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.