Unusual Guaiane Sesquiterpenoids from Artemisia rupestris.

Two new guaiane sesquiterpenoids, (1 β,5 β)-1-hydroxyguaia-4(15),11(13)-dieno-12,5-lactone ( 1) and 1,5-epoxy-4-hydroxyguai-11(13)-en-12-oic acid ( 2), together with five known compounds, rupestonic acid ( 3), strobilactone A ( 4), antiquorin ( 5), isosclerone ( 6), and 5-hydroxy-2′,3′,4′,7,8-pentamethoxyflavone ( 7), were isolated from a 95% EtOH extract of Artemisia rupestris. Compounds 1 and 2 are rare examples of guaiane sesquiterpenoids, incorporating a 12,5-lactone group or featuring a 1,5-epoxy ring, respectively. The structures of 1 and 2 were identified by various spectroscopic methods. Compounds 1, 4, and 5 exhibited moderate cytotoxic activities against the human lung cancer 95-D cell line with IC₅₀ values of 11.3, 19.8, and 34.5 μ M, respectively. [ABSTRACT FROM AUTHOR]