Magnodelins A and B, Two New Tetrahydrofuran Lignans From the Fruits of <i>Magnolia delavayi</i> Franch. and Structural Revision of Magnostellin B and Magnone A

Two previously undescribed tetrahydrofuran lignans, named magnodelins A and B (1 and 2), were isolated from the fruits of Magnolia delavayi Franch., together with two known lignans magnostellin B (3) and magnone A (4). The assignments of their structures were elucidated by extensive spectral analysis, electronic circular dichroism experiments, and single-crystal X-ray diffraction analysis. Moreover, the structures of magnostellin B and magnone A were revised by the coupling constants, rotating frame overhauser effect spectroscopy experiment, and X-ray crystallography. Compound 4 was found to enhance neurite outgrowth of nerve growth factor-induced PC12 cells at a concentration of 10 µM.