Abstract
The role of genipin in the choleretic action of geniposide, the principle component of gardenia fruit, was examined. Geniposide showed a delayed and prolonged action by intraduodenal administration of 1 g/kg or over, while genipin showed a fast choleretic action with 50 mg/kg. Geniposide did not show choleretic action after intraportal administration of 10-400 mg/kg but genipin showed a choleretic action with 2.5 mg/kg. Geniposide and genipin appeared in portal blood after intraduodenal administration of geniposide, while genipin appeared after intraduodenal administration of genipin. Genipin and genipin glucuronide appeared in the bile after oral and intraduodenal administration of geniposide and oral administration of genipin. Genipin and genipin glucuronide that appeared in portal blood and bile after administration of geniposide and genipin showed a periodical pattern similar to that of choleretic action of these two substances. These evidences indicate that the choleretic action of geniposide is due to genipin formed by hydrolysis of geniposide in the digestive tract.
