Publikationen - Molekulare Signalverarbeitung

Racemic jasmonic acid (3R,7R/3S,7S)-(±)-JA) was chemically conjugated with different biogenic amines originating from aliphatic and aromatic α-amino acids by decarboxylation. The resulting isomeric compounds were subjected to reversed-phase high-performance liquid chromatography (HPLC) and to HPLC on the chiral stationary phases Chiralpak AS and Nucleodex β-PM. Under reversed-phase conditions, all the homologous amine derivatives tested could be separated from each other except the JA-conjugates containing 2-phenyl-ethylamine and 3-methylbutylamine. On both chiral supports the (3R,7R)-(−)-JA conjugates eluted earlier than those of the enantiomeric counterpart (3S,7S)-(+)-JA. On Chiralpak AS all the isomers studied could be separated to baseline with a mobile phase containingn-hexane and 2-propanol. The calculated resolution factors were between 1.80 and 4.17. The pairs of isomers were also chromatographed on the cyclodextrin stationary phase Nucleodex β-PM with methanol-triethylammonium acetate buffer as mobile phase. Under these conditions resolution factors were between 0.74 and 1.29. The individual isomers were chiroptically characterized by measurement of their circular dichroism.

The effect of osmotically active substances on the alteration of endogenous jasmonates was studied in barley (Hordeum vulgare L. cv. Salome) leaf tissue. Leaf segments were subjected to solutions of d-sorbitol, d-mannitol, polyethylene glycol 6000, sodium chloride, or water as a control. Alterations of endogenous jasmonates were monitored qualitatively and quantitatively using immunoassays. The structures of jasmonates isolated were determined on the basis of authentic substances by capillary gas chromatography-mass spectrometry. The stereochemistry of the conjugates was confirmed by high performance liquid chromatography with diastereoisomeric references. In barley leaves, jasmonic acid and its amino acid conjugates, for example, with valine, leucine, and isoleucine, are naturally occurring jasmonates. In untreated leaf segments, only low levels of these native jasmonates were found. After treatment of the leaf tissues with sorbitol, mannitol, as well as with polyethylene glycol, an increase of both jasmonic acid and its conjugates could be observed, depending on the stress conditions used. In contrast, salt stress was without any stimulating effect on the levels of endogenous jasmonates. From barley leaf segments exposed to sorbitol (1m) for 24 h, jasmonic acid was identified as the major accumulating compound. Jasmonic acid-amino acid conjugates increased likewise upon stress treatment.