Interactions between ascorbic acid and linear and cyclized bile pigments. A thin-layer chromatographic study.

Physico-chemical interactions between ascorbic acid and the linear or cyclized bile pigment dimethyl esters were determined by thin-layer chromatography on silica gel. The interacting barrier technique allows a reactivity to be established that is a function of the degree of cyclization of the molecule. Thus, linear pigments of the biliverdin type are of low reactivity whereas the monocyclic neopterobilin phorcabilin shows a medium-strength interaction and isophorcabilin a strong interaction, the natural sarpedobilin being definitely captured by the ascorbic acid barrier on the silica gel layer. Spectrophotometric studies of the ascorbate-sarpedobilin interaction led to the conclusion that more than 2 mol of ascorbic acid are required per mole of pigment. The results are discussed in connection with the possible biochemical role of such bilins.