Pharmacophagous feeding stimulant activity of neo-clerodane diterpenoids for the turnip sawfly, Athalia rosae ruficornis

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• 作者：Nishida ; Ritsuo ; Kawai ; Kunji ; Amano ; Takashi ; Kuwahara ; Yasumasa
• 关键词：Ajuga ; Clerodendron ; Athalia rosae ruficornis ; Turnip sawfly ; Tenthredinidae ; Clerodendrin ; Ajugareptone ; Neo-clerodane diterpenoids ; Pharmacophagy ; Defense substance
• 刊名：Biochemical Systematics and Ecology
• 出版年：2004
• 出版时间：January, 2004
• 年：2004
• 卷：32
• 期：1
• 页码：15-25
• 全文大小：106 K

文摘

Adults of the turnip sawflies, Athalia rosae ruficornis (Jakovlev), are “pharmacophagously” stimulated to feed on glandular trichomes distributed on leaves of two specific plant genera, Clerodendron (Verbenaceae) and Ajuga (Labiatae). A series of neo-clerodane diterpenoids were responsible for the feeding activity in adults of both sexes. Twenty-one neo-clerodane diterpenes were obtained from various sawfly-attracting Clerodendron and Ajuga plants as well as from bodies of the sawflies which had sequestered the compounds from Clerodendron plants. Among them a new neo-clerodane analogue, named here as ajugareptone, was isolated from a cultivar of Ajuga reptans L. and characterized as 6α,19-diacetoxy-4α,18-epoxy-3β-hydroxy-12(S)-(2-methylbutanoyl)-oxy-1-oxoneoclerod-13-ene-15,16-olide. The feeding stimulant activity of each compound was tested on A. rosae ruficornis adults. The sawflies were found to respond strongly to a limited number of compounds (clerodendrins B, D, H, ajugachin A, athaliadiol, 3-epicaryoptin and clerodin) which possess a tetrahydrofurofuran moiety with a 7,8-saturated structure. Clerodendrin derivatives with a 7,8-unsaturation (A, E, F, G and I) showed a marginal activity only at high doses. Analogues with an α,β-unsaturated γ-lactone moiety were entirely inactive. These data indicate a fairly restricted structural requirement for induction of the specific feeding stimulant activity in the sawfly. The sawflies selectively incorporate specific neo-clerodanes (e.g. clerodendrin D) as defense substances, and the sequestered compounds play a role as a sex pheromone to stimulate male’s mating behavior. Thus, the selective chemosensory response of the sawfly to the specific molecules implies an ecological adaptation mechanism via pharmacophagy.