Identification and Synthesis of a Male-Produced Pheromone for the Neotropical Root Weevil Diaprepes abbreviatus

Abstract

An unsaturated hydroxy-ester pheromone was isolated from the headspace and feces of male Diaprepes abbreviatus, identified, and synthesized. The pheromone, methyl (E)-3-(2-hydroxyethyl)-4-methyl-2-pentenoate, was discovered by gas chromatography-coupled electroantennogram detection (GC-EAD), and identified by gas chromatographymass spectrometry (GC-MS) and nuclear magnetic resonance spectroscopy (NMR). The synthesis yielded an 86:14 mixture of methyl (E)-3-(2-hydroxyethyl)-4-methyl-2-pentenoate (active) and methyl (Z)-3-(2-hydroxyethyl)-4-methyl-2-pentenoate (inactive), along with a lactone breakdown product. The activity of the synthetic E-isomer was confirmed by GC-EAD, GC-MS, NMR, and bioassays. No antennal response was observed to the Z-isomer or the lactone. In a two-choice olfactometer bioassay, female D. abbreviatus moved upwind towards the synthetic pheromone or natural pheromone more often compared with clean air. Males showed no clear preference for the synthetic pheromone. This pheromone, alone or in combination with plant volatiles, may play a role in the location of males by female D. abbreviatus.

Pheromones as management tools for non-Scolytinae Curculionidae: development and implementation considerations

“…Because blends of odorants can be presented simultaneously to antennae, this method has the advantage of facilitating the detection of additive or synergistic interactions among volatiles (Budenberg et al 1993). Gas-chromatography coupled to electroantennographic detection (GC-EAD) can also be used to identify active chromatographic fractions (Struble and Arn 1984) or chromatographic peaks (Perez et al 1994;Lapointe et al 2012) directly from complex mixtures.…”

“…It is possible that a compound is not present in the mass spectral databases. In these cases a large amount [micro-to milligrams] of the purified compound is needed for structural elucidation through nuclear magnetic resonance (NMR) (Booth et al 1983;Eller et al 1994;Eller and Bartelt 1996;Zarbin et al 2010;Lapointe et al 2012;Romero-Frías et al 2016;Reis et al 2018). The fraction inducing electroantennographic or behavioural response must first be identified (Booth et al 1983;Lapointe et al 2012;Romero-Frías et al 2016).…”

“…In these cases a large amount [micro-to milligrams] of the purified compound is needed for structural elucidation through nuclear magnetic resonance (NMR) (Booth et al 1983;Eller et al 1994;Eller and Bartelt 1996;Zarbin et al 2010;Lapointe et al 2012;Romero-Frías et al 2016;Reis et al 2018). The fraction inducing electroantennographic or behavioural response must first be identified (Booth et al 1983;Lapointe et al 2012;Romero-Frías et al 2016). Then, in some cases this fraction is chromatographed again for further purification to ultimately determine which compound(s) are active (Tumlinson et al 1969).…”

“…Techniques like high resolution mass spectrometry can be used to assign an empirical formula to unknown compounds if amounts of purified extract material are not sufficient for NMR analysis (Zarbin et al 2010;Lapointe et al 2012). This requires that the molecular ion is detected with sufficient accuracy to establish the unique combination of elements that make up of the unknown compound (Tumlinson et al 1969;Collins 1996;Zarbin et al 2003).…”

Biology, Chemical Ecology, and Sexual Dimorphism of the Weevil Myllocerus undecimpustulatus undatus (Coleoptera: Curculionidae)

“…Compounds were identified by comparing spectral data with those from commercially available standards and spectra from mass spectrometer libraries, and confirmed by retention times of authentic standards. Identified odorants were used in electroantennogram recordings (n = 6) as described by Lapointe et al (2012). Headspace volatiles of synthetic odorant were puffed into a filtered and humidified airflow upstream to the male and female antenna.…”