| Abstrakt: |
We have tested the insect antifeedant and toxic activity of 43 norditerpenoid alkaloids on Spodoptera littoralisand Leptinotarsa decemlineataincluding eserine (physostigmine), anabasine, and atropine. Antifeedant effects of the test compounds were structure- and species-dependent. The most active antifeedants to L. decemlineatawere 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), ajadine (24), and 8-O-methylcolumbianine (6) (EC50<1 μg/cm2). This insect showed a moderate response to atropine. S. littoralishad the strongest antifeedant response to 24, 18, 14-O-acetyldelcosine (19), and delphatine (29) (EC50<3 μg/cm2). None of the model substances affected the feeding behavior of this insect. The most toxic compound to L. decemlineatawas 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) (% mortality >45). Orally injected S. littoralislarvae were negatively affected by 1, cardiopetaline (8), 10, 1,14-O-acetylcardiopetalidina (11), 12, 14, 1,18-O-diacetyl-19-oxo-gigactonine (41), olivimine (43), and eserine in varying degrees. Their antifeedant or insecticidal potencies did not parallel their reported nAChR binding activity, but did correlate with the agonist/antagonist insecticidal/antifeedant model proposed for nicotininc insecticides. A few compounds [14, tuguaconitine (38), 14-demethyldelboxine (40), 19, dehydrodelsoline (36), 18-O-demethylpubescenine (13), 41, 9, and delcosine (23)] had selective cytotoxic effects to ward insect-derived Sf9 cells. None were cytotoxic to mammalian CHO cells and none increased Trypanosoma cruzimortality. The selective cytotoxic effects of some structures indicate that they can act on biological targets other than neuroreceptors. |
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