Unusual sesquiterpene lactones with a new carbon skeleton and new acetylenes from Ajania przewalskii

Four new compounds, a noreudesmanolide (1), a guaianolide (4), and acetylenes (7-8), together with 16 other known compounds, were isolated from Ajania przewalskii. The novel sesquiterpenolide (1) possesses a rare carbon skeleton. Acetylation of 1 gave 1a. New compounds were elucidated as 1 beta-hydroxyl-2-noreudesm-4(15)-en-5 alpha,6 beta,7 alpha,11 alpha H-12,6-olide (1), 1 beta-acetoxyoxyl-2-noreudesm-4(15)-en-5 alpha,6 beta,7 alpha 11 alpha H-12,6-olide (1a), 8 alpha-angeloyloxyl-3 alpha,4 alpha-dihydroxyguaia-1,9,11(13)-trien-6,12-olide (4), (E)-3 beta,4 alpha-dihydroxyl-2-(2',4'-hexadiynylidene)-1,6-dioxaspiro[4,5]decane (7) and 2-hydroxyl-2-[(E)]-1 alpha,2 beta,3-trihydroxyl-3-nonaene-5,7-diyne]-4H-pyran (8), by chemical and spectroscopic methods, including HRESIMS, I D and 2D NMR. Cytotoxicity of nine compounds was assessed by their effects on selected cancer cell lines, K562, K562/ADM, BGC-823, and Hep-G2 cells. Phenolic acid 12 exhibited strong activity against K562 and K562/ADM cells and sesquiterpenolide 3 strong activity against K562/ADM cells. Radical-scavenging activities of 12 compounds, the mixed solvent extract (petrol ether-ether-methanol = 1: 1: 1), and the n-butanol extract were determined by ABTS and DPPH radical-scavenging assays. Phenols and coumarins (11-16). MSE, and n-BE displayed significant antioxidation (IC50 < 20 mu g/ml). (C) 2009 Elsevier Ltd. All rights reserved.