Fig. 5.

Molecular structure of spike protein of SARS-CoV-2 and interactions with plant-based drugs. A furin cleavage site is present at the interface between S1 and S2 subunits of the spike protein. Amino acid positions of spike protein that can be interacted by different groups of plant-based inhibitors (steroids, quinones, terpenoids, flavonoids, and tannins) are also shown. Please refer Table-1 for precise details. SP- signal peptide; RBD- Receptor binding domain; RBM- Receptor binding motif; TM-transmembrane motif; FP- fusion peptide; HR1-Heptad repeat-1, HR2-heptad repeat-2; NTD- N-terminal domain, CP- cytoplasmic domain(adapted from Joshi et al., 2020[40] with some modifications).