Illicium verum essential oil versus (R)-(+)-limonene. A comparative study of antimicrobial and insecticidal properties

This study presents a parallel comparative assessment of Illicium verum essential oil (IVEO) and the pure monoterpene (R)-(+)-limonene across multiple biological models relevant to food protection and pest control. GC-MS analysis showed that the essential oil was dominated by anethole (86.9 %), with limonene (5.2 %) and minor amounts of mono- and sesquiterpenes. In vitro antimicrobial activity was assessed by agar disc diffusion and broth microdilution against Gramnegative (Escherichia coli, Salmonella enterica, Yersinia enterocolitica), Gram-positive (Enterococcus faecalis, Listeria monocytogenes, Staphylococcus aureus) bacteria and Candida spp. IVEO and 6.418 mg/mL for limonene. Vapor phase antimicrobial activity (concentration 62.5-500 μL/L) was evaluated on strawberry, apple, beetroot and potato models. At 500 μL/L, IVEO inhibited bacterial growth on strawberry and apple by approximately 90-97 %, while inhibition on beetroot and potato was in the range of 80-90 %. In contrast, (R)-(+)-limonene achieved only 50-55 % inhibition on strawberry and apple and approximately 30-50 % on beetroot and potato at the same concentration. MALDI-TOF MS profiles revealed more pronounced treatment-dependent spectral changes in biofilms exposed to IVEO than to (R)-(+)-limonene on both plastic and stainless-steel surfaces. Insecticidal assays demonstrated that IVEO caused 98.67 % mortality of Callosobruchus maculatus and Megabruchidius dorsalis at 100 μL/L, whereas (R)-(+)-limonene reached 87.33 % and 87.67 %, respectively. At 25 μL/L, mortality remained 61.67 % and 58.67 % for IVEO but decreased to 45.67 % and 37.67 % for (R)-(+)-limonene. These results demonstrate consistently higher biological activity of the complete essential oil compared to the isolated monoterpene across all experimental models, providing comparative baseline data for application-oriented research in natural food protection and pest management.