title: Novel spectrophotometric method for the quantitation of urinary xanthurenic acid and its application in identifying individuals with hyperhomocysteinemia associated with Vitamin B₆ deficiency.
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  μ mole/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.
authors.affiliation: Clinical Laboratories, Yuan's General Hospital, Kaohsiung 802, Taiwan.
authors.forename: Chi-Fen
authors.initials: CF
authors.lastname: Chen
authors.forename: Tsan-Zon
authors.initials: TZ
authors.lastname: Liu
authors.forename: Wu-Hsiang
authors.initials: WH
authors.lastname: Lan
authors.forename: Li-An
authors.initials: LA
authors.lastname: Wu
authors.forename: Chin-Hung
authors.initials: CH
authors.lastname: Tsai
authors.forename: Jeng-Fong
authors.initials: JF
authors.lastname: Chiou
authors.forename: Li-Yu
authors.initials: LY
authors.lastname: Tsai
mesh_terms: D002851:Chromatography, High Pressure Liquid; D006801:Humans; D020138:Hyperhomocysteinemia / Q000150:complications / Q000175:diagnosis* / Q000201:enzymology / Q000473:pathology / Q000652:urine; D013053:Spectrophotometry / Q000379:methods*; D013624:Taiwan; D025101:Vitamin B 6 / Q000378:metabolism; D026681:Vitamin B 6 Deficiency / Q000150:complications / Q000175:diagnosis* / Q000201:enzymology; D014977:Xanthurenates / Q000302:isolation & purification* / Q000652:urine
chemical_list: D014977:Xanthurenates; C028330:xanthurenic acid; D025101:Vitamin B 6