Biological activity and biosynthesis of pentacyclic oxylipins: The linoleic acid pathway

The relevance of the postulated pathway from linoleic acid to dihydrojasmonic acid is analysed. Pentacyclic oxylipins having pentenyl or pentyl side chains were tested for their secondary metabolite inducing activity in seven different plant cell culture species which all responded well to 12-oxo-phytodienoic acid and jasmonic acid. The response towards the dihydro-derivatives 15,16-dihydro-12-oxo-phytodienoic acid and 9,10-dihydrojasmonic acid ranged from strong activity in Eschscholzia californica to no activity in Lycopersicon esculentum. 15,16-Dihydro-12-oxo-phytodienoic acid can be formed from linoleic acid (18:2) by a linseed acetone powder enzyme preparation. Application experiments with linoleic (18:2) and linolenic acid (18:3) showed that the bottleneck of the 18:2 pathway is most likely the cyclization of the intermediate allene oxide when compared to the ease by which 15,16-dihydro-12-oxo-phytodienoic acid is converted to dihydrojasmonic acid in plant systems. The metabolism of potential precursors of jasmonic and dihydrojasmonic acid was extensively studied in various cell cultures.