Non-indolyl cruciferous phytoalexins: Nasturlexins and tridentatols, a striking convergent evolution of defenses in terrestrial plants and marine animals?

Nasturlexins A and B and tridentatol C are the phenyl containing cruciferous phytoalexins; tridentatol C is also produced by a marine animal, where it functions as a chemical defense against predators. •Elicited metabolites from the crucifer Nasturtium officinale are investigated.•The first isolation of cruciferous phytoalexins not derived from tryptophan is reported.•Previously one of these phytoalexins was only found in a marine animal (Tridentata marginata).•The antifungal activity of the phytoalexins nasturlexins A and B and tridentatol C against pathogens of crucifers is evaluated. Highly specialized chemical defense pathways are a particularly noteworthy metabolic characteristic of sessile organisms, whether terrestrial or marine, providing protection against pests and diseases. For this reason, knowledge of the metabolites involved in these processes is crucial to producing ecologically fit crops. Toward this end, the elicited chemical defenses of the crucifer watercress (Nasturtium officinale R. Br.), i.e. phytoalexins, were investigated and are reported. Almost three decades after publication of cruciferous phytoalexins derived from (S)-Trp, phytoalexins derived from other aromatic amino acids were isolated; their chemical structures were determined by analyses of their spectroscopic data and confirmed by synthesis. Nasturlexin A, nasturlexin B, and tridentatol C are hitherto unknown phenyl containing cruciferous phytoalexins produced by watercress under abiotic stress; tridentatol C is also produced by a marine animal (Tridentata marginata), where it functions in chemical defense against predators. The biosynthesis of these metabolites in both a terrestrial plant and a marine animal suggests a convergent evolution of unique metabolic pathways recruited for defense.