Very Long-Chain Methyl-Branched Alcohols and Their Acetate Esters in the Internal Lipids of Lepidopteran Pupae: Cochylis hospes, Diatraea grandiosella, Homoeosoma electellum, Heliothis virescens and Helicoverpa zea

Abstract

Very long-chain methyl-branched alcohols (VLMA; C35 > C46) and their acetate esters were characterized in the internal lipids of developing mid-stage pupae of the banded sunflower moth Cochylis hospes, the southwestern corn borer Diatraea grandiosella, the sunflower moth Homoeosoma electellum, the tobacco budworm Heliothis virescens and the corn earworm Helicoverpa zea. Minor amounts of long-chain methyl-branched alcohols (LMA; C25–C34) were also found largely in H. virescens and H. zea. Five homologous series of primary alcohols were identified in all species: n-alcohols, internally branched monomethyl alcohols, 2 series of dimethyl branched alcohols, and a series of trimethyl branched alcohols. The 4 methyl-branched series were characterized, e.g., by one of their major components: 24-methyltetracontanol, 24,28-dimethyltetracontanol, 24,36-dimethyltetracontanol, and 24,28,36-trimethyltetracontanol. A fifth methyl-branched series was identified only in H. electellum, the internally branched trimethyl alcohols characterized by 22,26,30-trimethyltetracontanol. The incorporation of [3H]acetate and [1-14C]propionate into the internal lipids of mid-stage pupae (developing pharate adults) of H. electellum and H. virescens, showed that polar lipids, and VLMA and their acetate esters, were the major lipid classes synthesized from acetate. The major lipid classes synthesized from propionate, the precursor of the methyl branches, were the methyl-branched lipids, e.g., VLMA and their acetate esters and hydrocarbons. Aldehydes also were a component in H. virescens but did not incorporate radioactivity. The wax ester fraction of H. virescens incorporated radioactivity which was limited to the fatty acid moieties.