Quaternary Ammonium Compounds (QACs) and Ionic Liquids (ILs) as Biocides: From Simple Antiseptics to Tunable Antimicrobials

Abstract

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.

Synthesis, Antibacterial and Antifungal Activity of New 3-Aryl-5H-pyrrolo[1,2-a]imidazole and 5H-Imidazo[1,2-a]azepine Quaternary Salts

“…QACs are a well-known class of cationic biocides with a broad spectrum of antimicrobial activity. QACs kill bacteria by impairing the permeability of cell membranes and do not contribute to antimicrobial resistance [ 24 ].…”

Antimicrobial Activity of Gemini Surfactants with Ether Group in the Spacer Part

“…Microbiocides, in terms of chemicals, are classified as oxidizing substances, alcohols, phenols and their derivatives, aldehydes, organic and inorganic acids, halogen compounds, and quaternary ammonium compounds [ 7 , 8 , 9 ]. They are used as antiseptics, disinfectants, and preservatives in a wide variety of fields: water purification, personal care products, food and beverage, wood preservation, paints and coatings, plastics, cleaning products, ventilation and air conditioning, medical products, and also in oil, gas, fuel, and paper industry [ 3 , 10 ].…”

Design, Synthesis, Antibacterial, and Antitumor Activity of Linear Polyisocyanide Quaternary Ammonium Salts with Different Structures and Chain Lengths

“…Hence, they have been extensively applied in the fields of antibacterial and antitumor materials [ 10 , 11 , 12 ]. For example, some review articles have summarized the relationship between the antibacterial properties of quaternary ammonium salts and its structure [ 13 , 14 , 15 ]. Furthermore, Linda et al developed a series of quaternary ammonium compounds (QACs) derived from quinuclidin-3-ol and an alkyl chain of variable length, and found that it is necessary for new compounds to get better antimicrobial potentials by the addition of alkyl chains containing at least ten carbon atoms [ 16 ].…”