title: Identification of a Free Non-tryptophan Fluorophore in Water-soluble Fraction of Human Brunescent Cataractous Lens Nucleus.
abstract: Purpose: 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.Methods: 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.Results: 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.Conclusions: The Fl-Glc and the Fl-X are identifical, and the Fl-X (= Fl-Glc) is a glucoside of xanthurenic acid.
authors.affiliation: Department of Ophthalmology, Kanazawa University School of Medicine, Kanazawa, Japan
authors.initials: K
authors.lastname: Ando
authors.initials: E
authors.lastname: Shirao
authors.initials: Y
authors.lastname: Iwakuchi
authors.initials: Y
authors.lastname: Shirao
authors.initials: A
authors.lastname: Inoue