Biological activities of lignans and stilbenoids associated with plant-insect chemical interactions

Lignans and biogenetically-related secondary metabolites derived from phenylpropanoid precursors play a significant role in the defence of plants against insects. They act largely as regulators of insect feeding, but in a few cases they can influence also specific physiological functions of insects. The antifeedant activities of a series of lignans are summarised and compared with previously published data. The compounds represent either natural substances isolated from plants or their chemically transformed structural analogues. The precise mode of action of such compounds is mostly unknown. One possible mechanism might be interaction with, and disruption of, the endocrine system, which is crucial for proper development of insects and is dependent on the action of moulting hormones (ecdysteroids). This hypothesis has been tested using the specific Drosophila melanogaster BII cell line bioassay for ecdysteroid agonists and antagonists, in which the potency of the test compound reflects the affinity of binding to the ligand-binding site of the D. melanogaster ecdysteroid receptor. The activity data are evaluated in terms of a structure-activity relationship. To explore this phenomenon, the compounds were prepared and tested alongside ecdysteroid analogues and some insect ecdysis/metamorphosis-disturbing steroidal and non-steroidal natural compounds. Several phenylpropanoids, including lignans and stilbenoids (derived from resveratrol), were evaluated with promising results. The results indicate that such phenylpropanoid-derived compounds can possess ecdysteroid antagonistic activity, which could potentially influence insect development.