Identification of the Biotransformation Products of 2-Ethylhexyl 4-(N,N-Dimethylamino)benzoate

Biodegradation of 2-ethylhexyl-4-methoxycinnamate in river sediments and its impact on microbial communities

Numerous studies have evaluated the toxicity and endocrine disrupting properties of organic UV filters for aquatic organisms, but little is known about their biodegradation in river sediments and their impact on microorganisms. We have set up the sterile and microbiological systems in the laboratory, adding 2-ethylhexyl-4-methoxycinnamate (EHMC), one of organic UV filters included in the list of high yield chemicals, at concentrations of 2, 20 and 200 μg/L, and characterized the microbial community composition and diversity in sediments. Monitoring of EHMC degradation within 30 days revealed that the half-life in the microbial system (3.49 days) was much shorter than that in the sterile system (7.55 days). Two potential degradation products, 4-mercaptobenzoic acid and 3-methoxyphenol were identified in the microbial system. Furthermore, high-throughput 16s and 18s rRNA gene sequencing showed that Proteobacteria dominated the sediment bacterial assemblages followed by Chloroflexi, Acidobacteria, Bacteroidetes and Nitrospirae; Eukaryota_uncultured fungus dominated the sediment fungal assemblages. Correlation analysis demonstrated that two bacterium genera (Anaerolineaceae_uncultured and Burkholderiaceae_uncultured) were significantly correlated with the biodegradation of EHMC. These results illustrate the biodegradability of EHMC in river sediments and its potential impact on microbial communities, which can provide useful information for eliminating the pollution of organic UV filters in natural river systems and assessing their potential ecological risks.

Human metabolism and urinary excretion kinetics of the UV filter Uvinul A plus® after a single oral or dermal dosage

Hexyl 2-[4-(diethylamino)-2-hydroxybenzoyl]benzoate, better known under its trading name Uvinul A plus® is a UV filter mainly used in sunscreens, but also present in other cosmetic products with a maximum concentration of 10% (w/w) according to the EU directive. In this study we investigated the human metabolism after a single oral and a single dermal dose of Uvinul A plus®, respectively. Samples collected within 72 h of administration were analyzed with a newly developed UHPLC-MS/MS method. Results of the study revealed three major urinary metabolites, namely 2-(4-amino-2-hydroxybenzoyl)benzoic acid (AHB), 2-(4-(ethylamino)-2-hydroxybenzoyl)benzoic acid (EHB) and 2-(4-(diethylamino)-2-hydroxybenzoyl)benzoic acid (DHB), representing 52% of the administered oral dose. The three major metabolites are further converted into four minor metabolites with an additional hydroxyl group in the aniline moiety. Toxicokinetic parameters (amount excreted, t_max, elimination constant and half-life t_1/2) and conversion factors were determined for the three major metabolites. The conversion factors were used to estimate the mean daily exposure to Uvinul A plus® in spot urine samples from 58 volunteers not intentionally exposed to Uvinul A plus® derived from a pilot study. The three major metabolites were quantifiable in 26% of the samples. In 35% of the samples, at least one major metabolite could be quantified. The daily systemic exposure to Uvinul A plus® was estimated to approximately 8.1-9.3 μg/d by applying the combined conversion factor for all three major metabolites. In conclusion, a very low systemic exposure to DHHB was observed with regard to the no observed adverse effect level (NOAEL) as an established threshold for chronic uptake.

A validated UPLC-MS/MS method for the determination of urinary metabolites of Uvinul® A plus

Uvinul® A plus (DHHB) is a synthetic benzophenone derivative mainly used in sunscreens, and also in other skin care products. The compound is authorized by the EU as UV filter and a maximum concentration of 10% in consumer products is permitted. Despite its high production volume and usage in consumer products,to date, no information about the systemic exposure to Uvinul® A plus in humans is available. Therefore, we developed a human biomonitoring method which allows the simultaneous determination of three major metabolites of Uvinul® A plus in human urine samples. Furthermore, three minor metabolites of Uvinul® A plus were identified by ion trap experiments. Urine samples were enzymatically hydrolyzed, extracted via liquid-liquid extraction with ethyl acetate, and analyzed by means of UPLC-MS/MS. The final method was validated according to FDA guidelines and applied to 58 urine samples retrieved from the general German population. The three major and specific metabolites of Uvinul® A plus were found in about 36% of the samples, proving the suitability of the method for future human biomonitoring studies.

Fate of UV filter Ethylhexyl methoxycinnamate in rat model and human urine: Metabolism, exposure and demographic associations

Ethylhexyl methoxycinnamate (EHMC) is one of the most frequently used UV filters in sunscreens and other cosmetic products. Its ubiquitous presence in various environmental matrices and its endocrine disrupting properties have been widely reported. However, we know little about the effect of EHMC exposure on humans, mainly due to its fast metabolism. In this study, urine and plasma of EHMC-dosed rats were analysed to identify its major metabolites. Five metabolites were found, with four firstly reported. Two metabolites were putatively identified as 4-methoxycinnamic acid (4-MCA) and 4'-methoxyacetophenone (4'-MAP). Quantitative results revealed that their excretion concentrations were much higher than the parent compound. Because of these high concentrations, for the human biomonitoring study, EHMC and these two metabolites were detected simultaneously in urine samples from Chinese children and adolescents. The results indicated wide exposure to EHMC, 4-MCA and 4'-MAP. The correlation between urinary concentration of EHMC and 4-MCA as well as 4-MCA and 4'-MAP provided important clues as to the sources and metabolic pathways among these three compounds. Several demographic factors were also assessed with the exposure level. As the first human exposure study of EHMC in a Chinese population, this report would help to establish an exposure database facilitating health risk assessment of EHMC.

Estimation of physicochemical properties of 2-ethylhexyl-4-methoxycinnamate (EHMC) degradation products and their toxicological evaluation

The organic UV filters, commonly used in personal protection products, are of concern because of their potential risk to aquatic ecosystems and living organisms. One of UV filters is ethylhexyl-4-methoxycinnamate (EHMC) acid. Studies have shown that, in the presence of oxidizing and chlorinating factors, EHMC forms a series of products with different properties than the substrate. In this study, the toxicities of EHMC and its transformation/degradation products formed under the influence of NaOCl/UV and H₂O₂/UV systems in the water medium were tested using Microtox® bioassay and by observation of mortality of juvenile crustaceans Daphnia magna and Artemia Salina. We have observed that oxidation and chlorination products of EHMC show significantly higher toxicity than EHMC alone. The toxicity of chemicals is related to their physicochemical characteristic such as lipophilicity and substituent groups. With the increase in lipophilicity of products, expressed as log K_OW, the toxicity (EC₅₀) increases. On the basis of physicochemical properties such as vapour pressure (VP), solubility (S), octanol-water partition coefficient (K_OW), bioconcentration factor (BCF) and half-lives, the overall persistence (P_OV) and long-range transport potential (LRTP) of all the products and EHMC were calculated. It was shown that the most persistent and traveling on the long distances in environment are methoxyphenol chloroderivatives, then methoxybenzene chloroderivatives, EHMC chloroderivatives, methoxybenzaldehyde chloroderivatives and methoxycinnamate acid chloroderivatives. These compounds are also characterised by high toxicity.

Stereoselective metabolism of the UV-filter 2-ethylhexyl 4-dimethylaminobenzoate and its metabolites in rabbits in vivo and vitro

.The stereoselective metabolism of the enantiomers of the UV-filter 2-ethylhexyl 4-dimethylaminobenzoate (EDP) and its two major metabolites were studied in rabbits in vivo and in vitro. Cytotoxicity of EDP and its two metabolites was also investigated in hepatocytes.

Mild and selective labeling of malondialdehyde with 2-aminoacridone: assessment of urinary malondialdehyde levels

Malondialdehyde (MDA) has become a well-established biomarker for oxidative stress. The most commonly used way to determine urinary MDA levels is the thiobarbituric acid (TBA) assay, which suffers from several drawbacks. In this manuscript, we describe a novel derivatization strategy for the highly sensitive and selective fluorescence-based determination of MDA in urinary samples. The methodology is based on the mild labeling of MDA with 2-aminoacridone, which can be carried out in aqueous citrate buffer at 40 °C, yielding a highly fluorescent substance. No further sample preparation than mixing with the necessary chemicals is necessary. The formed MDA derivative can conveniently be separated from the label itself and matrix constituents by gradient LC in less than 5 minutes on a cyano-based reversed-phase material. The method was validated with respect to matrix effects, linearity, selectivity and sensitivity (values as low as 1.8 nM for the LOD and 5.8 nM for the LOQ could be achieved). Standard addition quantitation was applied for the determination of MDA in human urine samples. Additionally, the protocol was applied to the measurement of a stability indicating analysis of MDA in urine at different storage conditions.