Iodosulfuron-Methyl-Based Herbicidal Ionic Liquids Comprising Alkyl Betainate Cation as Novel Active Ingredients with Reduced Environmental Impact and Excellent Efficacy

Rethinking the Esterquats: Synthesis, Stability, Ecotoxicity and Applications of Esterquats Incorporating Analogs of Betaine or Choline as the Cation in Their Structure

Esterquats constitute a unique group of quaternary ammonium salts (QASs) that contain an ester bond in the structure of the cation. Despite the numerous advantages of this class of compounds, only two mini-reviews discuss the subject of esterquats: the first one (2007) briefly summarizes their types, synthesis, and structural elements required for a beneficial environmental profile and only briefly covers their applications whereas the second one only reviews the stability of selected betaine-type esterquats in aqueous solutions. The rationale for writing this review is to critically reevaluate the relevant literature and provide others with a "state-of-the-art" snapshot of choline-type esterquats and betaine-type esterquats. Hence, the first part of this survey thoroughly summarizes the most important scientific reports demonstrating effective synthesis routes leading to the formation of both types of esterquats. In the second section, the susceptibility of esterquats to hydrolysis is explained, and the influence of various factors, such as the pH, the degree of salinity, or the temperature of the solution, was subjected to thorough analysis that includes quantitative components. The next two sections refer to various aspects associated with the ecotoxicity of esterquats. Consequently, their biodegradation and toxic effects on microorganisms are extensively analyzed as crucial factors that can affect their commercialization. Then, the reported applications of esterquats are briefly discussed, including the functionalization of macromolecules, such as cotton fabric as well as their successful utilization on a commercial scale. The last section demonstrates the most essential conclusions and reported drawbacks that allow us to elucidate future recommendations regarding the development of these promising chemicals.

Betaine- and L-Carnitine-Based Ionic Liquids as Solubilising and Stabilising Agents for the Formulation of Antimicrobial Eye Drops Containing Diacerein

The therapeutic efficacy of topically administered drugs, however powerful, is largely affected by their bioavailability and, thus, ultimately, on their aqueous solubility and stability. The aim of this study was to evaluate the use of ionic liquids (ILs) as functional excipients to solubilise, stabilise, and prolong the ocular residence time of diacerein (DIA) in eye drop formulations. DIA is a poorly soluble and unstable anthraquinone prodrug, rapidly hydrolysed to rhein (Rhe), for the treatment of osteoarthritis. DIA has recently been evaluated as an antimicrobial agent for bacterial keratitis. Two ILs based on natural zwitterionic compounds were investigated: L-carnitine C6 alkyl ester bromide (Carn6), and betaine C6 alkyl ester bromide (Bet6). The stabilising, solubilising, and mucoadhesive properties of ILs were investigated, as well as their cytotoxicity to the murine fibroblast BALB/3T3 clone A31 cell line. Two IL-DIA-based eye drop formulations were prepared, and their efficacy against both Staphylococcus aureus and Pseudomonas aeruginosa was determined. Finally, the eye drops were administered in vivo on New Zealand albino rabbits, testing their tolerability as well as their elimination and degradation kinetics. Both Bet6 and Carn6 have good potential as functional excipients, showing solubilising, stabilising, mucoadhesive, and antimicrobial properties; their in vitro cytotoxicity and in vivo ocular tolerability pave the way for their future use in ophthalmic applications.

Adjustment of the Structure of the Simplest Amino Acid Present in Nature-Glycine, toward More Environmentally Friendly Ionic Forms of Phenoxypropionate-Based Herbicides

The use of chemicals for various purposes in agriculture has numerous consequences, such as the contamination of ecosystems. Thus, nowadays it is perceived that their development should adhere to the principles of green chemistry elaborated by Paul Anastas. Consequently, to create more environment-friendly herbicides, we elaborated a 'green' synthesis method of a series of ionic liquids (ILs) containing cations derived from glycine. The appropriately modified cations were combined with an anion from the group of phenoxy acids, commonly known as 2,4-DP. The products were obtained with high yields, and subsequently, their properties, such as density, viscosity and solubility, were thoroughly examined to elucidate existing structure-property relationships. All ILs were liquids at room temperature, which enabled the elimination of some serious issues associated with solid active forms, such as the polymorphism or precipitation of an active ingredient from spray solution. Additionally, the synthesized compounds were tested under greenhouse conditions, which allowed an assessment of their effectiveness in regulating the growth of oilseed rape, selected as a model dicotyledonous plant. The product comprising a dodecyl chain exhibited the greatest reduction in the fresh weight of plants, significantly surpassing not only a commercially used reference herbicide but also the potassium salt of 2,4-DP.

Toward revealing the role of the cation in the phytotoxicity of the betaine-based esterquats comprising dicamba herbicide

In this study, two homologous series of esterquats comprising alkyl (from ethyl to octadecyl) betainate cations and bromide as well as dicamba anions were successfully synthesized, starting from a renewable raw material - glycine betaine. Due to the favorable octanol-water partition coefficient and utilization of biodegradable cations of natural origin, synthesized esterquats can be considered promising alternatives to currently applied dicamba-based formulations. In addition, the obtained results allowed us to verify whether the organic cations in quaternary ammonium salts containing herbicidally active anions (such as dicamba) play the role of biologically inactive adjuvants that only enhance the efficiency of the active ingredient or if they simultaneously exhibit a significant degree of phytotoxicity. Analysis of the influence of alkyl betainate esterquats containing nonherbicidal (bromide) anions on seedlings of white mustard revealed that alkyl betainate cations promote the germination of white mustard seeds; however, the subsequent growth of the seedlings was significantly inhibited. Further studies performed on white mustard and cornflower plants in a stage of 4-6 leaves allowed us to conclude that in the case of sensitive plants, the high phytotoxicity can be attributed to the presence of the dicamba anion, whereas for more resistant plants the additional influence of the cation on the phytotoxic effect is visible. Esterquats comprising a dodecyl substituent or longer had high surface active properties. Nonetheless, their contact angle values were not correlated with phytotoxicity data, indicating an additional influence of the cation on this stage of plant development. Interestingly, subsequent dose-response experiments conducted for two selected dicamba-based products confirmed that the greatest phytotoxicity was expressed by compounds containing a decyl substituent.

Construction, Pesticidal Activities, Control Effects, and Detoxification Enzyme Activities of Osthole Ester/Amide Derivatives

Pesticide research and development has entered an era of safety, efficiency, and environmental friendliness. Discovery of effective active products directly or indirectly from plant secondary metabolites as pesticide candidates has been one of the current research focuses. Herein, two series of new ester and amide derivatives were prepared by structural modifications of a natural coumarin-type product osthole at its C-4' position. Their structures were characterized by IR, mp, ¹H NMR, and HRMS. Confirmation of steric configuration of seven compounds was based on single-crystal analysis. Against Tetranychus cinnabarinus Boisduval (Acari: Tetranychidae), (2'E)-3'-ethoxycarbonylosthole (4b) and (2'E)-3'-(n)hexyloxycarbonylosthole (4e) exhibited 3.2 and 3.1 times acaricidal activity of osthole, and particularly, they also showed 2.4 and 2.2 times control efficiency on the 5th day of osthole. Against Aphis citricola Van der Goot (Homoptera: Aphididae), (2'E)-3'-(p-CF₃)benzyloxycarbonylosthole (4w), (2'E)-3'-benzylaminocarbonylosthole (5f), and (2'E)-3'-phenylethylaminocarbonylosthole (5g) showed 1.9-2.1-fold aphicidal activity of osthole. Furthermore, the changes in two detoxification enzyme [carboxylesterase (CarE) and glutathione S-transferase (GST)] activities over time in treated T. cinnabarinus were investigated. These results can pave the foundation for future design and preparation of osthole derivatives as botanical agrochemicals.

Sustainable Design of New Ionic Forms of Vitamin B3 and Their Utilization as Plant Protection Agents

This study demonstrates the utilization of naturally occurring nicotinamide (vitamin B₃) in the sustainable synthesis of organic salts with application potential as environmentally friendly agrochemicals. The designed ionic pairs, obtained with high yields, consisted of N-alkylnicotinamide cation and commercially available herbicidal anions: 2,4-dichlorophenoxyacetate (2,4-D) and 4-chloro-2-methylphenoxyacetate (MCPA). The study confirmed the strong influence of the length of alkyl chain in products on the physicochemical properties as well as the development of cornflower and oil-seed rape. The majority of tested salts showed significantly better herbicidal activity (by approx. 30-50%) compared to the reference herbicide. Furthermore, N-hexadecylnicotinamide 4-chloro-2-methylphenoxyacetate was significantly more effective than the commercial formulation in the dose-response test. Their negligible vaporization, multiple times lower than that of commonly used dimethylammonium salts, eliminates one of the greatest threats of currently applied plant protection agents. Additionally, the risk of product migration or bioaccumulation in the environment was assessed as extremely low.

Dicationic Herbicidal Ionic Liquids Comprising Two Active Ingredients Exhibiting Different Modes of Action

In the framework of this study, dicationic herbicidal ionic liquids (HILs) containing tetramethylene-1,4-bis(decyldimethylammonium) and dodecylmethylene-1,12-bis(decyldimethylammonium), including two different herbicidal anions exhibiting different modes of action, were synthesized and characterized. One herbicide incorporated into the HILs was a tribenuron-methyl belonging to ALS inhibitors, while the second herbicidal anion was a synthetic auxin that acts as a growth regulator, namely 2,4-dichlorophenoxyacetate (2,4-D), 2-(2,4-dichlorophenoxy)propionate, (2,4-DP), 2,4,5-trichlorophenoxyacetate (2,4,5-T), 4-chloro-2-methylphenoxyacetiate (MCPA), 2-(4-chloro-2-methylphenoxy)propionate (MCPP), and 4-chlorophenoxyacetate (4-CPA). The obtained products were found to be unstable and decomposed, which can be attributed to the presence of an additional methyl group within the sulfonylurea bridge of the tribenuron-methyl. The synthesized HILs exhibited good affinity with polar and semipolar solvents, with ethyl acetate and hexane as the only solvents that did not dissolve the HILs. Greenhouse tests demonstrated that most of the obtained HILs were more effective than the reference herbicide containing tribenuron-methyl. The length of the alkyl chain in the cation also influenced the effectiveness of the HILs. Better effects were observed for dodecylmethylene-1,12-bis(decyldimethylammonium) cations compared to tetramethylene-1,4-bis(decyldimethylammonium). Therefore, the novel dicatonic HILs showed to integrate the advent of the combination of the different herbicides into a single molecule, enhance herbicidal efficacy, and reduce the risk of weed resistance due to the various modes of action of the applied treatment.

Transformation of Iodosulfuron-Methyl into Ionic Liquids Enables Elimination of Additional Surfactants in Commercial Formulations of Sulfonylureas

Efficient use of herbicides for plant protection requires the application of auxiliary substances such as surfactants, stabilizers, wetting or anti-foaming agents, and absorption enhancers, which can be more problematic for environment than the herbicides themselves. We hypothesized that the combination of sulfonylurea (iodosulfuron-methyl) anion with inexpensive, commercially available quaternary tetraalkylammonium cations could lead to biologically active ionic liquids (ILs) that could become a convenient and environment-friendly alternative to adjuvants. A simple one-step synthesis allowed for synthesizing iodosulfuron-methyl based ILs with high yields ranging from 88 to 96% as confirmed by UV, FTIR, and NMR. The obtained ILs were found to possess several favorable properties compared to the currently used sodium salt iodosulfuron-methyl, such as adjustable hydrophobicity (octanol-water partition coefficient) and enhanced stability in aqueous solutions, which was supported by molecular calculations showing cation-anion interaction energies. In addition, soil mobility and volatility of ILs were more beneficial compared to the parental herbicide. Herbicidal activity tests toward oil-seed rape and cornflower revealed that ILs comprising at least one alkyl chain in the decyl to octadecyl range had similar or better efficacy compared to the commercial preparation without addition of any adjuvant. Furthermore, results of antimicrobial activity indicated that they were practically harmless or slightly toxic toward model soil microorganisms such as Pseudomonas putida and Bacillus cereus.

Synthesis and characterization of herbicidal ionic liquids based on (4-chloro-2-methylphenoxy)acetate and phenoxyethylammonium

Ten ionic liquids containing the (4-chloro-2-methylphenoxy)acetate (MCPA) anion and domiphen derived phenoxyethylammonium cation were synthesized. The obtained compounds differed in terms of the substitution of the phenoxyethylammonium group in the ring (the presence of a methyl group in the meta or para positions and the presence of chlorine in the para position) as well as the length of the alkyl chain (from hexyl to tetradecyl). The basic physicochemical properties of the obtained ionic liquids (solubility and thermal stability) were characterized and their structures were confirmed. The herbicidal activity of the compounds was tested under greenhouse conditions using cornflower (Centaurea cyanus L.) as the test plant.

Glycine betaine-based ionic liquids and their influence on bacteria, fungi, insects and plants

Natural origin ionic liquids with betaine-based cations as new agrochemicals.