Long chain oxoaldehydes and oxoalcohols from esters as major constituents of the surface lipids of Manduca sexta pupae in diapause.

J S Buckner,D R Nelson,H Hakk,J G Pomonis

doi:10.1016/s0021-9258(17)39752-1

Abstract

Lipid constitutents of diapausing pupae of the tobacco hornworm, Manduca sexta (L), were identified by thin layer and gas-liquid chromatography, IR spectroscopy, and gas-liquid chromatography-mass spectrometry. Surface wax was a mixture of long chain polar compounds: oxoalcohol esters, oxoaldehydes, primary alcohol esters, and oxoalcohols, as listed in descending order of abundance. The distribution of the alcohols and aldehydes was C28 (75-85%), C27 (5%), and C26 (10-15%). The C26 compounds were largely 11-oxo isomers, but the C28 compounds consisted of similar amounts of 11- and 12-oxo isomers. The identities of the oxoaldehydes were confirmed by selective and complete NaBH4 reductions to yield oxoalcohols and diols, respectively. Mass spectral interpretations were verified with mass spectra of the oxoaldehyde, oxoalcohol, and diol synthesized from 12-hydroxystearic acid. Reduction of the total lipids with NaBH4 and hydrolysis of the product with ethanolic KOH gave oxoalcohols (85%), primary alcohols (8%), and oxoacids (5%); 30-40% of the oxoalcohols were derived from NaBH4-reduced oxoaldehydes, 5-10% were from free oxoalcohols, and 50% were from esters. Primary alcohols only existed as esters. Large quantities of fatty oxoalcohols relative to fatty oxoacids in the saponified mixture suggested the presence of esters other than those composed of long chain acids and alcohols. Oxoacids appeared to be mainly oxidation products of the oxoaldehydes.

Highlights

Hornworm, Manduca sexta (L),were identified by thin Examples of quantitative differences within the same spelayer andgas-liquid chromatography, IR spectroscopy, cies have been reported for pupae of the Lepidoptera, Manand gas-liquid chromatography-mass spectrometry. duca sextu (L.) and Mamestru configurata Walker
40% of the oxoalcohols were derived from NaBH4- paper, we report on the occurrence, composition and identireduced oxoaldehydes, 5-10% were from free oxoal- fication of novel chemicals as major components of the surface cohols, and 50%were from esters
Large quantitiesof fatty oxoal- constituents of the wax were determined by IR spectroscopy, cohols relative to fatty oxoacids in the saponified mixture suggested the presence of esters other than those composed of long chain acids and alcohols

Summary

AND RESULTS*

Terrestrial organisms are packaged in envelopes which consist of some type of a polymeric structural component and the outer surface is usually covered with a waxy layer consisting of complex mixtures of long chain compounds [1].The waxy layer that covers the surface of insects provides protection against possible adverse effects of the environment such as dessication during timesof lowhumidity, abrasive damage, and penetrationof the cuticle by microorganisms, insecticides, or toxic chemicals [2]. A typical EI-MS spectrum of this fraction showed a small molecular ion at m/z 422 and a significant fragment ion at M - 43 (Fig. 3A). The fragment ion at m/t 379 (M - 43) was characteristic of alkyl chains with a terminal aldehyde functional group [13] The identification of this fraction as oxoaldehydes was supported by its relative position on TLC plates; more polar than ketone or secondary alcohol standards, but less polar than a primary alcohol (Fig. 1, A and B). The GLC-EI-MS tion temperatures indicated an increase in ECofL1.2 carbon mass spectrum for component 1 showed a molecular ion at units for each homolog. The E1 mass spectral fragmentation the 11- and 12-oxo isomers of the Cz8homolog, and solvent pattern of the Me3Si derivatives established that component

I-OXO-HEXACOSANAL

Findings

DISCUSSION