Rapid Communication 8GAcetylharpagide is a Nonsteroidal Ecdysteroid Agonist

We have identified a novel nonsteroidal ecdysteroid agonist. This compound was isolated from a methanol extract of Ajugu reptuns L. (Lamiaceae) and the structure was identified by spectroscopic methods as 8-0-acetylharpagide. We have characterised this compound as an ecdysteroid agonist in a transactivation assay using P-galactosidase as the reporter gene regulated by ecdysteroid response elements. In khis assay, 8-Gacetylharpagide has an EC,, of 22 ~.LM. The compound also competes with tritiated-ponasterone A for binding to the Drosophila ecdysteroid receptor. Finally, it induces differentiation of Drosophila Kc cells as would be expected of an ecdysteroid agonist. This iridoid glycoside is common to several plant species and may play a role in the natural defense mechanisms of plants. Copyright 0 1996 Elsevier Science Ltd