Novel Spectrophotometric Method for the Quantitation of Urinary Xanthurenic Acid and Its Application in Identifying Individuals with Hyperhomocysteinemia Associated with VitaminB6Deficiency

Abstract

A novel spectrophotometric method for the quantification of urinary xanthurenic acid (XA) is described. The direct acid ferric reduction (DAFR) procedure was used to quantify XA after it was purified by a solid-phase extraction column. The linearity of proposed method extends from 2.5 to 100.0 mg/L. The method is precise, yielding day-to-day CVs for two pooled controls of 3.5% and 4.6%, respectively. Correlation studies with an established HPLC method and a fluorometric procedure showed correlation coefficients of 0.98 and 0.98, respectively. Interference from various urinary metabolites was insignificant. In a small-scale screening of elderly conducted at Penghu county in Taiwan (n = 80), we were able to identify a group of twenty individuals having hyperhomocysteinemia (>15 μmole/L). Three of them were found to be positive for XA as analyzed by the proposed method, which correlated excellently with the results of the activation coefficient method for RBC's AST/B6 functional test. These data confirm the usefulness of the proposed method for identifying urinary XA as an indicator of vitamin B6 deficiency-associated hyperhomocysteinemic condition.

Xanthurenic Acid Is the Main Pigment of Trichonephila clavata Gold Dragline Silk

“…The average concentration of xanthurenic acid in gold spider silk was 181 µmol/L in 100 µL 0.1% SDS per 1 mg thread, which corresponds to 0.371% of the weight of the dragline. As an alternative confirmation of the amount of xanthurenic acid, we used spectrophotometry coupled to the reduction of the Fe 3+ —TPTZ complex [ 47 ] by xanthurenic acid ( Supplemental Figure S4 ). This measurement resulted in a 260 µM concentration in a 40 µL 0.1% SDS per 1 mg thread, corresponding to 0.213% weight.…”

Electrochemical Determination of Kynurenine Pathway Metabolites—Challenges and Perspectives

“…A fluorescent bioprobe based on nitrogen doped carbon quantum dots immobilized with quinolinate phoshphoribosyl transferase has been designed for QA determination in serum [85], but other analytical approaches offer much better LODs (Table 3). Urinary Kyna can be determined by fluorometry after reaction with hydrogen peroxide on irradiation with UV light [86], while urinary XA can be measured by spectrophotometric procedure in the presence of Fe(III)-2,4,6-tris-(pyridyl)-s-triazine complex in acidic buffer [87]. Besides the simplicity of the above protocols, the obtained LODs are much higher than for other analytical methods (Table 3).…”