Evaluating the inhibitory effect of eight compounds from Daphne papyracea against the NS3/4A protease of hepatitis C virus.

Hepatitis C virus (HCV) infection is a global threat to human health with an estimated 1.75 million new cases in 2015. Our previous studies showed that the ethyl acetate extraction of Daphne papyracea exhibited an inhibitory effect towards the HCV NS3/4A protease and eight compounds were identified from the extract. In this study, we investigated which of the eight compounds was responsible for the inhibitory effect of the extract against the HCV NS3/4A protease. From both molecular docking and enzyme inhibition studies, (+)-usnic acid was shown to be the most active compound and could be used as a lead compound in developing novel anti-HCV agents.