A sesquiterpenoid tropolone and 1,2,3,4-tetrahydronaphthalene derivatives from Olax imbricata roots.

The methanol extract of Olax imbricata roots afforded one new sesquiterpenoid tropolone and three new 1,2,3,4-tetrahydronaphthalene derivatives, olaximbrisides A-D (1-4). Their structures were determined by 1D and 2D NMR experiments in combination of HRESIMS. The relative configurations were assigned by the NOESY experiments. The absolute configurations were established by a combination of X-ray diffraction analysis and electronic circular dichroism (ECD) experiments. All isolated compounds were evaluated for their cytotoxic effects against some cancer cell lines. Among them, compound 1 exhibited the cytotoxicities against MCF-7, HepG2 and LU cell lines with IC50 values of 16.3, 34.3 and 8.0 μM, respectively.