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Coronalon, a synthetic 6-ethyl indanoyl isoleucine conjugate, has been designed as a highly active mimic of octadecanoid phytohormones that are involved in insect and disease resistance. The spectrum of biological activities that is a¡ected by coronalon was investigated in nine di¡erent plant systems speci¢cally responding to jasmonates and/or 12-oxo-phytodienoic acid. In all bioassays analyzed, coronalon demonstrated a general strong activity at low micromolar concentrations. The results obtained showed the induction of (i) defense-related secondary metabolite accumulation in both cell cultures and plant tissues, (ii) speci¢c abiotic and biotic stress-related gene expression, and (iii) root growth retardation. The general activity of coronalon in the induction of plant stress responses together with its simple and e⁄cient synthesis suggests that this compound might serve as a valuable tool in the examination of various aspects in plant stress physiology. Moreover, coronalon might become employed in agriculture to elicit plant resistance against various aggressors.

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Two new amide-linked conjugates of jasmonic acid, N-[(3R,7R)-(-)-jasmonoyl]-(S)-dopa (3) and N-[(3R,7R)-(-)-jasmonoyl]-dopamine (5), were isolated in addition to the known compound N-[(3R,7R)-(-)-jasmonoyl]-(S)-tyrosine (2) from the methanolic extract of flowers of broad bean (Vicia faba). Their structures were proposed on the basis of spectroscopic data (LC-MS/MS) and chromatographic properties on reversed and chiral phases and confirmed by partial syntheses. Furthermore, tyrosine conjugates of two cucurbic acid isomers (7, 8) were detected and characterized by LC-MS. Crude enzyme preparations from flowers of V. faba hydroxylated both (+/-)-2 and N-[(3R,7R/3S,7S)-(-)-jasmonoyl]tyramine [(+/-)-4] to (+/-)-3 and (+/-)-5, respectively, suggesting a possible biosynthetic relationship. In addition, a commercial tyrosinase (mushroom) and a tyrosinase-containing extract from hairy roots of red beet exhibited the same catalytic properties, but with different substrate specificities. The conjugates (+/-)-2, (+/-)-3, (+/-)-4, and (+/-)-5 exhibited in a bioassay low activity to elicit alkaloid formation in comparison to free (+/-)-jasmonic acid [(+/-)-1].