A Spectrophotometric Method for the Identification and Assay of Tryptophol and Other Indole Derivatives.

A spectrophotometric method for the identification of tryptophol, indole-3- acetic acid (IAA), and indole-3-acetonitrile (IAN) is described. The method can probably also be applied to other indole derivatives. If the components of a mixture of indolic compounds are to be identified, these must first be separated by chromatographic methods. Procedure. Eluate containing approximately 100 μg. of the indole compound is dissolved in 2.75 ml. of methanol. Ehrlich's reagent (l.5 ml.) is O added. The mixture is heated at 95°C for 2 min., after which 0.25 ml. 1 % NaNO₂ in water are added. The mixture is cooled for 30 min. at room temperature. The volume is adjusted to 4.5 ml. with methanol, and the optical density at wavelengths between 470 and 700 mμ is read on a spectrophotometer. Absorption spectra for the reaction products of tryptophol, IAA, and IAN are presented. The method can be used for quantitative determinations of tryptophol in the range 10 to 100 μg. and for IAA between 100 and 500 μg. Supporting evidence for the occurrence of tryptophol in the culture medium from Acetobacter xylinum was provided by using this method. [ABSTRACT FROM AUTHOR]