Volatiles from the Mandibular Gland Reservoir Content of Colobopsis explodens Laciny and Zettel, 2018, Worker Ants (Hymenoptera: Formicidae).

Michaela Hoenigsberger,Alexey Kopchinskiy,Alexandra Parich,Rainer Schuhmacher,Linda Lim,Christoph Bueschl,Kamariah Salim,Herbert Zettel,Alice Laciny,Irina Druzhinina

doi:10.3390/molecules24193468

Abstract

Forty-five volatile organic compounds (VOCs) were identified or annotated in the mandibular gland reservoir content (MGRC) of the Southeast Asian ant Colobopsis explodens Laciny and Zettel, 2018 (Hymenoptera: Formicidae), using headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS) and liquid extraction combined with GC-MS. In extension of previous reports on VOCs of C. explodens, members of different compound classes, such as alkanes, aliphatic and aromatic carboxylic acids, and phenolics, were detected. The ketone 2-heptanone and the biochemically related phenolics benzene-1,3,5-triol (phloroglucinol, PG), 1-(2,4,6-trihydroxyphenyl)ethanone (monoacetylphloroglucinol, MAPG), 5,7-dihydroxy-2-methylchromen-4-one (noreugenin), and 1-(3-Acetyl-2,4,6-trihydroxyphenyl)ethanone (2,4-diacetylphloroglucinol, DAPG) dominated the GC-MS chromatograms. The identities of the main phenolics MAPG and noreugenin were further verified by liquid chromatography-high resolution-tandem mass spectrometry (LC-HRMS/MS). A comparative study of MGRC samples originating from three distinct field expeditions revealed differences in the VOC profiles, but the presence and relative abundances of the dominating constituents were largely consistent in all samples. Our study considerably extends the knowledge about the number and type of VOCs occurring in the MGRC of C. explodens. Based on the type of the detected compounds, we propose that the likely irritant and antibiotic phenolic constituents play a role in defense against arthropod opponents or in protection against microbial pathogens.

Highlights

According to the World Health Organization (WHO), volatile organic compounds (VOCs) are small molecules with high vapor pressure at room-temperature and boiling points between 50 and approximately 260 ◦ C at atmospheric pressure [1]
Our study demonstrates that C. explodens accumulates a remarkable number of phenolic compounds in its mandibular gland reservoirs (MGRs) which may be of relevance for the defense against other insects or for protection against microbial pathogens
headspace solid-phase microextraction (HS-SPME)-gas chromatography-mass spectrometry (GC-MS) and liquid-injection GC-MS measurements of mandibular gland reservoir content (MGRC) samples originating from a total of 380 C. explodens minor worker ants (Table S1) resulted in the detection of 151 and compounds, respectively, with an overlap between the two methods of 102 VOCs

Summary

Introduction

According to the World Health Organization (WHO), volatile organic compounds (VOCs) are small molecules with high vapor pressure at room-temperature and boiling points between 50 and approximately 260 ◦ C at atmospheric pressure [1]. VOCs present in secretions of insects have diverse roles, especially as pheromones and defense compounds [12,13,14]. Many alarm- and defense-related VOCs are known and have been found in diverse ant species [14,18,19,20,21]. For the vast majority of VOCs, their function(s) has (have) not been elucidated so far [22]. This holds true for the compounds found in the special defensive secretion of Colobopsis explodens Laciny and Zettel, 2018, investigated in this study

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