Two new morphinane alkaloids from Sinomenium acutum

Two new morphinane alkaloids, 1-hydroxy-10-oxo-sinomenine (1) and 4,5-epoxy-14-hydroxy sinomenine N-oxide (2), have been isolated from the stems of Sinomenium acutum. Their structures were established by various spectral analyses, especially 2D NMR experiments. The structure of 2 was confirmed by single crystal X-ray diffraction. The absolute configurations of 1 and 2 were deduced by comparison of CD spectra with the known alkaloid sinomenine (3). Compound 1 was tested for DPPH inhibition and gave IC50 of 27.9 μM. Compound 2 was tested for neuroprotective effect and showed significant activity against β-amyloid25–35-induced oxidative injury (*P < 0.05) at 10 μM in PC-12 cells.