[Effect of Bryonia cucurbitacins on the biosynthesis of eicosanoids in human leukocytes]

2 beta,25-di (beta-D-glucopyranosyl)-16 alpha,20-dihydroxy-3,11,22- trioxocucurbit-5-en and 2 beta-(beta-D-glucopyranosyl)-16 alpha,20,25-trihydroxy-3,11,22-trioxocucurbit-5-en isolated from bryonia (Bryonia alba L.) roots have been demonstrated to inhibit in vitro the [1-14C]arachidonic acid release from neutrophils. Aglicon 2 beta,16 alpha,20,25-tetrahydroxy-3,11,22-trioxocucurbit-5-en is much less active. When the cells are stimulated by calcium ionophore A23187, the aglycon potentiates the release of arachidonic acid. In these conditions the glucosides show little activity. Both the glucosides and their aglycon suppress the biosynthesis of 5S,12R-dihydroxy-6,8,10,14(Z, E, E, Z)-eicosatetraenoic acid (LTB4) and 5S,12S-dihydroxy-6,8,10,14(E, Z, E, Z)-eicosatetraenoic acid (5S,12S-DHETE). Inhibition of the biosynthesis of these compounds by 2 beta,16 alpha,20,25-tetrahydroxy-3,11,22-trioxocucurbit-5-en also takes place on incubation of human neutrophils with exogenous arachidonic acid. The formation of other products of cycloxygenase and lipoxygenase oxidation pathways remains practically unchanged.