Inhibition of ova fertilizability by pseudolaric acid B in hamster

Pseudolaric acid B (PA), a diterpenoid compound isolated from the root of Pseudolarix kaempferi Gorden, was injected into hamster ovarian bursa with various concentration before ovulation. The successful rate of fertilization of ova was significantly decreased, but no effect was observed on spermatozoa activity and fertilizing ability. Hamster ova with or without cumulus were treated with PA at a concentration higher than 50 micrograms/ml in the medium, the fertilizing rate of ova was reduced markedly. At the concentration of 5 micrograms/ml, only the capacity of fertilization of the cumulus-free ova was inhibited. When PA was injected ig 20 mg/kg daily to hamsters (female) for 4 d before mating, partial antifertility effect was observed.