Design, Synthesis, and Biological Evaluation of Pyridazinone-Containing Derivatives As Novel Protoporphyrinogen IX Oxidase Inhibitor.

Protoporphyrinogen IX oxidase (PPO, E.C. 1.3.3.4) plays a pivotal role in chlorophyll biosynthesis in plants, making it a prime target for herbicide development. In this study, we conducted an investigation aimed at discovering PPO-inhibiting herbicides. Through this endeavor, we successfully identified a series of novel compounds based on the pyridazinone scaffold. Following structural optimization and biological assessment, compound 10ae, known as ethyl 3-((6-fluoro-5-(6-oxo-4-(trifluoromethyl)pyridazin-1(6H)-yl)benzo[d]thiazol-2-yl)thio)propanoate, emerged as a standout performer. It exhibited robust activity against Nicotiana tabacum PPO (NtPPO) with an inhibition constant (Ki) value of 0.0338 µM. Concurrently, we employed molecular simulations to obtain further insight into the binding mechanism with NtPPO. Additionally, another compound, namely, ethyl 2-((6-fluoro-5-(5-methyl-6-oxo-4-(trifluoromethyl)pyridazin-1(6H)-yl)benzo[d]thiazol-2-yl)thio)propanoate (10bh), demonstrated broad-spectrum and highly effective herbicidal properties against all six tested weeds (Leaf mustard, Chickweed, Chenopodium serotinum, Alopecurus aequalis, Poa annua, and Polypogon fugax) at the dosage of 150 g a.i./ha through postemergence application in a greenhouse. This work identified a novel lead compound (10bh) that showed good activity in vitro and excellent herbicidal activity in vivo and had promising prospects as a new PPO-inhibiting herbicide lead.

Synthesis of Mixed Phosphonate Esters and Amino Acid-Based Phosphonamidates, and Their Screening as Herbicides.

While organophosphorus chemistry is gaining attention in a variety of fields, the synthesis of the phosphorus derivatives of amino acids remains a challenging task. Previously reported methods require the deprotonation of the nucleophile, complex reagents or hydrolysis of the phosphonate ester. In this paper, we demonstrate how to avoid these issues by employing phosphonylaminium salts for the synthesis of novel mixed n-alkylphosphonate diesters or amino acid-derived n-alkylphosphonamidates. We successfully applied this methodology for the synthesis of novel N-acyl homoserine lactone analogues with varying alkyl chains and ester groups in the phosphorus moiety. Finally, we developed a rapid, quantitative and high-throughput bioassay to screen a selection of these compounds for their herbicidal activity. Together, these results will aid future research in phosphorus chemistry, agrochemistry and the synthesis of bioactive targets.

Design, Synthesis, and Biological Activity of Novel Triketone-Containing Phenoxy Nicotinyl Inhibitors of HPPD.

4-Hydroxyphenylpyruvate dioxygenase (HPPD) is a crucial target enzyme in albino herbicides. The inhibition of HPPD activity interferes with the synthesis of carotenoids, blocking photosynthesis and resulting in bleaching and necrosis. To develop herbicides with excellent activity, a series of 3-hydroxy-2-(6-substituted phenoxynicotinoyl)-2-cyclohexen-1-one derivatives were designed via active substructure combination. The title compounds were characterized via infrared spectroscopy, 1H and 13C nuclear magnetic resonance spectroscopies, and high-resolution mass spectrometry. The structure of compound III-17 was confirmed via single-crystal X-ray diffraction. Preliminary tests demonstrated that some compounds had good herbicidal activity. Crop safety tests revealed that compound III-29 was safer than the commercial herbicide mesotrione in wheat and peanuts. Moreover, the compound exhibited the highest inhibitory activity against Arabidopsis thaliana HPPD (AtHPPD), with a half-maximal inhibitory concentration of 0.19 µM, demonstrating superior activity compared with mesotrione (0.28 µM) in vitro. A three-dimensional quantitative structure-activity relationship study revealed that the introduction of smaller groups to the 5-position of cyclohexanedione and negative charges to the 3-position of the benzene ring enhanced the herbicidal activity. A molecular structure comparison demonstrated that compound III-29 was beneficial to plant absorption and conduction. Molecular docking and molecular dynamics simulations further verified the stability of the complex formed by compound III-29 and AtHPPD. Thus, this study may provide insights into the development of green and efficient herbicides.

A magnetic imprinted polymer nano-adsorbent with embedded quantum dots and mesoporous carbon for the microextraction of triazine herbicides.

A magnetic molecularly imprinted polymer (MMIP) adsorbent incorporating amino-functionalized magnetite nanoparticles, nitrogen-doped graphene quantum dots and mesoporous carbon (MIP@MPC@N-GQDs@Fe3O4NH2) was fabricated to extract triazine herbicides from fruit juice. The embedded magnetite nanoparticles simplified the isolation of the adsorbent from the sample solution. The N-GQDs and MPC enhanced adsorption by affinity binding with triazines. The MIP layer provided highly specific recognition sites for the selective adsorption of three target triazines. The extracted triazines were determined by high-performance liquid chromatography (HPLC) coupled with diode-array detection (DAD). The developed method exhibited linearity from 1.5 to 100.0 µg L-1 with a detection limit of 0.5 µg L-1. Recoveries from spiked fruit juice samples were in the range of 80.1- 108.4 %, with a relative standard deviation of less than 6.0 %. The developed MMIP adsorbent demonstrated good selectivity, high extraction efficiency, ease of fabrication and use, and good stability.

Chalcones-Features, Identification Techniques, Attributes, and Application in Agriculture.

This review article is a comprehensive and current overview on chalcones, covering their sources, identification methods, and properties with a particular focus on their applications in the agricultural sector. The widespread use of synthetic pesticides has not only led to increased resistance among weeds and pests, resulting in economic losses, but it has also raised significant health concerns due to the overuse of these chemicals. In line with the European Green Deal 2030 and its Farm to Fork strategy, there is a targeted 50% reduction in the use of chemical pesticides by 2030, emphasizing a shift towards natural alternatives that are more environmentally sustainable and help in the restoration of natural resources. Chalcones and their derivatives, with their herbicidal, fungicidal, bactericidal, and antiviral properties, appear to be ideal candidates. These naturally occurring compounds have been recognized for their beneficial health effects for many years and have applications across multiple areas. This review not only complements the previous literature on the agricultural use of chalcones but also provides updates and introduces methods of detection such as chromatography and MALDI technique.

Differential Resistance to Acetyl-CoA Carboxylase Inhibitors in Rice: Insights from Two Distinct Target-Site Mutations.

Weeds present a significant challenge to agricultural productivity, and acetyl-CoA carboxylase (ACCase)-inhibiting herbicides have proven to be effective in managing weed populations in rice fields. To develop ACCase-inhibiting herbicide-resistant rice, we generated mutants of rice ACCase (OsACC) featuring Ile-1792-Leu or Gly-2107-Ser substitutions through ethyl methyl sulfonate (EMS) mutagenesis. The Ile-1792-Leu mutant displayed cross-resistance to aryloxyphenoxypropionate (APP) and phenylpyrazoline (DEN) herbicides, whereas the Gly-2107-Ser mutants primarily exhibited cross-resistance to APP herbicides with diminished resistance to the DEN herbicide. In vitro assays of the OsACC activity revealed an increase in resistance to haloxyfop and quizalofop, ranging from 4.84- to 29-fold in the mutants compared to that in wild-type. Structural modeling revealed that both mutations likely reduce the binding affinity between OsACC and ACCase inhibitors, thereby imparting resistance. This study offers insights into two target-site mutations, contributing to the breeding of herbicide-resistant rice and presenting alternative weed management strategies in rice cultivation.

Migration mechanism of atrazine in the simulated lake icing process at different freezing temperatures based on density function theory.

Atrazine causes concern due to its resistant to biodegradation and could be accumulated in aquatic organisms, causing pollution in lakes. This study measured the concentration of atrazine in ice and the water under ice through a simulated icing experiment and calculated the distribution coefficient K to characterize its migration ability in the freezing process. Furthermore, density functional theory (DFT) calculations were employed to expatiate the migration law of atrazine during icing process. According to the results, it could release more energy into the environment when atrazine staying in water phase (-15.077 kcal/mol) than staying in ice phase (-14.388 kcal/mol), therefore it was beneficial for the migration of atrazine from ice to water. This explains that during the freezing process, the concentration of atrazine in the ice was lower than that in the water. Thermodynamic calculations indicated that when the temperature decreases from 268 to 248 K, the internal energy contribution of the compound of atrazine and ice molecule (water cluster) decreases at the same vibrational frequency, resulting in an increase in the free energy difference of the compound from -167.946 to -165.390 kcal/mol. This demonstrated the diminished migratory capacity of atrazine. This study revealed the environmental behavior of atrazine during lake freezing, which was beneficial for the management of atrazine and other pollutants during freezing and environmental protection.

Modulation of Electron Transfer Branches by Atrazine and Triazine Herbicides in Photosynthetic Reaction Centers.

Quinone analogue molecules, functioning as herbicides, bind to the secondary quinone site, QB, in type-II photosynthetic reaction centers, including those from purple bacteria (PbRC). Here, we investigated the impact of herbicide binding on electron transfer branches, using herbicide-bound PbRC crystal structures and employing the linear Poisson-Boltzmann equation. In contrast to urea and phenolic herbicides [Fufezan, C. Biochemistry 2005, 44, 12780-12789], binding of atrazine and triazine did not cause significant changes in the redox-potential (Em) values of the primary quinone (QA) in these crystal structures. However, a slight Em difference at the bacteriopheophytin in the electron transfer inactive branch (HM) was observed between the S(-)- and R(+)-triazine-bound PbRC structures. This discrepancy is linked to variations in the protonation pattern of the tightly coupled Glu-L212 and Glu-H177 pairs, crucial components of the proton uptake pathway in native PbRC. These findings suggest the existence of a QB-mediated link between the electron transfer inactive HM and the proton uptake pathway in PbRCs.

In situ formation of solidified supramolecular solvent based dispersive liquid-liquid microextraction for the enrichment of phenylurea herbicides in water, fruit juice, and milk.

A convenient, efficient, and green dispersive liquid-liquid microextraction based on the in situ formation of solidified supramolecular solvents combined with high performance liquid chromatography was developed for the determination of four phenylurea herbicides in liquid samples, including monuron, monolinuron, isoproturon, and chlortoluron. Herein, a novel supramolecular solvent was prepared by the in situ reaction of [P4448]Br and NH4PF6, which had the advantages of low melting point, high density, and good dispersibility. In addition, the microscopic morphology and physical properties of supramolecular solvent were characterized, and the extraction conditions were optimized. The results showed that the analytes had good linearity (R2 > 0.9998) within the linear range. The limits of detection and quantification for the four phenylurea herbicides were in the range of 0.13-0.19 µg L-1 and 0.45-0.65 µg L-1, respectively. The prepared supramolecular solvent is suitable for the efficient extraction of phenylurea herbicides in water, fruit juice, and milk.

Exploring the influence of invasive weed biochar on the sorption and dissipation dynamics of imazethapyr in sandy loam soil.

The management of invasive weeds on both arable and non-arable land is a vast challenge. Converting these invasive weeds into biochar and using them to control the fate of herbicides in soil could be an effective strategy within the concept of turning waste into a wealth product. In this study, the fate of imazethapyr (IMZ), a commonly used herbicide in various crops, was investigated by introducing such weeds as biochar, i.e., Parthenium hysterophorus (PB) and Lantana camara (LB) in sandy loam soil. In terms of kinetics, the pseudo-second order (PSO) model provided the best fit for both biochar-mixed soils. More IMZ was sorbed onto LB-mixed soil compared to PB-mixed soil. When compared to the control (no biochar), both PB and LB biochars (at concentrations of 0.2% and 0.5%) increased IMZ adsorption, although the extent of this effect varied depending on the dosage and type of biochar. The Freundlich adsorption isotherm provided a satisfactory explanation for IMZ adsorption in soil/soil mixed with biochar, with the adsorption process exhibiting high nonlinearity. The values of Gibb's free energy change (ΔG) were negative for both adsorption and desorption in soil/soil mixed with biochar, indicating that sorption was exothermic and spontaneous. Both types of biochar significantly affect IMZ dissipation, with higher degradation observed in LB-amended soil compared to PB-amended soil. Hence, the findings suggest that the preparation of biochar from invasive weeds and its utilization for managing the fate of herbicides can effectively reduce the residual toxicity of IMZ in treated agroecosystems in tropical and subtropical regions.

Insights into interaction of triazine herbicides with three kinds of different alkyl groups (simetryne, ametryn and terbutryn) with human serum albumin via multi-spectral analysis.

In this study, the interaction of triazine herbicides with three kinds of different alkyl groups (simetryne, ametryn and terbutryn) with human serum albumin (HSA) are investigated through UV-vis, fluorescence, and circular dichroism (CD) spectra. The mechanisms on the fluorescence quenching of HSA initiated by triazine herbicides are obtained using Stern-Volmer, Lineweaver-Burk and Double logarithm equations. The quenching rate constant (Kq), Stern-Volmer quenching constant (Ksv), binding constant (KA), thermodynamic parameters such as enthalpy change (∆H), entropy change (∆S) and Gibbs free energy (∆G) and number of binding site (n) are calculated and compared. The variations in the microenvironment of amino acid residues are studied by synchronous fluorescence spectroscopy. The binding sites and subdomains are identified using warfarin and ibuprofen as site probes. The conformational changes of HSA are measured using CD spectra. The results reveal that the triazine herbicides with different alkyl groups can interact with HSA by static quenching. The combination of the three herbicides and HSA are equally proportional, and the binding processes are spontaneous. Hydrophobic interaction forces play important roles in simetryne-HSA and ametryn-HSA, while the interaction of terbutryn-HSA is Van der Waals forces and hydrogen bonding. Moreover, the three herbicides can bind to HSA at site I (sub-domain IIA) more than site II (subdomain IIIA), and combine with tryptophan (Trp) more easily than tyrosine (Tyr) residues, respectively. By comparison, the order of interaction strength is terbutryn-HSA > ametryn-HSA > simetryne-HSA. Terbutryn can destroy the secondary structure of HSA more than simetryne and ametryn, and the potential toxicity of terbutryn is higher. It is expected that the interactions of triazine herbicides with HSA via multi-spectral analysis can offer some valuable information for studying the toxicity and the harm of triazine herbicides on human health at molecular level in life science.

Ratiometric emission of Tb(III)-functionalized Cd-based layered MOFs for portable visual detection of trace amounts of diquat in apples, potatoes and corn.

Diquat (DQ) is a typical bipyridine herbicide widely used to control weeds in fields and orchards. The severe toxicity of diquat poses a serious threat to the environment and human health. Metal-organic frameworks (MOFs) have received widespread attention due to their unique physical and chemical properties and applications in the detection of toxic and harmful substances. In this work, a two-dimensional (2D) Tb(III) functionalized MOF Tb(III)@1 (1 = [Cd(HTATB)(bimb)]n·H2O (Cd-MOF), H3TATB = 4,4',4″-triazine-2,4,6-tribenzoicacid, bimb = 1,4-bis((1H-imidazol-1-yl)methyl)benzene) has been prepared and characterized. Tb(III)@1 has excellent optical properties and high water and chemical stability. After the Tb(III) is fixed by the uncoordinated -COO- in the 1 framework, Tb(III)@1 emits the typical green fluorescence of the lanthanide ion Tb(III) through the "antenna effect". It is worth noting that Tb(III)@1 can be used as a dual emission fluorescence chemical sensor for the ratio fluorescence detection of pesticide DQ, exhibiting a relatively low detection limit of 0.06 nM and a wide detection range of 0-50 nM. After the addition of DQ, a rapid color change of Tb(III)@1 fluorescence from green to blue was observed due to the combined effects of IFE, FRET and dynamic quenching. Therefore, a simple test paper box has been designed for direct on-site determination of pesticide DQ. In addition, the developed sensor has been successfully applied to the detection of DQ in real samples (fruits a Yin-Xia Sun and Bo-Tao Ji contributed equally to this work and should be considered co-first authors.nd vegetables) with satisfactory results. The results indicate that the probe developed in this study has broad application prospects in both real sample detection and actual on-site testing.

Central Chirality and Axial Chirality Recognition of the Enantioselective Antibodies to Herbicide Metolachlor.

Enantioselective antibodies have emerged as efficient tools in the field of chiral chemical detection and separation. However, it is complicated to obtain a highly stereoselective antibody due to the unclear recognition mechanism. In this study, the hapten of metolachlor was synthesized and enantio-separated. The absolute configuration of the four haptens obtained was identified by the computed and experimental electronic circular dichroism comparison. Five polyclonal antibodies against the Rac-metolachlor and its enantiomers were generated by immunization. The cross-activity of all the 5 antibodies with 44 structural analogues, including metolachlor enantiomers, was tested. It demonstrated that antibodies have higher specificity to recognize central chirality than axial chirality. Especially, αRR-MET-Ab exhibited excellent specificity and stereoselectivity. Accordingly, 3D-QSAR models were constructed and revealed that paired stereoisomers exhibited opposite interactions with the antibodies. It is the first time that the antibodies against four stereoisomers were prepared and analyzed, which will be conducive to the rational design of the stereoselective antibodies.

Investigation of the removal of diclofop methyl herbicide by peroxy electrocoagulation process and kinetic and cost analysis.

Pesticides containing chlorine, which are released during agricultural activities, are chemical substances that mix with surface and underground waters and have toxic, carcinogenic, and mutagenic effects on the entire living ecosystem. Due to their chemically stable structure, conventional water and wastewater treatment techniques such as coagulation, flocculation, and biological oxidation do not entirely remove these chemical substances. Therefore, before releasing them into the environmental receptor, these chemical substances must be transformed into harmless products or mineralized through advanced oxidation processes. When we look at the literature, there are not many studies on methods of removing diclofop methyl from aquatic media. Our study on the removal of diclofop methyl herbicide from aquatic media using the peroxy electrocoagulation method will provide the first information on this subject in the literature. In addition, this treatment method will contribute significantly to filling an important gap in the literature as an innovative approach for diclofop methyl removal. Moreover, peroxy electrocoagulation, which produces less sludge, provides treatment in a short time, and is economical, has been determined to be an advantageous process. The effects of conductivity, pH, H2O2 concentration, current, and time parameters on the removal of diclofop methyl were investigated using a GC-MS instrument. Kinetics, energy consumption, and cost calculations were also made. Under the optimum conditions determined (pH = 5, H2O2 = 500 mg/L, NaCl = 0.75 g/L, current density = 2.66 mA/cm2), the peroxydic electrocoagulation process resulted in a diclofop methyl removal efficiency of 79.2% after a 25-min reaction. When the experimental results were analyzed, it was found that the results fitted the pseudo-second-order kinetic model.

Interaction of different chloro-substituted phenylurea herbicides (diuron and chlortoluron) with bovine serum albumin: Insights from multispectral study.

In this work, the interaction between different chloro-substituted phenylurea herbicides (diuron (DIU) and chlortoluron (CHL)) and BSA were investigated and compared at three different temperatures (283 K, 298 K and 310 K) adopting UV-vis, fluorescence, and circular dichroism spectra. The quenching mechanism of the interaction was also proposed. The energy transfer between BSA and DIU/CHL was investigated. The binding sites of DIU/CHL and BSA and the variations in the microenvironment of amino acid residues were studied. The changes of the secondary structure of BSA were analyzed. The results indicate that both DIU and CHL can significantly interact with BSA, and the degree of the interaction between DIU/CHL and BSA increases with the increase of the DIU/CHL concentration. The fluorescence quenching of BSA by DIU/CHL results from the combination of static and dynamic quenching. The DIU/CHL has a weak to moderate binding affinity for BSA, and the binding stoichiometry is 1:1. Their binding processes are spontaneous, and hydrophobic interaction, hydrogen bonds and van der Waals forces are the main interaction forces. DIU/CHL has higher affinity for subdomain IIA (Site I) of BSA than subdomain IIIA (Site II), and also interacts with tryptophan more than tyrosine residues. The energy transfer can occur from BSA to DIU/CHL. By comparison, the strength of the interaction of DIU-BSA is always greater than that of CHL-BSA, and DIU can destroy the secondary structure of BSA molecules greater than CHL and thus the potential toxicity of DIU is higher due to DIU with more chlorine substituents than CHL. It is expected that this study on the interaction can offer in-depth insights into the toxicity of phenylurea herbicides, as well as their impact on human and animal health at the molecular level.

Design, Synthesis, and Herbicidal Evaluation of Pyrrolidinone-Containing 2-Phenylpyridine Derivatives as Novel Protoporphyrinogen Oxidase Inhibitors.

In this work, a series of pyrrolidinone-containing 2-phenylpyridine derivatives were synthesized and evaluated as novel protoporphyrinogen IX oxidase (PPO, EC 1.3.3.4) inhibitors for herbicide development. At 150 g ai/ha, compounds 4d, 4f, and 4l can inhibit the grassy weeds of Echinochloa crus-galli (EC), Digitaria sanguinalis (DS), and Lolium perenne (LP) with a range of 60 to 90%. Remarkably, at 9.375 g ai/ha, these compounds showed 100% inhibition effects against broadleaf weeds of Amaranthus retroflexus (AR) and Abutilon theophrasti (AT), which were comparable to the performance of the commercial herbicides flumioxazin (FLU) and saflufenacil (SAF) and better than that of acifluorfen (ACI). Molecular docking analyses revealed significant hydrogen bonding and π-π stacking interactions between compounds 4d and 4l with Arg98, Asn67, and Phe392, respectively. Additionally, representative compounds were chosen for in vivo assessment of PPO inhibitory activity, with compounds 4d, 4f, and 4l demonstrating excellent inhibitory effects. Notably, compounds 4d and 4l induced the accumulation of reactive oxygen species (ROS) and a reduction in the chlorophyll (Chl) content. Consequently, compounds 4d, 4f, and 4l are promising lead candidates for the development of novel PPO herbicides.

Engineering multi-degrading bacterial communities to bioremediate soils contaminated with pesticides residues.

Parallel to the important use of pesticides in conventional agriculture there is a growing interest for green technologies to clear contaminated soil from pesticides and their degradation products. Bioaugmentation i. e. the inoculation of degrading micro-organisms in polluted soil, is a promising method still in needs of further developments. Specifically, improvements in the understanding of how degrading microorganisms must overcome abiotic filters and interact with the autochthonous microbial communities are needed in order to efficiently design bioremediation strategies. Here we designed a protocol aiming at studying the degradation of two herbicides, glyphosate (GLY) and isoproturon (IPU), via experimental modifications of two source bacterial communities. We used statistical methods stemming from genomic prediction to link community composition to herbicides degradation potentials. Our approach proved to be efficient with correlation estimates over 0.8 - between model predictions and measured pesticide degradation values. Multi-degrading bacterial communities were obtained by coalescing bacterial communities with high GLY or IPU degradation ability based on their community-level properties. Finally, we evaluated the efficiency of constructed multi-degrading communities to remove pesticide contamination in a different soil. While results are less clear in the case of GLY, we showed an efficient transfer of degrading capacities towards the receiving soil even at relatively low inoculation levels in the case of IPU. Altogether, we developed an innovative protocol for building multi-degrading simplified bacterial communities with the help of genomic prediction tools and coalescence, and proved their efficiency in a contaminated soil.

Magnetite-driven Bio-Fenton degradation of chloroacetanilide herbicides by a newly isolated hydrogen peroxide producing bacterium Desemzia sp. strain C1.

The efficiency of the Fenton reaction is markedly contingent upon the operational pH related to iron solubility. Therefore, a heterogeneous Fenton reaction has been developed to function at neutral pH. In the present study, the Bio-Fenton reaction was carried out using magnetite (Fe(II)Fe(III)2O4) and H2O2 generated by a newly isolated H2O2-producing bacterium, Desemzia sp. strain C1 at pH 6.8 to degrade chloroacetanilide herbicides. The optimal conditions for an efficient Bio-Fenton reaction were 10 mM of lactate, 0.5% (w/v) of magnetite, and resting-cells (O.D.600 = 1) of strain C1. During the Bio-Fenton reaction, 1.8-2.0 mM of H2O2 was generated by strain C1 and promptly consumed by the Fenton reaction with magnetite, maintaining stable pH conditions. Approximately, 40-50% of the herbicides underwent oxidation through non-specific reactions of •OH, leading to dealkylation, dechlorination, and hydroxylation via hydrogen atom abstraction. These findings will contribute to advancing the Bio-Fenton system for non-specific oxidative degradation of diverse organic pollutants under in-situ environmental conditions with bacteria producing high amount of H2O2 and magnetite under a neutral pH condition.

Alleviating binary toxicity of polystyrene nanoplastics and atrazine to Chlorella vulgaris through humic acid interaction: Long-term toxicity using environmentally relevant concentrations.

In this study, microalgae Chlorella vulgaris (C. vulgaris) were simultaneously exposed to environmental concentrations of amino-functionalized polystyrene nanoplastics (PS-NH2; 0.05, 0.1, 0.2, 0.3 and 0.4 mg/L) and the world's second most used pesticide, the herbicide atrazine (ATZ; 10 µg/L), in the absence and presence of humic acid (HA; 1 mg/L) for 21 days. Due to the low concentrations of PS-NH2, the majority of them could not cause a significant difference in the end-points of biomass, chlorophylls a and b, total antioxidant, total protein, and superoxide dismutase and malondialdehyde compared to the control group (p > 0.05). On the other hand, by adding ATZ to the PS-NH2, all the mentioned end-point values showed a considerable difference from the control (p < 0.05). The exposure of PS-NH2+ATZ treatments to the HA could remarkably reduce their toxicity, additionally, HA was able to decrease the changes in the expression of genes related to oxidative stress (e.g., superoxide dismutase, glutathione reductase, and catalase) in the C. vulgaris in the most toxic treatment group (e.g., PS-NH2+ATZ). The synergistic toxicity of the PS-NH2+ATZ group could be due to their enhanced bioavailability for algal cells. Nevertheless, the toxicity alleviation in the PS-NH2+ATZ treatment group after the addition of HA could be due to the eco-corona formation, and changes in their zeta potential from positive to negative value, which would increase their electrostatic repulsion with the C. vulgaris cells, in such a way that HA also caused a decrease in the formation of C. vulgaris-NPs hetero-aggregates. This research underscores the complex interplay between PS-NH2, ATZ, and HA in aquatic environments and their collective impact on microalgal communities.

Culture optimization of Streptomyces sp. KRA16-334 for increased yield of new herbicide 334-W4.

This study aimed to isolate actinomycetes that exhibit strong herbicidal activity, identify compounds active against weeds, and researching methods to improve the production of these compounds through culture optimization to establish a foundation for the development of environmentally friendly bioherbicides. 334-W4, one of the herbicidal active substances isolated from the culture broth of Streptomyces sp. KRA16-334, exhibited herbicidal activity against various weeds. The molecular formula of 334-W4 was determined to be C16H26N2O6, based on ESI-MS (m/z) and 1H and 13C NMR spectral data. It had molecular weight 365.1689 [M+Na] and 343.1869 [M+H], indicating the presence of the epoxy-ß-aminoketone moiety based on HMBC correlations. Additionally, selective culture was possible depending on the addition of trifluoroacetic acid (TFA) during culture with GSS medium. Experiments confirmed that exposure of the KRA16-334 strain to UV irradiation (254 nm, height 17 cm) for 45 seconds improved the yield of the active substance (334-W4) by over 200%. As a result of examining yields of active materials of four mutants selected through optimization of culture conditions such as temperature, agitation, and initial pH, the yield of one mutant 0723-8 was 264.7 ± 12.82 mg/L, which was 2.8-fold higher than that of wild-type KRA16-334 at 92.8 ± 5.48 mg/L.