The nanomolar affinity of C-phycocyanin from virtual screening of microalgal bioactive as potential ACE2 inhibitor for COVID-19 therapy.

The global pandemic of COVID-19 caused by SARS-CoV-2 has caused more than 400 million infections with more than 5.7 million deaths worldwide, and the number of validated therapies from natural products for treating coronavirus infections needs to be increased. Therefore, the virtual screening of bioactive compounds from natural products based on computational methods could be an interesting strategy. Among many sources of bioactive natural products, compounds from marine organisms, particularly microalgae and cyanobacteria, can be potential antiviral agents. The present study investigates bioactive antiviral compounds from microalgae and cyanobacteria as a potential inhibitor of SARS-CoV-2 by targeting Angiotensin-Converting Enzyme II (ACE2) using integrated in silico and in vitro approaches. Our in silico analysis demonstrates that C-Phycocyanin (CPC) can potentially inhibit the binding of ACE2 receptor and SARS-CoV-2 with the docking score of -9.7 kcal mol-1. This score is relatively more favorable than the native ligand on ACE2 receptor. Molecular dynamics simulation also reveals the stability interaction between both CPC and ACE2 receptor with a root mean square deviation (RMSD) value of 1.5 Å. Additionally, our in vitro analysis using the surface plasmon resonance (SPR) method shows that CPC has a high affinity for ACE2 with a binding affinity range from 5 to 125 µM, with KD 3.37 nM. This study could serve as a reference to design microalgae- or cyanobacteria-based antiviral drugs for prophylaxis in SARS-CoV-2 infections.