Ionic Liquids Derived from Vitamin C as Multifunctional Active Ingredients for Sustainable Stored-Product Management

摘要

This study is focused on the utilization of naturally occurring ascorbic acid (vitamin C) in the synthesis of biologically inspired ionic liquids with attractive application potential. The ionic liquids with the ascorbate anion were obtained in high yield (90%) via a simple, "green" two-step procedure using well-known, cost-effective, and commercially available alkyltrimethylammonium, dialkyldimethylammonium, and alkylmethylbis(2-hydroxyethyl)ammonium cations. Three positive ions in this group used for syntheses are derived from renewable resources, such as vegetable oil or animal fat. The study confirmed the strong influence of the chemical structure of the cation on the stability of the compounds obtained in the air, as well as in aqueous solutions. In addition, the synthesized ionic forms of vitamin C exhibited very good antibacterial and antifungal properties against different microorganisms, including pathogens. The tests also revealed the excellent or good deterrent activity toward common stored-grain insects (granary weevil, confused flour beetle, and khapra beetle), reaching the values determined for azadirachtin, known as the reference antifeedant. The best results were achieved with products containing two long alkyl substituents in the cation (dimethyldioctylammonium and didecyldimethylammonium) that proved to be extremely effective against all the organisms tested. The results of the biological activity indicate that the products synthesized belong to the third generation of ionic liquids. In conclusion, ascorbate-based ionic liquids with multifunctional (antibacterial, antifungal, antifeedant, and antioxidant) properties have substantial potential to be used in the storage of crop protection products.