Xanthurenic acid 8-methyl ether

The cuts corresponding to kynurenic acid, N-acetylkynurenine, and xanthurenic acid 8-methyl ether are eluted with 5 ml ethanol (spectroscopic grade) and the absorbances are read at 243, 227, and 237 mp, respectively. 

Price and Dodge (P8) applied the same technique for separation of kynurenic and xanthurenic acids and xanthurenic acid 8-methyl ether. Dowex 50 (H+) was employed as the resin with water as eluent. A spectrophotofluorometric method is used for reading kynurenic acid is made highly fluorescent by concentrated sulfuric acid (cf. Table 1) and xanthurenic acid fluoresces with concentrated alkali, so that both compounds can be read in the presence of each other and of the methyl ether of xanthurenic acid. 

The excretion of N-a-acetylkynurenine and kynurenic, xanthurenic, and o-aminohippuric acids was, in all the cases investigated, within the normal range, while 2-amino-3-hydroxyacetophenone and xanthurenic acid 8-methyl ether were always absent. 

When both xanthurenic acid and its methyl ether are present it is necessary to run chromatograms in duplicate since, as was mentioned, their spots partially overlap. Xanthurenic acid does not interfere in the determination of its methyl ether by measurement of absorbance at 237 mp. 

P8. Price, J, M., and Dodge, L. W., Occurrence of the 8-methyl ether of xanthurenic acid in normal human urine. J. Biol. Ghent. 223, 699-704 (1956). 

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