<i>In vitro</i> antiviral activity of <i>Chlorella vulgaris</i> extracts and fractions against SARS-CoV-2

SARS-CoV-2 has been reported as one of the deadliest viruses in history. Currently, few antiviral treatments are available to prevent SARS-CoV-2 progression to severe disease, especially in low-income countries. Natural products stand as a potential source of bioactive compounds. The antiviral activity against SARS-CoV-2 of <i>Chlorella vulgaris</i> has been demonstrated, however, the nature of its antiviral compounds remains unexplored. In this study, <i>in vitro</i> antiviral activity of extracts and fractions derived from <i>C. vulgaris</i> algae dry powder, was assessed. To determine the <i>in vitro</i> antiviral activity Vero cells were incubated with different concentrations of extracts and fractions against 100 TCID50/ml of SARS-CoV-2 variants. <i>C. vulgaris</i> ethanolic and diethyl ether extracts showed no cytopathic effect in 100% of the replicates. Fractions F11, F12, and F21, composed of high-weight polysaccharides and small proteins, partially protect against viral infection. These results suggest that polysaccharides, proteins, and pigments are related to antiviral activity.