Elucidation of dimethylalkylpyrazines from the ant Streblognathus aethiopicus by GC-FTIR

The presumed mandibular gland secretions from the workers and gamergates of two colonies of Streblognathus aethiopicus have been found to contain a homologous series of 3,5-dimethyl-2-alkylpyrazines (3,5-dimethyl-2-butylpyrazine, 1; 3,5-dimethyl-2-pentylpyrazine, 2; and 3,5-dimethyl-2-hexylpyrazine, 3). The structures of these compounds were determined from their mass spectra along with a comparison of their GC-FTIR spectra with those of all the isomers of a lower homolog. This is the first time that this combination of techniques has been applied to the study of insect pyrazines. The relative amounts and proportions of these compounds were different for gamergates and workers, with the latter containing 2–10 times more total pyrazines and having a higher proportion of 2 and 3. The possible significance of this finding is discussed.