To Elucidate the Anti-Ebola Potency of the Active Leads Discovered Based on the Diversified Plants in Lingnan Region of China

There have been repeated outbreaks of Ebola virus disease (EVD) since its first outbreaks in Sudan and Zaire in 1976. The recent 2013-2016 EVD outbreak has killed more than 11,000 people among 28,652 infection cases. The mortality of each EVD outbreak ranges from 25-90%. The deadly disease is expected to continue to threaten humans not only because there are currently no effective antiviral drugs or vaccines available for treating and preventing EVD, but also because Ebola virus can increase the ability to infect human cells upon the viral mutations, which is evidenced by the current EVD epidemic in West Africa. The present project is designed to discover new anti- Ebola lead compounds from the selected plants in Lingnan Region of China. Three plant leads have been identified to effectively inhibit Ebola virus from evaluating more than 1,500 plant extracts in our drug discovery program. They are identified as the medicinal plants Agrimonia eupatoria (Rosaceae), Eurya nitida (Theaceae) and Maesa perlarius (Maesaceae). Bioassay-guided separation of the active plant extracts led to the identification of catechin and its isomers, and several condensed tannins. Two tannin compounds showed selective inhibition activity against Ebola virus with IC50 values of 4.6 and 12.5 M, respectively, without displaying antiviral activity against the other tested viruses. Because of the nature of our initially used anti-Ebola evaluation assay system, the active compounds most likely act at the entry steps. We thus examined the binding affinity of these compounds with the potential Ebola viral glycoprotein (GP) target using molecular docking analysis. The two tannins showed high affinity to bind the GP1/GP2 complex, suggesting the GP might be the right target for this type of compounds to inhibit viral growth of Ebola. The identification of the Ebola GP inhibitors has provided strong evidence that potent anti-Ebola agents exist in the three discovered plants. The current project is designed to discover new anti-Ebola compounds from the active plants, and to determine the antiviral potential of the isolates. To achieve these objectives, the following specific aims and tasks are proposed: 1) to isolate new antiviral compounds from the identified active plant extracts and to carry out structure modification study of the active compounds; 2) to perform biological evaluation of the fractions and pure compounds generated in the current project against Ebola; 3) to elucidate the anti-Ebola targets through GP binding and cell-cell fusion interaction assay study as well as through computer docking analysis.