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Melanins and lens pigments: a comparative study

A A Cuevas1, S García-Castiñeiras

  • 1Department of Ophthalmology, School of Medicine, Univeristy of Puerto Rico, San Juan 00936-5067.

Puerto Rico Health Sciences Journal
|June 1, 1993
PubMed
Summary

Human lens pigments contain pheomelanin, a type of melanin, as indicated by the presence of thiazole-4,5-dicarboxylic acid (TDCA). This finding suggests pheomelanin is integral to lens pigmentation, contributing approximately 9%.

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Area of Science:

  • Biochemistry
  • Ophthalmology
  • Melanin Chemistry

Background:

  • Lens pigments share physicochemical properties with melanins.
  • Previous studies suggest a link between lens pigmentation and melanin composition.

Purpose of the Study:

  • To investigate the presence and contribution of pheomelanin in human lens pigments.
  • To characterize lens pigments by analyzing their melanin components.

Main Methods:

  • Oxidation of human lens pigments, natural melanins (hair), and synthetic melanins using permanganate under acidic conditions.
  • Quantification of oxidation products, thiazole-4,5-dicarboxylic acid (TDCA) and pyrrole-2,3,5-tricarboxylic acid (PTCA), via high-performance liquid chromatography (HPLC).
  • Identification of TDCA and PTCA as markers for pheomelanin and eumelanin, respectively.

Main Results:

  • Both TDCA and PTCA were detected in human lens pigments across varying pigmentation levels.
  • TDCA concentration increased with lens pigmentation, reaching maximum levels in purified lens pigment.
  • The TDCA/PTCA ratio in lens pigments was comparable to that of pheomelanin from red hair.

Conclusions:

  • Pheomelanin is an integral component of human lens pigments.
  • The study estimates a 9% contribution of pheomelanin to the overall lens pigment composition.
  • These findings provide insights into the chemical nature and origin of lens coloration.

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