Enhancement of fertilization by piperine in hamsters.

The effect of piperine on the fertilization of eggs with sperm was investigated 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 the oestrous cycle. During piperine treatment, these females were superovulated and artificially inseminated (AI) with spermatozoa from untreated 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 percent 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, respectively. However, examination of the embryos retrieved 48 h after AI revealed no differences in the stage of embryonic development among different groups of animals. The possibility that this effect was due to the direct 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.