Essential Oils

Six plant species metabolized (18)O-labeled 12-oxo-cis,cis-10,15-phytodienoic acid (12-oxo-PDA) to short chain cyclic fatty acids. The plant species were corn (Zea mays L.), eggplant (Solanum melongena L.), flax (Linum usitatissimum L.), oat (Avena sativa L.), sunflower (Helianthus annuus L.), and wheat (Triticum aestivum L.). Among the products was jasmonic acid, a natural plant constituent with growth-regulating properties. The pathway is the same as the one recently reported by us for jasmonic acid synthesis in Vicia faba L. pericarp. First, the ring double bond of 12-oxo-PDA is saturated; then beta-oxidation enzymes remove six carbons from the carboxyl side chain of the ring. Substrate specificity studies indicated that neither the stereochemistry of the side chain at carbon 13 of 12-oxo-PDA nor the presence of the double bond at carbon 15 was crucial for either enzyme step. The presence of enzymes which convert 12-oxo-PDA to jasmonic acid in several plant species indicates that this may be a general metabolic pathway in plants. Show more

(-)-Jasmonic acid was identified as a plant growth inhibitor of the pericarp of Vicia faba by means of gas-liquid chromatography, high resolution mass spectrometry, (1)H-nuclear magnetic resonance ((1)H-NMR), and (13)C-NMR. Additionally, the pericarp contains very small amounts of abscisic acid (ABA) and 4'-dihydrophaseic acid. The highest level of jasmonic acid was reached prior to full pericarp length. This amount (3 μg g(-1) fresh weight) is similar to the maximal ABA content in the developing seed. Jasmonic acid is a plant growth inhibitor possessing a relative activity in the wheat seedling bioassay of 1-2.5%, compared to ABA. Contrary to ABA, jasmonic acid does not cause retardation of leaf emergence. The possible physiological role of jasmonic acid in the pericarp is discussed and compared with the assumed function of ABA in developing seeds. Show more