Spontaneous Isomerization of Lycopene

Abstract

DURING some experiments with benzene extracts of various fruits, it was observed that the calcium hydroxide chromatogram frequently, but not in every case, shows a rather brownish orange layer below the lycopene zone. Subsequent experiments have proved that this behaviour of carefully purified lycopene depends on the time which elapses between the dissolution and the adsorption analysis. A fresh solution forms a uniform chromatogram, but if the liquid has been kept at 20° for 1–2 days, the new polyene (“neo-lycopene”) is observed ; it then forms a very distinctly separated zone in the chromatogram developed with benzene and light petroleum (3: 1). The pigment content of this layer reached 3 per cent of the total lycopene in experiments of 24 hours duration; the absorption maxima are 511, 479·5, 450 mµ in benzene and 498·5, 468, 440 mµ in petroleum ether. When the benzene solution is kept at room temperature, neo-lycopene is partly transformed into lycopene (or into a very similar dye which cannot be separated from lycopene in the column).