The effect of piperine on the fertilization of eggs with sperm was inv
estigated in female hamsters. They were intragastrically treated with
piperine at doses of 50 and 100 mg/kg BW from day 1 through day 4 of t
he oestrous cycle. During piperine treatment, these females were super
ovulated and artificially inseminated (AI) with spermatozoa from untre
ated male hamsters at 12 h after hCG injection. The fertilization and
growth of embryos were examined at various times after AI. In control
hamsters, the percent fertilization increased with time, from 27.4 +/-
3.3% at 9 h after AI to 75.3 +/- 9.6 at 24 h after AI. Administration
of piperine to the superovulated animals markedly enhanced the percen
t fertilization at 9 h after AI. It was increased to 85.4 +/- 4.1 and
82.8 +/- 4.8% by piperine at doses of 50 and 100 mg/kg BW, respectivel
y. However, examination of the embryos retrieved 48 h after AI reveale
d no differences in the stage of embryonic development among different
groups of animals. The possibility that this effect was due to the di
rect action of vanillic acid, a major piperine metabolite, was tested
in vitro. Direct exposure of spermatozoa to vanillic acid at doses 25-
100 mg% did not significantly affect their motility, percent acrosome
reaction or fertilizing ability. This suggests that the enhancement of
fertilization by piperine treatment was not related to the secretion
of vanillic acid into the oviduct. (C) 1997 Academic Press Limited.