Glucuronic acid phenols from

II C—OH 0—C— ( + )-Glucuronic acid (13) From rat liver HPLC Phenolic drugs [22]... 

O-glucuronidation is catalysed by glucuronyl transferase that transfers a glucuronic acid moiety from uridine diphosphate glucuronide to an alcohol, phenol or carboxylic acid group (Fig. 8.36). This is the most important... 

UDP-glucuronyltransferases catalyze the addition of glucuronic acid onto phenol, hydroxyl and carboxylic acid functions of molecules. They are expressed in many tissues of the body, including the liver and intestine [2-5], Microsomes from human intestines have been shown to metabolize UDP-glucuronyltransferase substrates including p-nitrophenol [6], 1-naphthol, morphine, and ethinylestradiol [4]. The relative rates of metabolism of these substrates in liver and intestinal microsomes are shown in Table 13.1. 

Phenols are largely formed in the intestine from the aromatic amino acids tyrosine and phenylalanine. These amino acids are generally elevated in the early stages of HE. Phenols are detoxified in the liver by esterification with glucuronic acid and srrlphuric add. In severe cases of HE, free phenols and phenol derivatives are elevated in the serum and urine. 

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