Herbal approaches to system dysfunctions

Whereas cholesterol accounts for more than 90-95% of the sterols in bile, bile acids and their salts are the most important solutes; they are essential in the management of cholesterol levels and themselves help determine the extent of bile flow. Bile acids are synthesized from cholesterol in the liver. There are three groups. Primary bile acids, in humans mainly cholic and chenodeoxycholic acids and their salts, are produced directly. Secondary bile salts are created by the action of intestinal bacteria on primary bile salts with deoxycholate and lithocholate being formed from cholate and chenodeoxycholate, respectively. Tertiary bile salts are the result of modification of secondary bile salts by intestinal flora or hepatocytes; in humans these include the sulphate ester of lithocholate and ursodeoxycholate and the 7-beta-epimer of chenodeoxycholate.' Bile flow rates and composition are subject to a wide variety of neural, endocrine and paracrine influences. One of the main stimulants of bile flow are bile acids themselves, either in their primary form or reabsorbed as secondary or tertiary forms in the enterohepatic circulation (see below). The cholagogic effects of bile acids have led to their prescription in hepatobiliary disorders. One derivative, ursodeoxycholic acid, has been shown in controlled clinical studies to be a useful agent in the management of patients with primary biliary cirrhosis, autoimmune chronic active hepatitis* and cystic fibrosis.;