Further Studies of Some Plant Indoles and Auxins by Paper Chromatography

Abstract

Paper chromatography, using a modified Salkowski reagent and biological assay, was applied to a number of plant extracts believed to contain indole derivatives. Orange blossoms were shown to contain quantities of indole and indole-3-acetic acid (IAA) together with an unknown growth inhibitor. Yeast extract (Difco) contains IAA at a concentration of about 0.15 [mu]gm./g. Corn endosperm grown in vitro, using the yeast extract as medium, contains 1 mg. IAA per kg. fresh weight, as well as two other Salkowski reacting substances. These compounds are thus synthesized by the tissue and not merely taken up from the medium. Certain phenols give characteristic colors on chromatograms with the Salkowski reagent; on the other hand an extract of Abrus seeds, from which crystalline abrine was readily obtained, gave no indication of abrine on the chromatogram because of interference by lipides and pigments. Chromatograms of plant extracts must therefore be interpreted with caution.