Abstract:  【Aim】 The red imported fire ant, Solenopsis invicta, inhabits the soil environment rich in bacteria and fungi. Although they are vulnerable to infection of bacterial and fungal diseases, fire ants with defensive and antibacterial venom alkaloids can survive in such soil environment. This study aims to establish an optimal extraction method of alkaloids from the soil of the red imported fire ant nest and then to quantify the major components of venom alkaloids. 【Methods】 In the recovery experiment, S. invicta venom was added to soil obtained 3 m away from S. invicta nests. Venom alkaloids were then extracted from soil using a filtration method. GC-FID was used for quantitative analysis of venom alkaloids, screening of the optimal extraction solvent, and determination of the optimal volume of triethylamine. The optimized method was used for quantitative analysis of venom alkaloids from the soil of ant nest. 【Results】 Among the five extraction solvents including n-hexane, dichloromethane, ethyl acetate, acetone and methanol, the recovery rate of alkaloids by n-hexane extraction was relatively higher. The best extraction efficiency was achieved by adding 1 mL or more triethylamine. Among the venom alkaloids in the soil of S. invicta nest, the content of trans-C15∶1 was the highest, followed by that 
of trans-C13∶1. The content of total alkaloids in S. invicta nest soil was about 22 μg/g. 【Conclusion】 Triethylamine is very effective for extracting venom alkaloids from the soil of ant nests. The concentration of alkaloids in the soil of S. invicta nest is relatively high, which may have an important impact on the microbial community in the nest environment.

Key words: Solenopsis invicta, venom, nest soil, alkaloids, filtration method, recovery