Glucuronic acid labeled

Studies on the fate of D-glucuronic acid labeled with C14 have been mentioned previously in this review (Section IV, 2b). It is evident from these reports that extensive degradation of the molecule takes place, revealed by the large amount of carbon dioxide recovered. It is also clear that fragments of the acid are available for the resynthesis of D-glucuronic acid, and hence, perhaps, of D-glucose as well. 

For the synthesis of D-glucuronic acid, methods of oxidation of suitable D-glucose derivatives have been devised during the past two decades these procedures have been comprehensively reviewed by Marsh,6 Mehltretter,7 and Heyns and Paulsen.8 For special purposes, for example, for the preparation of 6-I4C-labelled D-glucuronic acid, chain-extension reactions of 1,2-O-isopropylidene-a-D-xy/o-pen-todialdo-I,4-fiiranose by the cyanohydrin synthesis9 or by ethynyla-tion10 are used, but these frequently yield mixtures of D-glucuronic acid and L-iduronic acid. 

Mai ins et al. (15) showed by TLC that rainbow trout exposed to l C-labeled naphthalene excrete 1-naphthyl glucuronic acid in the urine almost exclusively. Only 1% of the total radioactivity of the urine was in the form of non-conjugated derivatives. 

The metabolism of an oral dose of 50-100 mg/kg "C-1,3-DNB was followed in rabbits (Parke 1961). Of the metabolites detected in urine, 30% were conjugated with glucuronic acid and 6% with sulfate. The major urinary metabolites of 1,3-DNB were 2,4-diaminophenol (31%), 1,3-phenylenediamine (25%), 1,3-nitroaniline (18%), and 2-amino-4-nitrophenol (14%). Other minor metabolites comprising about 20% of the label were oxidation and reduction products and azoxy dimers. 

In these experiments, several doubly and triply labelled compounds were reported.108 So-called UDP-D-[U-I4C, 3,4- H]glucuronic acid was formed by mixing UDP-D-[U-14C]glucuronic acid, UDP-d-[3-3H]glucuronic acid, and UDP-D-[4-3H]glucuronic acid it was not, of course, a triply labelled compound, but a mixture of 3 singly labelled ones.108 This factor prevented any conclusions about intramolecular transfer with doubly or triply labelled compounds to be reached. 

Glucose, mandelamine, and hydrochlorothorazide decrease the amount of estriol found when acid hydrolysis is used to release estriol from its conjugate with glucuronic acid in urine. The destruction of estriol in diabetic urine can be monitored by the inclusion of internal standards of labeled estriol glucuronide and reduced by prior dilution of the urine. When glucuronidase is used to release the estriol, the results are not affected when glucose of diabetic urine is present. When this is done the internal standard is not necessary. 

As previously mentioned, Kauss (40) has shown that the methyl donor for the formation of 4-methyl-D-glucuronic acid of hemicellulose B proved to be S-adenosyl-L-methionine, the same as in pectin. A particulate preparation from immature com cobs containing hemicellulose B was found capable of transferring the 14C-labeled methyl group from S-adeno-syl-L-methionine to a macromolecular acceptor present in the particles. The radioactive product was shown to be hemicellulose B labeled in the 4-methyl-D-glucuronic acid residues. It was isolated chiefly as 4-methyl-glucuronosyl-( 1 - 2)-D-xylose. 

Sowden82 recently has prepared D-glucuronic acid isotopically labeled at carbon atom 6 for certain chemical and biochemical studies. In this novel synthesis, 5-aldehydo-l,2-isopropylidene-D-xylofuranose88 (XVI), prepared by periodate cleavage of 1,2-isopropylidene-a-D-glucofuranose (XV), was condensed with Cu-labeled sodium cyanide. Alkaline... 

Scheme 18 FDAM-labeling of cellulose by the example of a C6-carboxylic (glucuronic) acid structure...

Roberts, R.M., Shah, R., and Loewus, F., 1967a, Conversion of myo-inositol-2-14C to labeled 4-0-methyl-glucuronic acid in the cell wall of maize root tips. Arch. Biochem. Biophys. 119 590-593. 

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