Petroleum-soluble Fluorescent Constituents of Leaves

Abstract

WHEN petroleum ether extracts of dried leaf material are passed through Tswett adsorption columns composed of magnesia and siliceous earth, the leaf pigments are adsorbed, and colourless solution percolates through the column¹. The very first portions of the percolate contain colourless hydrocarbons recoverable in crystalline form. Other colourless substances are slightly adsorbed on the magnesia, and may be recovered from subsequent portions of the percolate. The weakly adsorbed, colourless leaf constituents absorb ultra-violet light, in contrast to the non-adsorbed hydrocarbons which are transparent. Of particular interest, however, are fcwo products which are strongly fluorescent in ultraviolet light. These substances form fluorescent bands or zones on the adsorption columns just below the a-carotene band. The light emitted by the fluorescent bands appears white to the eye, but, in the hand spectroscope, it ranges from the long green to the short red wave-lengths. Crystals, obtained after elution of the fluorescent bands with petroleum ether and ethanol, were strongly fluorescent, being comparable to anthracene and carbazole in this respect. Upon exposure to air the crystals slowly lost their fluorescent properties. Each fluorescent substance, dissolved in cyclohexane, exhibited strong absorption of ultra-violet light, particularly at shorter wavelengths, but no maxima or minima were observed.