Phenols and conjugates

Color bodies Sulfur, nitrogen, phenolic, and conjugated compounds formed during processing the result of oxidation and polymerization... 

Lindane is absorbed from the gastrointestinal tract, the respiratory tract, and skin. The metabolism of lindane is complex and involves a number of pathways depending on which isomer of hexachlorocyclohexane (HCH) is involved (lindane is the gamma (y) isomer). It is nonetheless rapid. Lindane is metabolized in the liver by microsomal enzymes. The main pathways include stepwise elimination of chlorines to form tri- and tetrachloro-phenols and conjugation with sulfates or glucuron-ides and subsequent elimination. Other metabolic pathways involve the production of mercaptura-tes. These water-soluble products are eliminated in the urine. Lindane is bound by serum proteins in the blood. Storage is in adipose tissue and other... 

Flow Injection Analysis of Phenols and Conjugates. In order to determine the mode of ionization giving maximum sensitivity, FIA was used to obtain mass spectra of the individual standards of the phenols and their conjugates in both acetonitrile and acetonitrile-pH 4.5 ammonium formate (2 3, v/v) using El, methane PCI and NCI, and isobutane PCI and NCI. Operating conditions were flow rate, 0.4 mL/min desolvation chamber temperature,... 

PB-HPLC-MS of Phenols and Conjugates. The SAX chromatographic separation of phenols, sulfates, and glucuronides is described in detail elsewhere (12). Briefly, a 25 cm x 4.6 mm SAX column (Supelco, Bellefonte, PA) is used with an acetonitrile-pH 4.5 ammonium formate buffer (2 3) mobile phase at a flow rate of 1.5 mL/min. Under these conditions, the nine model compounds were resolved to baseline in less than 20 minutes. 

Flow Injection Analysis of Phenols and Conjugates. A summary of the El spectra of the phenols and their conjugates obtained in FIA mode is found in Table II. Inexplicably, phenol was not... 

Table II. PB Electron Impact Mass Spectra for Phenols and Conjugates [Mass(relative intensity)] ...

Table IV. Signal/noise Ratio and Peak Heights of Phenols and Conjugates ...

In terrestrial animals, the excreted products of PAHs are mainly conjugates formed from oxidative metabolites. These include glutathione conjugates of epoxides, and sulfate and glucuronide conjugates of phenols and diols. 

Finally, the fact that anthocyanins can reach the brain represents a beginning of an explanation of the purported neuroprotection effects of anthocyanins. Anthocyanins may be eliminated via urinary and biliary excretion routes. " The extent of elimination of anthocyanins via urine is usually very low (< 0.2% intake) in rats and in humans, indicating either a more pronounced elimination via the bile route or extensive metabolism. As mentioned earlier, in the colon, non-absorbed or biliary excreted anthocyanins can be metabolized by the intestinal microflora into simpler break-down compounds such as phenolic acids that may be (re)absorbed and conjugated with glycine, glucuronic acid, or sulfate and also exhibit some biological... 

Initially formed polar metabolites such as phenols and amines may be conjugated to water-soluble terminal metabolites that are excreted into the medium and function as an effective mechanism of detoxification. For example, pentachlorophenol and pentachlorothiophenol produced from pentachloronitrobenzene conjugated represented the major metabolites. Although the naphthalene dihydrodiol was the major metabolite produced from naphthalene, the further transformation... 

A number of other chiral catalysts can promote enantioselective conjugate additions of silyl enol ethers, silyl ketene acetals, and related compounds. For example, an oxazaborolidinone derived from allothreonine achieves high enantioselectivity in additions of silyl thioketene acetals.323 The optimal conditions for this reaction also include a hindered phenol and an ether additive. 

The isolated double bonds in the dihydro product are much less easily reduced than the conjugated ring, so the reduction stops at the dihydro stage. Alkyl and alkoxy aromatics, phenols, and benzoate anions are the most useful reactants for Birch reduction. In aromatic ketones and nitro compounds, the substituents are reduced in preference to the Dissoiving-Memi... 

Aromatic amines 4 are metabolised in vivo by cytochrome P450 mediated oxidation to phenolic and hydroxylamine derivatives 5 and 6. Phase II conjugation of the latter with PAPS or acyl transferase results in formation of the sulfuric or acetic acid esters 7. Nitrogen conjugation to give the A-acetyl analogues is also possible (Scheme l).54 65... 

T. Yamamoto and H. Hayashi, ir-Conjugated soluble and fluorescent poly(thiophene-2,5-diyl)s with phenolic, hindered phenolic and /j-C6H4OCH3 substituents. Preparation, optical properties, and redox reaction, J. Polym. Set, Part A Polym. Chem., 35 463-474, 1997. 

Similar to the analysis above, phenol and the conjugate acid of amphetamine both have a pVa of 10 (Fig. 2.6), but phenol is un-ionized at pH 7.4 and amphetamine is mostly ionized. When the pVa of a base is reported, as in Figure 2.6, it is understood that it represents the pl< A of the protonated form and is calculated from the ratio of protonated to unprotonated as shown in the equation above. 

Many drugs and metabolites are metabolized by conjugation with sulfate or glucuronic acid as described in Chapter 7. Sulfate conjugates can be hydrolyzed back to the alcohol or phenol. Glucuronide conjugates can involve a wider variety of functional groups and... 

A study39 of substituent effects on the 15N chemical shift (515N) (Table 10) for 4-substituted anilines in DMSO was interpreted in terms of substituent solvation-assisted resonance (SSAR) effects. Solvation of certain conjugated jr-electron-acceplor (+R) substituents has been found to give significant enhancements in the acidities of anilines, phenols and other acids40,41, and the magnitudes of these enhancements increase with... 

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