STRUCTURE-ACTIVITY-RELATIONSHIPS FOR UNSATURATED DIALDEHYDES .8. COMPARATIVE EFFECTS OF 10 SESQUITERPENOIDS ON THE SEA-URCHIN GAMETE FERTILIZATION

The effects of 10 sesquiterpenoids with unsaturated dialdehyde functio nalities were studied on fertilization, first cleavage, and calcium pe rmeability of egg membranes of sea urchin gametes. Fertilization was i nhibited by nine compounds when sperm was exposed and by five compound s when eggs were exposed (50 mug/ml for 5 min). All compounds except o ne (9alpha-hydroxymerulidial) inhibited the first cleavage in a dose-r esponse manner. Only one compound (velleral) increased the Ca2+ permea bility of egg membranes at 20 mug/ml. All compounds reduced to a varyi ng extent the ATP-driven Ca2+ sequestration by non-mitochondrial intra cellular compartments. In general, when hydroxylated and non-hydroxyla ted derivatives of the compounds are compared, the hydroxylated ones p resent a lower toxicity when measuring fertilization and cleavage inhi bition, and reduction of intracellular Ca2+ sequestration.