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 biogene
tic pathway from iridal, the parent compound of the family, to the spi
roiridals was shown to lead via 26-hydroxyiridal, which is dehydrogena
ted to form the corresponding 26-hydroxytriene. A dehydration of the 1
6- or 17-hydroxyiridals, respectively, was not observed. All triterpen
oids are readily taken up by the cells from the medium and are esterif
ied at C3, predominantly with medium-chain fatty acids.