Comparison of non-tryptophan fluorophores in protein-free extract of brunescent and non-brunescent human cataract

Purpose: To investigate whether any of the fluorophores in the human lens n uclei might be responsible for human brunescent cataract formation. Methods: Human lens nuclei (non-brunescent, from 13: brunescent, from 8) we re obtained after extracapsular cataract extraction in nondiabetic patients . Protein-free extract, prepared by filtrating the water-soluble fraction o f each nucleus through a centrifugal ultrafilter (molecular weight < 5,000) , was analytically separated by high-performance liquid chromatography. Results: No significant differences between non-brunescent and brunescent n uclei were observed in the concentrations (mean +/- SD) of 3-hydroxykynuren ine O-beta-glucoside (0.67 +/- 0.38 vs. 0.85 +/- 0.62 mu mol/g wet weight), 4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid O-glucoside (4.1 x 10(5) +/ - 2.9 x 10(5) vs. 6.3 x 10(5) +/- 5.0 x 10(5) area unit/g wet weight), and kynurenine (0.016 +/- 0.011 vs. 0.029 +/- 0.021 mu mol/g wet weight), A nov el fluorophore that has not been identified so far was significantly presen t more in brunescent than in non-brunescent nuclei (brunescent: 1.5 x 10(5) +/- 1.0 x 10(5) vs. non-brunescent: 2.6 x 10(3) +/- 6.3 x 10(3) area unit/ g wet weight, P <.01). Digestion of the protein-free extract with beta-gluc osidase eliminated the peak corresponding to the novel unidentified fluorop hore. Conclusion: The present results imply a novel protein-unbound fluorophore, presumably a beta-glucoside, might possibly be: involved in brunescent cata ract formation. Jpn J Ophthalmol 2000;44:198-204 (C) Japanese Ophtalmologic al Society.