Production of free indole by some aroids

The production of free indole by several arum lily species (Araceae) was studied. The compound was identified by paper chromatography and thin-layer chromatography in several solvent systems, colour reactions with various reagents, enzymatic conversion to tryptophan, UV absorption spectrum, and formation of a complex with polynitrofluorenone. The presence of indole is restricted to certain floral parts and is correlated with the flowering sequence of these plants. In general, indole is present for not more than one day during the flowering cycle. In the case of Sauromatum guttatum Schott, production of indole by the appendix starts on the eve of flowering between 6 and 8 p.m. and ends about 24 hours later. At the peak of the metabolic flare-up period, about 0.3 umoles indole is present per gram fresh tissue. There is a close connection between the indole cycle and the production of heat and stench in the respiratory flare-up. Some of the indole formed is released as a constituent of the stench.