<b>Secondary metabolites</b><b> of </b><b><i>Alternaria alternate</i></b><b> appraisal of their SARS-CoV-2 inhibitory and anti-inflammatory potentials</b>

This study identifies the secondary metabolites from <i>Alternaria alternate</i> and evaluates their ACE-2: Spike RBD (SARS-CoV-2) inhibitory activity confirmed <i>via</i> immunoblotting in human lung microvascular endothelial cells. In addition, their <i>in vitro</i> anti-inflammatory potential was assessed<i> </i>using<i> </i>a<i> </i>cell-based assay in LPS-treated RAW 264.7 macrophage cells. Two novel compounds, altenuline (<b>1</b>), phthalic acid bis (7'/7'' pentyloxy) isohexyl ester (<b>2</b>), along with 1-deoxyrubralactone (<b>3</b>) alternariol-5-<i>O</i>-methyl ether (<b>4</b>) and alternariol (<b>5</b>) were identified. Molecular docking and <i>in vitro</i> studies showed that compounds <b>2</b> and <b>4</b> were promising to counteract SARS-CoV-2 attachment to human ACE-2. Thus, they are considered promising natural anti-viral agents. Immunoblotting analysis confirmed that the tested compounds (<b>1-4</b>) demonstrated downregulation of ACE-2 expression in the endothelial cells from the lungs with variable degrees. Furthermore, the tested compounds (<b>1-4</b>) showed promising anti-inflammatory activities through TNF-α: TNFR2 inhibitory activity and their inhibitory effect on the proinflammatory cytokines (TNF-a and IL-6) in LPS-stimulated monocytes. In conclusion, our study, for the first time, provides beneficial experimental confirmation for the efficiency of the <i>A. alternate</i> secondary metabolites for the treatment of COVID-19 as they hinder SARS-CoV-2 infection and lower inflammatory responses initiated by SARS-CoV-2. <i>A. alternate</i> and its metabolites are considered in developing preventative and therapeutic tactics for COVID-19.