Chemistry of venom alkaloids in some Solenopsis (Diplorhoptrum) species from Puerto Rico

A number of 15-carbon alkaloids have been identified in venom extracts of four Puerto Rican species of ants in the genus Solenopsis (Diplorhoptrum). Workers of a species from El Verde produced the cis and trans isomers of 2-methyl-6-nonylpiperidine with the latter isomer predominating. The same compounds were identified in queens of a species from Rio Grande, but in this species no alkaloids were detected in worker extracts. Workers of a Diplorhoptrum species collected on Mona Island produced primarily a trans-2-methyl-6-(Z-4-nonenyl)piperidine, 3, with smaller amounts of the cis isomer, whereas the major compound found in the queens of the same species on Mona Island was (5Z,9Z)-3-hexyl-5-methylindolizidine, identical with the alkaloid produced by queens of a species collected on Cabo Rojo. Surprisingly, workers of the Cabo Rojo species produced (5Z,9Z)-and (5E,9E)-3-butyl-5-propylindolizidine (4 and 5, respectively) reported earlier as the 223AB indolizidines from skins of dendrobatid frogs. The possible significance of the qualitative and quantitative differences in the venom alkaloids synthesized by queens and workers is discussed as is the possibility that ants containing such alkaloids may serve as a dietary source for the skin alkaloids used by certain frogs in chemical defense