METABOLISM OF IRIDALS IN PLANT-CELL CULTURES OF IRIS PALLIDA

The metabolism of iridals, unusual triterpenoids found in sword lilies, was studied in a cell culture of Iris pallida. By incubation of the cells with radioactively labelled and unlabelled compounds the biogenetic pathway from iridal, the parent compound of the family, to the spiroiridals was shown to lead via 26-hydroxyiridal, which is dehydrogenated to form the corresponding 26-hydroxytriene. A dehydration of the 16- or 17-hydroxyiridals, respectively, was not observed. All triterpenoids are readily taken up by the cells from the medium and are esterified at C3, predominantly with medium-chain fatty acids.