The choleretic mechanism of coumarin compounds and phenolic compounds.

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Abstract
The choleretic properties and mechanism of coumarin compounds and phenolic compounds were studied by examining their effects on parameters such as bile flow, bile acids, electrolytes and biliary metabolites [in rats]. Choleretic intensity and property of each sample were significantly different. The choleretic efficacy of 6,7-dimethylesculetin (6,7-DME) was far weaker than that of 4-methylumbelliferone (4-MU). 4-Hydroxybenzyl alcohol (4-HBA), isoeugenol, vanillin, paeonol and phenolphthalein accelerated bile secretion, but 4-(.beta.-D-glucopyranosyloxy)-benzyl alcohol, safrol and arbutin did not. 4-MU and 4-HBA underwent conjugation in the liver to give mainly a glucuronide; their metabolites were rapidly excreted into bile, but 6,7-DME was converted into some metabolites which were excreted gradually over a long period of time. The biliary gap between cations (Na+,K+) and anions (Cl-,HCO3-, bile acids) produced after i.v. administration of 4-MU, 6,7-DME and 4-HBA was substantially offset by biliary concentrations of their metabolites. A hydroxyl group which can be mainly converted into a glucuronide is necessary in exerting a strong choleretic action. The choleretic mechanism of coumarin compounds and phenolic compounds is considered to be as follows: their metabolites (mainly glucuronide) are actively secreted into the biliary tree as an organic anion coupled with Na+ or K+, and water is passively excreted.