Bile acid glucuronides structure

Base peak in 3P-hydroxy-5-cholestanoate Characteristic of oxo-monohydroxy-C24 structure Feature of C-6 hydroxy bile acids Low intensity in bile acid glucuronides Prominent ion in THCA... 

These substrate molecules exhibit a wide variety of chemical structures. Some ABC proteins facilitate the transport of inorganic ions, whereas others pump various organic compounds, including lipids, bile acids, glutathione and glucuronide conjugates, or even short peptides. Most ABC family proteins utilize the energy of ATP hydrolysis for this transport activity (active transporters), but some ABC transporters form specific membrane channels. 

The liver, and also bacteria in the small and large intestine, can cause other structural modifications to bile acids as they undergo their entero-hepatic cycle. The formation of sulfate esters, already mentioned with respect to lithocholate in Section 4.2.1, is carried out primarily in the liver in man by a sulfotransferase (Lll). Other bile acids can also be sulfoconjugated to a small extent, mainly at the 3a-hydroxyl position. Bacteria, which have been isolated anaerobically from human feces, are known to possess bile acid sulfatase activity, which removes the 3a-sul te group of chenodeoxycholic and cholic acids (H24). The action of this bacterial enzyme probably explains why only trace amounts of sul ted bile acids, which are poorly absorbed in the intestine, are detected in the feces (12). Another type of bile acid conjugate, which has been identified in the urine of healthy subjects and patients with hepatobiliary disease, is the glucuronide (A7, S41). Both the liver and extrahepatic tissues, such as the kidney and small intestinal mucosa, are capable of glucuronidation of bile acids in man (M14). 

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. 

Feature of C-22 hydroxy C27 bile acid Me-TMS ether of glucuronide with m/z 204and m/z 317 Indicative of 7-hydroxy-3-oxo-A structure Observed in many 3-oxo-6- or 3-oxo-7-hydroxy structures... 

Steroid sulfates and glucuronides are best analyzed in the negative-ion ESI mode, where they give [M-H] ions. Structural information can then be obtained by performing MS/MS (Figure 14.5). However, steroids and bile acids exist in biological samples as part of complex mixtures and an [M-H] ion is likely to represent a number of isomers. These can, however, be separated by LC prior to ESI [27] and partially characterized by MS/MS [34]. 

Wen Z, Stern ST, Martin DE, Lee K-H, Smith PC. Structural characterization of anti-HIV drug candidate PA-457 [3-0-(3, 3 -dimethylsuccinyl)-betulinic acid] and its acyl glucuronides in rat bile and evaluation of in vitro stability in human and animal liver microsomes and plasma. Drug Metab Dispos 2006 34 1436-1442. 

The functions of the many and varied plant glycosides are unclear they do not serve as major food reserves or as structural material. Animal cells, particularly in liver and kidney, convert numerous alcohols, amines, and carboxylic acids to 9-glucuronides, which can be transported in the blood and excreted in urine or bile. This is a major route of detoxication of foreign substances. In plants, glucuronides are rare, and glucosides are the predominant sugar derivatives. (See reference 12.)... 

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