Insect Biochemistry and Molecular Biology 2001-10-01

8-O-acetylharpagide is not an ecdysteroid agonist.

L Dinan, P Whiting, P Bourne, J Coll

Index: Insect Biochem. Mol. Biol. 31(11) , 1077-82, (2001)

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Abstract

We have reinvestigated the activity of 8-O-acetylharpagide, an iridoid glucoside, as an ecdysteroid agonist. Elbrecht et al. (Insect Biochem. Mol. Biol. 26 (1996) 519) isolated a preparation of this compound from Ajuga reptans L. and ascribed ecdysteroid agonist activity on the basis of the induction of an ecdysteroid-like response in Drosophila melanogaster KcO cells, the displacement of [3H]ponasterone A from the Drosophila receptor and the activation of an ecdysteroid-regulated gene in a transactivation assay. We provide evidence that the agonist activity derives from contaminating ecdysteroids; A. reptans is a species rich in ecdysteroids. Purified 8-O-acetylharpagide is not active in the D. melanogaster B(II) cell bioassay, neither as an agonist nor as an antagonist, nor does it displace [3H]ponasterone A from dipteran or lepidopteran ecdysteroid receptor complexes.