Quaternary ammonium compounds (QACs) belong to a well-known class of cationic biocides with a broad spectrum of antimicrobial activity. They are used as essential components in surfactants, personal hygiene products, cosmetics, softeners, dyes, biological dyes, antiseptics, and disinfectants. Simple but varied in their structure, QACs are divided into several subclasses: Mono-, bis-, multi-, and poly-derivatives. Since the beginning of the 20th century, a significant amount of work has been dedicated to the advancement of this class of biocides. Thus, more than 700 articles on QACs were published only in 2020, according to the modern literature. The structural variability and diverse biological activity of ionic liquids (ILs) make them highly prospective for developing new types of biocides. QACs and ILs bear a common key element in the molecular structure–quaternary positively charged nitrogen atoms within a cyclic or acyclic structural framework. The state-of-the-art research level and paramount demand in modern society recall the rapid development of a new generation of tunable antimicrobials. This review focuses on the main QACs exhibiting antimicrobial and antifungal properties, commercial products based on QACs, and the latest discoveries in QACs and ILs connected with biocide development.

The possibility of using widely available stearin to produce fatty acid-derived ionic liquids (ILs) has been shown for the first time. New amphiphilic ILs based on imidazolium, pyridinium, and quaternary ammonium cations containing long-chain alkyl substituents have been prepared. The synthesized compounds have been shown to have biological activity comparable to known antimicrobial compounds. ILs with one alkyl substituent have higher cytotoxicity and antimicrobial activity compared to disubstituted derivatives.

For the first time, the possibility of using widely available stearin for the production of fatty acid-derived ionic liquids (ILs) has been shown. New amphiphilic ILs based on imidazolium, pyridinium, and quaternary ammonium cations containing long-chain alkyl substituents were obtained. The synthesized compounds are shown to have biological activity comparable to known antimicrobial compounds. ILs with one alkyl substituent have higher cytotoxicity and antimicrobial activity compared to disubstituted derivatives.