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.

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Potent New Cell Adhesion Inhibitory Compounds from the Root of Trichilia rubra.-The structures of the new seco-limonoids rubrin A, B, D, F, G (Ia) -( Ie) and the known compounds rubrin C (If) and rubrin E (Ig) are determined by spectroscopic methods. All of these compounds exhibit inhibitory activity in the LFA-1:ICAM-1 (lymphocyte function associated antigen-1 to intercellular adhesion molecule-1) mediated cell adhesion assay. The results suggest that the uncommon hemi ortho ester A-ring is crucial to potency. -(MUSZA, L. L.; KILLAR, L. M.; SPEIGHT, P.; MCELHINEY, S.; BARROW, C. J.; GILLUM, A. M.; COOPER, R.; Tetrahedron