Changes in the concentrations of testosterone, luteinising hormone and progesterone associated with administration of embelin.

The mode of action of embelin, a naturally occurring plant benzoquinone with male fertility regulating potential, was investigated. Sexually mature white New Zealand male rabbits were injected intra-muscularly with embelin (30 mg/kg body wt) on alternate days for 14 days (7 injections). Blood was collected on alternate days over 27-day period from the beginning of embelin administration. Testosterone and progesterone levels were measured by radioimmunoassay and luteinising hormone (LH) by mouse interstitial cell testosterone bioassay. There was a marked reduction of testosterone concentrations within two days of embelin administration and up to 90% reduction by the 6th day. LH showed a corresponding rise with the falling testosterone levels. Similarly, there was rapid increase in progesterone levels with the administration of embelin. Both the concentrations of progesterone and LH declined when embelin dosage was stopped. Evidence from the observed changes in the levels of the three hormones suggest that embelin disrupts production of testosterone at the testicular level.