Menthol glucuronide

Mendes, A.C., M.M. Caldeira, C. Silva, S.C. Burgess, M.E. Merritt, F. Gomes, C. Barosa et al., 2006. Hepatic UDP-glucose 13C isotopomers from [U- C] glucose A sample analysis by NMR of urinary menthol glucuronide. Magn. Reson. Med, 56 1121-1125. 

Disposition in the Body. Menthol is excreted in the bile and urine as a glucuronide conjugate the various stereoisomers differ quantitatively in the extent to which they conjugate with glucuronic acid. Menthol may occur in the conjugated form as a metabolite of pulagone which is a constituent of pulegium oil. 

Bergmann and Wolff S reported a small yield (1 g.) of menthol a-D-glucuronide by the oxidation of 12 g. of menthol a-n-glucoside in pyridine solution with sodium hypobromite. Better yields were obtained by Smolenski, who oxidized methyl a-n-glucopyranoside with bromine and sodium carbonate a 30% yield of the methyl n-glucuronide (as the brucine salt) was reported. Jackson and Hudson obtained a 12% yield of the brucine salt of methyl a-n-mannuronide by the barium hypobromite oxidation of methyl a-n-mannopyranoside. 

A further degradation of methyl a-n-glucoside by the action of barium hypobromite was observed by Bergmann and Wolff. From 12 g. of the glycoside, 4.6 g. of glyoxylic acid benzylphenylhydrazone was obtained. The experimental conditions differed from those used in the preparation of menthol a-D-glucuronide in that about twice as much bromine was used. 

A novel in vitro glucuronidation of a phenolic substrate was carried out with rat liver microsomes [22]. The method is simple, the reagent is optically pure, only the (4- )-glucuronic acid (13) is present, and the individual enantiomers are readily recovered by a simple enzymatic hydrolysis. Glucosidation with acetobromo-a-D-glucose (14) has also been used to separate the enantiomers of menthol [23]. 

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