One-step solvolysis of 3-, 7- and 12-sulfated free and conjugated bile acids

Abstract

A substantial proportion of the bile acids in biological fluids like serum, bile and urine is found to be sulfated. The formation of these sulfated bile acids is increased in patients with hepatobiliary diseases and thought to represent an important protective mechanism for the liver during cholestasis ]1,2]. In addition, we and others recently showed that hepatocytes from rat [3,4] and pig [S] in primary monolayer culture and the human hepatoma cell line Wep G2 [6] also synthesize sulfated bile acids. For a reliable quantitation of all bile acids solvolysis is necessary, since most methods used do not measure bile acid sulfates [2]. Several methods for solvolysis have been described [7-141. A survey of these procedures with number of steps and side-reactions is given in Table I. Major drawbacks of the procedures are that they are laborious and time-consuming [7-91 and that esters [7,8,10-131 and acetonides [9-121 are formed, which are undesirable for various detection procedures. In addition, changes in the chemical structure of bile acids have been reported after solvolysis 1121. A recently published method may be usefuf for solvolysis of 3-sulfated bile acids [14], but 7- and 12-sulfated and disulfated bile acids, known to be more resistant to solvolysis [10,12,13,18] were not investigated, and a limited number of sulfates was tested. In this report we describe a new mild and rapid one-step solvolysis procedure for simultaneous solvolysis of 3-, 7- and 1Zsulfated free and taurine- or glycine-con- jugated bile acids. With this procedure unmodified bile acids are obtained without undesirable formation of esters, acetonides and acylation products, which interfere