Choleretic activity of phloracetophenone in rats: structure-function studies using acetophenone analogues.

The relationship between the chemical structure and choleretic activity of phloracetophenone (2,4,6-trihydroxyacetophenone) was investigated in adult male rats. Fourteen acetophenone analogues, with different substituents on the benzene nucleus, were intraduodenally administered and bile samples were collected via a bile fistula. All of the compounds tested immediately induced choleresis. For the same number of substituents on the benzene ring, hydroxy analogues induced a greater choleresis. The number and position of hydroxy substituents on the benzene nucleus play an important role in determining choleretic activity and biliary secretion of bile acid, but had no relation to biliary excretion of cholesterol. The choleretic activity of the hydroxylated compounds was inversely related to hydrophobicity, as inferred by thin-layer chromatography (TLC). Among the hydroxylated acetophenone analogues, 2,4,6-trihydroxyacetophenone was identified as the most potent, with a choleretic activity of 231.8+/-6.1 microl/mmol/min. It induced both a high bile flow rate and a high bile salt output and led to lower plasma cholesterol levels. This bile had a low lithogenic potential. The results suggest that a structural requirement for high choleretic activity of 2,4,6-trihydroxyacetophenone is a substituent hydroxy group at 4-position. Additional hydroxy groups at 2- and 6-positions are essential for the induction of higher an output of bile acid, and possibly, other solid materials.