Identification and ecdysteroid antagonist activity of three oligostilbenes from the seeds of Carex pendula (Cyperaceae)

Abstract

Methanolic extracts of seeds of several Carex species were found to antagonise the action of 20-hydroxyecdysone in the Drosophila melanogaster microplate-based B II cell bioassay. Bioassay-guided HPLC analysis of seeds of Carex pendula (drooping sedge) provided one previously unknown tetrastilbene ( cis-miyabenol A) and two known oligostilbenes (kobophenol B and cis-miyabenol C) as the biologically active compounds (EC 50 values were 31, 37 and 19 μM, respectively, vs. 5×10 −8 M 20-hydroxyecdysone). The structures and relative stereochemistries of these compounds were deduced by comprehensive 1D- and 2D-NMR experiments. These compounds are isolated from Carex pendula for the first time. In vitro experiments with dipteran and lepidopteran ecdysteroid receptor proteins demonstrate that the oligostilbenes are able to compete with radiolabelled ecdysteroid ([ 3H]ponasterone A) for occupancy of the ligand binding site. IC 50/ K i values are similar to the EC 50 values obtained in the B II bioassay.