Photostability assessment of natural pyrethrins using halloysite nanotube carrier system

Natural pyrethrins are one of the most used pesticides and insect repellents employed for domestic or agronomicuse. However, they are highly hydrophobic and suffer from insolubility in water media and ready decompositionby photochemical, and oxidative actions. These aspects hamper their long-term storage and applicability. Herein,we report the synthesis and characterization of a nanomaterial based on the loading of pyrethrum extract (PE)into natural, low-cost, and eco-compatible halloysite nanotubes (Hal). The Hal/PE nanomaterial was thoroughlycharacterized, and the morphology was imaged by TEM and SEM investigations.Release experiments showed a slow release of pyrethrins from the carrier, and photodegradation studies, bothin solution and in a solid state, highlighted that the pyrethrum extract in the Hal/PE nanomaterial showed highstability to UV irradiation, as proved by UPLC-ESI-MS, UV–vis, and circular dichroism measurements.Furthermore, to check if the obtained nanomaterial possesses the insecticidal activity of the pyrethrum, in vivotests on two model insects, Galleria. mellonella and Tenebrio molitor, were performed. The pyrethrins loaded ontoHal showed the same activity as standard pyrethrins, at half dose compared to them.