Identification of a free non-tryptophan fluorophore in water-soluble fraction of human brunescent cataractous lens nucleus

• Published in: Nippon Ganka Gakkai zasshi Vol. 104; no. 4; p. 207
• Main Authors: Ando, K, Shirao, E, Iwakuchi, Y, Shirao, Y, Inoue, A
• Format: Journal Article
• Language: Japanese
• Published: Japan 01.04.2000
• Subjects: Aged; Cataract - metabolism; Chromatography, High Pressure Liquid; Gas Chromatography-Mass Spectrometry; Glucosides - analysis; Humans; Lens, Crystalline - chemistry; Xanthurenates - analysis
• ISSN: 0029-0203

We previously reported that a unique free fluorophore (Fl-Glc), presumably a beta-glucoside, is particularly abundant in human brunescent cataractous lens nuclei. Our preliminary experiments indicated that incubation of low-molecular weight (MW) fraction of non-brunescent lens nuclei causes an increase in a particular fluorophore (Fl-X). This study was undertaken to compare the Fl-Glc with the Fl-X and subsequently to identify the Fl-X. Experiment 1. The purified Fl-X and its beta-glucosidase digest (aglycon) were compared with the Fl-Glc and its aglycon, respectively, by high-performance liquid chromatography (HPLC). Experiment 2. i) The Fl-X and its aglycon were analysed by liquid chromatography/mass spectrometry (LC/MS). ii) Authentic xanthurenic acid was analysed by HPLC and LC/MS. Experiment 1. The retention times of the Fl-X and the Fl-Glc exactly coincided. The fluorescence peaks of both disappeared after beta-glucosidase treatment. Experiment 2. i) LC/MS results suggested that the MWs of the Fl-X and its aglycon were 367 and 205, respectively. ii) HPLC and LC/MS results for xanthurenic acid (MW = 205) were exactly the same as those for the aglycon of the Fl-X. The Fl-Glc and the Fl-X are identical, and the Fl-X (= Fl-Glc) is a glucoside of xanthurenic acid.