Abscisic acid detection

Some phenolic acids such as ellagic acid can be used as floral markers of heather honey (Cherchi et al., 1994 Ferreres et al., 1996a,b), and the hydroxyciimamates (caffeic, p-coumaric, and ferulic acids) as floral markers of chestnut honey (Cherchi et al., 1994). Pinocembrin, pinobanksin, and chrysin are the characteristic flavonoids of propolis, and these flavo-noid compounds have been found in most European honey samples (Tomas-Barberan et al., 2001). However, for lavender and acacia honeys, no specific phenolic compoimds could be used as suitable floral markers (Tomas-Barberan et al., 2001). Other potential phytochemical markers like abscisic acid may become floral markers in heather honey (Cherchi et al., 1994). Abscisic acid was also detected in rapeseed, lime, and acacia honey samples (Tomas-Barberan et al., 2001). Snow and Manley-Harris (2004) studied antimicrobial activity of phenolics. 

Plant products have also been detected in non-plant organisms. Morphine 1, the archetypal plant alkaloid, has in fact been shown to be a physiological plasma constituent and its production in mammals could be traced to the liver expression of the critical enzymes of its biosynthesis.17 In addition, the plant hormone abscisic acid 12 has been detected as an endogenous constituent of human brain,18 while caffeine 13 was isolated from a marine gorgonian (Paramuricea chamaelon)19 and the atisane diterpenoid serofendic acid 14, an inhibitor of the oxidant-induced mitochondrial death pathway and putative activator of mitoK(ATP) channels, has been characterised from foetal calf serum.20... 

In the rice test with both cultivars, a linear correlation was obtained between 5 x 10-3 and 5 x 10 5 ig/ml for BL and CS. The induced angles leveled off at higher concentrations. Indole-3-acetic acid (IAA) was tested and was found to produce only a weak effect, five orders of magnitude less than BL. Cytokinins were inactive and actually counteracted the effect of BL. Abscisic acid (ABA) also counteracted the effect of BL. This assay is thus highly specific for BRs and is also the most sensitive, concentrations as low as 0.05 ng/ml of BL being readily detected. 

Mass spectrometry is the most recently introduced technique to be widely applied to carotenoid structural studies. Many spectra are recorded by Enzell et Recent advances include the recognition that a loss of 106 and 92 m.u. (rationalised as xylene and toluene) is characteristic of the polyene chain. The remaining fragments on either side of the polyene may be recognised by bisallylic fission. Ketonic carotenoids show characteristic fragmentation. MacMillan and Gaskin were able to detect 0.3 pg of abscisic acid or phaseic acid using... 

The final fate of C-20, which is lost during the biosynthesis of the C19 gibberellin lactones, is as carbon dioxide. Gibberellin A13 aldehyde may be an intermediate in gibberellin biosynthesis prior to this step. The conversion of gibberellin A9 into gibberellin A20 in excised lettuce hypocotyls has been observed. " Gibberellins Ag, Aie, and A24 and abscisic acid have been detected by g.c.-m.s. in rye. 

Abscisic acid (ABA) 3-1 was originally detected because of its growth inhibitory properties. It is now known to play an important role in the control of a-amylase synthesis, and regulation of stomatal aperture during water stress. Phaseic acid (PA) 3-3 is an important metabolite of ABA. Over a hundred derivatives of ABA are known, activity correlations have been reviewed, and the difficulty of drawing firm conclusions due to differences in uptake, metabolism and sequestration between the different molecules assayed has been discussed [16-20]. In many correlations, racemates have been used, and it is possible that each enantiomer may be active, have a different type of activity, and/or interfere with the action of the other enantiomer. 

Two compounds common in plant metabolism are believed to be precursors of isoprenoid cytokinins in plants adenosine-5 -monophosphate (AMP) and A -isopentenylpyrophos-phate (iPP). As a final product of the mevalonate pathway, the latter substance serves also as a precursor for a wide spectrum of metabolites including some other plant hormones, as abscisic acid, gibberellins and brassinosteroids. The hypothetical scheme of reactions resulting in the formation of iPA, Z and DHZ is given in Fig. 2. The enzyme of entry into isoprenoid cytokinin formation is A -isopentenylpyrophosphate 5 -AMP-A -iso-pentenyltransferase (EC 2.5.1.8, trivially named cytokinin synthetase ). This enzyme activity was first detected in a cell-free preparation from the slime mould Dictyostelium discoideum [7,8]. Later the enzyme from higher plants (cytokinin-independent tobacco callus [9,10] and immature Zea mays kernels [11]) was described and the data were recently summarised in [12], The enzyme is very specific as far as the substrate is concerned [13,14] only the nucleotide AMP can be converted and only iPP (with a double bond in A position) may function as a side chain donor. 

The plant hormone abscisic acid (110) may be a degraded carotenoid or a sesquiterpenoid. Studies using [2/ - H,2- C,3/ ]-, [2S- H,2- C,3R]-, and [2- C,3I. 5S- H]-mevalonic acid show that either route is possible." Xanthoxin (111) may be involved also, it being formed in turn from violaxanthin (108). Two new metabolites of abscisic acid have been detected. 

C 5H2203, Mr 250.34, cryst., mp. 85 - 86 °C, [alp - 56° (CHCI3), a cyclofamesane sesquiterpene formed by photochemical oxidation of violaxanthin. It has been detected in several marine and higher plants. Naturally occurring X. exists as a mixture of -isomers of the 2,3-double bond of the 2,4-pentadienal side chain. It is an inhibitor of plant growth and is involved in the winter rest phase of plants (senescence), in some cases it is also involved in the damage to trees X. is closely related structurally and in its biological activity to abscisic acid and presumably functions as an intermediate in the biosynthesis of it. 

Effects on Abscisic Acid and Cytokinins. Lepage-Digivry (1973) reported an increase in bound ABA at the expense of free ABA in seeds of Taxus baccata during stratification. Enu-Kwesi and Dumbroff (1977) also reported a cold-induced reduction in detectable ABA in Acer fruits but, in most cases, changes in ABA levels have not shown a close correlation with thermodormancy (Berrie and Robertson 1976). 

Lenton JR, Bowen MR, Saunders PF (1968) Detection of abscisic acid in the xylem sap of willow by gas chromatography. Nature 220 86-87 Leopold AC (1961) The transport of auxin. In Ruhland W (ed) Encyclopedia of plant physiology Vol 14. Springer, Berlin Gottingen Heidelberg, pp 671-682 Leopold AC (1963) The polarity of auxin transport. Brookhaven Symp Biol 16 218-234 Leopold AC, de la Fuente RK (1967) The polarity of auxin transport. Ann NY Acad Sci144 94 101... 

Mention should be made of abscisic acid and related compounds. Abscisic acid (373) was first isolated from young cotton fruit as an abscission-accelerating principle. It has since been found to be ubiquitous in higher plants and has been detected in the roots of several plants. It is now recognized as a natural plant growth regulatory hormone. Although structure 373 is clearly that of a monocyclofarnesane and could arise from cyclization of FPP and further modification, there is some evidence that it may be a catabolic product of a carotenoid, such as violaxanthin. Considerable biosynthetic work has been carried out, but no clear-cut answer is available yet (110, 179, 276). 

Abscisic acid is a terpenoid (Fig. 171). Abscisic acid is the name recently proposed. In addition, the older names dormin and abscisin II are still in use. Dormin refers to the fact that abscisic acid brings about the dormancy of buds and abscisin to the fact that abscisic acid can promote the shedding of leaves and fruit. Abscisic acid seems to be ubiquitous in the plant kingdom. Chemically closely related substances exhibiting, to some extent, a similar effect have also been detected repeatedly. 

Only a few sesquiterpenoids have been encountered in studies of lichens (3-caryophyllene, a-copaene, (3-elemene, farnesane, p-gurjunene, longifolene, a-muurolene, P-selinene, and thujopsene from Evernia prunastri 319) and fukinanolide A (bakkanolide A) from Cetraria islandica ((555). Abscisic acid (ABA) was detected in all 26 lichen species investigated (175). 

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