Dispensing Essential Oil Components through Cocrystallization: Sustainable and Smart Materials for Food Preservation and Agricultural Applications

Abstract

The ever-increasing attention on environmental problems and sustainability has highlighted several problems related to the use of conventional pesticides in the agricultural industry, e.g., toxic residues in the soil and hazards to the environment and human health. In the search for natural antimicrobial and insecticide alternatives, essential oils (EOs) and their active components have emerged as promising candidates, but they suffer from some drawbacks related to their physical properties. We exploited cocrystallization with isonicotinamide, pyrazine, 2,3,5,6-tetramethylpyrazine, and 2,3-dimethylquinoxaline as a workaround to extend the applicability of carvacrol and thymol as natural pesticides, improving their ambient delivery profile. The cocrystals were prepared mechanochemically in a green solvent-free manner, and their purity, structure, and stability were investigated via powder and single-crystal X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and density functional theory (DFT) calculations. Moreover, each cocrystal was also tested in terms of EO release by headspace–gas chromatography–mass spectrometry (GC–MS) analysis over 14 days. We also report the conversion of a cocrystal to a new structure with different stoichiometry, which seems to afford a delayed boost of EO release that could be very interesting for food preservation applications.