Bioactive Dibenzocyclooctadiene Lignans from the Stems of <i>Schisandra neglecta</i>

Abstract

Seven new unusual dibenzocyclooctadiene lignans, neglignans A–G (<b>1</b>–<b>7</b>), together with 16 known dibenzocyclooctadiene lignans, were isolated from the stems of <i>Schisandra neglecta</i>. Compounds <b>1</b> and <b>2</b> are the first dibenzocyclooctadiene lignans bearing a carboxyl group at C-4, and compounds <b>3</b> and <b>4</b> are the first 7,8-<i>seco</i>-dibenzocyclooctadiene lignans found from Nature. The new compounds (<b>1</b>–<b>7</b>) and several of the known compounds were evaluated for their anti-HIV activity and cytotoxicity. Compounds <b>2</b> and <b>6</b> showed anti-HIV-1 activities with therapeutic index values greater than 50, and compound <b>4</b> showed cytotoxicity against the NB4 and SHSY5Y cancer cell lines with IC₅₀ values of 2.9 and 3.3 μM, respectively