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

Abstract

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: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022359842.Results: 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.