(+/-)-Alashanoid N, Two Enantiomeric Sesquiterpenes from Syringa pinnatifolia.

Two enantiomeric humulane sesquiterpenes, namely (+)-alashanoid N (1a) and (-)-alashanoid N (1b), along with two known analogs ((2R,3R,5R)-2,3-epoxy-6,9-humuladien-5-ol-8-one (2) and (2R,3S,5R)-2,3-epoxy-6,9-humuladien-5-ol-8-one (3)), were described from the peeled stems of a folk Mongolian herbal medicine Syringa pinnatifolia. Their structures were characterized based on UV, IR, NMR, and HR-ESI-MS data analyses, and the absolute configurations were determined by data analysis of X-ray diffraction and quantum chemical calculations. (+/-)-Alashanoid N showed inhibition against NO production in RAW 264.7 macrophage cells with IC50 values of 90.1 μM and 71.7 μM, and protective effect against oxygen-glucose deprivation injury to H9c2 cells at a concentration of 20 μM and 5 μM, respectively.