Biosynthesis of sex pheromone components from linolenic acid in arctiid moths

Sex pheromone components of two species of arctiid moths, Estigmene acrea and Phragmatobia fuliginosa, were shown to be derived from linolenic acid. Female pupae were injected with radiolabeled malonic acid or an 18‐, 20‐, 21‐, or 22‐carbon triunsaturated fatty acid, and the pheromone components from emerged adults analyzed for radioactivity. The data support a biosynthetic pathway in which the 21‐carbon pheromone component,(Z, Z)‐3,6‐cis‐9,10‐epoxyheneicosadiene, of these moths is produced by chain elongation of linolenic acid to docosatrienoic acid with subsequent reductive decarboxylation. The 18‐carbon aldehyde components,(Z, Z)‐9,12‐octadecadienal and (Z, Z, Z)‐9,12,15‐octadecatrienal, of E. acrea are produced from linoeic and linolenic acids directly. No detectable amounts of intermediate 20‐, 21‐, or 22‐carbon fatty acid precursors were found in the gland of E. acrea.