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Bioactive Sesquiterpenoids from the Peeled Stems of Syringa pinnatifolia

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posted on 19.07.2018, 13:28 by Ruifei Zhang, Xiao Feng, Guozhu Su, Zejing Mu, Hexinge Zhang, Yanan Zhao, Shungang Jiao, Lan Cao, Suyile Chen, Pengfei Tu, Xingyun Chai
Fourteen new sesquiterpenoids, alashanoids A–H (1, 2, and 49), (+)-2,9-humuladien-6-ol-8-one (3b), and five pairs of enantiomers (1 and 47), along with eight known analogues (3a and 1016) were isolated from the stems of Syringa pinnatifolia. The structures were established using IR, UV, MS, and NMR data. The absolute configurations of the new compounds were resolved by X-ray diffraction, a modification of Mosher’s method, and experimental and calculated ECD data analysis. The new sesquiterpenoids represent three skeletons: a rare 2,2,5,9-tetramethylbicyclo[6.3.0]-undecane (1), a humulane-type (28), and a caryophyllene-type (9) skeleton. Compounds 6a, 7, and 11 showed protective effects against hypoxia-induced injury to H9c2 cells at a concentration of 40 μM, and 57, 11, and 13 inhibited NO production in LPS-induced RAW264.7 macrophage cells with IC50 values ranging from 13.6 to 70.6 μM. These compounds decreased the TNF-α and IL-6 levels in RAW264.7 cells in a concentration-dependent manner at 20–80 μM.