Inhibitory Oxidation Products of Indole-3-Acetic Acid: 3-Hydroxymethyloxindole and 3-Methyleneoxindole as Plant Metabolites

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Abstract
Extracts of pea seedlings (Pisum sativum, variety Alaska) oxidize IAA to a bacteriostatic compound which was identified as 3-hydroxymethyloxlndole. At physiological pH this compound is readily dehydrated to 3-methyleneoxindole, another bacteriostatic agent. The extracts of pea seedlings also contain a reduced TPN linked enzyme which reduces 3-methyleneoxindole to 3-methyloxindole, a non-toxic compound. These enzymatic reactions also take place in intact seedlings; thus, a pathway of IAA degradation via oxindoles appears to be pertinent to plant metabolism. A key intermediate of this pathway, 3-methyleneoxindole, is a sulfhydryl reagent capable of profound effects on metabolism and growth.