Binding of boswellic acids to functional proteins of the SARS-CoV-2 virus: Bioinformatic studies

Abstract

Boswellic acids (BAs) have been shown to possess antiviral activity. Using bioinformatic methods, it was tested whether or not acetyl-11-keto-β-boswellic acid (AKBA), 11-keto-β-boswellic acid (KBA), β-boswellic acid (BBA), and the phosphorylated active metabolite of Remdesivir® (RGS-P3) bind to functional proteins of SARS-CoV-2, that is, the replicase polyprotein P0DTD1, the spike glycoprotein P0DTC2, and the nucleoprotein P0DTC9. Using P0DTD1, AKBA and KBA showed micromolar binding affinity to the RNA-dependent RNA polymerase (RdRp) and to the main proteinase complex Mpro. Phosphorylated BAs even bond in the nanomolar range. Due to their positive and negative charges, BAs and RGS-P3 bond to corresponding negative and positive areas of the protein. BAs and RGS-P3 docked in the tunnel-like cavity of RdRp. BAs also docked into the elongated surface rim of viral Mpro. In both cases, binding occurred with active site amino acids in the lower micromolecular to upper nanomolar range. KBA, BBA, and RGS-P3 also bond to P0DTC2 and P0DTC9. The binding energies for BAs were in the range of −5.8 to −6.3 kcal/mol. RGS-P3 and BAs occluded the centrally located pore of the donut-like protein structure of P0DTC9 and, in the case of P0DTC2, RGS-P3 and BAs impacted the double-wing-like protein structure. The data of this bioinformatics study clearly show that BAs bind to three functional proteins of the SARS-CoV-2 virus responsible for adhesion and replication, as does RGS-P3, a drug on the market to treat this disease. The binding effectiveness of BAs can be increased through phosphate esterification. Whether or not BAs are druggable against the SARS-CoV-2 disease remains to be established.