Table 1.

Structure–activity relationship of the Coumestan analogues

Compounds	Structure	NS5B inhibition (IC50 μM)	Log P	Gscorea	Gscoreb
Wedelolactone		36.1	0.87	−7.34	−6.71
LQB16		311	1.70	−4.61	−4.72
LQB34		18.5	0.82	−7.53	−6.91
LQB93		174	1.52	−6.63	−6.32
LQB96		63.8	0.98	−6.91	−6.28

The concentration of DMSO in all reactions was kept constant at 10%. The IC₅₀ values of the coumestan analogues were determined from dose–response curves using 8–12 concentrations for each compound in duplicate. Curves were fitted to data points and IC₅₀ values were interpolated from the resulting curves using SigmaPlot 8.0 software. The values represent an average from at least two independent experiments. N,N-disubstituted phenylalanine derivative 14 (IC₅₀ = 0.3 μM) was included as an internal reference standard. The predicted hydrophobicity of the coumestans was determined from their log P values employing QikProp 3.0 program (Schrodinger software package). Gscore^a and Gscore^b values were determined by docking of coumestans into NS5B NNI binding site for tetracyclic indole (PDB ID: 2DXS) and N,N-disubstituted phenylalanine (PDB ID: 1NHU), respectively. A more negative Gscore indicates a better fit at the binding site.