Cucurbitacins, cell adhesion inhibitors from Conobea scoparioides

In the course of screening natural products for antagonists of CD18-mediated cell adhesion, an extract with inhibitory activity was identified from the stem and leaves of Conobea scoparioides. Bioassay-guided fractionation led to a pure compound, identified by spectroscopy as cucurbitacin E [1]. Although many biological activities have been reported for the cucurbitacins, this is the first report of cell adhesion inhibition. Furthermore, closely related cucurbitacin analogues had different potencies, pointing to substructural features that are important for the activity.