Nanoformulations from olive pomace to enhance the efficacy of hydroxytyrosol as a natural pest control agent

Abstract

Bioactive principles administered in the form of finely dispersed particles are a major innovation in plant protection. At present, the most promising formulations are those in which natural functional compounds are transported by vectors obtained from agrifood by-products, in that these systems are able to maximize both efficacy and biocompatibility. Here we present new nanovectors obtained by combining olive pomace (OP) and egg yolk phosphatidylcholine (EPC) to deliver hydroxytyrosol (HT) as a pest control agent. In this way, a valuable antioxidant found in agricultural waste can be reused to develop biopesticides according to the concept of circular economy. Specifically, nanocarriers obtained by natural lipid mixtures were loaded with HT and dispersed in water. The stable and reproducible character of these formulations was assessed by in-depth physicochemical characterization. For this purpose, empty and HT-loaded nanosystems were investigated by dynamic light scattering, zeta potential, and small-angle X-ray scattering. Combining these tools allowed reaching a comprehensive picture of the obtained particles in terms of size and structure at the submicron scale. The concentration of HT used was 2.5–5 mg mL⁻¹, a range of values which are not attainable in the absence of encapsulating objects. The newly prepared biopesticides were subsequently tested against the Mediterranean fruit fly Ceratitis capitata (Wiedemann, 1824), belonging to Diptera, Tephritidae, and Sitophilus oryzae (Linnaeus, 1763), belonging to Coleoptera, Curculionidae. Multifactorial analysis was used to examine the relationships among different groups of variables, such as number of insect eggs and number of egg clusters. This in-depth data treatment showed increased repellency and limited oviposition in samples protected by formulations, thus opening new perspectives for applications in sustainable agriculture.