25 1.5 1.75 2+ Di Pierro (RCT) 86% 0.14 [0.01-2.72] death 0/76 3/76 Improvement, RR [CI] Treatment Control Di Pierro (RCT) 67% 0.33 [0.01-7.74] death 0/21 1/21 Tau​2 = 0.00; I​2 = 0.0% Early treatment 79% 0.21 [0.02-1.82] 0/97 4/97 79% improvement Onal (RCT) -29% 1.29 [0.16-10.5] death 1/49 6/380 CT​1 Improvement, RR [CI] Treatment Control Zupanets (RCT) 29% 0.71 [0.32-1.58] no recov. 9/99 13/101 Tau​2 = 0.00; I​2 = 0.0% Late treatment 24% 0.76 [0.36-1.62] 10/148 19/481 24% improvement Arslan (RCT) 92% 0.08 [0.01-0.79] cases 1/71 9/42 CT​1 Improvement, RR [CI] Treatment Control Tau​2 = 0.00; I​2 = 0.0% Prophylaxis 92% 0.08 [0.01-0.79] 1/71 9/42 92% improvement All studies 56% 0.44 [0.17-1.13] 11/316 32/620 56% improvement 5 quercetin COVID-19 studies Dec 3, 2021 1 CT: study uses combined treatmentTau​2 = 0.29; I​2 = 23.5%; Z = 1.70 Effect extraction pre-specified Favors quercetin Favors control
Database of all quercetin COVID-19 studies. Submit updates/corrections.
Restrict:    All    Early    Late    Prophylaxis
Nov 14
In Vitro Bahun et al., Food Chemistry, doi:10.1016/j.foodchem.2021.131594 (Peer Reviewed) (In Vitro)
in vitro
Inhibition of the SARS-CoV-2 3CLpro main protease by plant polyphenols
Details   In Silico and In Vitro study of plant polyphenols identifying quercetin, curcumin, ellagic acid, epigallocatechin gallate and resveratrol as SARS-CoV-2 3CLpro inhibitors with IC50 between 11.8µM and 23.4µM. Real-time binding was analyzed..
Sep 29
In Silico Şimşek et al., Journal of Molecular Graphics and Modelling, doi:10.1016/j.jmgm.2021.108038 (Peer Reviewed) In silico identification of SARS-CoV-2 cell entry inhibitors from selected natural antivirals
Details   In SIlico study identifying quercetin derivatives as SARS-CoV-2 spike protein, ACE2, and neuropilin inhibitors.
Sep 1
Late Zupanets et al., Zaporozhye Med. J., doi:10.14739/2310-1210.2021.5.231714 (Peer Reviewed)
no recov., ↓29.4%, p=0.50
Quercetin effectiveness in patients with COVID-19 associated pneumonia
Details   RCT 200 patients in Ukraine, 99 treated with IV quercetin/polyvinylirolidone followed by oral quercetin/pectin, showing improved recovery with treatment.
Jul 6
PrEPPEP Margolin et al., Journal of Evidence-Based Integrative Medicine, doi:10.1177/2515690X211026193 (Peer Reviewed)
cases, ↓94.4%, p=0.003
20-Week Study of Clinical Outcomes of Over-the-Counter COVID-19 Prophylaxis and Treatment
Details   Retrospective 113 outpatients, 53 (patient choice) treated with zinc, quercetin, vitamin C/D/E, l-lysine, and Quina, showing lower cases with treatment. Results are subject to selection bias and limited information on the groups is provid..
Jun 24
Early Di Pierro et al., International Journal of General Medicine, doi:10.2147/IJGM.S318949 (Peer Reviewed)
death, ↓66.7%, p=1.00
Potential Clinical Benefits of Quercetin in the Early Stage of COVID-19: Results of a Second, Pilot, Randomized, Controlled and Open-Label Clinical Trial
Details   RCT 42 outpatients in Pakistan, 21 treated with quercetin phytosome, showing faster viral clearance and lower symptom severity with treatment.
Jun 8
Early Di Pierro et al., International Journal of General Medicine, doi:10.2147/IJGM.S318720 (Peer Reviewed)
death, ↓85.7%, p=0.25
Possible Therapeutic Effects of Adjuvant Quercetin Supplementation Against Early-Stage COVID-19 Infection: A Prospective, Randomized, Controlled, and Open-Label Study
Details   RCT 152 outpatients in Pakistan, 76 treated with quercetin phytosome, showing lower mortality, ICU admission, and hospitalization with treatment.
Apr 8
Early Aguilar et al., Journal of Advances in Medical and Pharmaceutical Sciences, doi:10.9734/jamps/2021/v23i330222 (Peer Reviewed) Oral Quercetin in Adult Patients as a Potential Nutraceutical against Coronavirus Disease 2019 (COVID-19)
Details   Prospective study of 52 patients treated with quercetin. There was no control group.
Jan 19
Late Onal et al., Turk. J. Biol., 45:518-529 (preprint 1/19/2021) (Peer Reviewed)
death, ↑29.3%, p=0.57
Treatment of COVID-19 patients with quercetin: a prospective, single center, randomized, controlled trial
Details   RCT 447 moderate-to-severe hospitalized patients in Turkey, 52 treated with quercetin, bromelain, and vitamin C, showing no statistically significant difference in clinical outcomes. NCT04377789.
Nov 16
PrEPPEP Arslan et al., SSRN, doi:10.2139/ssrn.3682517 (Preprint)
cases, ↓91.7%, p=0.03
Synergistic Effect of Quercetin and Vitamin C Against COVID-19: Is a Possible Guard for Front Liners
Details   Small prophylaxis RCT with 113 patients showing fewer cases with quercetin + vitamin C + bromelain prophylaxis. NCT04377789. Note that this paper disappeared from SSRN without explanation.
Oct 9
Review Derosa et al., Phytotherapy Research, doi:10.1002/ptr.6887 (Review) (Peer Reviewed)
A role for quercetin in coronavirus disease 2019 (COVID-19)
Details   Review noting that quercetin has a theoretical, but significant, capability to interfere with SARS‐CoV‐2 replication, with results showing this to be the fifth best compound out of 18 candidates.
Jun 19
Review Biancatelli et al., Frontiers in Immunology, doi:10.3389/fimmu.2020.01451 (Review) (Peer Reviewed)
Quercetin and Vitamin C: An Experimental, Synergistic Therapy for the Prevention and Treatment of SARS-CoV-2 Related Disease (COVID-19)
Details   Review of the evidence for the use of vitamin C and quercetin both for prophylaxis in high-risk populations and for the treatment of COVID-19 patients.
Apr 24
In Silico Sekiou et al., ChemRxiv, doi:10.26434/chemrxiv.12181404.v1 (Preprint) In-Silico Identification of Potent Inhibitors of COVID-19 Main Protease (Mpro) and Angiotensin Converting Enzyme 2 (ACE2) from Natural Products: Quercetin, Hispidulin, and Cirsimaritin Exhibited Better Potential Inhibition than Hydroxy-Chloroquine Against COVID-19 Main Protease Active Site and ACE2
Details   In silico study of natural compounds identifying quercetin, curcumin, hispidulin, cirsimaritin, sulfasalazine, and artemisin as potential compounds that inhibit SARS-CoV-2.
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