The flavouring agent, 2-octenoic acid kills Galleria mellonella (Lepidoptera: Pyralidae) by affecting their immunocompetent cells and cuticular FFA profiles

Abstract

This study investigates the effects of the naturally occurring flavouring agent, trans-2-octenoic acid, on the insect model Galleria mellonella by examining its impact on immunocompetent cells and free fatty acid (FFA) profiles in the cuticle. The value of LD50 for 2-octenoic acid has been calculated as 9.66 µg/mg of insect body mass, this value is outside the GHS scale, indicating that the compound is unlikely to cause acute toxicity after dermal application and is safe for humans and mammals. The treatment with 2-octenoic acid caused several changes in the insect defence mechanismes, viz. changes in cuticular FFA profiles and death of immunocompetent cells. In larvae, topical treatment of 2-octenoic acid increased the concentration of cuticular FFAs, particularly C6:0 (245 times higher), C15:0 (110 times higher), and C16:1 (1608 times higher), and 2-octenoic acid (C8:1) accumulated significantly on the surface of the cuticle. In adults, treatment resulted in lower cuticular C8:1concentrations than in larvae, which might indicate that 2-octenoic acid penetrates more effectively through the adult cuticle. The 2-octenoic acid application demonstrated considerable cytotoxicity against insect cell line Sf9 and G. mellonella hemocytes, with both in vivo and in vitro treatment. Our findings contribute to the broader understanding of how synthetic and naturally occurring chemicals may interact with the immune and physiological systems of insects, particularly focusing on G. mellonella as a model organism for toxicological studies. Given the increasing interest in the ecological and physiological impacts of food additives, our research provides novel insights into the biological interactions of 2-octenoic acid and its potential role as an insecticide.