Journal of Chemical Ecology, Vol. 30, No. 7, July 2004 (  C 2004) STRUCTURAL DIVERSITY AND DEFENSIVE PROPERTIES OF NORDITERPENOID ALKALOIDS AZUCENA GONZ ´ ALEZ-COLOMA, 1,∗ MAT ´ IAS REINA, 2 ALBERTO MEDINAVEITIA, 2 ANA GUADA ˜ NO, 1 OMAR SANTANA, 1,5 RAFAEL MART ´ INEZ-D ´ IAZ, 3 LASTENIA RUIZ-MES ´ IA, 2,6 ALLENGER ALVA, 2,6 MARITZA GRANDEZ, 4,6 RAFAEL D ´ IAZ, 4 JOS ´ E A. GAV ´ IN, 4 and GABRIEL DE LA FUENTE 2 1 Centro de Ciencias Medioambientales, CSIC, Serrano 115-dpdo. 28006 Madrid, Spain 2 Instituto de Productos Naturales y Agrobiolog´ ıa, CSIC, Avda. Astrof´ ısico F. S´ anchez 3, 38206 La Laguna, Tenerife, Spain 3 Departamento de Medicina Preventiva (Parasitolog´ ıa), Facultad de Medicina Universidad Aut´ onoma de Madrid, Spain 4 Instituto Universitario de Bio-Org´ anica “Antonio Gonz ´ alez,” Universidad de La Laguna Avenida Astrof´ ısico Francisco S´ anchez 2, 38206 La Laguna, Tenerife, Spain (Received November 18, 2003; accepted March 13, 2004) Abstract—We have tested the insect antifeedant and toxic activity of 43 norditer- penoid alkaloids on Spodoptera littoralis and Leptinotarsa decemlineata in- cluding eserine (physostigmine), anabasine, and atropine. Antifeedant effects of the test compounds were structure- and species-dependent. The most active antifeedants to L. decemlineata were 1,14-diacetylcardiopetaline (9) and 18-hydroxy-14- O-methylgadesine (33), followed by 8- O-methylconsolarine (12), 14- O-acetyldelectinine (27), karakoline (7), cardiopetaline (8), 18- O- demethylpubescenine (13), 14- O-acetyldeltatsine (18), takaosamine (21), aja- dine (24), and 8- O-methylcolumbianine (6) (EC 50 <1 µg/cm 2 ). This insect showed a moderate response to atropine. S. littoralis had the strongest an- tifeedant response to 24, 18, 14- O-acetyldelcosine (19), and delphatine (29) (EC 50 <3 µg/cm 2 ). None of the model substances affected the feeding behavior of this insect. The most toxic compound to L. decemlineata was aconitine (1), followed by cardiopetalidine (10) (% mortality >60), 14-deacetylpubescenine (14), 18- O-benzoyl-18- O-demethyl-14- O-deacetylpubescenine (17), 14- O- acetyldelcosine (19), 14-deacetylajadine (25) and methyllycaconitine (30) ∗ To whom correspondence should be addressed. E-mail: azu@ccma.csic.es 5 Current address: INICA-MINAZ, Carretera Central km 156, CP: 42600, Jovellanos, Matanzas, Cuba. 6 Current address: Laboratorio de Productos Naturales, Facultad de Ingenier´ ıa Qu´ ımica, Universidad Nacional de la Amazon´ ıa Peruana (UNAP), Iquitos, Per´ u. 1393 0098-0331/04/0700-1393/0 C  2004 Springer Science+Business Media, Inc.