Synthesis of DEHP metabolites as biomarkers for GC–MS evaluation of phthalates as endocrine disrupters

Competition-Induced Binding Spherical Nucleic AcidFluorescence Amplifier for the Detection of Di (2-ethylhexyl) Phthalate in the Aquatic Environment

Di-2-ethylhexyl phthalate (DEHP) is a toxic plasticizer and androgen antagonist. Its accumulation in water exceeds national drinking water standards and it must be continuously and effectively regulated. Currently, methods used to detect DEHP are still unsatisfactory because they usually have limited detection sensitivity and require complex operating procedures. A competition-induced fluorescence detection method was developed for the selective detection of DEHP in an aquatic environment. An aptamer with walking function was used as the recognition element for DEHP, and its quantification was induced by competition to change the fluorescence signal. The detection range was 0.01~100 µg/L, and the detection limit was 1.008 μg/L. This high-sensitivity DEHP detection capability and simplified process facilitates real-time fields and other monitoring tasks.

Comparative Effects of Di-(2-ethylhexyl)phthalate and Di-(2-ethylhexyl)terephthalate Metabolites on Thyroid Receptors: In Vitro and In Silico Studies

Plasticizers added to polyvinylchloride (PVC) used in medical devices can be released into patients' biological fluids. Di-(2-ethylhexyl)phthalate (DEHP), a well-known reprotoxic and endocrine disruptor, must be replaced by alternative compounds. Di-(2-ethylhexyl) terephthalate (DEHT) is an interesting candidate due to its lower migration from PVC and its lack of reprotoxicity. However, there is still a lack of data to support the safety of its human metabolites with regard to their hormonal properties in the thyroid system. The effects of DEHT metabolites on thyroid/hormone receptors (TRs) were compared in vitro and in silico to those of DEHP. The oxidized metabolites of DEHT had no effect on T3 receptors whereas 5-hydroxy-mono-(ethylhexyl)phthalate (5-OH-MEHP) appeared to be primarily an agonist for TRs above 0.2 µg/mL with a synergistic effect on T3. Monoesters (MEHP and mono-(2-ethylhexyl)terephthalate, MEHT) were also active on T3 receptors. In vitro, MEHP was a partial agonist between 10 and 20 µg/mL. MEHT was an antagonist at non-cytotoxic concentrations (2-5 µg/mL) in a concentration-dependent manner. The results obtained with docking were consistent with those of the T-screen and provide additional information on the preferential affinity of monoesters and 5-OH-MEHP for TRs. This study highlights a lack of interactions between oxidized metabolites and TRs, confirming the interest of DEHT.

Advancement in Determination of Phthalate Metabolites by Gas Chromatography Eliminating Derivatization Step

A gas chromatography-mass spectrometry (GC-MS) method to determine polar and thermally unstable phthalate metabolites [monomethyl phthalate-MMP, monoethyl phthalate-MEP, mono-n-butyl phthalate-MnBP, mono-(2-ethylhexyl) phthalate-MEHP] has been developed. This is the first report presenting the separation of monophthalates without derivatization step and any additional equipment or special injection port. Injection parameters (temperature, pressure, time, and volume of injection), chromatographic separation (retention gap, temperature program), and MS detection/identification (working parameters, ion selection) were investigated. Mechanisms and phenomena occurring under different conditions in the GC injector were evaluated and discussed. The limits of detection (LODs) of MMP, MEP, MnBP, MEHP in the protocol were 0.049, 0.036, 0.038, and 0.029 ng (per 2 μL of injection), respectively. The response of the monophthalates was found to be linear in the tested concentration range (for MMP: 0.15-100 ng, MEP and MnBP: 0.11-100 ng, MEHP: 0.087-100 ng per 2 μL) with the coefficient of determination higher than 0.9817 and inter-day precision in the range of 1.4-5.4%. The developed method is fast, easy and repeatable. Moreover, it allows for the elimination of derivatization agents, reduction of toxic waste production and simplification of analytical procedure.

Inter-Day Variability of Metabolites of DEHP and DnBP in Human Urine-Comparability of the Results of Longitudinal Studies with a Cross-Sectional Study

In the current paper, we compare the inter-day variability of the metabolite concentration of di(2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DnBP) in 247 morning urine samples obtained from 19 probands of different age and sex with the metabolite concentration in morning urine obtained from 215 probands of the “Tübingen Survey” cross-sectional study. In the first longitudinal study the morning urine of seven volunteers was collected four times a year for seven consecutive days (course of the year study). In a second study the morning urine of 12 students of a boarding school was collected on five consecutive days (course of a week study). For participants of the two different longitudinal studies we obtained mean concentrations in first void morning urine for mono(2-ethyl-5-hydroxyhexyl) phthalate (5OH-MEHP) in the range from 21.3 to 110 µg/L, 10.5 to 35.6 µg/L for mono(2-ethyl-5-oxohexyl) phthalate (5oxo-MEHP), and 45.5 to 143 µg/L for mono(2-ethyl-5-carboxypentyl) phthalate (5cx-MEPP). The corresponding relative standard deviations (rel. Std.D in %) for these DEHP-metabolites vary between 45.2% and 262%. The 50th percentiles vary for 5OH-MEHP between 17.5 and 65.6 µg/L, for 5oxo-MEHP between 9.0 and 20.3 µg/L and for 5cx-MEPP between 42.5 and 82.0 µg/L. For participants of the “Tübingen Survey” cross-sectional study the means vary for 5OH-MEHP between 58.2 and 85.0 µg/L, between 33.6 and 38.7 µg/L for 5oxo-MEHP and between 110 and 158 µg/L for 5cx-MEPP with rel. standard deviations in a range between 86.5 to 175%. The corresponding 50th percentiles vary for 5OH-MEHP between 26.5 and 42.3 µg/L, for 5oxo-MEHP between 18.0 and 26.3 µg/L, and for 5cx-MEPP between 57.2 and 77.6 µg/L. In order to compare the data from the longitudinal studies with the data from the cross-sectional study, the frequency distribution of the results of both types of studies was compared first. In a second step, the results of a t-test (p-values) was used to check whether the results of the long-term studies differ statistically significantly from the results of the cross-sectional study (p < 0.05). The present data show that the frequency distributions of DEHP-metabolites are comparable. For most of the participants respectively subject groups t-test results prove that no statistical significant difference between results obtained from longitudinal studies compared to the results of the cross-sectional study are apparent. The available data on the exposure of individual subjects mirror the data obtained from cross-sectional studies of the general population and give hints to the risk of individual increased DEHP exposure. Results also highlight the importance of living conditions on the risk of increased DEHP exposure.

Facts about phthalate toxicity in humans and their occurrence in alcoholic beverages

Phthalates are esters of phthalic acid and aliphatic alcohol added to plastic to improve its softness, flexibility, and extensibility. They easily migrate from plastic products into the environment because of their physical and chemical properties. This review summarises their characteristics, distribution in the environment, monitoring, use, toxic effects on human health, regulatory limits in different matrices and products, and tolerable daily intake. The studies we have reviewed suggest that phthalates have a potential to affect reproduction and development in humans. Due to the inconsistent data, further studies are needed and, in the meantime, precautionary policies must be implemented. Here we draw attention to the methods of determining phthalate levels in alcoholic beverages and reported levels in plum spirits produced in Croatia. Legally produced and moderately consumed plum spirits do not seem to increase the risk of phthalate toxicity for human health. We conclude with recommendations for the effective monitoring of phthalate exposure in humans and for the implementation of alternative materials in alcohol production.

In vitro cytotoxic effects of DEHP-alternative plasticizers and their primary metabolites on a L929 cell line

Phthalic acid esters have been widely used to improve the plasticity of PVC medical devices. They carry a high exposure risk for both humans and the environment in clinical situations. Our study focuses on the cytotoxicity of alternative plasticizers. Postulated primary metabolites were synthesized, not being commercially available. Cytotoxicity assays were performed on L929 murine cells according to the ISO-EN 10993-5 standard design for the biocompatibility of medical devices. The tested concentrations of plasticizers (0.01, 0.05 and 0.1 mg/ml) covered the range likely to be found in biological fluids coming into direct contact with the medical devices. DEHP, DINP and DINCH were cytotoxic at the highest concentration (0.1 mg/ml) for 7 days of exposure. Their corresponding metabolites were found to be more cytotoxic, for the same concentration. By contrast, TOTM and its corresponding metabolite MOTM were not found to be cytotoxic. DEHA showed no cytotoxicity, but its corresponding monoester (MEHA) produced a cytotoxic effect at 0.05 mg/ml. In clinical situations, medical devices can release plasticizers, which can come into contact with patients. In vivo, the plasticizers are quickly transformed into primary metabolites. It is therefore important to measure the effects of both the plasticizers and their corresponding metabolites. Standard first-line cytotoxicity assays should be performed to ensure biocompatibility.

Di-(2-ethylhexyl) phthalate metabolites in urine show age-related changes and associations with adiposity and parameters of insulin sensitivity in childhood

OBJECTIVES

Phthalates might be implicated with obesity and insulin sensitivity. We evaluated the levels of primary and secondary metabolites of Di-(2-ethylhexyl) phthalate (DEHP) in urine in obese and normal-weight subjects both before and during puberty, and investigated their relationships with auxological parameters and indexes of insulin sensitivity.

DESIGN AND METHODS

DEHP metabolites (MEHP, 6-OH-MEHP, 5-oxo-MEHP, 5-OH-MEHP, and 5-CX-MEHP), were measured in urine by RP-HPLC-ESI-MS. Traditional statistical analysis and a data mining analysis using the Auto-CM analysis were able to offer an insight into the complex biological connections between the studied variables.

RESULTS

The data showed changes in DEHP metabolites in urine related with obesity, puberty, and presence of insulin resistance. Changes in urine metabolites were related with age, height and weight, waist circumference and waist to height ratio, thus to fat distribution. In addition, clear relationships in both obese and normal-weight subjects were detected among MEHP, its products of oxidation and measurements of insulin sensitivity.

CONCLUSION

It remains to be elucidated whether exposure to phthalates per se is actually the risk factor or if the ability of the body to metabolize phthalates is actually the key point. Further studies that span from conception to elderly subjects besides further understanding of DEHP metabolism are warranted to clarify these aspects.

Food emulsifier polysorbate 80 increases intestinal absorption of di-(2-ethylhexyl) phthalate in rats

The aim of the present research was to explore whether food emulsifier polysorbate 80 can enhance the absorption of di-(2-ethylhexyl) phthalate (DEHP) and its possible mechanism. We established the high-performance liquid chromatography (HPLC) method for detecting DEHP and its major metabolite, mono-ethylhexyl phthalate (MEHP) in rat plasma, and then examined the toxicokinetic and bioavailability of DEHP with or without polysorbate 80 in rats. The study of its mechanism to increase the absorption of phthalates demonstrated that polysorbate 80 can induce mitochondrial dysfunction in time- and concentration-dependence manners in Caco-2 cells by reducing mitochondrial membrane potential, diminishing the production of the adenosine triphosphate, and decreasing the activity of electron transport chain. Our results indicated that food emulsifier applied in relatively high concentrations in even the most frequently consumed foods can increase the absorption of DEHP, and its role may be related to the structure and function damages of mitochondria in enterocytes.

Di 2-ethylhexylphtalate in the aquatic and terrestrial environment: a critical review

Phthalates are being increasingly used as softeners-plasticizers to improve the plasticity and the flexibility of materials. Amongst the different plasticizers used, more attention is paid to di (2-ethylhexylphtalate) (DEHP), one of the most representative compounds as it exhibits predominant effects on environment and human health. Meanwhile, several questions related to its sources; toxicity, distribution and fate still remain unanswered. Most of the evidence until date suggests that DEHP is an omnipresent compound found in different ecological compartments and its higher hydrophobicity and low volatility have resulted in significant adsorption to solids matrix. In fact, there are important issues to be addressed with regard to the toxicity of this compound in both animals and humans, its behavior in different ecological systems, and the transformation products generated during different biological or advanced chemical treatments. This article presents detailed review of existing treatment schemes, research gaps and future trends related to DEHP.

Phthalates in indoor dust in Kuwait: implications for non-dietary human exposure

Phthalates are semivolatile organic compounds with a ubiquitous environmental distribution. Their presence in indoor environments is linked to their use in a variety of consumer products such as children's toys, cosmetics, food packaging, flexible PVC flooring among others. The goal of this study was to investigate the occurrence and concentration of phthalates in dust from homes in Kuwait and to assess non-dietary human exposure to these phthalates. Dust samples were randomly collected from 21 homes and analyzed for eight phthalates. The concentrations of total phthalates were log normally distributed and ranged from 470 to 7800 μg/g. Five phthalates [Di(2-ethylhexyl) phthalate (DEHP), Di-n-octyl phthalate (DnOP), Di-n-butyl phthalate (DBP), Benzyl butyl phthalate (BzBP), and Dicyclohexyl phthalate (DcHP)] were routinely detected. The major phthalate compound was DEHP at a geometric mean concentration of 1704 μg/g (median, 2256 μg/g) accounting for 92% of the total phthalates measured. Using the measured concentrations and estimates of dust ingestion rates for children and adults, estimated human non-dietary exposure based on median phthalate concentrations ranged from 938 ng/kg-bd/day for adults to 13362 ng/kg-bd/day for toddlers. The difference in exposure estimates between children and adults in this study supports previous reports that children are at greater risk from pollutants that accumulate indoors.

Di-(2-ethylhexyl) phthalate and autism spectrum disorders

ASDs (autism spectrum disorders) are a complex group of neurodevelopment disorders, still poorly understood, steadily rising in frequency and treatment refractory. Extensive research has been so far unable to explain the aetiology of this condition, whereas a growing body of evidence suggests the involvement of environmental factors. Phthalates, given their extensive use and their persistence, are ubiquitous environmental contaminants. They are EDs (endocrine disruptors) suspected to interfere with neurodevelopment. Therefore they represent interesting candidate risk factors for ASD pathogenesis. The aim of this study was to evaluate the levels of the primary and secondary metabolites of DEHP [di-(2-ethylhexyl) phthalate] in children with ASD. A total of 48 children with ASD (male: 36, female: 12; mean age: 11 ± 5 years) and age- and sex-comparable 45 HCs (healthy controls; male: 25, female: 20; mean age: 12 ± 5 years) were enrolled. A diagnostic methodology, based on the determination of urinary concentrations of DEHP metabolites by HPLC-ESI-MS (HPLC electrospray ionization MS), was applied to urine spot samples. MEHP [mono-(2-ethylhexenyl) 1,2-benzenedicarboxylate], 6-OH-MEHP [mono-(2-ethyl-6-hydroxyhexyl) 1,2-benzenedicarboxylate], 5-OH-MEHP [mono-(2-ethyl-5-hydroxyhexyl) 1,2-benzenedicarboxylate] and 5-oxo-MEHP [mono-(2-ethyl-5-oxohexyl) 1,2-benzenedicarboxylate] were measured and compared with unequivocally characterized, pure synthetic compounds (>98%) taken as standard. In ASD patients, significant increase in 5-OH-MEHP (52.1%, median 0.18) and 5-oxo-MEHP (46.0%, median 0.096) urinary concentrations were detected, with a significant positive correlation between 5-OH-MEHP and 5-oxo-MEHP (rs = 0.668, P<0.0001). The fully oxidized form 5-oxo-MEHP showed 91.1% specificity in identifying patients with ASDs. Our findings demonstrate for the first time an association between phthalates exposure and ASDs, thus suggesting a previously unrecognized role for these ubiquitous environmental contaminants in the pathogenesis of autism.

Synthesis and evaluation of novel dental monomer with branched aromatic carboxylic acid group

A new glycerol-based dimethacrylate monomer with an aromatic carboxylic acid, 2-((1,3-bis(methacryloyloxy)propan-2-yloxy)carbonyl)benzoic acid (BMPB), was synthesized, characterized, and proposed as a possible dental co-monomer for dentin adhesives. Dentin adhesives containing 2-hydroxyethyl methacrylate (HEMA) and 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]propane (BisGMA) in addition to BMPB were formulated with water at 0, 5, 10, and 15 wt % to simulate wet, oral conditions, and photo-polymerized. Adhesives were characterized with regard to viscosity, real-time photopolymerization behavior, dynamic mechanical analysis, and microscale 3D internal morphologies and compared with HEMA/BisGMA controls. When formulated under wet conditions, the experimental adhesives showed lower viscosities (0.04-0.07 Pa s) as compared to the control (0.09-0.12 Pa s). The experimental adhesives showed higher glass transition temperature (146-157°C), degree of conversion (78-89%), and rubbery moduli (33-36 MPa), and improved water miscibility (no voids) as compared to the controls (123-135°C, 67-71%, 15-26 MPa, and voids, respectively). The enhanced properties of these adhesives suggest that BMPB with simple, straightforward synthesis is a promising photocurable co-monomer for dental restorative materials.