Melatonin and viral infections: A review focusing on therapeutic effects and SARS-CoV-2

      Viral infections can cause serious diseases which lead to significant morbidity and mortality of patients. In most cases, effective therapeutic approaches are lacking. Melatonin (MEL), a multifunctional molecule produced in the pineal gland and many other organs, is known as a potent anti-inflammatory and antioxidant, a positive regulator of immune functions and a suppressor of apoptosis, with therapeutic effects in diverse diseases. These actions suggest the potential of MEL to treat viral infections. A variety of studies have shown that MEL supplementation is effective against a number of viral infections. Many of these reports have strongly suggested its use as an adjuvant or therapeutic agent. Notably, the efficacy of this molecule as a prophylactic or therapeutic weapon against COVID-19 has been demonstrated both in experimental conditions and in clinical trials, and it can reduce the severity and mortality of the patients. This review summarizes actions of MEL on viral infections and focuses on its therapeutic effects against COVID-19 and generally highlights MEL as an attractive therapy in other viral infections.