Indole acetaldehyde

Besides its role as an intermediate in indole glucosinolate biosynthesis, it has been suggested that IAOX is involved in IAA biosynthesis.40,41 This has been supported by the biochemical characterization of LAOX-metabolizing enzymes that convert IAOX to either indole-3-acetaldehyde,42,43 indole-3-acetonitrile,42,44 or... 

H) lndole-3-acetaldehyde pathway The natural occurrence of indole-3-acetaldehyde (IAAld) in plants was first described in the extracts of cucumber seedlings98 where the concentration of IAAld was --(I. ngg-1 fresh weight. Possibly arising via IAOx or indole-3-pyruvate (IPyA), IAAld may act as a convergence point for tryptophan-dependent pathways.78 In an early study, the capacity to metabolize [14Ci]tryptophan via IPyA and IAAld was determined.99 Two primarily cytoplasmic enzymes were involved and the process was NAD-dependent. 

The presence of an ethylidene group in echitamine chloride was also demonstrated by oxidation with periodic acid, which was reported to give acetaldehyde and indole-3-acetaldehyde (78). Alkali fusion and selenium dehydrogenation experiments gave inconclusive results, but the basic fractions were suspected to contain derivatives of jS-carboline (77, 78). Oxidation of echitamine with alkaline potassium permanganate afforded a low-melting base, which was considered to be Nb-methyl-tryptamine (80). 

Synthesis of radioactively labelled indole-3-acetaldehyde, indole-3-ace-taldoxime and indole-3-acetonitrile... 

Rommelsbacher, in following the concept of Holtz that mammalian alkaloids are formed from chemically reactive biogenic amines and amino acids by reaction with endogenously formed ketonic substrates under physiological conditions, has extended this idea to include indole-3-acetaldehyde. It was found that tryptamine, on incubation with pig brain and bovine brain, but not with liver tissue, formed the thiazolidine carboxylic acid 60 shown in Fig. 20 Ml). 

Compound 60 is a mixture of diastereomers, and the structures were proposed on the basis of spectral data and proved to be correct by synthesis from indole-3-acetaldehyde and L-cysteine. It was demonstrated that tryptamine is first converted by MAO to indole-3-acetaldehyde, which spontaneously cyclizes with free L-cysteine present in brain tissues 142). The reaction was strongly inhibited by addition of the MAO inhibitor pargyline, indicating participation of the enzyme in the formation of the aldehyde, but not in the condensation with L-cysteine, which was found to be pH-dependent and probably nonenzymatic 143). It seems possible that compound 60 is identical with material obtained during metabolic degradation of tryptamine in brain tissue 144,145). 

One of the most efficient enzymatic systems that generates triplet state acetone is the horse radish peroxidase(HRP)-catalyzed oxygenation of isobutyraldehyde (Eq. 79). Related enzymatic processes include the autoxidation of linear carbox-aldehydes, malonaldehyde, a-formylphenylacetic acid, indole-3-acetal-dehyde, indole-3-pyruvic acid, ° and indole-3-acetaldehyde. Consequently, there is no question about the existence of enzymatically generated electronic excitation in the cell however, what do these excited states do in the biological system ... 

Figure 5.42 Proposed tryptophan-dependent indole acetic acid biosynthesis pathways for Arabidopsis. Dashed arrows indicate that neither a gene nor enzyme activity has been identified in Arabidopsis. lAM, indole-3-acetamide IPA, indole-3-pyruvic acid lAAld, indole-3-acetaldehyde lAOx, indole-3-acetaldoxime 5-lAH-L-cys,...

The chemical structure of heteroauxin was established to be indole-3-acetic acid (indole-P-acetic acid (lAA)). It is considered that lAA is formed by the enzymatic oxidation of indole-3-acetaldehyde derived from tryptophan via indole-3-pyruvic acid or tryptamine. Between these two routes, the main route is thought to be through indole-3-pyruvic acid. 

Indoleacetic acid (lAA) (17) is involved in many aspects of plant growth and development (Bonner and Varner, 1976 Kosuge and Sanger, 1986). This hormonal substance is derived in most plants by conversion of tryptophan to indole 3-pyruvic acid (15) (tryptophan amino transferase), decarboxylation to the indole 3-acetaldehyde (16) (indole pyruvate decarboxylase), and oxidation to indole 3-acetic acid (17) (indole acetaldehyde oxidase) (Fig. 7.6) (Goodwin and Mercer, 1983). 

Two different methods can be used to measure hormone turnover. Both have sources of error, but as these are different a comparison of values obtained by each method should give a reliable estimate of turnover, as was accomplished successfully for ABA in stressed Xanthium leaves [4,20]. incorporation might also be used to measure lAA turnover, as oxygen is incorporated during the final oxidation of indole-3-acetaldehyde. 

When the in vitro conversion of indolic compounds in plants was investigated, tryptophol was one of the most commonly detected metabolites. Tryptophan, tryptamine, ILA, and indole-3-acetaldoxime were among its precursors [9,38]. All these compounds are metabolized via indole-3-acetaldehyde (Fig. 1), which would... 

Hydrolysis of the nitrile 199 gave 2-trifluoromethylindole-3-acetic acid 201 in moderate yield [60], A partial reduction of the nitrile group in 199 provided indole-3-acetaldehyde 202 in 51 % yield. The latter was used for the synthesis of the 2-trifluoromethylated analogue of oxypertine (an antipsychotic used in the treatment of schizophrenia) 203 upon treatment with IV-phenylpiperazine and sodium cyanoborohydride [64]. 

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