Disposition and confirmation of ochratoxins in rats and biological samples
Ochratoxin A (OA) and its analogs are a family of structurally related secondary metabolites produced by fungi, 'Aspergillus ochraceus' and 'Penicillium verrucosum'. The objectives of this study were to develop procedures for the confirmation of the ochratoxins and to determine their half-lives and the nature of their clearance from the body. The ochratoxins that were studied were OA, OC (ethyl ester of OA), OP-OA (newly discovered lactone opened form of OA), O_ (ochratoxin alpha, hydrolyzed OA), OA-OH (hydroxylated OA), OB (dechlorinated OA) and OB (hydrolyzed OB). Two procedures were developed for the confirmation of ochratoxins in biological samples. This involved either their esterification or the opening of the lactone groups. HPLC analysis of the different ochratoxins showed that more than 20 different ochratoxins and their metabolites were detected in bile and urine of treated rats. The results from the pharmacokinetic studies suggested that all of the ochratoxin analogs were distributed following a two compartment open model. The elimination half-lives of OA, OP-OA, O_, OA-OH, OB and OC were 103 +- 16, 50.5 +- 2.8, 9.6 +- 2.3, 6 +- 0.9, 4.2 +- 1.2 and 0.6 +- 0.2 h, respectively. Total body clearance of OA, OP-OA, O_, OA-OH and OB via the bile, urine and metabolic routes were 3.1, 3.6, 40, 65 and 43 ml/h kg, respectively. OA, OB and O_ were mainly cleared in the urine (>=48%). OA-OH in the bile (41%) and OP-OA mainly as metabolites (43%). Metabolism accounted for 43, 44, 33 and 29% of the total clearance of OA, O_, OA-OH and OB, respectively. The results show that OA has a long half-life and is very slowly cleared from the body and that its metabolites are cleared at a much faster rate with much shorter half-lives. This research resulted in the development of two procedures for the confirmation of different forms of OA, demonstrated that many metabolites of OA are produced in the rat, established the half-lives of several of the ochratoxins, most for the first time, and provided new information on the clearance of ochratoxins from the body.