Polyphenols are potential nutritional adjuvants for targeting COVID-19

The newly emerging severe acute respiratory syndrome, coronavirus-2 (SARS-CoV-2) is a dangerous pathogen that causes global health problems. It causes a disease called coronavirus disease 2019 (COVID-19) with high morbidity and mortality rates. In SARS-Cov-2-infected patients, elevated oxidative stress and upsurge of inflammatory cytokines are the main pathophysiological events that contribute to the severity and progression of symptoms and death. The polyphenols are natural compounds abundant in fruits and vegetables that are characterized by their high antioxidant and anti-inflammatory effects. Polyphenols have potential as an intervention for preventing respiratory virus infection. The beneficial effects of polyphenols on COVID-19 might be due to multiple mechanisms. Polyphenols can strengthen the body's anti-inflammatory and antioxidant defenses against viral infection. Targeting virus proteins and/or blocking cellular receptors are other plausible antiviral approaches to prevent the entry of the virus and its replication in the host cells. The results on the antiviral effects of various polyphenols, especially on SARS-CoV-2, are promising. The aim of this review is to clarify the role of polyphenols in strengthening antioxidant defenses and upregulating the immune systems of COVID-19 patients and to prevent replication and spreading of the virus.