Alkaloid chemistry of the venom of Solenopsis fire ants

Dialkylpiperidines are characteristic of fire ants in the genus Solenopsis (Hymenoptera: Formicidae). Workers of the black imported fire ant, S. richteri Forel, the red imported fire ant, S. invicta Buren, and their hybrid S. richteri x S. invicta, produce cis and trans stereoisomers of 2,6-dialkylpiperidines with the trans isomer predominating. cis Stereoisomers of alkaloids in the venom of worker ants were separated from trans stereoisomers by using silica gel short column chromatography and identified by coupled gas chromatography mass spectrometry (GC–MS). GC profiles verified the presence of both cis and trans stereoisomers in imported fire ants. Seven pairs of known cis and trans stereoisomers were identified based on relative retention times and mass spectral data. In addition to the previously described components of Solenopsis venom, eleven novel 2,6-dialkyl-∆^1,2-piperideines and 2,6-dialkyl-∆^1,6-piperideines were detected. The chemical identities of these minor components were determined by comparing with fragmentations of known compounds. Possible biosynthetic pathways for the production of cis and trans solenopsins by Solenopsis fire ants and the evolutionary significance of these piperideines in Solenopsis fire ants are discussed. Alate queens show significantly different alkaloid chemistry from workers. And the alkaloids chemistry of alate queens from above three types of fire ants is very similar with the cis 2,6-dialkylpiperidines predominating. The similarity in alkaloid chemistry of alate queens may provide partial support that hybridization can easily occur among the three types of fire ant in USA.