An open-label randomized controlled clinical trial published in The European Journal of Pharmacology depicted the safety and effectiveness of quercetin in decreasing the serum levels of alkaline phosphatase, quantitative C-reactive protein, and lactate dehydrogenase as critical markers implicated in the severity of SARS-CoV-2 infection. Furthermore, quercetin therapy was reported to reduce the duration of hospitalization.

Mojtaba Shohan et al. aimed to determine the efficacy of quercetin in combination with favipiravir and remdesivir for the management of severe hospitalized coronavirus-infected people. The primary aim was to investigate quercetin's ability to prevent the advancement of the disease into the critical phase and minimize the levels of inflammatory markers associated with coronavirus pathogenesis.

A total of 60 participants were randomly segregated into (i) Control group (n=30): Participants were given antivirals such as favipiravir or remdesivir, and (ii) Intervention group (n=30): Participants were given 1000 mg of quercetin daily plus the antiviral drugs. The intervention group exhibited partial earlier discharge and decreased serum levels of alkaline phosphatase, quantitative C-reactive protein, and lactate dehydrogenase.

Despite the fact that the values were in the normal range, the statistical outputs revealed a considerable rise in the respiratory rate and hemoglobin level in people receiving quercetin. In terms of mortality, duration of intensive care unit admission, and the number of intensive care unit-admitted cases, no profound differences were noted.

Thus, the combination of quercetin and antiviral drugs might be therapeutically effective in minimizing the time to clinical improvement. Additional studies are warranted for further clarifying the potential of quercetin for COVID-19 management.