Glucuronides, formation from phenols

Glucuronide conjugates of pentachlorobenzene were observed following the initial phenol formation from hexachlorobenzene in rainbow trout (Oncorhynchus mykiss) fry following dietary exposure27. Other metabolites included traces of 2,5-dichloro-, 2,3,6-trichloro- and 2,4,5-trichloro-phenol. The biotransformation of pentachlorophenol... 

Formation of diastereomeric esters from phenols and D( -t- )-glucuronic acid using an in vitro glucuronidation with rat liver microsomes. 

Only the small amounts of T and T that are free in the circulation can be metabolized. The main route is deiodination of T to T and i-T, and from these to other inactive thyronines (21). Most of the Hberated iodide is reabsorbed in the kidney. Another route is the formation of glucuronide and sulfate conjugates at the 4 -OH in the Hver. These are then secreted in the bile and excreted in the feces as free phenols after hydrolysis in the lower gut. 

Studies on the metabolic fate of phenol in several species have indicated that four urinary products are excreted (Figure 9.5). Although extensive phenol metabolism takes place in most species, the relative proportions of each metabolite produced varies from species to species. In contrast to the cat, which selectively forms sulfate conjugates, the pig excretes phenol exclusively as the glucuronide. This defect in sulfate conjugation in the pig is restricted to only a few substrates, however, and may be due to the lack of a specific phenyl sulfotransferase because the formation of substantial amounts of the sulfate conjugate of 1-naphthol clearly indicates the occurrence of other forms of sulfotransferases. 

The compounds were separated on a strong anion exchange (SAX) HPLC column with a pH 4.5 ammonium formate-acetonitrile mobile phase. Molecular ions were not obtained for any of the conjugate structures due to decomposition, but the phenols were detected in all cases as the M or [M+H] ion. The phenol formed from each conjugate as a decomposition product could usually be identified by computerized library search. In SIM mode, limits of detection ranged from 0.25 ng for 4-nitrophenyl glucuronide to 51 ng for phenol. 

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