New obovatol trimeric neolignans with NO inhibitory activity from the leaves of Magnolia officinalis var. biloba

Six new obovatol trimeric neolignans, houpulignans A–F (1–6) were isolated from the leaves of Magnolia officinalis var. biloba. Their structures were determined on the basis of the interpretation of HRESIMS, NMR data, and electronic circular dichroism (ECD) calculations. Compounds 1 and 2 are the first examples of neolignans derived from three units of obovatol bearing a rare 1,4-benzodioxepane moiety. Compound 3 possesses a benzodihydropyran...