Cations impact the biodegradation of iodosulfuron-methyl herbicidal ionic liquids by fungi

In the framework of this study, six fungal isolates which demonstrated a high capability for biodegrading iodosulphuron-methyl sodium as well as herbicidal ionic liquids based on this herbicide were isolated from different soil samples. The isolates were identified based on the ITS region, whereas biodegradation residues were determined based on LC-MS/MS. Depending on the isolate, the half-lives values of the biodegraded herbicide or herbicidal ionic liquid ranged significantly from just 1.25 days to more than 40 days. The research findings unveiled that the structure of cations is a central limiting factor affecting fungal growth and herbicide transformation in case of ionic liquids. The length of the alkyl chain has been identified as the primary driver of herbicide toxicity, emphasizing the importance of structural factors in herbicide design. In cases when dodecyl(2-hydroxyethyl)dimethyl cation was used, its biodegradation ranged from 0 to approx. 20% and the biodegradability of the iodosulfuron-methyl was notably limited for the majority of the studied isolates. This knowledge provides guidance for development and selection of herbicides with reduced environmental impact. This study highlights the ecological importance of soil fungi, their potential role in herbicide biodegradation, the influence of cations on fungal growth and herbicide transformation, and the structural factors governing herbicide toxicity. Further research in these areas may lead to more efficient and environmentally friendly approaches to herbicide management.

A comprehensive study demonstrating the influence of the solvent composition on the phytotoxicity of compounds, as exemplified by 2,4-D-based ILs with a choline-type cation

BACKGROUND

Growing concern for the protection of the environment and existing ecosystems has resulted in increasing consideration of phytotoxicity tests as valid ecotoxicological indicators of the potential hazards of the use of ionic liquids (ILs) or any other chemical. The objective of this study was to gain a detailed understanding of the influence of the solvent composition of spray solutions on the phytotoxic effect of foliar application of ionic pairs with weak (choline 2,4-dichlorophenoxyacetate, [Chol][2,4-D]), medium (N-hexylcholine 2,4-dichlorophenoxyacetate, [C6 Chol][2,4-D]) and good (N-dodecylcholine 2,4-dichlorophenoxyacetate, [C12 Chol][2,4-D]) surface-active properties.

RESULTS

Experimental results unambiguously demonstrated that the biological activity of the test salt solutions, particularly [Chol][2,4-D] and [C6 Chol][2,4-D], can be strongly affected by the addition of an organic solvent, such as methanol, ethanol, dimethylformamide (DMF) or dimethylsulfoxide (DMSO) compared to solutions in pure water. However, the observed tendency is less pronounced for the compound exhibiting good surface activity, [C12 Chol][2,4-D].

CONCLUSIONS

The collected findings show that caution is warranted in the exploitation or modification of methodologies for assessing phytotoxicity to ensure the reliable interpretation of obtained results for environmental risk assessment or building quantitative structure-activity relationship (QSAR) models. © 2023 Society of Chemical Industry.

Prodrug Based on Ionic Liquids for Dual-Triggered Release of Thiabendazole

The application of triggered release pesticides can provide active ingredient release at required environmental conditions, reduce environmental problems, and toxicity to nontarget organisms. In this work, a novel prodrug that responds to water and enzymes as release triggers for thiabendazole was prepared. The release behaviors under different conditions, bioactivity against Penicillium italicum, and acute toxicity to Danio rerio of prodrugs were investigated. The results showed that the prodrug had remarkable water- and enzyme-triggered release properties, and the correlation coefficients (r ²) fitted by the Weibull model were all >0.99. Meanwhile, the prodrug showed improved antifungal efficacy against Penicillium italicum and reduced toxicity to Danio rerio. Overall, the prodrug developed offers an efficient way to triggered release pesticides, control fungal, and reduce the risk of harm to aquatic organisms.

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.

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.

Supramolecular Self-Assembly of Herbicides with Reduced Risks to the Environment

The side effects caused by some pesticides with high off-target movement have brought great risks to the environment and human health. Here, taking 2,4-dichlorophenoxyacetic acid (2,4-D) as a model herbicide to reduce its volatilization and leaching, a supramolecular self-assembly mediated by branched polyethylenimine (B-PEI) was constructed through noncovalent molecular recognition. The results showed that 2,4-D/B-PEI nanoparticles (NPs) with a mean particle size of 168 nm can be formed by electrostatic interaction, hydrophobic effect, and π-π stacking when the mass ratio of 2,4-D to B-PEI with the average molecular weight of 10 000 (B-PEI 10k) was 40:20, and their generation was not susceptible to common inorganic ions such as Ca²⁺, Na⁺, Cl^-, and SO₄^2-. Compared with 2,4-D, the self-assembled NPs with improved physicochemical properties including strong positive charges (+58.2 mV), reduced volatilization rate (2.50%), low surface tension (56.10 mN m^-1), and decreased leaching potential could minimize the adverse impacts of this herbicide on the environment. The biological activity experiments in the greenhouse and field demonstrated that the control efficacy of NPs without using any surfactant against weeds was almost the same as that of the 2,4-D sodium salt form containing Tween 80. The safety tests showed that the self-assembled NPs had the same genotoxicity as 2,4-D to Vicia faba and little effect on the soil enzyme activities. Overall, the development of self-assembled herbicidal nanoformulations with desirable physicochemical properties and low risks to the environment would have potential application in agricultural production.

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

A new family of bio-based herbicidal ionic liquids (HILs) has been synthesized starting from the renewable resource glycine betaine (a derivative of natural amino acids). After esterification, the obtained alkyl betainate bromides containing straight alkyl chains varying from ethyl to octadecyl were combined with a herbicidal anion from the sulfonylurea group (iodosulfuron-methyl). The melting points of the iodosulfuron-methyl-based salts were in a range from 51 to 99 °C, which allows their classification as ionic liquids (ILs). In addition, the new HILs exhibited good affinity for polar and semipolar organic solvents, such as DMSO, methanol, acetonitrile, acetone, and chloroform, while the presence of bulky organic cations reduced their solubility in water. The synthesized products turned out to be stable during storage at 25 °C for over 6 months; however, at 75 °C they underwent fast, progressive degradation and released volatile byproducts. The values of the logarithm of the octanol-water partition coefficient of ILs with alkyls longer than hexyl occurred in the "safe zone" (between 0 and 3); hence, the risk of their migration into groundwater after application or the possibility of their bioaccumulation in the environment is lower in comparison with the currently available commercial form (iodosulfuron-methyl sodium salt). Greenhouse studies confirmed a very high herbicidal efficacy for the obtained salts toward tested plants of oilseed rape, indicating that they may become an attractive replacement for the currently available sulfonylurea-based formulations.

Synthesis and efficacy of herbicidal ionic liquids with chlorsulfuron as the anion

In the framework of this research, four new herbicidal ionic liquids (HILs) comprising chlorsulfuron as the anion were synthesized and characterized. The new salts with chlorsulfuron contained the following cations: tetramethylammonium, didecyldimethylammonium, benzyltrimethylammonium and cholinium. All products were obtained with high yields exceeding 90% via acid–base reaction or ion exchange reaction, by the use of environment-friendly solvents. The structures of all synthesized HILs were confirmed by FT-IR, 1H NMR and 13C NMR analyses. Their efficacy against weeds has been studied under field conditions in fiber flax. All HILs showed herbicidal activity but efficiency was highly dependent on the type of cation and weed species. There were no statistically significant differences in the effectiveness of HILs toward common lambsquarters compared to the reference herbicide, except for salt with cholinium cation that showed significantly lower efficiency. As regards barnyard grass control, all HILs exhibited significantly lower efficacy than that of the reference herbicide, except for didecyldimethylammonium salt that showed similar activity. The synthesized products did not cause damage to flax plants. The obtained results confirmed that the herbicidal effectiveness of the active ingredient (chlorsulfuron) in the form of an ionic liquid can be adjusted by the selection of an appropriate cation in the synthesis.

Herbicidal Ionic Liquids: A Promising Future for Old Herbicides? Review on Synthesis, Toxicity, Biodegradation, and Efficacy Studies

The transformation of agrochemicals into herbicidal ionic liquids (HILs) has been suggested as a solution to problems associated with commercial forms of herbicides. The aim of this review was to summarize the latest progress in the field of HILs, including their synthesis as well as physicochemical and biological properties, and to address the areas that require further research in order to ensure their safe commercialization (e.g., data regarding biodegradability, toxicity, and environmental fate). The first part of the review provides an in-depth summary of the current state of knowledge regarding HILs, particularly the anions and cations used for their synthesis. The second part highlights the employed synthesis methods and elucidates their respective advantages and limitations. The third section is focused on the characterization of HILs with emphasis on the methods and factors that are significant in terms of their practical application. Subsequently, the issues associated with the biodegradation and toxic effects of HILs are discussed based on the relevant literature reports. All sections include comprehensively tabulated data in order to enable rapid comparison of utilized approaches. Finally, all the findings are critically analyzed in terms of crucial disadvantages (especially the lack of standardization), which allowed us to establish future recommendations and basic guidelines that are presented in the last section.

Preparation of Acifluorfen-Based Ionic Liquids with Fluorescent Properties for Enhancing Biological Activities and Reducing the Risk to the Aquatic Environment

In this work, 12 novel herbicidal ionic liquids (HILs) based on acifluorfen were prepared by pairing with the fluorescent hydrazides or different alkyl chains for increasing activities and reducing negative impacts on the aquatic environment. The results showed that the fluorescence of coumarin hydrazide in the HILs was applied as the internal and supplementary light source to meet the requirement of light wavelength range of acifluorfen, which improved the phytotoxicity of acifluorfen to weeds by enhancing singlet oxygen generation with increased sunlight utilization. The herbicidal activities of HILs were related positively with the length of chain of cation under high light intensity and depended mainly on the fluorescence characteristic of the cation under low light intensity, and the double salt IL forms of acifluorfen containing coumarin hydrazide and n-hexadecyltrimethylammonium had enhanced efficacies against broadleaf weeds in the field. Compared with acifluorfen sodium, HILs had lower water solubility, better surface activity, weaker mobility in soils, and higher decomposition temperature. These results demonstrated that HILs containing different cations provided a wider scope for fine-tuning of the physicochemical and biological properties of herbicides and established a promising way for the development of environmentally friendly herbicidal formulations.

Dicamba-Based Herbicides: Herbicidal Ionic Liquids versus Commercial Forms

Dicamba is a widely applied herbicide for crop protection and has potential for volatility. New formulations containing dicamba with greatly reduced volatility, introduced to the market in 2017, still caused foliar injury to crops and other plants in Arkansas and neighboring states in the United States. In response, we proposed the transformation of dicamba into protic as well as aprotic dicamba-based organic salts called herbicidal ionic liquids (HILs). All of the HILs were characterized by high stability, whereas the biological activity of the most effective products, evaluated during greenhouse studies, was found to be greater than that of currently used commercial analogues. Furthermore, the possibility of introducing an alkyl chain of a specific length allows one to obtain plant protection products with the desired physicochemical properties while maintaining herbicidal effectiveness. These studies are expected to aid in the design and development of new herbicidal formulations, which, depending on the weed species, could increase the efficacy of the applied active ingredient. Simultaneously, the volatility of the synthesized compounds, particularly those containing quaternary ammonium cations, was multiple times lower than that of the free acid of dicamba. This strategy minimizes the risk of off-site movement via volatilization, which may cause significant damage to neighboring broadleaf crops and pose a threat to existing ecosystems.

Herbicidal Ionic Liquids Containing the Acetylcholine Cation

This study presents a new group of herbicidal ionic liquids (HILs) based on a cation occurs commonly in nature-acetylcholine. The HILs were obtained with a high yield through ion exchange between acetylcholine chloride and potassium or sodium salts of selected acids with herbicidal activity. The results of the herbicidal activity measurement against common oilseed rape (Brassica napus L.) exceeded those of the commercial products. Spray solutions of the synthesized HILs revealed high surface activity and wetting properties which further manifested as higher herbicidal activity. The reduction of surface tension and low contact angles together with the specific action of acetylcholine allowed for better penetration of synthesized HILs into plant tissues. In addition, OECD 301F tests confirmed high mineralization of the HILs. The simple transformation of commercial herbicides into acetylcholine HILs proved to be a very effective method of increasing their activity, and constitutes an interesting solution to the problem of weed infestation with the use of a substance commonly found in nature.

Application of seven different clay types in sorbent-modified biodegradability studies with cationic biocides

The cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC) can exert inhibitory effects on micro-organisms responsible for their biodegradation. However, under environmentally relevant exposure scenarios the presence of and sorption to organic and inorganic matter can lead to significant reduction of inhibitory effects. In our studies we investigated silica gel and seven clays as inert sorbents to mitigate these inhibitory effects in a 28 day manometric respirometry biodegradation test. CTAB was not inhibitory to the used inoculum, but we did observe that seven out of eight sorbents increased maximum attainable biodegradation, and four out of eight decreased the lag phase. The strongly inhibitory effect of CPC was successfully mitigated by most sorbents, with five out of eight allowing >50% biodegradation within 28 days. Results further indicate that bioaccessibility of the sorbed fractions in the stirred manometric test systems was higher than in calmly shaken headspace test systems. Bioaccessibility might also be limited depending on characteristics of test chemical and sorbent type, with montmorillonite and bentonite apparently providing the lowest level of bioaccessibility with CPC. Clay sorbents can thus be used as environmentally relevant sorbents to mitigate potential inhibitory effects of test chemicals, but factors that impede bioaccessibility should be considered. In addition to apparently increased bioaccessibility due to stirring, the automated manometric respirometry test systems give valuable and highly cost-effective insights into lag phase and biodegradation kinetics; information that is especially relevant for test chemicals of gradual biodegradability.

“Sweet” ionic liquids comprising the acesulfame anion – synthesis, physicochemical properties and antifeedant activity towards stored product insects

The synthesized “sweet” ionic liquids comprising acesulfame anion proved to be effective antifeedants with designer physicochemical properties.

Sorbent-modified biodegradation studies of the biocidal cationic surfactant cetylpyridinium chloride

Biodegradability studies for the cationic surfactant cetylpyridinium chloride (CPC) are hampered by inhibitory effects on inoculum at prescribed test concentrations (10-20 mg organic carbon/L). In this study, we used ¹⁴C labeled CPC in the 28 d Headspace Test (OECD 310) and demonstrated that CPC was readily biodegradable (10->60% mineralization within a 10 day window) at test concentrations 0.006-0.3 mg/L with CPC as single substrate. Biodegradation efficiency was comparable over this concentration range. CPC inhibited degradation at 1 mg/L and completely suppressed inoculum activity at 3 mg/L. In an extensive sorbent modified biodegradation study we evaluated the balance between CPC bioaccessibility and toxicity. A non-inhibitory concentration of 0.1 mg/L CPC was readily biodegradable with 83% sorbed to SiO₂, while biodegradation was slower when 96% was sorbed. SiO₂ mitigated inhibitory effects of 1 mg/L CPC, reaching >60% biodegradation within 28 d; inhibitory effects were also mitigated by addition of commercial clay powder (illite) but this was primarily reflected by a reduced lag phase. At 10 mg/L CPC SiO₂ was still able to mitigate inhibitory effects, but bioaccessibility seemed limited as only 20% biodegradation was reached. Illite limited bioaccessibility more strongly and was not able to sustain biodegradation at 10 mg/L CPC.

Hybrid electrochemical and biological treatment of herbicidal ionic liquids comprising the MCPA anion

The present study was focused on the application of an electrochemical oxidation process combined with biodegradation for the removal of novel Herbicidal Ionic Liquids (HILs) -promising protection plant products which incorporate herbicidal anions and ammonium cations. The influence of carbon chain length (n = 8, 10, 12, 14, 16, 18) in the dialkyldimethylammonium cations on electrochemical oxidation kinetics, degradation efficiency and biodegradation by activated sludge was investigated. It was established that the applied cation influenced the heterogeneous rate constant and diffusion coefficient of electrochemical oxidation. The oxidation efficiency ranged from 17% in case of HILs with C8 alkyl chain to approx. 60% in case of HILs comprising C14 and C16 alkyl chains after 3 h of electrochemical treatment. Subsequent biodegradation studies revealed that electrochemical oxidation improved the mineralization efficiency of the studied HILs. The mineralization efficiency of electrochemically-treated HILs ranged from 28% in case of HILs comprising the C8 alkyl chain to 57% in case of HILs with C14 and C16 alkyl chains after 28 days. In case of untreated HILs, the corresponding mineralization efficiency ranged from 0 to 8%, respectively. This confirms the feasibility of a hybrid electrochemical-biological approach for treatment of herbicidal ionic liquids based on MCPA.

Novel herbicide ionic liquids based on nicosulfuron with increased efficacy

Nicosulfuron is widely used in agriculture because of its high selectivity, wide weeding spectrum, and excellent herbicide performance.

Dicationic Ionic Liquids of Herbicide 2,4-Dichlorophenoxyacetic Acid with Reduced Negative Effects on Environment

Due to high volatility and water solubility, 2,4-dichlorophenoxyacetic acid (2,4-D) can easily enter into the atmosphere and water bodies by volatilization, drift, leaching, or runoff, which results in potential threats to the environment and human health. The physicochemical properties of pesticides can be regulated by preparing their ionic liquids. In this work, a series of dicationic ionic liquids (DILs) of 2,4-D were prepared to reduce its environmental risk and enhance herbicidal activity. The solubility, octanol-water partition coefficient, surface tension, and volatilization rate results of DILs showed that these properties could be optimized by choosing appropriate countercations. Compared to 2,4-D ammonium salt, DILs have lower volatility, water solubility, and surface tension as well as higher lipophilicity. Benefiting from optimized physicochemical properties, DILs HIL8-12 exhibited better herbicidal activity against three typical broadleaf weeds than 2,4-D ammonium salt, and their fresh weight inhibition rates increased by 2.74-46.84%. The safety assessment experiment indicated that DILs were safer to wheat than commercialized forms of 2,4-D. The DILs could reduce the environmental risk of 2,4-D caused by high volatility and water solubility and would be potential alternatives to its commercialized formulations.

Synthesis and Structure-Property Relationships in Herbicidal Ionic Liquids and their Double Salts

In this study, two homologous series of novel herbicidal ionic liquids (HILs) were synthesized in a simple metathesis reaction between alkyl[2-(2-hydroxyethoxy)ethyl]dimethylammonium bromides and alkali metal salts of 4-chloro-2-methylphenoxyacetic acid (MCPA) or 3,6-dichloro-2-methoxybenzoic acid (dicamba), known as popular herbicides from the class of growth regulators. These HILs were subsequently mixed to prepare double-salt herbicidal ionic liquids (DSHILs). The DSHILs were characterized by substantially altered parameters of viscosity, refractive index, glass transition temperatures and surface activity compared to the average values expected for ideal mixtures of their individual components (HILs). Interestingly, DSHILs possessed superior physicochemical properties such as relatively low viscosity or facilitated formation of micelles, which emphasizes the complex nature of multi-ion interactions in the microstructures of ionic liquid mixtures. The biological tests showed improved efficiency of DSHILs against tested weeds compared to the reference herbicides and parent HILs.

Developing ionic liquid forms of picloram with reduced negative effects on the aquatic environment

As a widely used herbicide, picloram has been frequently detected in the aquatic environment due to its high leaching potential and low adsorption by soil. To reduce aquatic environmental risk of this herbicide caused by leaching and runoff, five herbicidal ionic liquids (HILs) based on picloram were prepared by pairing isopropylamine, octylamine, octadecylamine, 1-methylimidazole, 4-methylmorpholine respectively. Their physicochemical properties including water solubility, octanol-water partition coefficient, surface activity, leaching, as well as soil adsorption were compared. The results showed that these properties could be adjusted by appropriate selection of counter cations. The HILs with long alkyl chains in cations had low water solubility and leaching characteristics, good surface tension and lipophilicity, as well as high soil adsorption. Compared with currently used picloram in the forms of potassium salts, HIL3 had more excellent herbicidal activity against broadleaf weeds and may offer a lower use dosage. The HILs based on picloram can reduce its negative effects on the aquatic environment and can be used as a desirable alternative to commercial herbicidal formulations of picloram in future.