Defensive Chemistry of Senecio miser Matı ´as Reina,* ,† Azucena Gonza ´ lez-Coloma, ‡ Carmen Gutie ´rrez, ‡ Raimundo Cabrera, § Matı ´as L. Rodrı ´guez, ⊥ Vı ´ctor Fajardo, | and Luis Villarroel ∇ Instituto de Productos Naturales y Agrobiologı ´a (IPNA), CSIC, La Laguna, Tenerife, Spain, Centro de Ciencias Medioambientales (CCMA), CSIC, Madrid, Spain, UDI Fitopatologı ´a, Facultad de Biologı ´a, Universidad de La Laguna, Tenerife, Spain, Instituto Universitario de Bio-Orga ´ nica “Antonio Gonza ´ lez” (IUBO), Universidad de La Laguna, Tenerife, Spain, Facultad de Quı ´mica y Biologı ´a, Universidad de Santiago de Chile (USACH), Santiago, Chile, and Facultad de Ciencias, Universidad de Magallanes, Punta Arenas, Chile Received March 6, 2000 Three eremophilanolides, 1R-acetoxy-8-methoxy-10H-eremophil-7(11)-en-8R,12-olide (1); 1R-angeloyloxy- 6-hydroxy-8-methoxy-10H-eremophil-7(11)-en-8R,12-olide (2); and 1R-angeloyloxy-8H,10H-eremo- phil-7(11)-en-8R,12-olide (3), and two pyrrolizidine alkaloids, integerrimine (4) and its N-oxide (5), were isolated from bioactive fractions of Senecio miser. The structures of the new compounds 1 and 2 were established by NMR spectroscopic analysis and chemical transformation. The X-ray analysis of compound 1 was also performed. Eremophilanolides 1 and 2 and alkaloids 4 and 5 were found to be strong insect antifeedants, further supporting a proposed defensive role for these classes of compounds. The genus Senecio (Asteraceae), widely distributed throughout the world, is known to be a source of pyrrolizi- dine alkaloids, eremophilanolides, and furanoeremo- philanes. 1-3 There are about 210 Senecio species in Chile, and a large number of endemic members of this genus are present in Chilean Patagonia, 4 where they have had a negative impact on the local economy because of their toxic effects on cattle. 5-7 The toxicity exhibited by these plants has been attributed to their content of pyrrolizidine alka- loids (PAs). 8 As part of an ongoing collaborative study on bioactive metabolites of Senecio species endemic to Chilean Patago- nia, we have studied the defensive chemistry of the herbaceous species S. miser Hook f. 4 In the present work we report on the isolation, structure determination, and biological activity of two new eremophilanolides (1 and 2), the known compound 3, the acetylated derivative of 2 (6), and the pyrrolizidine alkaloid, integerrimine (4), and its N-oxide (5). The antifeedant, insecticidal, and fungicidal effects of the active fractions and the pure compounds were evaluated against several herbivorous insects [the aphid Myzus persicae; the Colorado potato beetle (CPB), Lepti- notarsa decemlineata; and the lepidopteran Spodoptera littoralis] and the plant pathogen Fusarium moniliforme. Results and Discussion The methanolic extract of the aerial parts of S. miser strongly inhibited the feeding activity of M. persicae and L. decemlineata adults, but was innocuous to S. littoralis larvae. Bioassay-guided fractionation of the extract showed that fractions Fr-1 and Fr-2 (EtOAc in n-hexane) and Fr-5 (MeOH in EtOAc) had the strongest antifeedant effects. Fr-1 had a strong antifungal effect on F. moniliforme. Therefore, the bioactive constituents of S. miser could be grouped into two according to their polarity (Fr-1-Fr-2 and Fr-5). The chromatographic purification of the active fractions of S. miser afforded five compounds (1-5). Compounds 1-3 (isolated from Fr-1 and Fr-2) proved to be sesquiterpene lactones of the eremophilanolide type, while 4 and 5 (isolated from Fr-5) are PAs. The IR and UV spectra of compound 1 showed bands at 1765 and 1731 cm -1 and λ max 231 (log ǫ 3.46) nm, respectively, characteristic of an R,- unsaturated γ-lactone and a saturated ester. The HREIMS showed a molecular ion peak at m/z 322.1789 corresponding to the molecular formula C 18 H 26 O 5 . The 13 C NMR spectrum (DEPT experiment) showed 18 carbon atoms, five methyls, four methylenes, three methines, and six quaternary carbon atoms. Moreover, the 1 H and 13 C NMR spectra suggested the presence of an acetate group [δ H 2.04 (3H, s); δ C 170.3 (s) and 21.2 (q)], the characteristic signals of a methyl substituted R,-unsaturated lactone with an endo- double bond [δ H 1.86 (3H, s); δ C 8,3 (q), 171.6 (s), 125.1 (s), and 156.5 (s)], and a methoxy group [3.11 (3H, s); 105.9 * To whom correspondence should be addressed. Tel.: 34-922-256848. Fax: 34-922-260135. E-mail: mreina@ipna.csic.es. † IPNA. ‡ CCMA. § Facultad de Biologı ´a, Universidad de La Laguna. ⊥ IUBO, Universidad de La Laguna. | Universidad de Magallanes. ∇ USACH. 6 J. Nat. Prod. 2001, 64, 6-11 10.1021/np000114o CCC: $20.00 © 2001 American Chemical Society and American Society of Pharmacognosy Published on Web 12/05/2000