Spirocyclohexadienone-Type Neolignans with Neuroprotective and Neurite Outgrowth Enhancing Activities from Magnolia liliiflora

Three rare spirocyclohexadienone-type neolignans, magnoflorins A-C (1-3), and three known analogs (4-6), were isolated from the leaves of Magnolia liliiflora. Magnoflorin D (4) was obtained from natural resources for the first time. The chemical structures and absolute configurations of 1-4 were elucidated through detailed analysis of HR-ESI-MS, IR, H-1, C-13, and 2D NMR, and ECD experiments. The absolute configuration of 5 were characterized by X-ray crystallography in present study. Moreover, compounds 4 and 5 displayed moderate neuroprotective activity against corticosterone-induced PC12 cells injury at 20 mu M with cell viability of 71.5 +/- 0.99 % and 73.0 +/- 1.42 %, respectively, compared to the model group with 60.83 +/- 0.93 %. Compound 6 could enhance neurite outgrowth of nerve growth factor (NGF)-induced PC12 cells at 10 mu M with the differentiation rate of 11.98 %, compared with 20.49 % of 50 ng/ml NGF.