Isolation and Identification of Acetylenic Spiroketal Enol Ethers from Artemisia lactiflora as Inhibitors of Superoxide Generation induced by a Tumor Promoter in Differentiated HL-60 Cells

Six acetylenic compounds were isolated from the leaves of Artemisia lactiflora (Compositae), an edible plant of Thailand. Four of them were identified as the stereoisomers of 3,4-epoxy-2-(2,4-hexadiynylidene)-l,6-dioxaspiro[4.5]decane and its derivatives, whose planar structures have already been reported. The other two were identified as novel chlorohydrin derivatives of the corresponding diacetylene spiroketal enol ethers. The inhibitory effects of the polyacetylenes isolated in the present study together with genistein on TPA-induced O₂^- generation were examined. It was revealed that an acyloxyl group at the C-2 position enhanced the inhibitory effect, while the absolute configurations at C-5, -6, and -7 were not important. While polyacetylenes are known to possess several biological roles in various ecosystems, we first found inhibitory effects of the diacetylenes on TPA-induced O₂^- generation in differentiated HL-60 cells.