A comprehensive breakthrough for the industrial exploitation of Acmella oleracea (L.) R.K. Jansen and Carlina acaulis L. as novel insecticidal agents

The extensive use of insecticidal products has provoked several issues in the last decades. Although agrochemical industries are increasingly shifting towards the replacement of synthetic insecticides with plant-based products, only a limited number of them has successfully reached the marketplace. Acmella oleracea (L.) R.K. Jansen and Carlina acaulis L. are two species of the Asteraceae family containing spilanthol (N-alkylamide) and carlina oxide (polyacetylene) as the main active constituents, respectively. These compounds are primarily responsible for the insecticidal properties recently found for these plants. Given the promising potential of A. oleracea, an attempt was made to cultivate the plant through a sustainable technique, namely aquaponics, which turned out to be suitable for plant cropping. Subsequently, different solvents and extraction techniques were screened to find the most efficient for spilanthol extraction. While n-hexane yielded the extract with the highest concentration of the compound, methanol resulted in the highest overall recovery. The extracts prepared with the two solvents demonstrated strong insecticidal activity against a wide range of stored-product and agricultural pests. Notably, the n-hexane extract also proved its effectiveness at sublethal doses. In order to find an eco-friendly and industrially scalable process, supercritical CO2 extraction was combined with wiped film short-path molecular distillation, and a N-alkylamide- enriched fraction (AEF) was produced. If compared with spilanthol, the latter showed comparable insecticidal effects against mosquitoes and lower toxicity against human keratinocytes cell line (HaCaT). Regarding C. acaulis, the most interesting product is the essential oil (EO), containing more than 90% of carlina oxide. A one-step design of experiment (DoE) was employed to optimize the microwave assisted extraction (MAE) of the EO. This technique resulted to be more performant if compared with the traditional hydrodistillation (HD). Then, the EO was tested for the first time against stored-product pests, demonstrating strong insecticidal efficacy. Moreover, it proved to have lethal and sublethal effects against mites and aphids and no toxicity against non-target species. Being worthy of further investigation, AEF, spilanthol, and C. acaulis EO were formulated in Tween 80 at 200 g/L and their insecticidal efficacy was assessed through field trials. The results highlighted the strong insecticidal potential of all prototypes in real world conditions. Moreover, notwithstanding the low stability of these products, different antioxidant compounds were encountered to prolong their shelf-life. Overall, the results of this thesis fill some of the major gaps related to the effective manufacturing of botanical products at industrial level and lays the foundation for their commercialization. However, further studies will be needed to fill all regulatory requirements for market approval.