Therapeutic and prophylactic effects of quercetin in the treatment of Covid-19: a systematic review


  • Giselly de Oliveira Silva
  • Elizabeth Fernanda de Oliveira Borba
  • Amanda Damasceno Leão
  • Maria das Graças Carneiro-da-Cunha
  • Maria Aparecida Medeiros Maciel
  • José Lamartine Soares Sobrinho
  • Maria Tereza dos Santos Correia
  • Teresinha Gonçalves da Silva



ARDS, SARS-CoV-2, Coronavirus disease 2019, flavonoid, quercetin, pulmonary inflammation, randomized controlled trial


Background: With the COVID-19 pandemic, the need for pharmacological and clinical studies in the search for substances with anti-inflammatory action became evident. To perform a systematic review of randomized controlled trials that evaluated the efficacy and safety of quercetin as a treatment and prevention option for COVID-19 in humans relative to an active comparator, placebo, or standard care alone. Methods: The search for studies was carried out in the following databases: Medline via PubMed, LILACS, Science Direct, Web of Science, and Scopus via Capes periodicals with the descriptors: “Quercetin” AND ''COVID-19” AND “randomized controlled trial”. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations. Protocol registration number in the PROSPERO database: CRD42022359842, available: 455 articles were found, and after reading the titles, abstracts, and full text, only 8 randomized clinical trials were included. According to the Cochrane RoB 2 tool, most included studies have some concerns about the risk of bias. The use of quercetin in the treatment and prevention of COVID-19 contributed to the rapid evolution of patients compared to standard treatment and protected them against the development of COVID-19 compared to placebo. No adverse events were reported. Conclusion: It is inferred that drug supplementation with quercetin can help in the treatment and prevention of COVID-19, reducing recovery time, laboratory parameters and symptom manifestation, when compared to standard treatment. Thus, further research is needed to confirm the relationship between quercetin in the immune system and the development of COVID-19 in its most severe form. A systematic review carried out with randomized clinical trials for quercetin in COVID-19 is not yet available in the indexes, and this work is unprecedented.


ANSARI, Mubeen Ahmad et al. Protective effect of quercetin in primary neurons against Abeta(1-42): relevance to Alzheimer’s disease. The Journal of Nutritional Bio-chemistry, v. 20, n. 4, p. 269–275, 2009.

BASTAMINEJAD, Saiyad; BAKHTIYARI, Salar. Quercetin and its Relative Thera-peutic Potential Against COVID-19: A Retrospective Review and Prospective Over-view. Current Molecular Medicine, v. 21, n. 5, p. 385–391, 2021.

BIANCATELLI, Ruben Manuel Luciano Colunga et al. Quercetin and Vitamin C: An Experimental, Synergistic Therapy for the Prevention and Treatment of SARS-CoV-2 Related Disease (COVID-19). Frontiers in Immunology, v. 11, p. 1451, 2020.

BOGOCH, Isaac I. et al. Pneumonia of unknown aetiology in Wuhan, China: potential for international spread via commercial air travel. Journal of Travel Medicine, v. 27, n. 2, p. taaa008, 2020.

CHILAMAKURI, Rameswari; AGARWAL, Saurabh. COVID-19: Characteristics and Therapeutics. Cells, v. 10, n. 2, p. 206, 2021.

D’ANDREA, Gabriele. Quercetin: A flavonol with multifaceted therapeutic applica-tions?. Fitoterapia, v. 106, p. 256–271, 2015.

DEROSA, Giuseppe et al. A role for quercetin in coronavirus disease 2019 (COVID-19). Phytotherapy research: PTR, v. 35, n. 3, p. 1230–1236, 2021.

DI PIERRO, Francesco et al. Possible Therapeutic Effects of Adjuvant Quercetin Sup-plementation Against Early-Stage COVID-19 Infection: A Prospective, Randomized, Controlled, and Open-Label Study. International Journal of General Medicine, v. 14, p. 2359–2366, 2021a.

DI PIERRO, Francesco et al. Potential Clinical Benefits of Quercetin in the Early Stage of COVID-19: Results of a Second, Pilot, Randomized, Controlled and Open-Label Clinical Trial. International Journal of General Medicine, v. 14, p. 2807–2816, 2021b.

DI PIERRO, Francesco et al. Quercetin as a possible complementary agent for early-stage COVID-19: Concluding results of a randomized clinical trial. Frontiers in Pharmacology, v. 13, p. 1096853, 2023.

DINIZ, Lúcio Ricardo Leite et al. Mechanistic Aspects and Therapeutic Potential of Quercetin against COVID-19-Associated Acute Kidney Injury. Molecules (Basel, Switzerland), v. 25, n. 23, p. 5772, 2020.

FENG, Ying et al. Yindan Jiedu granules exhibit anti-inflammatory effect in patients with novel Coronavirus disease (COVID-19) by suppressing the NF-κB signaling path-way. Phytomedicine: International Journal of Phytotherapy and Phytopharmacol-ogy, v. 95, p. 153784, 2022.

FERNANDES, Queenie et al. Emerging COVID-19 variants and their impact on SARS-CoV-2 diagnosis, therapeutics and vaccines. Annals of Medicine, v. 54, n. 1, p. 524–540, 2022.

GASMI, Amin et al. Quercetin in the Prevention and Treatment of Coronavirus Infec-tions: A Focus on SARS-CoV-2. Pharmaceuticals (Basel, Switzerland), v. 15, n. 9, p. 1049, 2022.

HU, Biying; HUANG, Shaoying; YIN, Lianghong. The cytokine storm and COVID-19. Journal of Medical Virology, v. 93, n. 1, p. 250–256, 2021.

IMRAN, Mohd et al. The Therapeutic and Prophylactic Potential of Quercetin against COVID-19: An Outlook on the Clinical Studies, Inventive Compositions, and Patent Literature. Antioxidants (Basel, Switzerland), v. 11, n. 5, p. 876, 2022.

JARROTT, Bevyn et al. “LONG COVID”-A hypothesis for understanding the biologi-cal basis and pharmacological treatment strategy. Pharmacology Research & Perspec-tives, v. 10, n. 1, p. e00911, 2022.

KHAN, Amjad et al. Oral Co-Supplementation of Curcumin, Quercetin, and Vitamin D3 as an Adjuvant Therapy for Mild to Moderate Symptoms of COVID-19-Results From a Pilot Open-Label, Randomized Controlled Trial. Frontiers in Pharmacology, v. 13, p. 898062, 2022.

KIM, Seungtaek. COVID-19 Drug Development. Journal of Microbiology and Bio-technology, v. 32, n. 1, p. 1–5, 2022.

MARGOLIN, Leon et al. 20-Week Study of Clinical Outcomes of Over-the-Counter COVID-19 Prophylaxis and Treatment. Journal of Evidence-Based Integrative Medi-cine, v. 26, p. 2515690X211026193, 2021.

MOHER, David et al. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. PLoS medicine, v. 6, n. 7, p. e1000097, 2009.

ÖNAL, Hasan et al. Treatment of COVID-19 patients with quercetin: a prospective, single center, randomized, controlled trial. Turkish Journal of Biology = Turk Biy-oloji Dergisi, v. 45, n. 4, p. 518–529, 2021.

OWONA, Brice Ayissi; ABIA, Wilfred Angie; MOUNDIPA, Paul Fewou. Natural compounds flavonoids as modulators of inflammasomes in chronic diseases. Interna-tional Immunopharmacology, v. 84, p. 106498, 2020.

PARVATHANENI, Vineela; GUPTA, Vivek. Utilizing drug repurposing against COVID-19 - Efficacy, limitations, and challenges. Life Sciences, v. 259, p. 118275, 2020.

POLLARD, Casey A.; MORRAN, Michael P.; NESTOR-KALINOSKI, Andrea L. The COVID-19 pandemic: a global health crisis. Physiological Genomics, v. 52, n. 11, p. 549–557, 2020.

POURKARIM, Fariba; POURTAGHI-ANVARIAN, Samira; REZAEE, Haleh. Mol-nupiravir: A new candidate for COVID-19 treatment. Pharmacology Research & Per-spectives, v. 10, n. 1, p. e00909, 2022.

RASHEDI, Ronak et al. COVID-19 vaccines mix-and-match: The concept, the efficacy and the doubts. Journal of Medical Virology, v. 94, n. 4, p. 1294–1299, 2022.

RONDANELLI, Mariangela et al. Promising Effects of 3-Month Period of Quercetin Phytosome® Supplementation in the Prevention of Symptomatic COVID-19 Disease in Healthcare Workers: A Pilot Study. Life (Basel, Switzerland), v. 12, n. 1, p. 66, 2022.

SAEED, Mohammed Abdel Monem; MOHAMED, Alaa Hussein; OWAYNAT, Ah-med Hassan. Cholecalciferol level and its impact on COVID-19 patients. The Egyptian Journal of Internal Medicine, v. 34, n. 1, p. 23, 2022.

SAEEDI-BOROUJENI, Ali; MAHMOUDIAN-SANI, Mohammad-Reza. Anti-inflammatory potential of Quercetin in COVID-19 treatment. Journal of Inflammation (London, England), v. 18, n. 1, p. 3, 2021.

SHOHAN, Mojtaba et al. The therapeutic efficacy of quercetin in combination with antiviral drugs in hospitalized COVID-19 patients: A randomized controlled trial. Eu-ropean Journal of Pharmacology, v. 914, p. 174615, 2022.

STERNE, Jonathan A. C. et al. RoB 2: a revised tool for assessing risk of bias in ran-domised trials. BMJ (Clinical research ed.), v. 366, p. l4898, 2019.

SUSIANTI, Hani et al. Low levels of vitamin D were associated with coagulopathy among hospitalized coronavirus disease-19 (COVID-19) patients: A single-centered study in Indonesia. Journal of Medical Biochemistry, v. 40, n. 4, p. 341–350, 2021.

UJJAN, Ikram Din et al. The possible therapeutic role of curcumin and quercetin in the early-stage of COVID-19-Results from a pragmatic randomized clinical trial. Frontiers in Nutrition, v. 9, p. 1023997, 2023.

WEN, Wen et al. Efficacy and safety of three new oral antiviral treatment (mol-nupiravir, fluvoxamine and Paxlovid) for COVID-19:a meta-analysis. Annals of Med-icine, v. 54, n. 1, p. 516–523, 2022.

WHO CORONAVIRUS (COVID-19) DASHBOARD. 2023. Disponível em: Acesso em: 14 nov. 2023.

XIA, Lu et al. Shufeng Jiedu, a promising herbal therapy for moderate COVID-19:Antiviral and anti-inflammatory properties, pathways of bioactive compounds, and a clinical real-world pragmatic study. Phytomedicine: International Journal of Phyto-therapy and Phytopharmacology, v. 85, p. 153390, 2021.



How to Cite

Silva, G. de O., Borba, E. F. de O., Leão, A. D., Carneiro-da-Cunha, M. das G., Maciel, M. A. M., Sobrinho, J. L. S., Correia, M. T. dos S., & da Silva, T. G. (2024). Therapeutic and prophylactic effects of quercetin in the treatment of Covid-19: a systematic review. OBSERVATÓRIO DE LA ECONOMÍA LATINOAMERICANA, 22(1), 3668–3693.