Toxicokinetics, disposition and metabolism of fluoxetine in crabs

Mediterranean mussels (Mytilus galloprovincialis) exposure to fluoxetine: bioaccumulation and biotransformation products

The significant rise in antidepressant consumption in recent years was accentuated by COVID-19 pandemic. Among these antidepressant, fluoxetine, a selective serotonin re-uptake inhibitor (SSRI), is the most prescribed worldwide. The present study investigated its bioaccumulation and metabolization in the mussel Mytilus galloprovincialis, generally recognized as a reliable bioindicator for assessing environmental quality and the accumulation of various contaminants. Mussels were exposed to a nominal concentration of fluoxetine (3.1μg/L) for 28 days. Mussels were sacrificed at day 2, 7, 14 and 28 of exposure. The order of accumulation level was gills > digestive glands > soft tissues, and a regular increase in fluoxetine and norfluoxetine was observed across the various sampling days for both digestive glands and soft tissues. The calculated bioconcentration factor (BCF) ranged from 253 at D2 to 1734 at D28 for fluoxetine, and pseudo-BCF from 7 at D2 to 64 at D28 for norfluoxetine. Non-targeted approaches highlighted ten metabolites, which are reported for the first time in Mytilus, in addition to norfluoxetine. Notably, this study highlighted two phase I metabolites and one phase II metabolite previously unreported. These findings contribute to the understanding of fluoxetine accumulation and metabolism in Mytilus and enhance the knowledge of pharmaceuticals detoxification processes in non-target organisms.

Environmentally relevant concentrations of the tricyclic antidepressant, amitriptyline, affect feeding and reproduction in a freshwater mollusc

Antidepressant drugs (ADDs) are one of the most extensively used pharmaceuticals globally. They act at particularly low therapeutic concentrations to modulate monoamine neurotransmission, which is one of the most evolutionary conserved pathways in both humans and animal species including invertebrates. As ADDs are widely detected in the aquatic environment at low concentrations (ng/L to low µg/L), their potential to exert drug-target mediated effects in aquatic species has raised serious concerns. Amitriptyline (AMI) is the most widely used tricyclic ADD, while monoamines, the target of ADDs, are major bioregulators of multiple key physiological processes including feeding, reproduction and behaviour in molluscs. However, the effects of AMI on feeding, reproduction and mating behaviour are unknown in molluscs despite their ecological importance, diversity and reported sensitivity to ADDs. To address this knowledge gap, we investigated the effects of environmentally relevant concentrations of AMI (0, 10, 100, 500 and 1000 ng/L) on feeding, reproduction and key locomotor behaviours, including mating, in the freshwater gastropod, Biomphalaria glabrata over a period of 28 days. To further provide insight into the sensitivity of molluscs to ADDs, AMI concentrations (exposure water and hemolymph) were determined using a novel extraction method. The Fish Plasma Model (FPM), a critical tool for prioritization assessment of pharmaceuticals with potential to cause drug target-mediated effects in fish, was then evaluated for its applicability to molluscs for the first time. Disruption of food intake (1000 ng/L) and reproductive output (500 and 1000 ng/L) were observed at particularly low hemolymph levels of AMI, whereas locomotor behaviours were unaffected. Importantly, the predicted hemolymph levels of AMI using the FPM agreed closely with the measured levels. The findings suggest that hemolymph levels of AMI may be a useful indicator of feeding and reproductive disruptions in wild population of freshwater gastropods, and confirm the applicability of the FPM to molluscs for comparative pharmaceutical hazard identification.

Antidepressants - The new endocrine disruptors? The case of crustaceans

Antidepressants are high-volume pharmaceuticals that accumulate to concentrations in the μg·L-1 range in surface waters. The release of peptide hormones via neurosecretory cells appears as a natural target for antidepressants. Here I review research that suggests that antidepressants indeed disrupt endocrine signalling in crustaceans, by acting on the synthesis and release of neurohormones, such as crustacean hyperglycaemic hormone, moult inhibiting hormone and pigment dispersing hormone in decapods, as well as methyl farnesoate in Daphnids. Hence, antidepressants can affect hormonal regulation of physiological functions: increase in energy metabolism and activity, lowered ecdysteroid levels, potentially disrupting moult and somatic growth, reducing colour change capacity and compromising camouflage, as well as induction of male sex determination. Several studies further suggest effects of antidepressants on crustacean reproduction, but the hormonal regulation of these effects remains elusive. All things considered, a body of evidence strongly suggests that antidepressants are endocrine disrupting compounds in crustaceans.

Unraveling the combined toxicity and removal mechanisms of fluoxetine and sertraline co-contaminants by the freshwater microalga Chlorella pyrenoidosa

Selective serotonin reuptake inhibitors (SSRIs), such as fluoxetine (FLX) and sertraline (SER), are among the most widely detected pharmaceuticals in aquatic environments, and they usually occur as mixtures. However, little is known about the combined toxicity of SSRI mixtures to microalgae and the associated removal mechanisms. This study investigated the combined toxicity of FLX and SER to the growth, photosynthetic activity, and antioxidant system of Chlorella pyrenoidosa and their removal mechanisms. The results showed that FLX and SER strongly inhibited microalgal growth with 96 h EC50 values of 493 and 61.1 μg/L, respectively. Additionally, the combined toxicity of FLX and SER towards microalgal growth exhibited an additive effect. After 4 days of short-term exposure, FLX, SER, and their mixtures caused photosynthetic damage and oxidative stress in microalgae, and the mixture's toxicity was stronger than those of individuals. However, the adverse effects on microalgal growth, photosynthetic activity, and antioxidant system were alleviated with increasing exposure time. Meanwhile, C. pyrenoidosa efficiently removed FLX (67.59%-99.08%) and SER (94.92%-99.11%) individually after 11 days of cultivation. Biodegradation (59.25%-86.21%) was the prominent removal mechanism of FLX, while both biodegradation (48.08%-88.17%) and bioaccumulation (4.74%-43.38%) contributed significantly to SER removal. The co-existence of FLX and SER lowered the removal rate and biodegradation amount of both compounds. Besides, SER inhibited C. pyrenoidosa's N-demethylation and O-dealkylation of FLX, while co-existing with FLX inhibited the excretion of the N-deamination product of SER from microalgal cells. Furthermore, the principal component analysis indicated that the removal performance of FLX, SER, and their mixtures correlated strongly to the microalgae's physiological and biochemical states. These results highlighted the significance of co-contamination during ecological risk assessments and microalgae-based bioremediation of SSRIs.

The occurrence of typical psychotropic drugs in the aquatic environments and their potential toxicity to aquatic organisms - A review

Psychotropic drugs (PDs) and their bioactive metabolites often persist in aquatic environments due to their typical physical properties, which made them resistant to removal by traditional wastewater treatment plants (WWTPs). Consequently, such drugs and/or their metabolites are frequently detected in both aquatic environments and organisms. Even at low concentrations, these drugs can exhibit toxic effects on non-target organisms including bony fish (zebrafish (Danio rerio) and fathead minnows) and bivalves (freshwater mussels and clams). This narrative review focuses on the quintessential representatives of three different categories of PDs-antiepileptics, antidepressants, and antipsychotics. The data regarding their concentrations occurring in the environment, patterns of distribution, the degree of enrichment in various tissues of aquatic organisms, and the toxicological effects on them are summarized. The toxicological assessments of these drugs included the evaluation of their effects on the reproductive, embryonic development, oxidative stress-related, neurobehavioral, and genetic functions in various experimental models. However, the mechanisms underlying the toxicity of PDs to aquatic organisms and their potential health risks to humans remain unclear. Most studies have focused on the effects caused by acute short-term exposure due to limitations in the experimental conditions, thus making it necessary to investigate the chronic toxic effects at concentrations that are in coherence with those occurring in the environment. Additionally, this review aims to raise awareness and stimulate further research efforts by highlighting the gaps in the understanding of the mechanisms behind PD-induced toxicity and potential health risks. Ultimately, the study underscores the importance of developing advanced remediation methods for the removal of PDs in WWTPs and encourages a broader discussion on mitigating their environmental impacts.

The metabolites could not be ignored: A comparative study of the metabolite norfluoxetine with its parent fluoxetine on zebrafish (Danio rerio)

The ubiquitous pharmaceuticals in aquatic environments have attracted huge attention due to their significant risks to humans and ecosystems. However, even though the knowledge of the negative effects induced by the parent pharmaceuticals is quite extensive, little is known about their metabolites for a long time. This study provides systematical knowledge about the potential toxicity of metabolite norfluoxetine and its parent fluoxetine on zebrafish (Danio rerio) at the early life stage. The results showed that the metabolite norfluoxetine had similar acute toxicity in fish with the parent fluoxetine. For the altered fish development, there was no significant difference in most cases between the two pharmaceuticals. Compared to the control, the metabolite markedly inhibited the locomotor behavior under light-to-dark transitions, which was comparable to the parent. Norfluoxetine could easily accumulate but hardly eliminate from fish, relative to fluoxetine. In addition, the accumulated fluoxetine in zebrafish may rapidly metabolize to norfluoxetine and then be eliminated through different metabolic pathways. The functional genes related to serotonergic process (5-ht1aa, 5-ht2c, slc6a4b, and vmat), early growth (egr4), and circadian rhythm (per2) were downregulated by both the norfluoxetine and fluoxetine, indicative of the same mode-of-action of norfluoxetine with its parent in these functions. Meanwhile, the alterations caused by norfluoxetine were more pronounced than that of fluoxetine in the genes of 5-ht2c, slc6a4b, vmat, and per2. The molecular docking also confirmed that norfluoxetine could bind with serotonin transporter protein in the same as fluoxetine with a lower binding free energy. Overall, the metabolite norfluoxetine could induce similar and even more toxic effects on zebrafish with the same mode of action. The different and binding energy of the metabolite norfluoxetine and its parent fluoxetine on zebrafish may be responsible for the differentiated effects. It highlights the risks of the metabolite norfluoxetine in the aquatic environment could not be ignored.

Ecotoxicological effects of the antidepressant fluoxetine and its removal by the typical freshwater microalgae Chlorella pyrenoidosa

The antidepressant fluoxetine (FLX) has gained increasing attention due to its frequent detection in aquatic environments and negative effects on non-target organisms. However, knowledge on the ecotoxicological effects of FLX and its removal by microalgae is still limited. In this study, the ecotoxicological effects of FLX (10 -1000 μg/L) were assessed using batch cultures of the freshwater microalgae Chlorella pyrenoidosa for 10 days based on changes in growth, antioxidant response, and photosynthetic process. The removal efficiency, removal mechanism, and degradation pathway of FLX by C. pyrenoidosa were also investigated. The results showed that the growth of C. pyrenoidosa was inhibited by FLX with a 4 d EC₅₀ of 0.464 mg/L. Additionally, FLX significantly inhibited photosynthesis and caused oxidative stress on day 4. However, C. pyrenoidosa can produce resistance and acclimatize to FLX, as reflected by the declining growth inhibition rate, recovered photosynthetic efficiency, and disappearance of oxidative stress on day 10. Despite the toxicity of FLX, C. pyrenoidosa showed 41.2%- 100% removal of FLX after 10 days of exposure. Biodegradation was the primary removal mechanism, accounting for 88.2%- 92.8% of the total removal of FLX. A total of five metabolites were found in the degradation processes of FLX, which showed less toxicity than FLX. The main degradation pathways were proposed as demethylation, O-dealkylation, hydroxylation, and N-acylation. Our results not only highlight the potential application of microalgae in FLX purification, but also provide insight into the fate and ecological risk of FLX in aquatic environments.

Proteomics of sea bass skin-scales exposed to the emerging pollutant fluoxetine compared to estradiol

Teleost fish skin-scales are essential for protection and homeostasis and the largest tissue in direct contact with the environment, but their potential as early indicators of pollutant exposure are hampered by limited knowledge about this model. This study evaluated multi-level impacts of in vivo exposure of European sea bass to fluoxetine (FLX, a selective serotonin-reuptake inhibitor and an emerging pollutant) and 17β-estradiol (E2, a natural hormone and representative of diverse estrogenic endocrine-disrupting pollutants). Exposed fish had significantly increased circulating levels of FLX and its active metabolite nor-FLX that, in contrast to E2, did not have estrogenic effects on most fish plasma and scale indicators. Quantitative proteomics using SWATH-MS identified 985 proteins in the scale total proteome. 213 proteins were significantly modified 5 days after exposure to E2 or FLX and 31 were common to both treatments and responded in the same way. Common biological processes significantly affected by both treatments were protein turnover and cytoskeleton reorganization. E2 specifically up-regulated proteins related to protein production and degradation and down-regulated the cytoskeleton/extracellular matrix and innate immune proteins. FLX caused both up- and down-regulation of protein synthesis and energy metabolism. Multiple estrogen and serotonin receptor and transporter transcripts were altered in sea bass scales after E2 and/or FLX exposure, revealing complex disruptive effects in estrogen/serotonin responsiveness, which may account for the partially overlapping effects of E2 and FLX on the proteome. A large number (103) of FLX-specifically regulated proteins indicated numerous actions independent of estrogen signalling. This study provides the first quantitative proteome of the fish skin-scale barrier, elucidates routes of action and biochemical and molecular signatures of E2 or FLX-exposure and identifies potential physiological consequences and candidate biomarkers of pollutant exposure, for monitoring and risk assessment.

Proteome dataset of sea bass (Dicentrarchus labrax) skin-scales exposed to fluoxetine and estradiol

Contamination of aquatic ecosystems with anthropogenic pollutants, including pharmaceutical drugs, is a major concern worldwide. Aquatic organisms such as fish are particularly at risk of exposure to pollutants. The surface of fish is the first point of contact with pollutants, but few studies have considered the impact of pollutants on the skin-scale barrier. The present proteome data are the basis of the findings discussed in the associated research article “Proteomics of sea bass skin-scales exposed to the emerging pollutant fluoxetine compared to estradiol” [1]. Juvenile sea bass were exposed by intraperitoneal injections to: a) the antidepressant fluoxetine (FLX), a widely prescribed psychotropic drug and an emerging pollutant; b) the natural estrogen 17β-estradiol (E2) and c) the vehicle, coconut oil (control). The scale proteome of fish exposed to these compounds for 5 days was analysed using quantitative label-free proteomics technology SWATH-MS (sequential windowed data-independent acquisition of the total high-resolution-mass spectra). The proteome data generated was submitted to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD020983. LC-MS data from pooled protein extracts from the scales of all experimental groups was acquired using information-dependent acquisition (IDA) and 1,254 proteins were identified by searching against the sea bass genome database. 715 proteins were quantified by SWATH acquisition, and 213 proteins had modified levels (p < 0.05) between the E2- or FLX-exposed fish compared to the control. The main biological processes and KEGG pathways affected by E2 or FLX treatments were identified using Cytoscape/ClueGO enrichment analyses.

The functions of fluoxetine and identification of fluoxetine-mediated circular RNAs and messenger RNAs in cerebral ischemic stroke

Fluoxetine is used to improve cognition, exercise ability, depression, and neurological functions in patients with cerebral ischemic stroke. Circular RNAs (circRNAs) play important regulatory roles in multiple diseases. However, studies regarding the fluoxetine-mediated circRNA-microRNA-messenger RNA (mRNA) axis have not been conducted. This study is aim to investigate the functions of fluoxetine and identification of fluoxetine-mediated circRNAs and mRNAs in cerebral ischemic stroke. The middle cerebral artery occlusion (MCAO) rat models were successfully established at fisrt, and then rats were intraperitoneally injected with 10-mg/kg fluoxetine hydrochloride for 14 d. Afterward, the cerebral infarction area was evaluated using triphenyltetrazolium chloride staining. High-throughput sequencing was adopted to screen the differential circRNAs and mRNAs. The candidate circRNAs, mRNAs, and potential microRNAs were verified using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). In addtion, microRNA and circRNA binding was verified using the dual-luciferase reporter assay. Results revealed that fluoxetine markedly diminished the cerebral infarction area in rats after MCAO. The circRNAs and mRNAs were differentially expressed, which includes 879 circRNAs and 815 mRNAs between sham and MCAO groups, respectively, and 958 circRNAs and 838 mRNAs between MCAO and fluoxetine groups, respectively. In which, circMap2k1 and Pidd1 expression was significantly increased in the MCAO group but suppressed after fluoxetine treatment. Moreover, circMap2k1 directly binds with miR-135b-5p. Taken together, we verified that fluoxetine could improve brain injury after cerebral ischemic stroke. Moreover, the circMap2k1/miR-135b-5p/Pidd1 axis is potentially involved in cerebral ischemic stroke.

Effects of environmental antidepressants on colour change and locomotor behaviour in juvenile shore crabs, Carcinus maenas

Juvenile crabs of Carcinus maenas thrive in coastal waters reputed to be the receptacle of continental pollution. Amongst the many pollutants encountered, antidepressants, such as fluoxetine (FLX) and venlafaxine (VEN), often detected at the ng•L^-1 range, are particularly worrying because of their action on the levels of monoamines, such as serotonin, noradrenaline and dopamine. In crustaceans, those monoamines are involved in colour change through their action on neuropeptide hormones. In addition, they are known to have a role in different behaviours, such as locomotion. Both colour change and locomotion are strategies used by juvenile crabs to hide and escape from predators. To investigate if the presence of antidepressants may alter behaviours of ecological importance, juvenile crabs were exposed to environmentally realistic concentrations of either 5 ng•L^-1 of FLX alone or in combination with VEN at 5 ng•L^-1. The ability to change colour depending on the environment and the locomotor activity of juvenile crabs were monitored weekly over 25 days. Animals exposed to antidepressants displayed a different pattern of colour change than the controls, especially those exposed to the combination of FLX and VEN at 5 ng•L^-1 each, and were less efficient to adapt to their environment, i.e., they were not as pale and not as dark as controls or crabs exposed to FLX at 5 ng•L^-1. Moreover, juvenile crabs exposed to the combination of antidepressants exhibited an enhanced locomotor activity throughout the exposure period with a higher velocity and distance moved as well as more time spend moving. The alteration of cryptic behaviours, such as colour change and locomotion by antidepressants persistently present in marine environment at low concentrations may have an impact on the survival of juvenile of C. maenas on the long term.

Hidden in the sand: Alteration of burying behaviour in shore crabs and cuttlefish by antidepressant exposure

Pharmaceuticals such as antidepressants are constantly released into the aquatic environment. Consequently, fluoxetine (FLX) and venlafaxine (VEN), the active molecules of Prozac© and Effexor©, are detected up to several µg.L^-1 in freshwater and marine coastal waters. Both compounds act on the serotoninergic system, which may result in behavioural impairment, especially in juvenile animals presumed to be more susceptible to low concentrations than adults. The objective of this study was to determine whether environmental concentrations of FLX alone or combined with VEN modulate innate burying behaviour in two juvenile marine invertebrates, i.e. Sepia officinalis and Carcinus maenas. Juvenile cuttlefish were exposed from hatching to 30 days post-hatching to either FLX alone (i.e. 5 ng.L^-1) or in mixture with VEN (i.e. either 2.5 ng.L^-1 or 5 ng.L^-1 of each antidepressant). Juvenile crabs (<2 cm carapace width) were exposed for a period of 22 days to 5 ng.L^-1 of FLX and a mixture of 5 ng.L^-1 of FLX and VEN each. Several parameters of sand-digging behaviour were analysed weekly in both species. The occurrence of sand-digging behaviour decreased in cuttlefish exposed to a mixture of FLX and VEN at the lowest concentration (2.5 ng.L^-1 each). Because sand-digging behaviour improved in controls, this decrease was likely to be related to a modification of maturation and/or learning processes. At the mixture of 5 ng.L^-1 VEN and FLX each, a better body covering was observed in juvenile crabs. In both species, innate behaviour was modified under exposure to mixtures of FLX and VEN at environmentally realistic concentrations. These alterations were observed at an early developmental stage, when animals are particularly prone to predation. Hence, modified maturation of behavioural traits and, putatively, learning processes by exposure to pseudo-persistent antidepressants may affect the survival of these two species in the long term.

In vitro exposure of vitellogenic rainbow trout ovarian follicles to endocrine disrupting chemicals can alter basal estradiol-17β production and responsiveness to a gonadotropin challenge

Endogenous estrogens play major roles in many aspects of female reproductive development in fish. In order to develop a relatively high-throughput assay to determine the potential impact on reproductive development, vitellogenic rainbow trout ovarian follicles were exposed to a suite of contaminants in vitro and then assessed for the ability to produce estradiol-17β (E2) after a 500 ng/ml salmon gonadotropin (sGTH) challenge. There was a positive correlation between ovarian follicle size and E2 production, but an inverse correlation between size and responsiveness to sGTH. Significant impacts on E2 levels were observed following treatment with different endocrine disrupting chemicals, such as 17α-ethinylestradiol (EE2), prochloraz, or trenbolone. EE2 was remarkably potent and significantly reduced ovarian follicle responsiveness to sGTH at concentrations as low as 0.1 nM. Of the other contaminants tested, only tamoxifen impacted E2 levels, and only at concentrations near the limits of solubility. Flutamide, fluoxetine, 4-hydroxy tamoxifen, hydroxyflutamide, and norfluoxetine had little or no impact. Quantitative PCR analyses of steroidogenesis-related genes were carried out on EE2 treated ovarian follicles, but significant transcriptional responses to EE2 were not observed. Overall, this study suggests that xenoestrogens and anti-estrogens are more likely to interfere with ovarian E2 synthesis than other classes of EDCs. This also provides a template for further testing of the effects of EDCs on ovarian function.

Comparison of the accumulation and metabolite of fluoxetine in zebrafish larva under different environmental conditions with or without carbon nanotubes

Few studies have focused on the influence of environmental conditions on the bioavailability of pollutants interacted with nanomaterials in organisms. In this study, we primarily compared the influence of multiwalled carbon nanotubes (MWCNTs) on the bioavailability of fluoxetine in zebrafish (Danio rerio) larva under different environmental conditions: natural organic matter (NOM) and salinity. The results showed that fluoxetine accumulated in the larvae and then transformed into the metabolite norfluoxetine, with the metabolic rates from 2.8 to 3.5. Following co-exposure to MWCNTs, the accumulation of fluoxetine and norfluoxetine were further enhanced, suggesting a superior carrier of MWCNTs for fluoxetine, especially the functional MWCNTs. The consistent increase in the fluoxetine and norfluoxetine accumulation highlights the bioavailability of absorbed fluoxetine on MWCNTs in zebrafish larvae. The presence of NOM promoted the accumulation of fluoxetine and norfluoxetine in zebrafish, but alleviated the carrier effects of MWCNTs, acting as a natural antidote. Salinity negatively influenced the bioavailability of fluoxetine in the larvae, and further reversed the enhancements caused by MWCNTs. These findings provide a new insight into the influence of environmental conditions on the interactions between nanomaterials and pollutants in organisms.

In vivo effects of serotonin and fluoxetine on cardio-ventilatory functions in the shore crab Carcinus maenas (L. 1758)

Serotonin (5-HT) takes a key position in regulating vital functions, such as cardio-ventilatory activity, locomotion and behaviour. Selective serotonin reuptake inhibitors (SSRIs) modulate the serotonergic system and thus affect these functions. Rhythmic behaviours, such as cardio-ventilatory activity, are controlled by central pattern generators, which in turn are regulated by 5-HT. In crustaceans, 5-HT also regulates the synthesis and secretion of crustacean hyperglycaemic hormone, a pleiotropic hormone involved in the mobilisation and release of glucose into the haemolymph, thus stimulating the animal's activity. As a matter of consequence, SSRIs may affect cardio-ventilatory activity. In order to examine how the SSRIs affect fundamental physiological parameters based on rhythmic behaviours in decapods, cardio-respiratory activity in the shore crab Carcinus maenas was assessed after pericardial injection of a single dose of either 0.5 μM, 0.75 μM or 1 μM fluoxetine, respectively. Simultaneous recordings of heart and scaphognathite movements in both brachial chambers were conducted by measuring impedance changes in the respective body compartments. Injection of 5-HT had an immediate effect on cardio-ventilatory activities and strongly upregulated both cardiac and ventilatory activities. Fluoxetine showed similar effects, entailing moderate tachycardia and increased ventilation rates. Compared to 5-HT, these effects were delayed in time and much less pronounced. Metabolism of fluoxetine into the active compound nor-fluoxetine might account for the delayed action, whereas compensatory regulation of cardio-ventilatory frequencies and amplitudes are likely to explain the attenuation of the responses compared to the strong and immediate increase by 5-HT. Overall, the results suggest increased 5-HT levels in invertebrates following fluoxetine exposure, which are able to disturb physiological functions regulated by 5-HT, such as cardiac and respiratory activity.

Toxicokinetics, Tissue Distribution, and Excretion of Dufulin Racemate and Its R ( S)-Enantiomers in Rats

Dufulin is a plant antiviral agent with a novel molecular structure and has been used widely to prevent and control tobacco and rice viral diseases. In this study, an UHPLC-MS/MS method was developed for rapid determination of dufulin racemate ( rac-DFL) and its R ( S)-enantiomers in rat plasma, tissues, urine, and feces. A MALDI-MSI method was further used for visual research on tissue distribution after intragastric administration of the three analytes. Toxicokinetic study showed that both ( R)-enantiomer of dufulin (( R)-DFL) and ( S)-enantiomer of dufulin (( S)-DFL) had a faster ability to reach C_max than that of rac-DFL. ( R)-DFL and ( S)-DFL had a similar T_1/2, though both were significantly lower than rac-DFL. C_max of rac-DFL was obviously higher than ( R)-DFL or ( S)-DFL. Meanwhile, C_max of ( S)-DFL was only about 60% of ( R)-DFL. Rac-DFL and its R ( S)-enantiomers had a dose-dependent toxicokinetic profile. Tissue distribution results revealed rac-DFL, ( R)-DFL, and ( S)-DFL mainly distributed in the liver and kidney, but the maximum concentration was only ng/g grade and could significantly degrade within 3 h. This indicates that dufulin does not cause liver and kidney toxicity in animals. In addition, rac-DFL and its R ( S)-enantiomers have not been detected in brain tissue. Cumulative excretion of rac-DFL and its R ( S)-enantiomers within 24 h in urine and feces were less than 22.85% indicating that they mainly excreted as metabolites. These results could provide evidence for the in-depth toxicity evaluation of dufulin pesticide. In addition, its metabolic selectivity information in vivo has also been obtained.