The presence of ethylenic bonds and vic-glycol groups in neuromelanin and lipofuscin in the human brain.

Abstract

Through use of oxidation and blockading reactions, chemical group precursors of aldehyde demonstrable with Schiff reaction staining were identified in the soluble lipid-free lipofuscin component of neuromelanin of human substantia nigra and in lipofuscin of human inferior olive. Aldehyde generation was implied by moderate staining after bleaching neuromelanin and oxidizing lipofuscin with potassium permanganate followed by oxalic acid. Confirmation of aldehyde generation was achieved when diminished staining followed a sulfite addition blockade obtained by replacing oxalic acid with metabisulfite or bisulfite as well as by condensation blockades obtained with phenylhydrazine or aniline without replacing oxalic acid. Vic-glycol precursors of aldehyde were demonstrated in both pigments when acetylation or bromination preceded permanganate-oxalic acid and staining was unequivocally diminished only after acetylation. Vic-glycols were also demonstrated in lipofuscin by diminished staining when acetylation preceded periodic acid oxidation. Ethylenic precursors of aldehyde were suggested in performic acid-bleached neuromelanin when the minimal staining that followed this peracid's generation of Schiff reaction-negative dihydroxy groups became greatly intensified following an additional oxidation with periodic acid. This additional oxidation converted the dihydroxys to Schiff reaction-positive aldehyde. Ethylenes in lipofuscin were indicated when bromination before performic acid reduced subsequent staining.