Anti‐Coronavirus Activity of Certain Herbacetin Derivatives, A Theoretical Study

Abstract

Flavonoids are natural products commonly found in the human diet with anti‐viral activity. The electrochemical activity of flavonoids is effective in their inhibitory properties. Herbacetin is an anti‐coronavirus drug from the flavonoid family. To understand structure‐electrochemical activity relations, ab initio calculations on some selected herbacetin derivatives were carried out using Gaussian 09 in B3LYP/6‐311G*. The effect of the position and type of the various substituents in the ring A of the flavone backbone are considered. The oxygen charge density of the hydroxyl group on C8 (O8) in the considered herbacetins was compared using nuclear quadrupole coupling constants (NQCC) calculations. Results showed that the presence of the amino group in the ortho position of O8 has the most significant effect on increasing the charge density of the O8 atom (O8‐NQCC=9.23 MHz). Based on the proposed mechanism of these drugs, ortho‐amino herbacetin is expected to show a significant anti‐coronavirus effect. Comparison of calculated O8‐NQCCs of tangeretin and nobiletin with herbacetin shows that with the replacement of OH with OCH3, the charge density of oxygen atoms decreases (about 2 MHz). Therefore tangeretin and nobiletin have a lower drug effect than herbacetin. Natural bond orbital (NBO) results are in agreement with calculated NQCCs.