Lignans from the heartwood of Streblus asper and their inhibiting activities to hepatitis B virus.

Three new lignans, erythro-strebluslignanol (1), threo-7'-methoxyl strebluslignanol (2) and erythro-7'-methoxyl strebluslignanol (3), together with twelve known compounds were isolated from the n-butanol and chloroform fractions of the heartwood of Streblus asper. Their structures were elucidated through extensive spectroscopic methods, including MS and 2D NMR experiments (HMQC and HMBC). The stereochemistry at the chiral center was determined using CD spectra, as well as analysis of coupling constants and optical rotation data, respectively. Primary bioassays showed that 6-hydroxyl-7-methoxyl-coumarin (5) and ursolic acid (10) showed anti-HBV activities, with IC(50) values of 29.60 μM and 89.91 μM for HBsAg at no cytotoxicity, and IC(50) values of 46.41 μM and 97.61 μM for HBeAg at no cytotoxicity, respectively.