Ionic Liquids with Natural Origin Component: A Path to New Plant Protection Products

摘要

One of the major problems in environmental industries is plant protection using ecologically and human friendly plant resistance inducers. To address this problem in an advantageous way, we used plant sources and substance that is responsible for plant resistance induction as the starting materials to synthesize new ionic liquids (ILs). Engineered ammonium and imidazolium salts with excellent yields of >= 98% were obtained under mild process conditions, using the (-)-menthol moiety, which is economically viable, widely used in many industries, and easily available from natural origins. This monoterpene alcohol, derived from renewable raw resources, was introduced to the cation part of the synthesized ILs. As a counterion, benzo[1.2.3]thiadiazole-7-carboxylate, which has resistance induction properties in plants, was introduced. In this study, we demonstrated that the careful design of IL's cations and anions leads to new dual function compounds. This biological property manifests itself as a high level of antimicrobiological activity of the obtained salts, which allows new compounds to be concurrently classified as antimicrobial agents and at the same time as plant resistance inducers. Tested ammonium and imidazolium ILs exhibited antimicrobial activities higher than benzalkonium chloride, which is commonly used in biocides. When analyzing ILs, it was noted that the length of the alkyl chain, presence of the naturally occurring substituent, type of anion, type of cation core, and steric hindrance of the cyclic group are the principal factors determining antimicrobial properties. Work presented in this article shows one of the possibilities of enhancing biological properties, such as resistance induction, of the ILs, by pairing them in a sustainable manner with the antibiocidal agent to form bifunctional salts. Using this approach, it is possible to prepare bifunctional salts that maintain their systemic acquired resistance induction activity at very high levels, enhance solubility in water owing to their ionic characteristics, and deliver additional activities, such as antibacterial. Our design strategy indicates that the choice of the IL components can result in antimicrobial SAR plant resistance inducers, which might be successfully applied as disinfectants or plant resistance inducers.