A new biflavonoid with antiviral activity from the roots of Wikstroemia indica.

A new biflavonoid, 4'-methoxydaphnodorin E, was isolated from the antiviral fraction of Wikstroemia indica against respiratory syncytial virus (RSV). Its structure was determined on the basis of extensive spectroscopic data including HR-ESI-MS and 2D NMR. The biflavonoid was tested for its in vitro anti-RSV activity with cytopathic effect (CPE) reduction assay, and displayed potent effect with 50% inhibitory concentration (IC50) value of 2.8 µM and selective index (SI) value of 5.4.