Metabolism of Tryptophol in Higher and Lower Plants

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Abstract
Bacteria, thallophytes, and seed plants (107 species), supplied with exogenous indole-3-ethanol (tryptophol), formed one or more of the following metabolites: O-acetyl tryptophol, an unknown tryptophol ester (or a set of structurally closely related esters), tryptophol glucoside, tryptophol galactoside, indole-3-acetic acid (IAA), and indole-3-carboxylic acid. The unknown ester was formed by all species examined; O-acetyl tryptophol appeared sporadically in representatives of most major taxonomic groups. Tryptophol galactoside was found in the algae Chlorella, Euglena, and Ochromonas. The glucoside was formed by many eucaryotic plants, but not by bacteria; it was a significant tryptophol metabolite in vascular plants. IAA, if detectable at all, was usually a minor metabolite, as should be expected, if tryptophol oxidase responds to feedback inhibition by IAA. Indole-3-carboxylic acid, formed by a few fungi and mosses, was the only tryptophol metabolite detected which is likely to be formed via IAA.