Ultimate fate, transformation, and toxicological consequences of herbicide pretilachlor to biotic components and associated environment: An overview.

Herbicides are applied for effective weed management in order to increase the crop yield. In recent decades, the overuse of these chemicals has posed adverse effects on different biotic components of the environment. Pretilachlor has been widely used during last few decades for weed management in paddy crop. Its excessive use may prove fatal for environment, various organisms, and nontarget plants. Thus, it is pertinent to know the extent to which herbicide residues remain in environment. The potential mobility and the release rate of herbicide in the soil are important factors governing ecotoxicological impact and degradation rate. Therefore, several techniques are being investigated for its effective removal from the contaminated sites. Furthermore, efforts have also been made to study the degradation of pretilachlor by various physicochemical processes, resulting into the formation of different types of metabolites. This review summarizes the available information on environmental fate, various degradation processes, microbial biotransformation, metabolites formed, ecotoxicological effects, techniques for detection in environmental samples, effect of safener, and various control release formulations for sustained release of pretilachlor in applied fields. The information so obtained will be very advantageous in deciding the future policies for safe and judicious use of the herbicide by maintaining health and environmental sustainability.

Ultimate fate and possible ecological risks associated with atrazine and its principal metabolites (DIA and DEA) in soil and water environment.

Atrazine (AT) is a triazine herbicide widely used to control weeds in several crops. De-isopropylatrazine (DIA) and de-ethylatrazine (DEA) are two of the eight primary metabolites produced by AT breakdown in soil and water. The physico-chemical properties of the soil determine their final fate. So, this study aimed to assess the function of clay loam and sandy loam soils in determining their ultimate fate and the potential ecological risks to non-target species during their persistence in soil and transportation to water bodies. The soil in pots was spiked with standard solutions of AT, DEA, and DIA at 0.3 and 0.6 mg/kg for the persistence study. The leaching potential was determined by placing soils in Plexi columns and spiking them with 50 and 100 µg standard solutions. Liquid-liquid extraction was used to prepare the samples, which were then analyzed using GC-MS/MS. The dynamics of dissipation were first-order. AT, DEA and DIA disappeared rapidly in sandy loam soil, with half-lives ranging from 6.2 to 8.4 days. AT and its metabolites had a significant amount of leaching potential. In sandy loam soil, leaching was more effective, resulting in maximal residue movement up to 30-40 cm soil depth. The presence of a notable collection of residues in leachate fractions suggests the potential for surface and groundwater contamination. In particular, DEA and DIA metabolites caused springtail Folsomia candida and earthworm Eisenia fetida to have longer and greater unacceptable risks. If the residues comparable to the amount acquired in leachate fractions reach water bodies, they could cause toxicity to a variety of freshwater fish, aquatic arthropods, amphibians, and aquatic invertebrates. Future studies should take a more comprehensive approach to evaluate ecological health and dangers to non-target species.

Persistence, leaching and associated toxicity risks of insecticide pyriproxyfen in soil ecosystem.

Pyriproxyfen is a pyridine-based insecticide used for pest control in fruits and vegetables. It is a potent endocrine disruptor and hormone imitator. Considering its potential hazards to non-target organisms and the associated environment, a lab study was conducted for assessing persistence, mobility in sandy loam soil and associated risk to various non-target organisms and soil enzymes. Pyriproxyfen formulation was applied at 0.05 and 0.10 µg g-1 soil which was equivalent to recommended and double dose of 100 and 200 g a.i. ha-1, respectively. Three methods namely QuEChERS, liquid-solid extraction (LSE) and matrix solid phase dispersion (MSPD) were compared for achieving efficient sample preparation. MSPD was applied for final analysis as it gave better recoveries (94.2 to 104.3%) over other methods with limits of detection and quantification (LOD and LOQ) as 0.0001 and 0.0005 µg g-1, respectively. Dissipation followed first order kinetics with half-lives of 7.6 and 8.2 days in both doses but residues retained over 45 days in soil. Leaching studies conducted at 50 and 100 µg of pyriproxyfen showed extremely poor leaching potential. Retention of over 90% residues in top 5 cm soil surface indicated minimal threat of ground and surface water contamination. Toxicological study demonstrated very different behaviour toward different enzymatic activities. Pyriproxyfen was relatively toxic for alkaline phosphatase and fluorescein diacetate hydrolase enzymes. ß-glucosidase activity was triggered whereas arylsulfatase activity remained unaffected. Unacceptable risk to soil invertebrates at double dose application clearly indicated that its longer persistence in soil could be toxic to other non-target organisms and needs further investigations.

Ultimate fate of herbicide tembotrione and its metabolite TCMBA in soil.

Tembotrione is a triketone group herbicide having worldwide applications for weed management in maize. It is considered to be less stable in the environment and its degradation products may have toxicological consequences due to longer persistence and off-site movements. We studied the persistence behavior and leaching potential of tembotrione and its major metabolite TCMBA in clay loam and sandy loam soils having different physico-chemical properties. The rapid transformation of parent tembotrione to degradation products and their high interactions with soil provided challenging task of residues separation from complex soil matrix. Therefore, a novel sample preparation method (modified QuEChERS) was optimized for trace estimation of tembotrione and TCMBA which offered 86.6-95.6% recoveries with limit of detection (LOD) and quantification (LOQ) as 0.001 and 0.003 µg/g, respectively in both soils without any matrix interference. A first order dissipation kinetics was followed by tembotrione and TCMBA residues with half-life ranged from 7.2 to 13.4 days in both soils. Residues reached below detectable limit on 45-60 days after treatments in two application doses. Leaching experiment revealed maximum retention of tembotrione residues from 15 to 25 cm depth in both soils whereas TCMBA show appreciable leaching potential. It was concluded that tembotrione can be phytotoxic to the succeeding crops if applied at late post-emergence stage. TCMBA can contaminate surface and ground water due to continuous and prolonged use of tembotrione particularly in light textured soils.

Purification, characterization and antibacterial spectrum of a compound produced by Bacillus cereus MTCC 10072.

Awareness of the consumer has increased the demand of safe and chemical-free foods, and consequently it has increased the demand of antibacterial bioactive compounds. In the present study, antibacterial compound produced by a local bacterial isolate NSD MTCC 10072, showing antagonistic activity against six human pathogens, was isolated, partially purified and characterized. Maximum production of antibacterial compound was observed between 51 and 60 h after seeding. The antibacterial activity of the compound was found to be thermostable up to 80 °C for 60 min and its efficacy was very good between pH 4 and 12. Minimum inhibitory concentration (25.84 µg/µl) of the antibacterial compound was observed against Streptococcus aureus NICM 2901. GC-MS analysis of the bacterium secreted chemical compound (C11H18N2O2) was used to identify the antimicrobial compound as Pyrrolo(1,2-a) pyrazine-1,4-dione, hexahydro-3-(2-methylpropyl). In Silico studies showed that the antimicrobial compound is non-toxic, non-irritating and followed Lipinski-type properties which suggested that the compound could be used as potential drug against different human pathogens.

Degradation Dynamics of Halosulfuron-methyl in Two Textured Soils.

A laboratory experiment was conducted to study the degradation dynamics of halosulfuron-methyl residues in sandy loam and clay loam soil. The herbicide formulation was applied at 0.034 and 0.068 mg kg- 1 equivalent to field application dose of 67.5 and 135 g a.i. ha- 1 as single and double dose respectively. Soil samples were collected on 0 (1 h), 1, 3, 7, 10, 15, 30 and 45 days after treatments. Extraction was done using modified QuEChERS method. Residues were estimated by UPLC coupled with quadrupole Dalton mass detector. Average recoveries ranged from 85.5% to 94.5% for both soils at different fortification levels of 0.005 to 0.1 mg kg- 1 with limit of detection (LOD) and limit of quantification (LOQ) as 0.001 and 0.005 mg kg- 1, respectively. Dissipation followed first order kinetics with half-life of 8.4 to 10.7 days in both soil at two doses. The residues reached below LOQ of 0.005 mg kg- 1 after 45 days of herbicide application.

Aonla phytochemicals: extraction, identification and quantification.

Methanolic, ethanolic and ethyl acetate extracts of five aonla varieties were analyzed for phytochemical characterization using RP-HPLC. Five compounds viz. ascorbic acid, gallic acid, ellagic acid, ethyl gallate and quercetin were identified in aonla extracts by RP-HPLC at 270 nm. Significant variations were observed in amount of identified phytochemical among the varieties. The highest level of phytochemical was observed in methanolic extract of variety Desi followed by varieties Kanchan, NA-7, Banarasi and Chakaiya. Among the solvent, methanol extracted the maximum phytochemicals while yield was least in ethyl acetate extract of aonla varieties. Gallic acid and ellagic acid were the most abundant phenolic compounds in extracts of aonla varieties. Ellagic acid (349.51 mg/100 g) and gallic acid (233.49 mg/100 g) were found maximum in methanolic extract of Desi variety. Results of the present study suggested that aonla is a good source of phenolic and flavonoid compounds.

Behavior of pre-mix formulation of imazethapyr and imazamox herbicides in two different soils.

Imidazolinone group herbicides are known for longer persistence in soil. Therefore, a laboratory study was performed to evaluate the persistence of pre-mix formulation of two imidazolinone herbicides-imazethapyr and imazamox in clay and sandy loam soils. Herbicide formulation was applied at 70 and 140 g a.i. ha-1 equivalent to recommended doses in legumes. For achieving efficient sample preparation, three methods namely ultrasonic-assisted extraction (UAE), matrix solid phase dispersion (MSPD), and solid phase extraction (SPE) were optimized. MSPD gave better recoveries (85.22 to 96.00%) over SPE (80.10 to 84.78%) and UAE (56.44 to 66.20%). Residues were estimated using gas chromatography tandem mass spectrometry (GC-MS/MS) which is previously not reported in open literature. Dissipation followed first-order kinetics and half-life period of 23.5 to 43.3 days in clay loam and 19.6 to 39.8 days in sandy loam soil. The results revealed the persistent nature of pre-mix formulation of both herbicides as only 64.2 to 86.6% residues dissipated after 90 days of application in both soils.

Influence of Long Term Application of Butachlor on its Dissipation and Harvest Residues in Soil and Rice.

The study delineates the effect of repeated application of butachlor to rice crop from 1997 onwards. Additionally, in 2014 and 2015, dissipation kinetics of butachlor in soil was studied under field and laboratory conditions. The average recovery of butachlor for soil, rice grain and rice straw ranged between 80.3%-93.2% and 82.8%-96.5% with quantification limit of 0.01 and 0.003 µg g-1 for HPLC and GC-MS/MS, respectively. The dissipation of butachlor followed first order kinetics and half-life under long term field trials in rice soil varied from 15.2 to 19.29 days and 25.94 to 29.79 days under field and laboratory conditions, respectively. The residue of butachlor in soil, rice grain and straw samples at harvest over the years was below the quantification limit and no quantifiable amount of metabolites were present in soil at harvest suggestive of its safe application.

Determination of residues of fipronil and its metabolites in cauliflower by using gas chromatography-tandem mass spectrometry.

Fipronil is a widely used insecticide with a well-described toxicological pathway. Recently it has been widely used in India to control vegetable pests. The present study has been carried out to observe the persistence pattern of fipronil and its metabolites-fipronil sulfone, fipronil sulfide, fipronil desulfinyl in cauliflower and soil so as to know the potential risk if any to consumers and environment. Fipronil was applied @ 56 g a.i. ha(-1). Samples of cauliflower and soil were collected periodically; processed using QuEChERS method and analyzed by GCMS/MS. In cauliflower, residues of fipronil and its metabolites reached below detectable level before 30 days of application whereas in soil about 95% of total fipronil residues got degraded within same time period. Washing and washing followed by cooking or boiling was found effective in reducing residues. A safe waiting period of 15 days is therefore suggested before consuming cauliflower.

Design, Synthesis, Nematicidal Evaluation, and Molecular Docking Study of Pyrano[3,2-c]pyridones against Meloidogyne incognita.

Root-knot nematodes pose a serious threat to crops by affecting production and quality. Over a period of time, substantial work has been done toward the development of effective and environmentally benign nematicidal compounds. However, due to the inefficiencies of previously reported synthetics in achieving the target of safe, selective, and effective treatment, it is necessary to develop new efficacious and safer nematicidal agents considering human health and environment on top priority. This work aims to highlight the efficient and convenient l-proline catalyzed synthesis of pyrano[3,2-c]pyridone and their use as potential nematicidal agents. In vitro results of larval mortality and egg hatching inhibition revealed maximum nematicidal activity against Meloidogyne incognita from compounds 15b, 15m, and 15w with LC50 values of 28.8, 46.8, and 49.18 µg/mL at 48 h, respectively. Under similar conditions, pyrano[3,2-c]pyridones derivatives 15b (LC50 = 28.8 µg/mL) was found at par with LC50 (26.92 µg/mL) of commercial nematicide carbofuran. The in vitro results were further validated with in silico studies with the most active compound 15b nematicidal within the binding to the pocket of acetylcholine esterase (AChE). In docking, binding free energy values for compound 15b were found to be -6.90 kcal/mol. Results indicated that pyrano[3,2-c]pyridone derivatives have the potential to control M. incognita.

A score years' update in the synthesis and biological evaluation of medicinally important 2-pyridones.

2-Pyridone core structure has attracted much attention due to its abundance in natural products of biological importance. 2-Pyridone derivatives display diverse biological activities. From being antimicrobial, antimalarial, antitumor, cardiotonic and anti-fibrotic agents to the induction of neurite outgrowth, they affect many biological processes. They find significant role in medicines, agriculture, pharmacophore designing and are also used as synthones for other heterocyclic compounds. Therefore, the main purpose of this review is to assess the biological pursuits of 2-pyridone compounds. In addition, this review presents the overview of synthesis of medicinally active 2-pyridones along with their biological activity done in the past two decades.

Persistence of dicofol residues in cotton lint seed, and soil.

A supervised field trial was conducted at the CCS Haryana Agricultural University, Hisar to assess the residues of dicofol on cotton, during Kharif season, 2008. Dicofol (Kelthane 18.5EC) was applied at 500 g a.i./ha (T(1)) and 1,000 g a.i./ha T(2)) after 105 days of sowing of cotton crop (Varity Cotton/H-1226). Soil samples were collected on 0 (1 h after treatment), 3, 7, 10, 15, 30, and 60 days after spray and cotton samples were collected at harvest. Samples were processed and residues were quantified by GC-ECD system equipped with capillary column. Limit of detection and limit of quantification (LOQ) were 0.001 and 0.010 mg kg( -1), respectively, for soil and LOQ for cotton lint and seed was 0.020 mg kg( -1). Initial residues of 0.588 and 1.182 mg kg( -1) in soil reached below detectable level (BDL) of 0.010 mg kg( -1) in T(1) and to the level of BDL (0.010 mg kg( -1)) in T(2) at harvest (60 days after treatment). In 60 days, residues dissipated almost completely (100 and >99%) in both the treatments. Half-life period was calculated as 8.57 days at single dose and 8.69 days at double dose in soil. Residues of dicofol were detected in cotton lint to the levels of 0.292 and 0.653 mg kg( -1) and in seed 0.051 and 0.090 mg kg( -1) in T(1) and T(2) doses, respectively at harvest. Residues in cotton seed were below MRL value of 0.01 mg kg( -1) in both the doses.

Degradation studies of fenazaquin in soil under field and laboratory conditions.

Degradation of fenazaquin in sandy loam soil was investigated under field and laboratory conditions. Fenazaquin (Magister 10EC) was applied @ 125 and 250 g a.i./ha in field and in pot under field capacity moisture in laboratory. Samples drawn periodically were analyzed on GC-NPD. The residues of fenazaquin in both the doses and conditions dissipated almost 90% in 90 days. Half-life period were 32.04 and 31.35 days at two doses, respectively at field conditions and 30.10 and 28.94 days at laboratory conditions. Dissipation was approximated to first order kinetics in both conditions having correlation coefficient ranging from -0.9848 to -0.9914.

Effect of household processing on fenazaquin residues in okra fruits.

Fenazaquin (4-[[4 (1,1-dimethylethyl) phenyl] ethoxy]quinazoline) is a new acaricide of the quinazoline class. Residue levels of fenazaquin were determined in unprocessed and processed okra fruits to evaluate the effect of different processes (washing, boiling and washing followed by boiling) in reduction of residues of this pesticide in okra. The study was carried out on okra crop (Variety, Varsha Uphar) in research farm of Chaudhary Charan Singh Haryana Agricultural University, Hisar with application of fenazaquin (Magister 10 EC) @ 125 ga.i./ha (Single Dose, T(1)) and 250 g a.i./ha (Double Dose, T(2)). Samples of okra fruits were collected on 0, 3, 7, 15 days after treatment and at harvest (30 days). Residues were estimated by gas chromatograph equipped with capillary column and nitrogen phosphorus detector. Residues reached below maximum residue limit of 0.01 mg/kg at harvest. The residues dissipated with half-life period of 3.13 days at lower dose and 4.43 days at higher dose. Processing is shown to be very effective in reducing the levels of fenazaquin residues in okra fruits. Maximum reduction (60-61%) was observed by washing + boiling followed by boiling/cooking (38-40%) and then by washing (31-32%).

Organic waste from sugar mills as a potential soil ameliorant to minimise herbicide runoff to the Great Barrier Reef.

We studied sorption potential for a range of herbicides using eleven waste materials (mill muds) containing organic matter (47.6 to 65.1%) produced by sugar mills and applied as soil conditioners by farmers. Sorption/desorption behaviour of five herbicides commonly used in sugarcane production (imazapic, atrazine, hexazinone, diuron and metribuzin) was studied on these mill muds, as is and after adding these to three soils at different rates (5-25%, dry weight basis). All mill muds had significant sorption capacity, especially for diuron, atrazine and metribuzin which was 6 to 26 times higher than the soil with 3.5% organic carbon (OC). Generally, sorption of the five herbicides assessed in all mill muds followed the order diuron > atrazine = metribuzin > hexazinone = imazapic. Eight out of 11 mill muds had similar sorption capacity for any given herbicides. Amending soils with selected mill muds significantly enhanced their sorption efficiency, depending on the rate of application especially in soil with low OC. Generally, application of mill muds at 5% w/w or 40 tons/ha increased sorption of studied herbicides by 2 to 10 folds. Soil amendment with mill muds also reduced the rate and extent of desorption of herbicides- especially mobile herbicides like metribuzin. Nearly 79% release of metribuzin was observed after three desorption steps in amended soil (at 5% w/w), whereas in unamended soil, 100% of metribuzin was released during first desorption step. The study demonstrates that wastes produced by sugar mills may have recycling use in enhancing the retention of mobile herbicides in soils with low OC content.

Effect of long-term application of pretilachlor on its persistence and residues in paddy crop.

The effect of long-term application of pretilachlor to paddy in rice-wheat cropping system was investigated from 1997 to 2015. Additionally, in 2013, field experiment was also conducted where pretilachlor was applied to paddy field having no background of its application. The residues of pretilachlor were quantified using high-performance liquid chromatography (HPLC). The average recoveries of pretilachlor from paddy soil, paddy grain and straw samples ranged from 80.7% to 93.8% using HPLC with standard deviation less than 10%. The dissipation rate of pretilachlor in paddy soil followed first-order kinetics and half-life ranged from 9.58 to 21.19 days. In 2015, HPLC was compared with gas chromatography-tandem mass spectrometry (GC-MS/MS) for quantification of residues. Average recoveries of pretilachlor using GC-MS/MS from paddy soil, paddy grain and straw samples ranged from 81.4% to 98.3% with standard deviation less than 10%. Both HPLC and GC-MS/MS offered high reproducibility; however GC-MS/MS was more sensitive and the limit of detection was 3.0 and 1.0 ng g-1 for HPLC and GC-MS/MS, respectively. At harvest, the residues of pretilachlor in the paddy soil and crop were below the maximum residue limit and no dangerous accumulation was observed after its prolonged application.