Lignans from the stem bark of Syringa pinnatifolia

Four new lignans, alashinols A-D (1-4), a new hydrolysis product, alashinols E (5), and seven known analogues were isolated from the stem bark of Syringa pinnatifolia Hemsl. These new lignans were characterized using 1D and 2D NMR and MS data, and their absolute configurations were determined by experimental and calculated electronic circular dichroism and X-ray diffraction analyses. Alashinol B (2) exhibited two conformers that adopted an unusual unit cell packing. Anti-inflammatory evaluation revealed that compounds 1, 4, 6, and 8 showed moderate inhibition against NO production in lipopolysaccharide-induced macrophages RAW 264.7 cells with IC₅₀ values range from 43.3-60.9μM, and 1 decreased the TNF-α and IL-6 level in a concentration-dependent manner at 40-160μM and exhibited considerable neuroprotective effect against the glutamate-induced injury in PC12 cell line. Analogues 3 and 9 showed protective effects against oxygen glucose deprivation/reoxygenation in H9c2 cells.