Biodegradation and metabolic pathway of quinalphos by Cunninghamella elegans ATCC36112

Quinalphos is a long-term, wide-spectrum organophosphate insecticide with residual problems in the natural environment. Cunninghamella elegans (C. elegans) is a member of Mucoromycotina. Since the degradation products of its exogenous compounds are similar to those of mammals, it is often used to simulate the metabolism pathways of mammals. In this study, the detailed metabolic pathways of quinalphos were investigated with C. elegans. Quinalphos was degraded by 92% in 7 days, while ten metabolites were produced. The metabolites were analyzed and identified by GC-MS. To determine the responsible enzymes in quinalphos metabolism, piperonyl butoxide (PB) and methimazole included in the culture flasks, and the kinetic responses of quinalphos and its metabolites by C. elegans were measured. Results indirectly demonstrated that cytochrome P450 monooxygenases were involved in the metabolism of quinalphos, but that methimazole inhibited the metabolism less efficiently. Comprehensive metabolic pathways can be deduced from the detailed analysis of metabolite profiles in control and inhibitor assays.

Toxicity analysis and biomarker response of Quinalphos Organophosphate Insecticide (QOI) on eco-friendly exotic Eudrilus eugeniae earthworm

An ever-increasing use of pesticides in agricultural fields has led to a catastrophic decline in crop quality and, ultimately soil fertility. To control various pests, quinalphos is commonly used in India's tea plantations. This study aims to investigate the effects of the Quinalphos organophosphate insecticide on the non-target beneficial organism Eudrilus eugeniae earthworms and the biomarkers that respond to its effects. Earthworm species, especially E. eugeniae, remains as the most trustworthy and well-suited model organism for conducting a wide variety of environmental studies. The median lethal concentration (LC₅₀) was identified as 3.561 µg cm^-2 (contact filter paper) and 1.054 mg kg^-2 (artificial soil toxicity). The 5% and 10% of LC₅₀ value 3.561 µg cm^-2 was exposed to earthworm to analyze the sublethal effects at pre-clitellum, clitellum, and post-clitellum segments. Specific enzymatic activities of neurotransmitter enzyme acetylcholinesterase; antioxidant enzymes such as lipid peroxidase, superoxide dismutase, and catalase; and detoxification enzymes including glutathione S transferase, reduced glutathione, carboxylesterase, and Cytochrome P450 were analyzed. Exposure of E. eugeniae earthworm to subacute exposures of pesticides caused significant alterations in these stress markers in a concentration-dependent manner. Morphological abnormalities like bulginess, coiling, and bleeding were observed after exposure of the insecticide treatments. Histological cellular disintegration, a reduced NRRT time, and an inhibited proteolytic zone were also identified in pesticide-exposed earthworms. Studies demonstrate that the organophosphate insecticide quinalphos causes acute toxicity in E. eugeniae; hence, it is suggested that non-target eco-friendly E. eugeniae earthworms may be at risk if exposed to the excessive concentrations of quinalphos organophosphate insecticide in soil.

Dose-Dependent Oxidative Damage in Erythrocytes and Hepatic Tissue of Wistar Rats Concurrently Exposed with Arsenic and Quinalphos: a Subacute Study

Concurrent exposure to a multitude of environmental toxicants pose serious health hazard to humans and animals. The present investigation was conceptualized to determine deleterious effects of concomitant subacute arsenic and quinalphos exposure on antioxidant responses of liver and erythrocytes of Wistar rats. Fifty-four Wistar rats were divided into nine groups with six animals in each. Animals were exposed to either quinalphos (1/100^th and 1/10^th of LD₅₀) through oral gavage daily or arsenic (50 and 100 ppb) in drinking water alone and in combination for 28 days. While treatment with different toxicants alone also significantly reduced hemoglobin concentration, hepatic biomarkers and levels of antioxidant parameters as compared with control values, concomitant exposure significantly (P < 0.05) elevated levels of hepatic transaminases and alkaline phosphatase. Moreover, along with significant depletion in activities of SOD, CAT, TTH, AChE, and enzymes of glutathione complex, a significant enhancement of lipid peroxidation was also recorded in liver and erythrocytes in co-exposed animals in a dose-dependent manner when compared with exposure to individual toxicant. More severe alterations occurred in hepatic histo-architecture of rats receiving combined treatment as compared with those treated with either toxicant. Results indicated that oxidative damage in erythrocytes was more than that of the liver of rats on concomitant exposure of arsenic and quinalphos in a dose-dependent manner. In nutshell, our results revealed that combined treatment of quinalphos with arsenic potentiated toxic effects of either toxicant on antioxidant machinery of liver and erythrocytes and hepatic histomorphology of exposed Wistar rats.

Eliminating pesticide quinalphos from surface waters using synthesized GO-ZnO nanoflowers: Characterization, degradation pathways and kinetic study

The presence of highly toxic and persistent pesticides in water bodies causes serious problems to human beings as well as aquatic life. Quinalphos is one such widely used organophosphorus pesticide in agricultural fields. Herein, for degradation and mineralization of quinalphos, ZnO nanoflowers and their hybrid nanocomposite with graphene oxide have been synthesized. FESEM analysis confirmed the formation of ZnO nanoflowers over nanosheets of graphene oxide having a thickness of 20 ± 10 nm. GO-ZnO composite exhibited remarkable photocatalytic activity in comparison to pure ZnO. 98 % degradation of quinalphos was achieved using GO-ZnO nano-catalyst at 6 pH within 45 min of irradiations, whereas it was 80 % for bare ZnO nanoflowers. Higher degradation with hybrid nanocomposite was attributed to improved surface area (36 m² g^-1), a substantial reduction in bandgap energy from 3.10 to 2.90 eV and enhanced charge separation (e^-/h⁺ pairs) after the addition of GO. Reaction kinetics study followed pseudo-first-order behaviour. Further, mineralization to the extent of 90 % in 90 min was confirmed by TOC analysis. Based on identified intermediates, using LCMS analysis, degradation pathways were proposed. The plausible pathways confirmed the presence of smaller and safer reaction intermediates supported by excitation of e^- from nanocomposite followed by oxidation of quinalphos with huge free radicals. Overall, this study is significant in terms of using photocatalysis as a tertiary treatment of quinalphos pesticide wastewater at pH 6 in a short duration.

Facile synthesis of carbon dots from Tagetes erecta as a precursor for determination of chlorpyrifos via fluorescence turn-off and quinalphos via fluorescence turn-on mechanisms

Convenient one-pot synthetic route for the fabrication of carbon dots (CDs) from Tagetes erecta flower (TEF), named as "TEF-CDs', through solvo(hydro)-thermal carbonization of the TEF was developed. The TEF-CDs revealed high selectivity towards chlorpyrifos and quinalphos, acting as a fluorescent probe. The CDs synthesized from T. erecta flower showed a strong blue color at 495 nm when excited at 420 nm, along with the exhibition of a strong quantum yield of 63.7%. The synthesized CDs revealed their richness in the surface-active organic group that synthesized CDs from T. erecta flower are mainly comprised of C, O, and N, which were crystalline in structure that was revealed by TEM image and XRD spectra. Furthermore, when the probe was exposed to different pH conditions, no major noticeable changes were recorded. Moreover, when the probe was exposed to chlorpyrifos and quinalphos, we have noticed that fluorescence spectra was turned off when the probe was exposed to chlorpyrifos and "turned on" after the exposure quinalphos. Moreover, fluorescence spectral changes showed a good linearity with chlorpyrifos and quinalphos concentrations in the range of 0.05-100.0 μM for chlorpyrifos and 0.01-50.0 μM for quinalphos. The limit of detection are 2.1 ng mL^-1 and 1.7 ng mL^-1 for chlorpyrifos and quinalphos, respectively. Finally, the TEF-CDs-based fluorescent nanoprobe was successfully applied to estimate chlorpyrifos and quinalphos with an effective accuracy in rice and fruit samples with rapid detection time.

Maximum contaminant level of arsenic in drinking water potentiates quinalphos-induced renal damage on co-administration of both arsenic and quinalphos in Wistar rats

This study was designed to determine alterations in renal biomarkers, antioxidant profile, and histomorphology of renal tissue following subacute exposure to quinalphos alone or in conjunction with arsenic in rats. A total of 54 adult Wistar rats were randomly divided into nine groups of six rats each and were administered sub-lethal concentrations of quinalphos (1/100^th and 1/10^th of LD₅₀) orally daily and arsenic (50 and 100 ppb) in drinking water for 28 days. Significantly (p < 0.05) decreased levels of antioxidant biomarkers in renal tissue, viz., total thiols, catalase, superoxide dismutase, glutathione peroxidase, glutathione-s-transferase, and glutathione reductase along with increased (p < 0.05) thiobarbituric acid reacting substance (TBRAS) levels indicated that significant oxidative damage to renal tissue occurred following repeated administrations of quinalphos at either dose levels or arsenic at the concentration of 100 ppb when compared with the control rats. The alterations in the antioxidant parameters were observed to be more pronounced in co-administered groups as compared with either toxicant administered group. Similarly, activity of renal acetylcholinesterase was decreased after repeated exposure to quinalphos or arsenic, but inhibition was higher (up to 48%) in rat renal tissue co-exposed with quinalphos and arsenic at the higher concentration. These findings corroborated with the histopathological alterations in renal tissue of toxicant exposed rats. The altered plasma and tissue antioxidant biomarkers along with histopathological changes in the kidney at higher dose level of either toxicant indicate that renal tissue is significantly impacted by these toxicants, and these effects become more pronounced after their co-administration.

Rapid biodegradation and biofilm-mediated bioremoval of organophosphorus pesticides using an indigenous Kosakonia oryzae strain -VITPSCQ3 in a Vertical-flow Packed Bed Biofilm Bioreactor

The widespread use of pesticides has been one of the major anthropogenic sources of environmental pollution. Organophosphorus (OP) pesticides are predominantly used in agriculture due to their broad-spectrum insecticidal activity and chemical stability. The study was focused on the biodegradation of OP pesticides, Profenofos (PF) and Quinalphos (QP) in culture media using bacterium isolated from wetland paddy rhizosphere. The strain VITPSCQ3 showed higher pesticide tolerance, efficient biofilm formation and was capable of synthesizing organophosphate degrading enzymes. Based on the 16S rRNA gene sequencing the isolate exhibited maximum sequence similarity with Kosakinia oryzae (GenBank accession number: KR149275). Biodegradation assay with various concentrations of PF and QP (200, 400, 600 and 800 mg L^-1) showed maximum degradation up to 82% and 92% within 48 h. The kinetic studies revealed the biodegradation rates (k) to be 0.0844 min^-1 and 0.107 min^-1 with half-lives (h) of 18 h and 14.8 h for PF and QP. The degradation products were identified by GCMS and possible degradation pathways were proposed using Insilico techniques. To the best of our knowledge, this is the first report on the biodegradation of PF and QP using Kosakonia oryzae. Bioremoval of PF and QP from aqueous solution was performed using the biofilm of VITPSCQ3 developed on selected substrates in a circulating Vertical-flow packed-bed biofilm (VFPBB) bioreactor. Charcoal, gravel and mushroom (Agaricus bisporus) were used as biofilm carriers. Mushroom showed strong biofilm formation with optimum biodegradation capacity of up to 96% for PF and 92% for QP within 120 min reaction time.

Determination of quinalphos in human whole blood samples by high-performance thin-layer chromatography for forensic applications

A simple and rapid procedure for the determination of quinalphos in human whole blood using liquid-liquid extraction and high-performance thin-layer chromatography was developed and validated. Seven different organic solvents were tested for optimum extraction of quinalphos from spiked blood samples. The effect of pH on the extraction yield of quinalphos was also examined. An average recovery of 93.61% was achieved from diethyl ether solvent at pH 3. Chromatographic separation was performed on silica gel 60F₂₅₄ plates using mobile phase n-hexane-acetone in the ration 9:1 (v/v). Densitometric detection was carried out at 325 nm in absorbance mode. The interference of other organophosphorus pesticides of forensic relevance was not observed. The linear regression analysis in spiked whole blood samples resulted in linear calibration plot in the range 1 to 100 μg mL^-1 with r² = 0.9981. Sensitivity was represented by LLOQ at 1 μg mL^-1. The within-day precision and between-day precision ranged from 0.18 to 1.04%, and 0.14 to 0.79% with an overall average recovery of 91.06% at three concentrations 1, 10, and 50 μg mL^-1. No significant decrease in the concentration of quinalphos was observed for samples under different storage conditions. Finally, the developed procedure was applied to postmortem blood samples obtained in three fatal cases of poisoning by quinalphos.

Biodegradation of Quinalphos by a Soil Bacterium-Bacillus subtilis

BACKGROUND AND OBJECTIVE

A widely used pesticide quinalphos (O, O-diethyl O-quinoxalin-2-yl phosphorothioate) may be an undesirable and persistent pollutant to non-target environments like rivers and other ecosystems. The objective of this study was to isolate a potential degradant bacterium of quinalphos from polluted soils and test its fitness under various culture conditions.

MATERIALS AND METHODS

A soil bacterium strain, capable of utilizing quinalphos as its sole source of carbon and energy was isolated from soil by enrichment method on a minimal salts medium (MSM). On the basis of morphological, biochemical and 16S rRNA gene sequence analysis the bacterium is a species of the genus Bacillus and it was closely related to Bacillus subtilis. Quinalphos degrading capabilities of this bacterium were assessed under different culture conditions. Quinalphos degradation data were analysed byusing a two-way ANOVA analysis with the Statistica v.10.

RESULTS

Bacillus subtilis grew on quinalphos with a generation time of 32.34 min or 0.54 h in the logarithmic phase. Maximum degradation of quinalphos was observed with an inoculum of 1.0 optical density, around pH-7.5 and at an optimum temperature of 35-37°C. Among the additional carbon and nitrogen sources, carbon source-glucose and nitrogen source-yeast extract marginally improved the rate of degradation of quinalphos. Gas chromatography-mass spectrometry (GC-MS) analysis of the culture of B. subtilis grown on quinalphos indicated the formation of one main metabolite-quinoxaline.

CONCLUSION

The B. subtilis strain discovered in this study has a unique combination of abilities to degrade quinalphos and it is therefore suitable candidate bioremediator of quinalphos polluted environments.

Mobility and dissipation of chlorpyriphos and quinalphos in sandy clay loam in an agroecosystem-a laboratory-based soil column study

Leaching potential of pesticides, apart from climatological factors, depends on soil physical properties, soil-pesticide interaction and chemical nature of the molecule. Recent investigations have revealed the presence of various organophosphate pesticides in various agroecosystems. The present study investigated the soil transport mechanism of commonly used organophosphate pesticides in acidic sandy clay loam soils of Kerala State, India. Packed soil column experiment was undertaken under laboratory condition for 30 days. Unsaturated flow was carried out using distilled water/0.01 M CaCl₂ solution after applying chlorpyriphos and quinalphos at the rate of 0.04% a.i.ha^-1 and 0.025% a.i.ha^-1, respectively. The study revealed the retention of residues of chlorpyriphos and quinalphos in the top 5-cm layer. Irrespective of the applied concentration of chlorpyriphos and quinalphos, the relative concentration of the pesticides in soil was similar. About 56% of the applied chemicals were dissipated in 30 days of unsaturated flow. A new dissipation compound iron, tricarbonyl [N-(phenyl-2-pyridinylmethyene) benzenamine-N, N'], was detected in GCMS analysis of soil extract from distilled water percolated soil. The dissipation of chlorpyriphos and quinalphos was faster in 0.01 M CaCl₂-treated soil column. Among the pesticides analysed, the residue of quinalphos was detected in leachate.

Influence of environmental factors on biodegradation of quinalphos by Bacillus thuringiensis

BACKGROUND

The extensive and intensive uses of organophosphorus insecticide-quinalphos in agriculture, pose a health hazard to animals, humans, and environment because of its persistence in the soil and crops. However, there is no much information available on the biodegradation of quinalphos by the soil micro-organisms, which play a significant role in detoxifying pesticides in the environment; so research is initiated in biodegradation of quinalphos.

RESULTS

A soil bacterium strain, capable of utilizing quinalphos as its sole source of carbon and energy, was isolated from soil via the enrichment method on minimal salts medium (MSM). On the basis of morphological, biochemical and 16S rRNA gene sequence analysis, the bacterium was identified as to be Bacillus thuringiensis. Bacillus thuringiensis grew on quinalphos with a generation time of 28.38 min or 0.473 h in logarithmic phase. Maximum degradation of quinalphos was observed with an inoculum of 1.0 OD, an optimum pH (6.5-7.5), and an optimum temperature of 35-37 °C. Among the additional carbon and nitrogen sources, the carbon source-sodium acetate and nitrogen source-a yeast extract marginally improved the rate of degradation of quinalphos.

CONCLUSIONS

Display of degradation of quinalphos by B. thuringiensis in liquid culture in the present study indicates the potential of the culture for decontamination of quinalphos in polluted environment sites.

Toxicomorphomics and toxicokinetics of quinalphos on embryonic development of zebrafish (Danio rerio) and its binding affinity towards hatching enzyme, ZHE1

This study outlines the toxic effects of Quinalphos (QP), an organophosphrous insecticide on the development of zebrafish (Danio rerio) embryos, with special emphasis on toxicomorphomics and toxicokinetics of target enzyme, AChE. A range of concentrations was used to elucidate the median lethal concentration (LC₅₀) of Quinalphos. Furthermore, embryos were exposed to two sub-lethal concentrations LC₁₀ (0.66mg/L) and LC₂₀ (1.12mg/L) along with a median lethal concentration (3.0mg/L) for 96h. Several morphological aberrations like lordosis, kyphosis, scoliosis, heart edema, breaks in the neuronal tube and underdeveloped facial parts were noticed, which were of concentration and time dependent. The QP has adequately hindered hatching process during the course of exposure which was upheld by the in silico docking studies with hatching enzyme, ZHE1. The length of hatchlings at 96h in LC₅₀ concentration was significantly reduced to 47% compared to control. A significant pericardial effusion (5 to 16 fold) was observed in >90% of LC₅₀ treated groups. Morphological changes in heart lead to the bradycardia, which ultimately leading to heart failure in some cases. The swimming behavior was significantly diminished in relation to the inhibition of AChE levels. From the in vitro kinetic studies, the kinetic constants K_m, V_max and inhibitory concentration K_i (4.45×10^-5M) was determined which supported the competitive nature of QP.

strain HZM

AIMS

Isolation and identification of bacteria capable of degrading organophosphate pesticide quinalphos and elucidation of its biodegradative pathway.

METHODS AND RESULTS

A bacterium capable of degrading organophosphate pesticides was isolated from the pesticide-contaminated soil samples by selective enrichment on quinalphos (QP) as a sole source of carbon and energy. The bacterial strain was identified as Ochrobactrum sp. strain HZM on the basis of its morphological and biochemical characteristics and by phylogenetic analysis based on 16S rRNA gene sequences. The organism utilized various organophosphate pesticides such as quinalphos, profenofos, parathion-methyl and chlorpyrifos as growth substrates. Response surface methodology (RSM) showed optimum conditions for quinalphos degradation at pH 7 and 27°C. 2-Hydroxyquinoxaline and diethyl phosphate were identified as metabolites of quinalphos degradation by HPLC and GC-MS analysis. Cell-free extract of Ochrobactrum sp. strain HZM grown on quinalphos contained the quinalphos hydrolase activity.

CONCLUSIONS

A bacterial strain capable of degrading quinalphos was isolated and identified as Ochrobactrum sp. strain HZM. The organism utilized organophosphate pesticides quinalphos, profenofos, parathion-methyl and chlorpyrifos as carbon sources. The organism degraded quinalphos by hydrolysis to yield 2-hydroxyquinoxaline and diethyl phosphate which were further utilized as carbon sources.

SIGNIFICANCE AND IMPACT OF THE STUDY

The isolated bacterium Ochrobactrum sp. strain HZM was versatile in degrading various organophosphate pesticides. There was complete mineralization of quinalphos by Ochrobactrum sp. This strain could potentially be useful in the bioremediation of soil and water contaminated with toxic organophosphate pesticides.

against quinalphos induced male reproductive toxicity

Quinalphos (QP) is speculated to cause endocrine disruption through the generation of reactive oxygen species (ROS) by oxidative stress (OS). Exposure of QP decreased testosterone level considerably which resulted in reduced viable sperms in mice. The QP induced toxicity is initiated by the formation of free radicals as it is evidenced from the increased Lipid peroxidation (LPO) and diminution of antioxidant enzymes in testicular tissue. Increased serum cholesterol and reduced testicular cholesterol indicated the inhibition of cholesterol transport and biosynthesis in testicular tissues. Lack of cholesterol in testicular tissue impaired the steroidogenesis by down-regulating the expression of StAR protein, Cytochrome P450, 3β-HSD and 17β-HSD leading to reduced testosterone level. Treatment of Commelina benganlensis (CBE) and Cissus quadrangularis (CQE) significantly recovered the alterations in antioxidant profiles as well as increased LPO, thereby recovering the decreased mRNA expression levels of intermediate enzymes. However, CQE effectively protected the OS and prevented the inhibition of steroidogenesis thereby preventing male infertility.