Indole-3-acetic acid conjugates

Chlorogenic acid forms a 1 1 complex with caffeine, which can be crystallized from aqueous alcohol and yields very little free caffeine on extraction with chloroform. Other compounds with which caffeine will complex in this way include isoeugenol, coumarin, indole-acetic acid, and anthocyanidin. The basis for this selection was the requirement for a substituted aromatic ring and a conjugated double bond in forming such a complex. This kind of complex does modify the physiological effects of caffeine.14 Complex formation will also increase the apparent aqueous solubility of caffeine in the presence of alkali benzoates, cinnamates, citrates, and salicylates.9... 

Fig. 1. Structures of indole acetic acid hapten-protein conjugates.

Another important factor of hormone-hormone interaction is the hormonal control of hormonal movement and polarity. Thus, various cytokinins have been reported to increase the polar movement of indole acetic acid and vice versa. Gibberellin treatment was shown also under cer- bain circumstances to increase the basipetal auxin movement. On the other hand, abscisic acid decreases the auxin movement and ethylene, according to some evidence, the gibberellin movement, perhaps through a promotion of conjugation of the auxins with aspartate and of the gibberellins with glucose (cf. Eef. 27). 

Bialek K, Cohen JD. Isolation and partial characterization of the major amide-linked conjugate of indole-3-acetic acid from Phaseolus vulgaris. Plant Physiol 1986 80 99-104. 

Indole and acetal 372 gave the carbazole 373 in 50% yield in acetic acid. ° It seems likely that conjugated ketone formed in situ isomerizes in two steps to the species 374 that initiates ring formation by attack at the indole -position. 

Indole-3-acetic acid is rather readily oxidized by peroxidases and is, in fact, probably not present in the plant in the free form to any appreciable extent. The nature of the complexing groups is not clear. The inherent instability of the compound in living tissue has made experimental observations difficult, and (the more stable) 1-naphthaleneacetic acid has often been used instead, although it is by no means certain that the biological activities are comparable. One view held is that auxin herbicides are effective either because they do not readily form conjugate systems, or because the conjugate retains the phytotoxic properties. 

Chemistry and Physiology of Conjugates of Indole-3-Acetic Acid... 

Reactions with otP-Unsaturated Ketones, Nitriles and Nitro-Compomds Such reactions are usually effected using acid (see below), or one of a number of mild Lewis acids, such as scandium iodide (with microwave heating), indium bromide " or hafnium triflate, and can be looked on as an extension of the reactions discussed in 20.1.1.6. In the simplest situation, indole reacts with methyl vinyl ketone in a conjugate fashion in acetic acid/acetic anhydride. ... 

The major natural auxin is indole-3-acetic acid (lAA) [42]. A number of related compounds exist in plants, including indolebutyric acid and indoleacetonitrile (Fig. la). These related compounds are active primarily when first converted to lAA [42]. In addition, there are a series of LAA conjugates with sugars and amino acids [43]. Some of these may be detoxification products, but others may be reservoirs of releasable lAA, especially in seeds. Phenylacetic acid (Fig. la) has auxin activity, and exists in sizable amounts in a few plants such as tobacco [42], but it is unclear that this compound actually moves from one part of a plant to another. In addition to the natural auxins, a whole host of synthetic auxins are known. The most widely used are a-naphthaleneacetic acid (NAA) and 2,4-dichlorophenoxyacetic acid (2,4-D) (Fig. la). 

Conjugates of indole-3-acetic acid. Listed are the naturally occurring conjugates of lAA and 4-Cl-IAA from plants and plant pathogenic bacteria described to date. With the exception of the Parthenocissus spp. callus tissue, these compounds have been isolated from tissues not exposed to exogenous sources of lAA. Compounds reported prior to 1982 are discussed in a comprehensive review of lAA conjugates (ref. 2 [83]). 

This reaction was initially reported by Diels and Reese in 1934. It is the conjugate addition between hydroazobenzene and dimethyl acetylene-dicarboxylate. The resulting adduct can be transformed into three different heterocyclic compounds under various experimental conditions (i.e pyrazolones with acid, indoles upon heating in xylene, and quinolones with base ). For example, l,2-diphenyl-3-carbomethoxy-5-pyrazolone will be generated from the adduct in acetic acid (acidic condition), whereas dimethyl indole-2,3-dicarboxylate is produced in xylene (neutral condition) and 2-hydroxy-3-anilino-4-carbomethoxy-quinoline is yielded in pyridine (basic condition). The latter can be further converted into 2,3-dihydroquinoline upon decarboxylation and hydrolysis." This reaction has been extended to heat the 1 1 adduct in picoline. ... 

Fig. 1. Indole-3-acetic acid levels in two different plant tissues, wheat caryopsis and bean seed. The data show the difference between levels of free lAA (F), free plus extractable conjugate (F+F) and total lAA (F). Values for free plus extractable conjugate were obtained by quantitative analysis of the aqueous acetone extract by GC-SIM-MS [7]. The values for total were obtained by direct tissue hydrolysis using 1 N NaOH at room temperature (wheat caryopsis [6]) or 7 N NaOH at 100°C (bean seed[4]). Hydrolysis of the wheat tissue with 7 N NaOH did not release additional lAA...

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