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

Abstract 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 β -hydroxyl-2-noreudesm-4(15)-en-5 α ,6 β ,7 α ,11 α H-12,6-olide ( 1 ), 1 β -acetoxyoxyl-2-noreudesm-4(15)-en-5 α ,6 β ,7 α ,11 α H-12,6-olide ( 1a ), 8 α -angeloyloxyl-3 α ,4 α -dihydroxyguaia-1,9,11(13)-trien-6,12-olide ( 4 ), (E)-3 β ,4 α -dihydroxyl-2-(2′,4′-hexadiynylidene)-1,6-dioxaspiro[4,5]decane ( 7 ) and 2-hydroxyl-2-[(E)-1 α ,2 β ,3-trihydroxyl-3-nonaene-5,7-diyne]-4H-pyran ( 8 ), by chemical and spectroscopic methods, including HRESIMS, 1D 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 (IC 50