Endogenous compounds glucuronidation

King, C.D. et al.. The glucuronidation of exogenous and endogenous compounds by stably expressed rat and human UDP-glucuronyltransferase, Arch. Biochem. Biophys., 332, 92, 1996. 

HPLC with immunoassay detection is useful for the analysis of those metabolites which are difficult to isolate from biological fluids by extraction (e.g. glucuronides). Such polar compounds cannot be observed at low concentrations with conventional detectors as they are obscured by endogenous compounds. HPLC with immunoassay detection can be applied to the determination of cannabin-oids, opiates, lysergide, and cardiac glycosides in biological fluids (A. C. Mof at,Analyl. Proc., 1981, IS, 115-116). 

FIGURE 3.4 Structures of endogenous compounds involved in glucuronidation bile adds, lithocholic add (LA) and hyodeoxycholic acid (HDCA) short chain bile acids, etianic add and isoetianic add, steroid hormones, androsterone, testosterone, estrone, estradiol, estriol. 

Glucuronidation is an important step in the elimination of many important endogenous substances from the body, including bilirubin, bile acids, steroid hormones, thyroid hormones, retinoic acids, and biogenic amines such as serotonin. Many of these compounds are also substrates for sulfonyltransferases (SULTs) (2). 

Phase II This phase consists of conjugation reactions. If the metabolite from Phase I metabolism is sufficiently polar, it can be excreted by the kidneys. However, many metabolites are too lipophilic to be retained in the kidney tubules. A subsequent conjugation reaction with an endogenous substrate, such as glucuronic acid, sulfuric acid, acetic acid or an amino acid results in polar, usually more water-soluble compounds that are most often therapeutically inactive. Glucuronidation is the most common and the most important conjugation reaction. Neonates are deficient in... 

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