Transformation of herbicide propachlor by an agrochemical thiourea

Insights into the metabolic pathways and biodegradation mechanisms of chloroacetamide herbicides

Chloroacetamide herbicides are widely used around the world due to their high efficiency, resulting in increasing levels of their residues in the environment. Residual chloroacetamides and their metabolites have been frequently detected in soil, water and organisms and shown to have toxic effects on non-target organisms, posing a serious threat to the ecosystem. As such, rapid and efficient techniques that eliminate chloroacetamide residues from the ecosystem are urgently needed. Degradation of these herbicides in the environment mainly occurs through microbial metabolism. Microbial strains such as Acinetobacter baumannii DT, Bacillus altitudinis A16, Pseudomonas aeruginosa JD115, Sphingobium baderi DE-13, Catellibacterium caeni DCA-1, Stenotrophomonas acidaminiphila JS-1, Klebsiella variicola B2, and Paecilomyces marquandii can effectively degrade chloroacetamide herbicides. The degradation pathway of chloroacetamide herbicides in aerobic bacteria is mainly initiated by an N/C-dealkylation reaction, followed by aromatic ring hydroxylation and cleavage processes, whereas dechlorination is the initial reaction in anaerobic bacteria. The molecular mechanisms associated with bacterial degradation of chloroacetamide herbicides have been explored, with amidase, hydrolase, reductase, ferredoxin and cytochrome P450 oxygenase currently known to play a pivotal role in the catabolic pathways of chloroacetamides. The fungal pathway for the degradation of these herbicides is more complex with more diversified products, and the degradation enzymes and genes involved remain to be discovered. However, there are few reviews specifically summarizing the microbial degrading species and biochemical mechanisms of chloroacetamide herbicides. Here, we briefly summarize the latest progress resulting from research on microbial strain resources and enzymes involved in degradation of these herbicides and their corresponding genes. Furthermore, we explore the biochemical pathways and molecular mechanisms for biodegradation of chloroacetamide herbicides in depth, thereby providing a reference for further research on the bioremediation of such herbicides.

Fitness assessment of Mytilus galloprovincialis Lamarck, 1819 after exposure to herbicide metabolite propachlor ESA

The lack of data on the chronic effects of chloroacetanilide herbicide metabolites on non-target aquatic organisms creates a gap in knowledge about the comprehensive impacts of excessive and repeated pesticide use. Therefore, this study evaluates the long-term effects of propachlor ethanolic sulfonic acid (PROP-ESA) after 10 (T1) and 20 (T2) days at the environmental level of 3.5 μg.L^-1 (E1) and its 10x fold multiply 35 μg.L^-1 (E2) on a model organism Mytilus galloprovincialis. To this end, the effects of PROP-ESA usually showed a time- and dose-dependent trend, especially in its amount in soft mussel tissue. The bioconcentration factor increased from T1 to T2 in both exposure groups - from 2.12 to 5.30 in E1 and 2.32 to 5.48 in E2. Biochemical haemolymph profile and haemocyte viability were not affected by PROP-ESA exposure. In addition, the viability of digestive gland (DG) cells decreased only in E2 compared to control and E1 after T1. Moreover, malondialdehyde levels increased in E2 after T1 in gills, and DG, superoxidase dismutase activity and oxidatively modified proteins were not affected by PROP-ESA. Histopathological observation showed several damages to gills (e.g., increased vacuolation, over-production of mucus, loss of cilia) and DG (e.g., growing haemocyte trend infiltrations, alterations of tubules). This study revealed a potential risk of chloroacetanilide herbicide, propachlor, via its primary metabolite in the Bivalve bioindicator species M. galloprovincialis. Furthermore, considering the possibility of the biomagnification effect, the most prominent threat poses the ability of PROP-ESA to be accumulated in edible mussel tissues. Therefore, future research about the toxicity of pesticide metabolites alone or their mixtures is needed to gain comprehensive results about their impacts on living non-target organisms.

Molecularly imprinted copolymer/reduced graphene oxide for the electrochemical detection of herbicide propachlor

The toxicity of propachlor (PROP) with its chloroacetanilide members is reported. Rapid and sensitive detection of PROP is critical for ecotoxicity evaluation and the removal process. A novel voltammetric sensor is developed based on imprinted poly (o-phenylene diamine-co-pyrrole) (o-PD-co-Py) and electrochemically reduced graphene oxide (ERGO) to detect PROP at a trace level. The use of ERGO provides a high density of imprinted cavities for better sensitivity. The imprinted layer of poly (o-PD-co-Py) improves the selectivity of the sensor. The electrode modification was characterized by scanning electron microscopy and electrochemical approaches. The working parameters of the sensor were investigated and optimized. The redox behavior of an external probe of [Fe(CN)6]3−/4− was recorded as the sensor signal for PROP selective binding. The proposed sensor presented wide linear responses to logarithmic PROP concentrations from 0.1 pM to 0.1 µM with a LOD of 0.08 pM. The sensor’s selectivity against some interference was demonstrated. This sensor was applied successfully to detect PROP in spiked water (lake and tap), red tea, and soil samples with good recoveries and reasonable RSD % values.

Graphical abstract

Effect of the Nucleophile's Nature on Chloroacetanilide Herbicides Cleavage Reaction Mechanism. A DFT Study

In this study, the degradation mechanism of chloroacetanilide herbicides in the presence of four different nucleophiles, namely: Br^-, I^-, HS^-, and S₂O₃^-2, was theoretically evaluated using the dispersion-corrected hybrid functional wB97XD and the DGDZVP as a basis set. The comparison of computed activation energies with experimental data shows an excellent correlation (R² = 0.98 for alachlor and 0.97 for propachlor). The results suggest that the best nucleophiles are those where a sulfur atom performs the nucleophilic attack, whereas the other species are less reactive. Furthermore, it was observed that the different R groups of chloroacetanilide herbicides have a negligible effect on the activation energy of the process. Further insights into the mechanism show that geometrical changes and electronic rearrangements contribute 60% and 40% of the activation energy, respectively. A deeper analysis of the reaction coordinate was conducted, employing the evolution chemical potential, hardness, and electrophilicity index, as well as the electronic flux. The charge analysis shows that the electron density of chlorine increases as the nucleophilic attack occurs. Finally, NBO analysis indicates that the nucleophilic substitution in chloroacetanilides is an asynchronous process with a late transition state for all models except for the case of the iodide attack, which occurs through an early transition state in the reaction.

Dechlorination-Hydroxylation of Atrazine to Hydroxyatrazine with Thiosulfate: A Detoxification Strategy in Seconds

Hydroxylation of atrazine to nontoxic hydroxyatrazine is generally considered an efficient detoxification method to remediate atrazine-contaminated soil and water. However, previous studies suggested that hydroxylation was not the dominant pathway for atrazine degradation in the hydroxyl radical-generating systems such as Fenton reaction, ozonation and UV/H₂O₂. Herein we report that the addition of sodium thiosulfate can realize rapid hydroxylation of atrazine to hydroxyatrazine at pH ≤ 4 under room temperature. High resolution mass spectra and isotope experiments results revealed that the hydroxylation of atrazine was involved with nucleophilic substitution and subsequent hydrolysis reaction as follows. HS₂O₃^-, as a species of thiosulfate only at pH ≤ 4, first attacked C atom connecting to chlorine of atrazine to dechlorinate atrazine and produce C₈H₁₄N₅S₂O₃^-. Subsequently, the S-S bond of C₈H₁₄N₅S₂O₃^- was cleaved easily to form SO₃ and C₈H₁₄N₅S^-. Next, C₈H₁₄N₅S^- was hydrolyzed to generate hydroxyatrazine and H₂S. Finally, the comproportionation of SO₃ and H₂S in situ produced S⁰ during hydroxylation of atrazine with thiosulfate. This study clarifies the importance of degradation pathway on the removal of pollutants, and also provides a nonoxidative strategy for atrazine detoxification in seconds.

Dansyl-carbazole AIEE material for selective recognition of thiourea derivatives

New dansyl-carbazole based compound 3 is designed and synthesized, which exhibits aggregation induced emission enhancement (AIEE) behaviour in H₂O : THF (60 : 40, v/v). Aggregates of compound 3 in H₂O : THF (60 : 40, v/v) selectively recognize thiourea motifs over urea motifs.

Characterization of the anticancer effects of S115, a novel heteroaromatic thiosemicarbazone compound, in vitro and in vivo

AIM

To investigate the anticancer effects of S115, a novel heteroaromatic thiosemicarbazone compound in vitro and in vivo.

METHODS

The anti-proliferative action of S115 was analyzed in 12 human and mouse cancer cell lines using MTT assay. Autograft and xenograft cancer models were made by subcutaneous inoculation of cancer cells into mice or nude mice. The mice were orally treated with S115 (2, 8, 32 mg·kg(-1)·d(-1)) for 7 d, and the tumor size was measured every 3 d. Cell apoptosis and cell cycle distribution were examined using flow cytometry, gene expression profile analyses, Western blots and RT-PCR.

RESULTS

The IC50 values of S115 against 12 human and mouse cancer cell lines ranged from 0.3 to 6.6 μmol/L. The tumor growth inhibition rate caused by oral administration of S115 (32 mg·kg(-1)·d(-1)) were 89.7%, 81.7%, 78.4% and 77.8%, respectively, in mouse model of B16 melanoma, mouse model of Colon26 colon cancer, nude mouse model of A549 lung cancer and nude mouse model of SK-OV-3 ovarian cancer. Furthermore, oral administration of S115 (7.5 mg·kg(-1)·d(-1)) synergistically enhanced the anticancer effects of cyclophosphamide, cisplatin, or 5-fluorouracil in mouse model of S180 sarcoma. Treatment of A549 human lung cancer cells with S115 (1.5 μmol/L) induced G0/G1 cell cycle arrest, and increased apoptosis. Furthermore, S115 downregulated the level of ubiquitin, and upregulated the level of Tob2 in A549 cells.

CONCLUSION

S115 exerts anticancer effects against a variety of cancer cells in vitro and in grafted cancer models by inducing apoptosis, downregulating ubiquitin and upregulating Tob2.

Kinetics and mechanism of propachlor reductive transformation through nucleophilic substitution by dithionite

Chloroacetanilide herbicides are extensively used in the control of weeds and have widely resulted in nonpoint contamination of groundwater and soil resources. In the attempt to achieve better remediation for herbicide-contaminated resources, we investigated the reductive transformation of propachlor through nucleophilic substitution by dithionite (S(2)O(4)(2-)). Results showed that propachlor underwent rapid dechlorination in the presence of dithionite. The reaction was of second-order kinetics and strongly influenced by pH and temperature. At pH 7.0 and temperature 308K, the rate constant of propachlor dechlorination was estimated at 123.4±0.7M(-1)h(-1). Within the pH range tested (3.0-9.5), higher pH promoted the ionization of dithionite, resulting in a more active nucleophilic reagent of S(2)O(4)(2-) to enhance the propachlor transformation rate. Similarly, higher reaction temperature overcame the activation barrier of steric hindrance in propachlor structure and accelerated the excitation of dithionite, in which higher rate constants of propachlor reductive dechlorination were obtained. Dechlorination was found to be the first and necessary step of propachlor nucleophilic substitution by dithionite. Sulfur nucleophile substituted compounds, including propachlor dithionite, propachlor ethanesulfonic acid (ESA), and hydroxyl propachlor, were identified as the dechlorination products of propachlor, indicating bimolecular nucleophilic substitution (S(N)2) as the mechanism for propachlor transformation initiated by dithionite.

Managing agricultural emissions to the atmosphere: state of the science, fate and mitigation, and identifying research gaps

The impact of agriculture on regional air quality creates significant challenges to sustainability of food supplies and to the quality of national resources. Agricultural emissions to the atmosphere can lead to many nuisances, such as smog, haze, or offensive odors. They can also create more serious effects on human or environmental health, such as those posed by pesticides and other toxic industrial pollutants. It is recognized that deterioration of the atmosphere is undesirable, but the short- and long-term impacts of specific agricultural activities on air quality are not well known or understood. These concerns led to the organization of the 2009 American Chemical Society Symposium titled . An outcome of this symposium is this special collection of 14 research papers focusing on various issues associated with production agriculture and its effect on air quality. Topics included emissions from animal feeding operations, odors, volatile organic compounds, pesticides, mitigation, modeling, and risk assessment. These papers provide new research insights, identify gaps in current knowledge, and recommend important future research directions. As the scientific community gains a better understanding of the relationships between anthropogenic activities and their effects on environmental systems, technological advances should enable a reduction in adverse consequences on the environment.

N-Benzyl-carbamothioyl-2-chloro-benzamide

In the title compound, C(15)H(13)ClN(2)OS, the dihedral angles between the sulfourea group and the benzene ring and the chloro-benzene ring are 35.8 (6) and 81.6 (6)° respectively. An intra-molecular N-H⋯O inter-action occurs. In the crystal, a combination of inter-molecular π-π stacking inter-actions [centroid-centroid distance = 4.0616 (16) Å] and N-H⋯S hydrogen bonds stabilizes the structure.

N-Cyclo-hexyl-N'-(4-nitro-benzo-yl)thio-urea

In the title compound, C₁₄H₁₇N₃O₃S, the nitro group is twisted slightly by 2.6 (3)° from the benzene ring plane and the thio­ureido group makes a dihedral angle of 52.06 (4)° with the benzene ring. The cyclo­hexyl ring displays a chair conformation. An intra­molecular N—H⋯O inter­action is present. In the crystal, inter­molecular N—H⋯S hydrogen bonds link the mol­ecules into centrosymmetric dimers. π–π inter­actions between inversion-related benzene rings (centroid–centroid distance = 4.044 Å) and C—H⋯π inter­actions (H⋯centroid distance = 3.116 Å) between one methyl­ene cyclo­hexyl H atom and the benzene ring are also present.

Ethyl 2-[3-(4-nitro-benzo-yl)thio-ureido]benzoate

In the title compound, C₁₇H₁₅N₃O₅S, the nitro and thio­ureido groups are twisted by 7.2 (7) and 21.4 (2)°, respectively, from the nitro­benzene ring plane whereas the thio­ureido and the ethyl ester group make dihedral angles of 43.0 (1) and 18.0 (2)°, respectively, with the benzene rings to which they are attached. Intra­molecular N—H⋯O hydrogen-bonding inter­actions are observed. In the crystal, inter­molecular N—H⋯O hydrogen bonds connect the mol­ecules into chains running along the a axis.

1-(4-Bromo-phen-yl)-1-(4-nitro-benzo-yl)thio-urea

The title compound, C(14)H(10)BrN(3)O(3)S, crystallizes as two concomitant polymorphs that differ in colour (one yellow and one colourless). Only the structure of the colourless form could be determined. The mol-ecule exists in the thio-amide form with an intra-molecular N-H⋯O=C hydrogen bond across the thio-urea system. Mol-ecules are linked into layers parallel to (120) by Br⋯O(nitro) contacts [3.103 (1) Å], classical hydrogen bonds from the other NH function to the S atom and N(nitro)⋯O=C contacts. The layers are linked by weak C-H⋯O(nitro) hydrogen bonds to produce the observed three-dimensional network.

1-(4-Acetyl-phen-yl)-3-butyrylthio-urea

The title compound, C₁₃H₁₆N₂O₂S, crystallizes in the thio­amide form with an intra­molecular hydrogen bond of type N—H⋯O_butyr­yl. Mol­ecules are linked into chains parallel to [10] by a further hydrogen bond of type N—H⋯O_acet­yl. C—H⋯O and C—H⋯S hydrogen bonds are also present.

Ethyl 4-(3-benzoyl-thio-ureido)benzoate

The title compound, C₁₇H₁₆N₂O₃S, crystallizes in the thio­amide form with an intra­molecular N—H⋯O hydrogen bond across the thio­urea system. Mol­ecules are connected in chains parallel to [10] by hydrogen bonds from the second thio­urea N—H group to the benzoate C=O function.