Synthesis of the Paba Conjugate of Udca

Accepted for publication 6 October 1992 Abstract The disulphate ester of ursodeoxycholyl-paminobenzoic acid (PABA-UDCA) was synthesised and compared with PABA-UDCA for its use in detection of intestinal bacteria. This compound, PABA-UDCA disulphate, had characters in common with PABA-UDCA in that it was deconjugated by cholylglycine hydrolase to release free PABA and bacteria that split glycocholic acid deconjugated PABA-UDCA disulphate. Further, in rat experiments urinary excretions of PABA were measured for six hours after oral administration of 15 mg PABA-UDCA disulphate. Ten control rats excreted (mean (SE) 188-2 (13-6) ,ug ofPABA; 10 rats with an intestinal stagnant loop excreted more (530.1 (30.1) [tg; p<0-001): whereas 10 rats in each of three groups pretreated by oral administration of various antibiotics excreted less (polymixin B+tinidazole, 4-9 (1.6) ,ug; kanamycin, 31-0 (4.7) Rg; clindamycin 40-9 (5.5) ig; p<0001). By contrast with PABA-UDCA, PABA-UDCA disulphate was not actively absorbed from any part of the small intestine in everted gut sac experiments, and showed poor recovery from bile after its intraileal instillation in rats. This indicated that PABA-UDCA disulphate is a single pass type substance in the gut and its oral administration test reflects the sum of the activities of bacteria in the small intestine and colon. The disulphate was easily soluble in water and this allowed its application in an in vitro test involving PABA-UDCA disulphate incubation with intraperitoneal pus (PABAUDCA disulphate incubation test) from patients with peritonitis. This test was carried out on six patients with peritonitis, and the severity of bacterial peritonitis was expressed quantitatively. From the results obtained PABA-UDCA disulphate was considered a good material to detect intestinal bacteria. (Gut 1993; 34: 823-828)