High-dose exposure to butylparaben impairs thyroid ultrastructure and function in rats

Parabens (PBs) are a class of preservatives commonly used in cosmetics and pharmaceuticals. Studies have shown that these compounds may act as endocrine disruptors, affecting thyroxine levels in humans. PBs with longer chain substituents, such as butylparaben (BuP), are less prone to complete biotransformation and are therefore more likely to accumulate in the body. In this study, the effect of high-dose exposure to BuP on thyroid microstructure, ultrastructure, and function was investigated in rats. 50 mg/kg bw per day of BuP was injected subcutaneously into the neck of rats for 4 weeks. Rat thyroid weight, microstructure, and ultrastructure were determined, and the levels of thyroid sodium/iodide symporter (NIS), serum thyroid hormones, and thyroid autoantibodies were measured. The human thyroid cell line was used to study the mechanism of BuP on thyroid epithelial cells. The weight of the thyroid gland of BuP-exposed rats was increased, the structure of the thyroid follicles was irregular and damaged, the mitochondria and rough endoplasmic reticulum were swollen and damaged, and the microvilli at the tip of the epithelium were reduced and disappeared. Serum total T3, total T4, free T3, and free T4 were decreased in BuP-exposed rats, and TSH, peroxidase antibody, and thyroglobulin antibody were increased. In vitro, BuP decreased the level of NIS in thyroid epithelial cells, inhibited proliferation and viability, and induced apoptosis in a dose-dependent manner. This study demonstrated that high-dose exposure to BuP induced structural, ultrastructural, and functional impairment to the thyroid gland of rats, which may be one of the factors leading to hypothyroidism.

Urinary concentrations of bisphenol A, parabens and benzophenone-type ultra violet light filters in relation to sperm DNA fragmentation in young men: A chemical mixtures approach

People are daily exposed to multiple endocrine disruptor compounds (EDCs) that may interfere with different molecular and cellular processes, promoting a potential estrogenic, androgenic, or anti-androgenic state. However, most epidemiological studies attempting to establish relationships between EDCs exposure and health effects are still considering individual compounds. A few studies have shown associations between exposure to individual non-persistent EDCs and sperm DNA fragmentation (SDF) in different male populations. Thus, the aim of this study was to investigate associations between combined exposure to non-persistent EDCs and SDF index in young men. A cross-sectional study was conducted with 158 healthy university students from Southeaster Spain. The participants provided spot urine and semen samples on the same day. The concentrations of urinary bisphenol A (BPA), benzophenones [2,4-dihydroxybenzophenone (BP-1); 2,2',4,4'-tetrahydroxybenzophenone (BP-2), 2-hydroxy-4-methoxybenzophenone (BP-3), 2,2'-dihydroxy-4-methoxybenzophenone (BP-8), 4-hydroxybenzophenone (4OHBP)], and parabens (methylparaben, ethylparaben, propylparaben, butylparaben) were measured by dispersive liquid-liquid microextraction and ultrahigh-performance liquid chromatography with tandem mass spectrometry detection. SDF was analysed using a Sperm Chromatin Dispersion test. Statistical analyses were carried out using Bayesian Kernel Machine Regression models to evaluate associations between combined exposure to these compounds and SDF index while adjusting by relevant covariates. The increase in urinary concentration of 4OHBP was found to be the most important contributor to the negative association between urinary EDCs concentrations and SDF index, being of -5.5 % [95 % CI: -10.7, -0.3] for those in percentile 50, and - 5.4 % [95 % CI: -10.8, -0.1] for those in percentile 75. No significant associations were observed between other EDCs and SDF index. Our findings show that urinary 4OHBP levels may be associated with a decrease in the SDF index. Nonetheless, the effects we observed were likely to be small and of uncertain clinical significance. Further research is needed to replicate our findings in other male populations.

Grouping of esters of 4-hydroxybenzoic acid for hazard assessment

Hazardous properties of a large number of esters of 4-hydroxybenzoic acid (parabens) have been proposed by ECHA to be assessed as a group. We recommend to restrict the grouping approach to short chain esters, i.e. methyl, ethyl, propyl and butyl paraben which are very similar in chemical structures, physicochemical properties, toxicokinetics, and hazardous properties. While these parabens show a weak estrogenicity in some in vitro or in vivo screening assays, they do not induce estrogen-receptor-mediated adverse effects in intact animals. Therefore, there is no support regarding classification and labeling of endocrine disruption or reproductive toxicity of these parabens.

A survey of parabens in aquatic environments in Hanoi, Vietnam and its implications for human exposure and ecological risk

Seven parabens including methylparaben (MeP), ethylparaben (EtP), propylparaben (PrP), iso-propylparaben (iPrP), butylparaben (BuP), benzylparaben (BzP), and heptylparaben (HepP) were determined in bottled water, tap water, river water, lake water, and wastewater samples collected from Hanoi, Vietnam, using solid phase extraction (SPE) followed by ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The highest total concentration of parabens were measured in wastewater (range, 27.3-1050 ng/L; mean/median, 268/175 ng/L), followed by lake water (range, 18.0-254 ng/L; mean/median, 51.7/58.5 ng/L), river water (range, 16.5-52.1 ng/L; mean/median, 32.1/42.6 ng/L), tap water (range, 5.01-54.3 ng/L; mean/median, 28.6/41.1 ng/L), and bottled water (range, 1.56-39.9 ng/L; mean/median, 6.92/9.19 ng/L). Methylparaben and propylparaben were the predominant compounds found in all samples. The mean estimated human exposure dose of parabens through drinking bottled water was 0.27 ng/kg-bw/day, which is 6 orders of magnitude below the safety threshold recommended by the Joint FAO/WHO Expert Committee on Food Additive in 1974 (10 mg/kg-bw/day). Concentrations of parabens measured in river water, lake water, and wastewater samples were assessed to pose low to moderate ecological risks to aquatic organisms (0.1 < RQ < 1). Methyl, ethyl, and propyl parabens exhibited significant correlations in water samples.

Identifying potential paraben transformation products and evaluating changes in toxicity as a result of transformation

Parabens are a class of compounds often used as preservatives in personal care products, pharmaceuticals, and food. They have received attention recently due to findings that demonstrate estrogenic impacts and other adverse effects of parabens. Release into wastewater effluent is considered a major contributor to the spread of parabens into surface water. Current regulations in areas such as Japan, Europe, and Southeast Asia limit the concentrations of parabens that can be used in formulations but do not address concentrations discharged into waterbodies. Recent studies suggest that parent parabens are effectively eliminated by transformation during the wastewater treatment processes. Common tertiary treatments include ultrafiltration, chlorination, UV disinfection and ozonation. Ultrafiltration is used to remove solids before a disinfection step. Of the disinfection steps, ozonation is often the most effective at removing parabens. Not much is known about the toxicities of paraben transformation products. Of the transformation products, chlorinated parabens and PHBA are the most studied. Previous studies have shown that chlorinated parabens have greatly reduced estrogen agonistic activity when compared with the activity of parents. However, more recent studies have found that halogenated parabens actually have estrogen antagonistic activity. Further research involving chlorinated parabens could include other toxic endpoints. No known studies have evaluated adverse effects of oxygenated parabens. Parabens can interact with chlorine residues in the environment and form chlorinated products, this will occur at a faster rate during chlorination. Ozonation will oxidize parabens and UV disinfection can both oxidize and halogenate parabens. All studies determining potential transformation products have been done in laboratory settings or specific conditions. Further research is needed to determine if these transformations occur in situ. PRACTITIONER POINTS: Common chemical processes utilized by wastewater treatment facilities are effective at transforming parabens. Paraben transformation products are released in greater concentration in effluent than parent paraben compounds. Halogenated transformation products have been identified as estrogen receptor antagonists.

Environmental obesogens (bisphenols, phthalates and parabens) and their impacts on adipogenic transcription factors in the absence of dexamethasone in 3T3-L1 cells

Endocrine-disrupting chemicals (EDCs) are exogenous compounds that are capable of blocking or mimicking the action of bioidentical hormones. Obesogenic EDCs, commonly called obesogens, play an important role in adipogenesis. This study was carried out to determine the effects of select obesogens and their alternatives on adipogenesis in 3T3-L1 cells under dexamethasone (DEX)-free conditions. Preadipocytes were treated with a cocktail of 3-isobutyl-1-methylxanthine (IBMX) and insulin to which an obesogen (viz., bisphenol A (BPA) or its analogs BPS and BPF; dioctyl terephthalate; tris (2-ethylhexyl) trimellitate; or various parabens) had been added. A mixture containing IBMX, insulin, and DEX, which constitute the typical hormonal cocktail required for adipocyte differentiation, was used as the control against which the other groups were measured. The obesogens and the PBA analogs all had evident adipogenic effects under DEX-free conditions, as was determined by estimating the lipid accumulation levels in the cells using Oil Red O staining. Furthermore, the expression of adipogenic transcription factors (CCAAT/enhancer-binding protein-alpha, peroxisome proliferator-activated receptor-gamma, and adipocyte protein 2) was induced by 20 μM of BPA, BPS, or BPF at both the mRNA and protein levels, as determined through reverse transcription-polymerase chain reaction and western blot assays. Taken together, the results reveal that adipocyte differentiation can be induced by obesogens and their alternatives in the absence of DEX.

Design of Multifaceted Antioxidants: Shifting towards Anti-Inflammatory and Antihyperlipidemic Activity

Oxidative stress and inflammation are two conditions that coexist in many multifactorial diseases such as atherosclerosis and neurodegeneration. Thus, the design of multifunctional compounds that can concurrently tackle two or more therapeutic targets is an appealing approach. In this study, the basic NSAID structure was fused with the antioxidant moieties 3,5-di-tert-butyl-4-hydroxybenzoic acid (BHB), its reduced alcohol 3,5-di-tert-butyl- 4-hydroxybenzyl alcohol (BHBA), or 6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid (Trolox), a hydrophilic analogue of α-tocopherol. Machine learning algorithms were utilized to validate the potential dual effect (anti-inflammatory and antioxidant) of the designed analogues. Derivatives 1–17 were synthesized by known esterification methods, with good to excellent yields, and were pharmacologically evaluated both in vitro and in vivo for their antioxidant and anti-inflammatory activity, whereas selected compounds were also tested in an in vivo hyperlipidemia protocol. Furthermore, the activity/binding affinity of the new compounds for lipoxygenase-3 (LOX-3) was studied not only in vitro but also via molecular docking simulations. Experimental results demonstrated that the antioxidant and anti-inflammatory activities of the new fused molecules were increased compared to the parent molecules, while molecular docking simulations validated the improved activity and revealed the binding mode of the most potent inhibitors. The purpose of their design was justified by providing a potentially safer and more efficient therapeutic approach for multifactorial diseases.

Nipagin-Functionalized Porphyrazine and Phthalocyanine-Synthesis, Physicochemical Characterization and Toxicity Study after Deposition on Titanium Dioxide Nanoparticles P25

Aza-porphyrinoids exhibit distinct spectral properties in UV-Vis, and they are studied in applications such as photosensitizers in medicine and catalysts in technology. The use of appropriate peripheral substituents allows the modulation of their physicochemical properties. Phthalocyanine and sulfanyl porphyrazine octa-substituted with 4-(butoxycarbonyl)phenyloxy moieties were synthesized and characterized using UV-Vis and NMR spectroscopy, as well as mass spectrometry. A comparison of porphyrazine with phthalocyanine aza-porphyrinoids revealed that phthalocyanine macrocycle exhibits higher singlet oxygen generation quantum yields, reaching the value of 0.29 in DMF. After both macrocycles had been deposited on titanium dioxide nanoparticles P25, the cytotoxicities and photocytotoxicities of the prepared materials were studied using a Microtox® acute toxicity test. The highest cytotoxicity occurred after irradiation with a red light for the material composed of phthalocyanine deposited on titania nanoparticles.

The application of pharmaceutical quality by design concepts to evaluate the antioxidant and antimicrobial properties of a preservative system including desferrioxamine

BACKGROUND

The purpose of the present study was to investigate the antioxidant and antimicrobial activities of a conventional preservative system containing desferrioxamine mesylate (DFO) and optimize the composition of the system through mathematical models.

METHODS

Different combinations of ethylenediaminetetraacetic acid (EDTA), sodium metabisulfite (SM), DFO and methylparaben (MP) were prepared using factorial design of experiments. The systems were added to ascorbic acid (AA) solution and the AA content over time, at room temperature and at 40 °C was determined by volumetric assay. The systems were also evaluated for antioxidant activity by a fluorescence-based assay. Antimicrobial activity was assessed by microdilution technique and photometric detection against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans and Aspergillus brasiliensis. A multi-criteria decision approach was adopted to optimize all responses by desirability functions.

RESULTS

DFO did not extend the stability of AA over time, but displayed a better ability than EDTA to block the pro-oxidant activity of iron. DFO had a positive interaction with MP in microbial growth inhibition. The mathematical models showed adequate capacity to predict the responses. Statistical optimization aiming to meet the quality specifications of the ascorbic acid solution indicated that the presence of DFO in the composition allows to decrease the concentrations of EDTA, SM and MP.

CONCLUSION

DFO was much more effective than EDTA in preventing iron-catalyzed oxidation. In addition, DFO improved the inhibitory response of most microorganisms tested. The Quality by Design concepts aided in predicting an optimized preservative system with reduced levels of conventional antioxidants and preservatives, suggesting DFO as a candidate for multifunctional excipient.

Single crystal, Hirshfeld surface and theoretical analysis of methyl 4-hydroxybenzoate, a common cosmetic, drug and food preservative-Experiment versus theory

Methyl 4-hydroxybenzoate, commonly known as methyl paraben, is an anti-microbial agent used in cosmetics and personal-care products, and as a food preservative. In this study, the single crystal X-ray structure of methyl 4-hydroxybenzoate was determined at 120 K. The crystal structure comprises three methyl 4-hydroxybenzoate molecules condensed to a 3D framework via extensive intermolecular hydrogen bonding. Hirshfeld surface analysis was performed to determine the intermolecular interactions and the crystal packing. In addition, computational calculations of methyl 4-hydroxybenzoate were obtained using the Gaussian 09W program, and by quantum mechanical methods, Hartree Fock (HF) and Density Functional Theory (DFT) with the 6–311G(d,p) basis set. The experimental FT-IR spectrum strongly correlated with the computed vibrational spectra (R² = 0.995). The energies of the frontier orbitals, HOMO and LUMO, were used to calculate the chemical quantum parameters. The lower band gap value (ΔE) indicates the molecular determinants underlying the known pharmaceutical activity of the molecule.

Synthesis of 4-Hydroxybenzoic Acid Derivatives in Escherichia coli

Hydroxybenzoic acids (HBAs) such as 4-hydroxybenzoic acid (4-HBA) and 3,4-dihydroxybenzoic acid (DHB; protocatechuic acid) and its ester with methanol (methylparaben [MP]) are known to have various functional biological properties, including antibacterial, anticancer, antidiabetic, antiaging, antiviral, and anti-inflammatory activities. Since these compounds are widely used in cosmetic, food, and pharmaceutical industries, the use of renewable feedstocks for the production of HBAs is an area of growing interest. In this study, we used Escherichia coli to synthesize these three hydroxybenzoic acid derivatives (4-HBA, DHB, and MP). We overexpressed ubiC in E. coli to synthesize 4-HBA from chorismate, a substrate that is produced by the shikimate pathway in E. coli. For the synthesis of DHB, an additional gene (pobA) was introduced, while hbad and EHT1 were co-expressed to synthesize MP. To supply more chorismate, we introduced the shikimate gene module construct and selected the best construct for increased yields. Using this approach, 723.5 mg/L 4-HBA, 942.0 mg/L DHB, and 347.7 mg/L MP were synthesized. Our study showed that the shikimate gene module constructs can be applicable to increase the yields of HBA derivatives in HBA-tolerant microorganisms.

Fluoro-functionalized stationary phases for electrochromatographic separation of organic fluorides

Fluorous affinity means remarkably specific interaction between highly organic fluorides. This work aims to explore the potential of fluoro-functionalized stationary phase for the separation of organic fluorides by means of fluorous-fluorous interaction. Here, by using the Michael addition strategy between 1H,1H,2H,2H-perfluorodecanethiol (PFDT) and polydopamine (PD), a novel fluoro-functionalized stationary phase was synthesized for open-tubular capillary electrochromatography (OT-CEC). The PFDT@PD was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray Photoelectron Spectrometer (XPS). The PFDT@PD@capillary exhibited outstanding separation performance towards neutral compounds (such as alkylbenzenes and chlorobenzenes) and organic fluorides (such as fluorobenzenes and perfluoroalkyl methacrylates etc.) with high resolution and high separation efficiency by hydrophobic interaction and fluorous-fluorous interaction. In addition, the column shows good stability and reproducibility. The relative standard deviations (RSDs) of the retention time for intra-day (n = 5) and inter-day (n = 3) runs and between columns (n = 3) are less than 0.39%, 1.22% and 3.87%, respectively. This novel type of fluoro-functionalized stationary phase represents a great application potential in organic fluorides separation field.

Biomass-derived functional porous carbons for adsorption and catalytic degradation of binary micropollutants in water

The biomass, bottlebrush flower, is exploited for the preparation of functionalized porous carbons by one-pot thermal activation using NaHCO₃ and dicyandiamide. An intensified cross-linking effect among the precursors boosts pore (especially mesopore) formation in the pyrolysis process, producing N-doped porous carbons (NPCs) with a large specific surface area (SSA, up to 2025 m²  g^-1). The biomass-derived carbon samples turn out to be highly effective in adsorption, and catalytic activation of peroxymonosulfate for degradation of aqueous phenol and p-hydroxybenzoic acid (HBA) in single and binary systems. The effects of N content, porous structure, and trace Ni species on the adsorptive and catalytic behavior of carbon are investigated. It is found that the porous structure plays a more critical role in adsorption than surface N functionality, while the contributions of various reactive species for phenol and HBA degradation are different.

Nanocrystalline ferrihydrite activated peroxymonosulfate for butyl-4-hydroxybenzoate oxidation: Performance and mechanism

Heterogeneous catalysts activated peroxymonosulfate (PMS) for degradation of refractory organic contaminants has been recognized as a promising removal technology for the environmental remediation. In this study, nanocrystalline ferrihydrite (NFH) was prepared to activate PMS for the degradation of butyl-4-hydroxybenzoate (BHB). XPS analysis indicates that calcination process played a key role in regulating the surface oxygen species of NFH, thus control its activation ability toward PMS. NFH exhibits excellent stability (the released concentration of Fe ions < 0.13 mg/L) and desirable reusability. Increasing solution temperature and NFH dosage exerted a positive role in PMS activation for BHB removal, while such positive correlation was not found in the case of increasing initial pH. Increasing the static solution dissolved oxygen remarkably enhanced BHB oxidation kinetics. However, continuous N₂ and air blowing caused a significant decline in BHB removal. Reaction mechanism study showed that SO₄^‒, OH, O₂^‒, and ¹O₂ were the main reactive oxygen species for degrading BHB by NFH/PMS. LC/MS analysis indicated BHB was degraded by the pathways of hydroxylation, carboxylation, decarboxylation, dehydrogenation, ring cleavage and chain cleavage reaction. This work suggests the ferrihydrite might be a promising catalyst to activate PMS to destroy refractory organic pollutants in the environmental remediation.

Biomonitoring of parabens in human milk and estimated daily intake for breastfed infants

In this study, we assessed the presence of four parabens in human milk of 120 mothers from Valencia (Spain) which took part in a human biomonitoring project (BETTERMILK). The detection frequency ranges of parabens were 41-60% and 61-89% for unconjugated- and total (unconjugated + conjugated)-parabens, respectively. The concentrations ranged from <LoQ to 31 ng/mL and from <LoQ to 49 ng/mL for unconjugated- and total-parabens, respectively. The frequency of use of some cosmetic products and human milk protein levels were the main predictors of parabens in milk. The study evidences the presence of both conjugated and unconjugated paraben forms in human milk. The newborns estimated daily intake of parabens through human milk was several orders of magnitude lower than the 0-10 mg/kg bw-day acceptable daily intake for the sum of methyl and ethyl paraben established by EFSA. To our knowledge, this is currently the largest biomonitoring study of parabens in human milk.

Comparison of radical-driven technologies applied for paraben mixture degradation: mechanism, biodegradability, toxicity and cost assessment

Parabens (esters of p-hydroxybenzoic acid) are xenobiosis belonging to endocrine disruptors and commonly used as a preservative in cosmetics, food, pharmaceutical, and personal care products. Their wide use is leading to their appearance in water and wastewater in the range from ng/L to mg/L. In fact, the toxicity of benzylparaben is comparable to bisphenol A. Therefore, it is important to find not only effective but also ecofriendly methods for their removal from aqueous environment since the traditional wastewater treatment approaches are ineffective. Herein, for the first time, such extended comparison of several radical-driven technologies for paraben mixture degradation is presented. The detailed evaluation included (1) comparison of ozone and hydroxyl peroxide processes; (2) comparison of catalytic and photocatalytic processes (including photocatalytic ozonation); (3) characterisation of catalysts using SEM, XRD, DRS, XPS techniques and BET isotherm; (4) mineralisation, biodegradability and toxicity assessment; and (5) cost assessment. O₃, H₂O₂/Fe²⁺, H₂O₂/UVC, O₃/H₂O₂, O₃/UVA, O₃/H₂O₂/UVA, UVA/catalyst, O₃/catalyst and O₃/UVA/catalyst were selected from advanced oxidation processes to degrade parabens as well as to decrease its toxicity towards Aliivibrio fischeri, Corbicula fluminea and Lepidium sativum. Research was focused on the photocatalytic process involving visible light (UVA and natural sunlight) and TiO₂ catalysts modified by different metals (Ag, Pt, Pd, Au). Photocatalytic oxidation showed the lowest efficiency, while in combining ozone with catalysis and photocatalysis process, degradation efficiency and toxicity removal were improved. Photocatalytic ozonation slightly improved degradation efficiency but appreciably decreased transferred ozone dose (TOD). Results indicate that the degradation pathway is different, or different transformation products (TPs) could be formed, despite that the hydroxyl radicals are the main oxidant. Graphical abstract.

Hydroxyl radical-mediated degradation of salicylic acid and methyl paraben: an experimental and computational approach to assess the reaction mechanisms

Advanced oxidation processes (AOPs) using various energy sources and oxidants to produce reactive oxygen species are widely used for the destruction of recalcitrant water contaminants. The current study is about the degradation of two emerging pollutants-salicylic acid (SA) and methyl paraben (MP)-by high-frequency ultrasonication followed by identification of the oxidation byproducts and modeling of the reaction mechanisms using the density functional theory (DFT). The study also encompasses prediction of the aquatic toxicity and potential risk of the identified byproducts to some aquatic organisms bussing the ECOSAR (Ecological Structure Activity Relationships) protocol. It was found that the degradation of both compounds was governed by •OH attack and the pathways consisted of a cascade of reactions. The rate determining steps were decarboxylation (~ 60 kcal mol^-1) and bond breakage reactions (~ 80 kcal mol^-1), which were triggered by the stability of the reaction byproducts and overcome by the applied reaction conditions. Estimated values of the acute toxicities showed that only few of the byproducts were harmful to aquatic organisms, implying the environmental friendliness of the experimental method.

Microwave synthesis of iodine-doped bismuth oxychloride microspheres for the visible light photocatalytic removal of toxic hydroxyl-contained intermediates of parabens: catalyst synthesis, characterization, and mechanism insight

The iodine-doped bismuth oxychloride (I-doped BiOCl) microspheres are synthesized as the visible light photocatalysts for the photocatalytic removal of three toxic hydroxyl-contained intermediates of parabens. With the aid of the unique heating mode of microwave method, the I-doped BiOCl photocatalysts with tunable iodine contents and dispersed energy bands, instead of a mixture of BiOI and BiOCl or solid solution, are synthesized under the controllable conditions. Due to the stretched architectures, high specific surface area, and effective separation of photogenerated carriers, they exhibit high activity to the photocatalytic degradation of methyl 2,4-dihydroxybenzoate (MDB), methyl 3,4-dihydroxybenzoate (MDHB), and ethyl 2,4-dihydroxybenzoate (EDB). As a typical result, it is indicated that though MDB as the most difficult intermediate of parabens to be degraded, a 91.2% removal ratio can still be achieved over the I-doped BiOCl with an energy band of 2.79 eV within 60 min. In addition, it is also confirmed that these photocatalysts remain stable throughout the photocatalytic reaction and can be reused, and more importantly, the photogenerated h⁺ and •O₂^- are the key reactive species, while •OH plays a negligible role in the photocatalytic reaction. Resorcinol was identified as the main photodegraded intermediate. These results demonstrate that this photocatalytic system not only exhibit a high efficiency but also avoid the consequent secondary pollutions due to the no formation of complex hydroxyl derivatives.

Structure and spectroscopic characterization of pharmaceutical co-crystal formation between acetazolamide and 4-hydroxybenzoic acid

Co-crystals have great potential for drug research and development because the formation of co-crystal is accompanied by changes inter-molecular interactions between starting materials that enable to improve both physical and chemical properties of active pharmaceutical ingredients. In order to provide a more profound insight into the structural changes of specific drugs upon co-crystallization, spectroscopic characterization of solid-state acetazolamide (ACZ), 4-hydroxybenzoic acid (4HBA) and their co-crystal prepared by mechanical grinding approach has been performed with spectral techniques including terahertz time-domain spectroscopy (THz-TDS) and Raman spectroscopy. Experimental THz spectra show that the ACZ-4HBA co-crystal has a few significantly different absorption peaks in 0.82, 1.16, 1.28 and 1.64 THz respectively compared with parent materials in the frequency region from 0.2 to 1.8 THz. Likewise, such differences between the co-crystal and starting compounds could also be characterized by Raman vibrational spectra. Moreover, density functional theory (DFT) calculations were performed to simulate optimized structures and vibrational modes of three kind of possible co-crystal theoretical forms (form I, II and III) between ACZ and 4HBA. Theoretical results and THz/Raman vibrational spectra of ACZ-4HBA co-crystal show that the 4HBA links to the thiadiazole acetamide fragment of ACZ via the double-bridged heterodimeric synthon C(N)NH⋯HOOC inter-molecular hydrogen bonding interaction establishing the theoretical form I, which is more consistent with experimental observations than other two possible theoretical co-crystal forms. These results provide rich information and unique method for characterizing the composition of co-crystal structures and also inter-molecular interactions shown within pharmaceutical co-crystallization process at the molecular level.

Effects of methylparaben, ethylparaben, and propylparaben on life parameters and sex ratio in the marine copepod Tigriopus japonicus

Parabens are used as a preservative substance in a wide range of man-made products causing deleterious effects on aquatic organisms and therefore, the concern of their effects to aquatic organisms has been increased. In this study, acute toxicity of methylparaben (MeP), ethylparaben (EtP), and propylparaben (PrP) was assessed in the marine copepod Tigriopus japonicus. The acute toxicity assessment resulted in the median lethal concentration (LC50) values of MeP, EtP, and PrP were 29,754, 11,659, and 113 μg/L, respectively, for male and 38,183, 15,371, and 357 μg/L, respectively, for female, indicating the strongest toxicity of PrP, compared to MeP and EtP and the higher sensitivity of males compared to females. Developmental retardation and reproduction rate were also measured under chronic exposure. Furthermore, significant alteration in sex ratio was shown in PrP-exposed group, indicating PrP would have feminization effect in T. japonicus. Here we report different toxicity of three types of parabens and also shows potential estrogenic effects of PrP in T. japonicus.

4-Hydroxybenzoic acid serves as an endogenous ring precursor for antroquinonol biosynthesis in Antrodia cinnamomea

Antrodia cinnamomea, an endemic fungus species of Taiwan, has long been used as a luxurious dietary supplement to enhance liver functions and as a remedy for various cancers. Antroquinonol (AQ), identified from the mycelium of A. cinnamomea, is currently in phase II clinical trials in the USA and Taiwan for the treatment of non-small-cell lung cancer. In the previous studies, we have demonstrated that AQ and 4-acetylantroquinonol B (4-AAQB) utilize orsellinic acid, via polyketide pathway, as the ring precursor, and their biosynthetic sequences are similar to those of coenzyme Q. In order to test 4-hydroxybenzoic acid (4-HBA), synthesized via shikimate pathway, is the ring precursor of AQ analogs, the strategy of metabolic labeling with stable isotopes was applied in this study. Here we have confirmed that 4-HBA serves as the ring precursor for AQ but not a precursor of 4-AAQB. Experimental results indicated that A. cinnamomea preferentially utilizes endogenous 4-HBA via shikimate pathway for AQ biosynthesis. Exogenous tyrosine and phenylalanine can be utilized for AQ biosynthesis when shikimate pathway is blocked by glyphosate. The benzoquinone ring of 4-AAQB is synthesized only via polyketide pathway, but that of AQ is synthesized via both polyketide pathway and shikimate pathway. The precursor-products relationships diagram of AQ and 4-AAQB in A. cinnamomea are proposed based on the experimental findings.

Sonocatalytic degradation of butylparaben in aqueous phase over Pd/C nanoparticles

In the present work, the sonocatalytic degradation of butylparaben was investigated using Pd immobilized on carbon black as the sonocatalyst. The presence of 25 mg/L 10Pd/C significantly increased the removal rate of butylparaben and the observed kinetic constant increased from 0.0126 to 0.071 min^-1, while the synergy index between sonolysis and adsorption was 70.7%. The BP degradation followed pseudo-first-order kinetics with the apparent kinetic constant decreased from 0.071 to 0.030 min^-1 when the initial concentration of butylparaben increased from 0.5 to 2 mg/L. The process was being favored slightly under alkaline conditions. The presence of organic matter (20 mg/L humic acid) reduced the apparent kinetic constant more than two times. The addition of chlorides up to 250 mg/L did not significantly reduce the rate of reaction, while the presence of 250 mg/L bicarbonates reduced the observed kinetic constant from 0.071 to 0.0472 min^-1. The prepared catalyst retains the efficiency after five subsequent experiments since the apparent kinetic constant was only slightly decreased from 0.071 to 0.059 min^-1.

De novo structure determination of 3-((3-aminopropyl)amino)-4-hydroxybenzoic acid, a novel and abundant metabolite in Acinetobacter baylyi ADP1

INTRODUCTION

Metabolite identification remains a major bottleneck in the understanding of metabolism. Many metabolomics studies end up with unknown compounds, leaving a landscape of metabolites and metabolic pathways to be unraveled. Therefore, identifying novel compounds within a metabolome is an entry point into the 'dark side' of metabolism.

OBJECTIVES

This work aimed at elucidating the structure of a novel metabolite that was first detected in the soil bacterium Acinetobacter baylyi ADP1 (ADP1).

METHODS

We used high resolution multi-stage tandem mass spectrometry for characterizing the metabolite within the metabolome. We purified the molecule for 1D- and 2D-NMR (¹H, ¹³C, ¹H-¹H-COSY, ¹H-¹³C-HSQC, ¹H-¹³C-HMBC and ¹H-¹⁵N-HMBC) analyses. Synthetic standards were chemically prepared from MS and NMR data interpretation.

RESULTS

We determined the de novo structure of a previously unreported metabolite: 3-((3-aminopropyl)amino)-4-hydroxybenzoic acid. The proposed structure was validated by comparison to a synthetic standard. With a concentration in the millimolar range, this compound appears as a major metabolite in ADP1, which we anticipate to participate to an unsuspected metabolic pathway. This novel metabolite was also detected in another γ-proteobacterium.

CONCLUSION

Structure elucidation of this abundant and novel metabolite in ADP1 urges to decipher its biosynthetic pathway and cellular function.

Experimental and numerical study of methylparaben decomposition in aqueous solution using the UV/H2O2 process

The present paper aims at presenting a kinetic model that is supposed to result in the decomposition of methylparaben in completely mixed batch reactor (CMBR) using the UV/H₂O₂ process. The proposed model incorporates photochemical, chemical reactions and their constant rates to formulate the overall kinetic rate expressions which are integrated into MATLAB. Thus, the changes in pH values during the process of oxidation are taken into consideration. In addition, the effects of hydrogen peroxide (HP) dosage, as well as the concentration of hydroxyl radicals, are examined. Accordingly, the pseudo-first-order rate constant, its variation as functions of HP concentration, incident UV-light intensity and the limitations of the adopted approach are discussed. In line with that, the authors provided evidence of the validity of the kinetic model through the exposure of previous experimental studies as reported in the literature review then through the evidence of the present experimental data.

Mechanisms of Methylparaben Adsorption onto Activated Carbons: Removal Tests Supported by a Calorimetric Study of the Adsorbent⁻Adsorbate Interactions

: In this study, the mechanisms of methylparaben adsorption onto activated carbon (AC) are elucidated starting from equilibrium and thermodynamic data. Adsorption tests are carried out on three ACs with different surface chemistry, in different pH and ionic strength aqueous solutions. Experimental results show that the methylparaben adsorption capacity is slightly affected by pH changes, while it is significantly reduced in the presence of high ionic strength. In particular, methylparaben adsorption is directly dependent on the micropore volume of the ACs and the π- stacking interactions, the latter representing the main interaction mechanism of methylparaben adsorption from liquid phase. The equilibrium adsorption data are complemented with novel calorimetric data that allow calculation of the enthalpy change associated with the interactions between solvent-adsorbent, adsorbent-adsorbate and the contribution of the ester functional group (in the methylparaben structure) to the adsorbate⁻adsorbent interactions, in different pH and ionic strength conditions. It was determined that the interaction enthalpy of methylparaben-AC in water increases (absolute value) slightly with the basicity of the activated carbons, due to the formation of interactions with π- electrons and basic functional groups of ACs. The contribution of the ester group to the adsorbate-adsorbent interactions occurs only in the presence of phenol groups on AC by the formation of Brønsted⁻Lowry acid⁻base interactions.

Degradation of propyl paraben by activated persulfate using iron-containing magnetic carbon xerogels: investigation of water matrix and process synergy effects

An advanced oxidation process comprising an iron-containing magnetic carbon xerogel (CX/Fe) and persulfate was tested for the degradation of propyl paraben (PP), a contaminant of emerging concern, in various water matrices. Moreover, the effect of 20 kHz ultrasound or light irradiation on process performance was evaluated. The pseudo-first order degradation rate of PP was found to increase with increasing SPS concentration (25-500 mg/L) and decreasing PP concentration (1690-420 μg/L) and solution pH (9-3). Furthermore, the effect of water matrix on kinetics was detrimental depending on the complexity (i.e., wastewater, river water, bottled water) and the concentration of matrix constituents (i.e., humic acid, chloride, bicarbonate). The simultaneous use of CX/Fe and ultrasound as persulfate activators resulted in a synergistic effect, with the level of synergy (between 35 and 50%) depending on the water matrix. Conversely, coupling CX/Fe with simulated solar or UVA irradiation resulted in a cumulative effect in experiments performed in ultrapure water.

Parabens and their effects on the endocrine system

Preservatives (ingredients which inhibit growth of microorganisms) are used to prolong shelf life of various foods, cosmetics, and pharmaceutical products. Parabens are one of the most popular preservatives used in the aforementioned products and is currently being used worldwide. Parabens are easily absorbed by the human body. Thus, it is important to discuss about their safety with respect to human physiology. In view of the current literature, which classifies parabens as a group of endocrine disrupting chemicals (EDCs), it seems that the precise assessment of their influence on the human endocrine system is particularly important. Disruption of the endocrine homoeostasis might lead to multidirectional implications causing disruption of fitness and functions of the body. Therefore, in this review article, we aimed to summarize the current literature on properties, occurrence, and metabolism of parabens as well as to present recent progress in knowledge about their influence on the human endocrine system.

The use of combined treatments for reducing parabens in surface waters: Ion-exchange resin and nanofiltration

In this study, the removal of parabens from waters, using a combined treatment of magnetic ion exchange resins and subsequent filtration through nanofiltration membranes, was investigated. The selected parabens were methylparaben, ethylparaben, propylparaben and butylparaben. Two different magnetic anionic exchanger resins, MIEX® DOC and MIEX® GOLD, and two nanofiltration membranes (NF), NF-90 and DESAL-HL, were tested. The study was carried out using mono and multicomponent systems, using deionized water and natural waters sampled from two different rivers. In this way, competitive and matrix effects could be evaluated. The results showed, that with the combined treatments, higher elimination rates were obtained. The best removal efficiencies were obtained when the DOC resin was combined with both NF-90 and DESAL-HL membranes. Thus, butylparaben and propylparaben reached removal yields around 100% with both membranes, whereas the corresponding values for methylparaben were 91%, when the NF-90 membrane was employed, or 92% when DESAL-HL membrane was utilized. The elimination rates of ethylparaben with the same treatments were 96% with the NF-90 and 97% when the DESAL-HL membrane was combined with the DOC resin. The elimination percentages were higher as the paraben alkyl chain length increased. In addition, no competitiveness or matrix effects were detected. When the MIEX® GOLD resin was used for pre-treatment, membrane fouling worsened which indicated that resin selection needs to be carefully considered to achieve the best results.

Fabrication of β-cyclodextrin modified mesostructured silica coated multi-walled carbon nanotubes composites and application for paraben removal

In this work, the novel β-cyclodextrin modified mesostructured silica coated multi-walled carbon nanotubes (MWCNTs) composites were synthesized and applied for the removal of parabens in aqueous solution. The prepared MWCNTs/SiO₂/β-CD composites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. The effects of the amount of adsorbent, pH and elution solvents on the removal efficiency of parabens from water solutions were investigated. Under the optimized conditions, over 95% removal efficiency was achieved by using 40 mg of MWCNTs/SiO₂/β-CD adsorbents to absorb the parabens from 60 mL of 0.5 μg/mL parabens solutions. The solution pH in the range from 5 to 9 has no influence on the removal efficiency and the parabens sorption capacity of the prepared adsorbents were around 0.75 μg/mg. Furthermore, the stability and reusability studies demonstrated that the prepared MWCNTs/SiO₂/β-CD composites are cost-effective adsorbents for the removal of parabens from water with high regeneration efficiency. The composites fabricated in this study could become an attractive candidate for water purification.

Ultraviolet absorption redshift induced direct photodegradation of halogenated parabens under simulated sunlight

As disinfection by-products of parabens, halogenated parabens are frequently detected in aquatic environments and exhibit higher persistence and toxicity than parabens themselves. An interesting phenomenon was found that UV absorption redshift (∼45 nm) occurs after halogenation of parabens at circumneutral pH, leading to overlap with the spectrum of terrestrial sunlight. This work presents the first evidence on the direct photodegradation of seven chlorinated and brominated parabens under simulated sunlight. These halogenated parabens underwent rapid direct photodegradation, distinguished from the negligible degradation of the parent compounds. The photodegradation rate depended on their forms and substituents. The deprotonation of halogenated parabens facilitated the direct photodegradation. Brominated parabens exhibited higher degradation efficiency than chlorinated parabens, and mono-halogenated parabens had higher degradation than di-halogenated parabens. The pseudo-first-order rate constants (k_obs) for brominated parabens (0.075-0.120 min^-1) were approximately 7-fold higher than those of chlorinated parabens (0.011-0.017 min^-1). A quantitative structure-activity relationship (QSAR) model suggested that the photodegradation was linearly correlated with the C-X bond energies, electronic and steric effects of halogen substituents. The photodegradation products were identified using QTOF-MS analyses and a degradation pathway was proposed. The yeast two-hybrid estrogenicity assay revealed that the estrogenic activities of the photoproducts were negligible. These findings are important for the removal of halogenated parabens and predictions of their fate and potential impacts in surface waters.

Oxidation of propyl paraben by ferrate(VI): Kinetics, products, and toxicity assessment

Propyl paraben (propyl 4-hydroxybenzoate, PPB), one of the typically used paraben species in various pharmaceutical and personal care products, has been found in different aquatic environment, which could affect the water quality and human health. In this paper, the degradation of PPB by aqueous ferrate (Fe(VI)) was investigated in different water matrix and reaction kinetics as a function of pH was determined. Intermediate products of the degradation process were isolated and characterized by the high performance liquid chromatography/mass spectrometry/mass spectrometry techniques. Acute and chronic toxicities during water treatment of PPB using Fe(VI) were calculated using the ECOSAR program at three trophic levels. The obtained apparent second-order rate constant (k_app) for PPB reaction with Fe(VI) ranged from 99.6 ± 0.4 M^-1 s^-1 to 15.0 ± 0.1 M^-1 s^-1 with the half-life (t_1/2) ranging from 154 s to 1026 s at pH 6.5-10.0 for an Fe(VI) concentration of 600 μM. The proposed pathway for the oxidation of PPB by Fe(VI) involves one electron transfer of phenoxyl radical and breaking of the ether bond. In general, the oxidation of PPB by ferrate resulted in a significant decrease in toxicity at three trophic levels.

Biodegradation of four selected parabens with aerobic activated sludge and their transesterification product

Parabens are preservatives widely used in foodstuffs, cosmetics and pharmaceuticals, which have led to elevated paraben concentrations in wastewater and receiving waters. Laboratory-scale batch experiments were conducted to investigate the adsorption and degradation of parabens in an aerobic activated sludge system. Results show that biodegradation plays a key role in removing parabens from the aerobic system of wastewater treatment plants, while adsorption on the sludge is not significant. The effects of parent paraben concentration, concentration of mixed liquor suspended solids (MLSS), initial pH and temperature on degradation were investigated using kinetic models. The data shows that the degradation of parabens could be described by the first-order kinetic model with the rate constant ranging from 0.10 to 0.88 h^-1 at 25 °C and pH 7.0. Paraben degradation can be enhanced by increasing the MLSS concentration and temperature, or by decreasing the parent paraben concentration. Furthermore, the pH of the incubation system should be lower than 8.0. The half-lives of the parabens were estimated to range between 0.79 and 6.9 h, with methylparaben exhibiting the slowest degradation rate. During degradation in the present system, transesterification occurred, with methylparaben being the major transformation product in the incubation systems of ethylparaben, propylparaben and butylparaben. These results were confirmed by mass spectrometry and aliphatic alcohol additive experiments. This is the first discovery of paraben transesterification in an activated sludge system, and it is associated with trace methanol in the system.

Estrogen agonistic/antagonistic activity of brominated parabens

The estrogen agonistic/antagonistic activity of 16 brominated by-products of parabens was assessed by using a yeast two-hybrid assay transfected with the human estrogen receptor α. Characterization of synthetic compounds including novel brominated parabens was performed using ¹H-NMR spectroscopy and high-resolution mass spectrometry. For the agonist assay, five C₃-C₄ alkylparabens exhibited significant activity (P < 0.05) relative to that of 17β-estradiol, ranging from 3.7 × 10^-5 to 7.1 × 10^-4. In contrast, none of the brominated alkyl parabens exhibited agonistic activity. In the antagonist assay, 12 brominated alkylparabens and butylparaben exhibited significant antagonistic activity (P < 0.05). Their antagonistic activity relative to 4-hydroxytamoxifen ranged from 0.11 to 2.5. The antagonist activity of C₁-C₄ alkylparabens increased with the number of bromine substitutions. Benzylparaben exhibited both agonistic and antagonistic activity, and these activities dissipated or were weakened with increased bromination. Thus, increased bromination appeared to attenuate the estrogen agonistic activity of most parabens such that it resulted in increased antagonistic activity, a feature of parabens that had not been previously described.

Removal of pharmaceuticals, perfluoroalkyl substances and other micropollutants from wastewater using lignite, Xylit, sand, granular activated carbon (GAC) and GAC+Polonite® in column tests - Role of physicochemical properties

This study evaluated the performance of five different sorbents (granular activated carbon (GAC), GAC + Polonite^® (GAC + P), Xylit, lignite and sand) for a set of 83 micropollutants (MPs) (pharmaceuticals, perfluoroalkyl substances (PFASs), personal care products, artificial sweeteners, parabens, pesticide, stimulants), together representing a wide range of physicochemical properties. Treatment with GAC and GAC + P provided the highest removal efficiencies, with average values above 97%. Removal rates were generally lower for Xylit (on average 74%) and lignite (on average 68%), although they proved to be highly efficient for a few individual MPs. The average removal efficiency for sand was only 47%. It was observed that the MPs behaved differently depending on their physicochemical properties. The physicochemical properties of PFASs (i.e. molecular weight, topological molecular surface area, log octanol water partition coefficient (K_ow) and distribution coefficient between octanol and water (log D)) were positively correlated to observed removal efficiency for the sorbents Xylit, lignite and sand (p < 0.05), indicating a strong influence of perfluorocarbon chain length and associated hydrophobic characteristics. In contrast, for the other MPs the ratio between apolar and polar surface area (SA/SP) was positively correlated with the removal efficiency, indicating that hydrophobic adsorption may be a key feature of their sorption mechanisms. GAC showed to be the most promising filter medium to improve the removal of MPs in on-site sewage treatment facilities. However, more studies are needed to evaluate the removal of MPs in field trials.

Commelinid Monocotyledon Lignins Are Acylated by p-Coumarate

Commelinid monocotyledons are a monophyletic clade differentiated from other monocotyledons by the presence of cell wall-bound ferulate and p-coumarate. The Poaceae, or grass family, is a member of this group, and most of the p-coumarate in the cell walls of this family acylates lignin. Here, we isolated and examined lignified cell wall preparations from 10 species of commelinid monocotyledons from nine families other than Poaceae, including species from all four commelinid monocotyledon orders (Poales, Zingiberales, Commelinales, and Arecales). We showed that, as in the Poaceae, lignin-linked p-coumarate occurs exclusively on the hydroxyl group on the γ-carbon of lignin unit side chains, mostly on syringyl units. Although the mechanism of acylation has not been studied directly in these species, it is likely to be similar to that in the Poaceae and involve BAHD acyl-coenzyme A:monolignol transferases.

Transformation of Methylparaben by aqueous permanganate in the presence of iodide: Kinetics, modeling, and formation of iodinated aromatic products

This work investigated impacts of iodide (I^-) on the transformation of the widely used phenolic preservative methylparaben (MeP) as well as 11 other phenolic compounds by potassium permanganate (KMnO₄). It was found that KMnO₄ showed a low reactivity towards MeP in the absence of I^- with apparent second-order rate constants (k_app) ranging from 0.065 ± 0.0071 to 1.0 ± 0.1 M^-1s^-1 over the pH range of 5-9. The presence of I^- remarkably enhanced the transformation rates of MeP by KMnO₄ via the contribution of hypoiodous acid (HOI) in situ formed, which displayed several orders of magnitude higher reactivity towards MeP than KMnO₄. This enhancing effect of I^- was greatly influenced by solution conditions (e.g., I^- or KMnO₄ concentration or pH), which could be well simulated by a kinetic model involving competition reactions (i.e., KMnO₄ with I^-, KMnO₄ with MeP, HOI with KMnO₄, and HOI with MeP). Similar enhancing effect of I^- on the transformation kinetics of 5 other selected phenols (i.e., p-hydroxybenzoic acid, phenol, and bromophenols) at pH 7 was also observed, but not in the cases of bisphenol A, triclosan, 4-n-nonylphenol, and cresols. This discrepancy could be well explained by the relative reactivity of KMnO₄ towards phenols vs I^-. Liquid chromatography-tandem mass spectrometry analysis showed that iodinated aromatic products and/or iodinated quinone-like product were generated in the cases where I^- enhancing effect was observed. Evolution of iodinated aromatic products generated from MeP (10 μM) treated by KMnO₄ (50-150 μM) in the presence of I^- (5-15 μM) suggested that higher I^- or moderate KMnO₄ concentration or neutral pH promoted their formation. A similar enhancing effect of I^- (1 μM) on the transformation of MeP (1 μM) by KMnO₄ (12.6 μM) and formation of iodinated aromatic products were also observed in natural water. This work demonstrates an important role of I^- in the transformation kinetics and product formation of phenolic compounds by KMnO₄, which has great implications for future applications of KMnO₄ in treatment of I^--containing water.

A comparative approach of methylparaben photocatalytic degradation assisted by UV-C, UV-A and Vis radiations

Due to the widespread use of methylparaben (MEP) and its high chemical stability, it can be found in wastewater treatment plants and can act as an endocrine disrupting compound. In this study, the photocatalytic degradation and mineralization of MEP solutions were evaluated under UV-A, UV-C and Vis radiations in the presence of the photocatalyst TiO₂. In this sense, the effects of the catalyst load, pH and MEP initial concentration were studied. Remarkably higher reaction rates and total photodegradation were achieved in systems assisted by UV-C radiation. The complete degradation was achieved after 60 min of reaction using the MEP concentration of 30 mg L^-1 at pH 9 and 500 mg L^-1 TiO₂. The experimental data apparently followed a Langmuir-Hinshelwood kinetic model, which could predict 88-98% of the reaction behavior. For the best photodegradation condition, the model predicted an apparent reaction rate constant (k_app) equal to 0.0505 min^-1 and an initial reaction rate of 1.5641 mg (L min)^-1. Mineralization analyses showed high removal for MEP and derived compounds from the initial solution when using UV-C after 90 min of reaction. The lower toxicity was also confirmed by in vivo tests using MEP solutions previously treated by photocatalysis.

Submicron sized water-stable metal organic framework (bio-MOF-11) for catalytic degradation of pharmaceuticals and personal care products

Water-stable and active metal organic frameworks (MOFs) are important materials for mitigation of water contaminants via adsorption and catalytic reactions. In this study, a highly water-stable Co-based MOF, namely bio-MOF-11-Co, was synthesized by a simplified benign method. Moreover, it was used as a catalyst in successful activation of peroxymonsulfate for catalytic degradation of sulfachloropyradazine (SCP) and para-hydroxybenzoic acid (p-HBA) as representatives of pharmaceuticals and personal care products, respectively. The bio-MOF-11-Co showed rapid degradation of both p-HBA and SCP and could be reused multiple times without losing the activity by simply water washing. The effects of catalyst and PMS loadings as well as temperature were further studied, showing that high catalyst and PMS loadings as well as temperature produced faster kinetic degradation of p-HBA and SCP. The generation of highly reactive and HO radicals during the degradation was investigated by quenching tests and electron paramagnetic resonance. A plausible degradation mechanism was proposed based on the functionalities in the bio-MOF-11-Co. The availability of electron rich nucleobase adenine reinforced the reaction kinetics by electron donation along with cobalt atoms in the bio-MOF-11-Co structure.

4-Hydroxybenzoic acid-a versatile platform intermediate for value-added compounds

4-Hydroxybenzoic acid (4-HBA) has recently emerged as a promising intermediate for several value-added bioproducts with potential biotechnological applications in food, cosmetics, pharmacy, fungicides, etc. Over the past years, a variety of biosynthetic techniques have been developed for producing the 4-HBA and 4-HBA-based products. At this juncture, synthetic biology and metabolic engineering approaches enabled the biosynthesis of 4-HBA to address the increasing demand for high-value bioproducts. This review summarizes the biosynthesis of a variety of industrially pertinent compounds such as resveratrol, muconic acid, gastrodin, xiamenmycin, and vanillyl alcohol using 4-HBA as the starting feedstock. Moreover, potential research activities with a close-up look at the future perspectives to produce new compounds using 4-HBA have also been discussed.

Paraben degradation using catalytic ozonation over volcanic rocks

Parabens are widely used as antimicrobial and preservatives in pharmaceutical and personal care products and are continuously reaching the water streams. Conventional wastewater treatments are proven inefficient on the removal of this kind of contaminants from wastewater. Therefore, catalytic ozonation appears as a suitable option, due to the oxidant power of ozone and its high capacity of hydroxyl radical generation in the presence of a suitable catalyst. The main drawback of catalytic ozonation is related with the choice of stable and active catalysts at low cost. On this way, two volcanic rocks were tested to enhance the removal of a mixture of parabens by ozonation, improving their degradation. Indeed, catalytic ozonation with volcanic rock allowed total paraben degradation using a transferred ozone dose (TOD) of 55 mg/L which corresponds to a reduction of about threefold the amount of TOD comparatively with single ozonation (170 mg/L of TOD). Due to the presence of semiconductors on volcanic rock composition, the effect of UVA irradiation on paraben degradation was analyzed. The neutral and basic conditions enhanced catalytic ozonation comparatively to acid conditions. Higher pH values allowed a total methylparaben degradation with 35 mg O₃/L, whereas for low pH values, 55 mg O₃/L was required. The use of a radical scavenger proven that hydroxyl radicals are the main responsible for paraben degradation with catalytic ozonation. This was confirmed through the analysis of the by-products, where 4-hydroxybenzoic acid, 3,4-dihydroxybenzoic acid (3,4-diHBA), 2,4-dihydroxybenzoic acid, and hydroquinone were quantified.

The photosensitized oxidation of mixture of parabens in aqueous solution

The work presents results of studies on the photosensitized oxidation of mixture of five parabens (methyl-, ethyl-, propyl-, n-butyl-, and benzylparaben) in aqueous solution. Aluminum phthalocyanine chloride tetrasulfonic acid and xenon lamp simulating solar radiation were used as a photosensitizer and a light source, respectively. The purpose was to investigate the influence of inhibitory effect compounds present in the mixture on the reaction rate. The influence of the addition of second photosensitizer on the parabens degradation rate was investigated. The effect of additives: tert-butanol - hydroxyl radical scavenger and sodium azide - singlet oxygen scavenger on reaction course was also determined. The transformation products formed during the photosensitized oxidation process were analyzed by UPLC-MS/MS. The efficiency of photosensitized oxidation of parabens with natural sunlight irradiation in the central Poland was checked.

Detection of bisphenol A, cumylphenol and parabens in surface waters of Greater Poland Voivodeship

Amounts of bisphenol A (BPA), 4-cumylphenol (CP) and 5 parabens - methylparaben (MP), ethylparaben (EP), propylparaben (PP), butylparaben (BP) and benzylparaben (BzP) in Greater Poland Voivodeship's surface waters are reported. The water samples were collected from selected 15 locations in 2015-2016 at seven different time points: in March, June, August, and October 2015 and March, June, and September 2016. MP was found in every tested sample with typical concentration at several dozen nanograms per liter and the highest level almost 1600 ng L^-1 in a sample collected from the Warta River in October 2015. The other four parabens were determined at considerably lower concentrations than MP at levels not exceeding 100 ng L^-1 with PP found at the highest and BzP at the lowest levels. BPA was determined at similar concentration level to parabens - between 5 ng L^-1 and 95 ng L^-1 and CP was found only in a limited number of samples. Noticeable seasonal changes of paraben concentrations were found showing that for these compounds the pollutant release factor dominates both the biodegradation factor and the water volume factor. These seasonal changes were not observed for BPA and CP. Out of all determined parabens only MP was found at considerably higher concentrations than BPA. However, MP's endocrine properties are much lower than those of BPA posing a lower environmental impact potential than BPA. Influence of other (more endocrine disrupting) parabens is also relatively weak in comparison to BPA due to their considerably lower concentrations in the environment.

Graphene: A new activator of sodium persulfate for the advanced oxidation of parabens in water

Graphene was successfully employed as a catalyst for the activation of sodium persulfate, towards the effective degradation of propylparaben, an emerging micro-pollutant, representative of the parabens family. A novel process is proposed which utilizes a commercial graphene nano-powder as the catalyst and sodium persulfate as the oxidizing agent. It was found that over 95% of micro-pollutant degradation occurs within 15 min of reaction time. The effects of catalyst loading (75 mg/L to 1 g/L), sodium persulfate (SPS) concentration (10 mg/L to 1 g/L), initial solution pH (3-9) and initial paraben concentration (0.5 mg/L to 5 mg/L) were examined. Experiments were carried out in different aqueous conditions, including ultrapure water, bottled water and wastewater in order to investigate their effect on the degradation rate. The efficiency of the process was lower at complex water matrices signifying the role of organic matter as scavenger of the oxidant species. The role of radical scavengers was also investigated through the addition of methanol and tert-butanol in several concentrations, which was found to be important only in relatively high values. An experiment in which propylparaben was substituted by methylparaben was conducted and similar results were obtained. The consumption of SPS was found to be high in all pH conditions tested, surpassing 80% in near neutral environment. However, the results indicate that the sulfate radicals formed react with water in alkaline conditions, which are the optimal for the reaction, producing hydroxyl radicals which appear to be the dominant species leading to the rapid degradation of propylparaben. To the best of our knowledge, this is the first time pristine graphene has been implemented as an activator of sodium persulfate for the effective oxidation of micro-pollutants.

Sterols from the Green Alga Ulva australis

Three new sterols, (24R)-5,28-stigmastadiene-3β,24-diol-7-one (1), (24S)-5,28-stigmastadiene-3β,24-diol-7-one (2), and 24R and 24S-vinylcholesta-3β,5α,6β,24-tetraol (3), together with three known sterols (4–6) were isolated from the green alga Ulva australis. The structures of the new compounds (1–3) were elucidated through 1D and 2D nuclear magnetic resonance spectroscopy as well as mass spectrometry. Compounds 4–6 were identified as isofucoterol (4), 24R,28S and 24S,28R-epoxy-24-ethylcholesterol (5), and (24S)-stigmastadiene-3β,24-diol (6) on the basis of spectroscopic data analyses and comparison with those reported in the literature. Compounds 4–6 were isolated from U. australis for the first time. These compounds, together with the previously isolated secondary metabolites of this alga, were investigated for their inhibitory effects on human recombinant aldose reductase in vitro. Of the compounds, 24R,28S and 24S,28R-epoxy-24-ethylcholesterol (5), 1-O-palmitoyl-3-O-(6′-sulfo-α-d-quinovopyranosyl) glycerol, (2S)-1-O-palmitoyl-3-O-[α-d-galactopyranosyl(1→2)β-d-galactopyranosyl] glycerol, 4-hydroxybenzoic acid, 4-hydroxyphenylacetic acid, and 8-hydroxy-(6E)-octenoic acid weakly inhibited the enzyme, while the three new sterols, 1–3, were almost inactive.

Interference of Paraben Compounds with Estrogen Metabolism by Inhibition of 17β-Hydroxysteroid Dehydrogenases

Parabens are effective preservatives widely used in cosmetic products and processed food, with high human exposure. Recent evidence suggests that parabens exert estrogenic effects. This work investigated the potential interference of parabens with the estrogen-activating enzyme 17β-hydroxysteroid dehydrogenase (17β-HSD) 1 and the estrogen-inactivating 17β-HSD2. A ligand-based 17β-HSD2 pharmacophore model was applied to screen a cosmetic chemicals database, followed by in vitro testing of selected paraben compounds for inhibition of 17β-HSD1 and 17β-HSD2 activities. All tested parabens and paraben-like compounds, except their common metabolite p-hydroxybenzoic acid, inhibited 17β-HSD2. Ethylparaben and ethyl vanillate inhibited 17β-HSD2 with IC₅₀ values of 4.6 ± 0.8 and 1.3 ± 0.3 µM, respectively. Additionally, parabens size-dependently inhibited 17β-HSD1, whereby hexyl- and heptylparaben were most active with IC₅₀ values of 2.6 ± 0.6 and 1.8 ± 0.3 µM. Low micromolar concentrations of hexyl- and heptylparaben decreased 17β-HSD1 activity, and ethylparaben and ethyl vanillate decreased 17β-HSD2 activity. However, regarding the very rapid metabolism of these compounds to the inactive p-hydroxybenzoic acid by esterases, it needs to be determined under which conditions low micromolar concentrations of these parabens or their mixtures can occur in target cells to effectively disturb estrogen effects in vivo.

Phenolics from Mikania micrantha and Their Antioxidant Activity

A phytochemical study on the aerial parts of Mikania micrantha led to the isolation of two new phenolic compounds, benzyl 5-O-β-d-glucopyranosyl-2,5-dihydroxybenzoate (1) and (7S,8R)-threo-dihydroxydehydrodiconiferyl alcohol 9-acetate (2), together with twelve known compounds, benzyl 2-O-β-d-glucopyranosyl-2,6-dihydroxybenzoate (3), 4-allyl-2,6-dimethoxyphenol glucoside (4), (+)-isolariciresinol (5), icariol A₂ (6), 9,10-dihydroxythymol (7), 8,9,10-trihydroxythymol (8), caffeic acid (9), p-coumaric acid (10), ethyl protocatechuate (11), procatechuic aldehyde (12), 4-hydroxybenzoic acid (13), and hydroquinone (14). Their structures were elucidated on the basis of extensive spectroscopic analysis. Except 8 and 9, all the other compounds were isolated from this plant species for the first time. The antioxidant activity of those isolated compounds were evaluated using three different assays. Compounds 1, 2, 3, 9, 10, 13, and 14 demonstrated significant 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) free radical cation scavenging activity ranging from SC50 0.31 to 4.86 µM, which were more potent than l-ascorbic acid (SC50 = 10.48 µM). Compounds 5, 9, 11, and 12 exhibited more potent 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity (SC50 = 16.24-21.67 µM) than l-ascorbic acid (39.48 µM). Moreover, the ferric reducing antioxidant power (FRAP) of compounds 2, 5, 9, and 11 were discovered to be also comparable to or even more potent than l-ascorbic acid.

Co-metabolic enhancement of organic removal from waste water in the presence of high levels of alkyl paraben constituents of cosmetic and personal care products

The enhanced removal of organic material from municipal waste water containing 50 mg/L of chemical oxygen demand and a given amount of alkyl paraben using a biofilm system was investigated. The parabens used were methyl, ethyl, and propyl paraben. The experiments were conducted at influent paraben concentrations of 10 and 50 mg/L. The influent pH was measured around 4.6 because of paraben hydrolysis. The effluent pH increased due to hydrogen consumption and small molecular acid generation. The higher removal rates were observed for the paraben with longer alkyl chains, which were more hydrophobic and capable of penetrating into microbial cells. The co-existing organic constituents in municipal waste water were found to be competitive with paraben molecules for microbial degradation at low paraben loading (i.e., 10 mg/L). Instead, the co-metabolic effect was observed at a higher paraben loading (i.e., 50 mg/L) due to more active enzymatic catalysis, implying the possible enhancement or organic removal in the presence of high levels of parabens. The difference in BOD and TOC removing ratios for parabens decreased with increasing HRT, implying their better mineralization than that of municipal organic constituents. This was because the microbial organism became more adapted to the reacting system with longer HRT, and more oxygenase was produced to facilitate the catechol formation and ring-opening reactions, causing apparent enhancement in mineralization.

Side Chains of Parabens Modulate Antiandrogenic Activity: In Vitro and Molecular Docking Studies

Parabens have been widely used in packaged foods, pharmaceuticals, and personal-care products. Considering their potential hydrolysis, we herein investigated structural features leading to the disruption of human androgen receptor (AR) and whether hydrolysis could alleviate such effects using the recombinant yeast two-hybrid assay. Parabens with an aryloxy side chain such as benzyl paraben and phenyl paraben have the strongest antiandrogenic activity. The antiandrogenic activity of parabens with alkyloxyl side chains decreases as the side chain length increases from 1 to 4, and no antiandrogenic effect occurred for heptyl, octyl, and dodecyl parabens with the number of alkoxyl carbon atoms longer than 7. The antiandrogenic activity of parabens correlates significantly with their binding energies (R² = 0.84, p = 0.01) and were completely diminished after the hydrolysis, particularly for parabens with aryloxy side chains. The K_m for the hydrolysis of parabens with aromatic moiety side chain is 1 order of magnitude higher than that of the parabens with alkyl side chains. Both in vitro and in silico data, for the first time, suggest parabens with aromatic side chains are less prone to hydrolysis. Our results provide an insight into risk of various paraben and considerations for design of new paraben-related substitutes.

Comparative studies of aerobic and anaerobic biodegradation of methylparaben and propylparaben in activated sludge

The biodegradability of two typical parabens (methylparaben and propylparaben) in activated sludge, at initial concentrations of 1mgL^-1 or 10mgL^-1, was investigated under aerobic and anaerobic conditions. The results showed that microorganisms played a key role in degradation of parabens in WWTPs, especially in aerobic systems. The half-lives of methylparaben and propylparaben under aerobic conditions have been estimated to range between 15.8 and 19.8min, and benzoic acid was found to be one of the major biodegradation products. The calculated biodegradation efficiency of methylparaben and propylparaben in activated sludge under aerobic conditions was significantly higher than that observed under anaerobic (nitrate, sulfate, and Fe (III) reducing) conditions, as methylparaben and propylparaben exhibited comparatively higher persistence in anaerobic systems, with half-lives ≥43.3h and ≥8.6h, respectively. Overall, the results of this study imply that the majority of these parabens can be eliminated by aerobic biodegradation during conventional wastewater treatment processes, whereas minor removal is possible in anaerobic systems if an insufficient hydraulic retention time was maintained.

Degradation of chlorinated paraben by integrated irradiation and biological treatment process

Chlorinated paraben, namely, methyl 3, 5-dichloro-4-hydroxybenzoate (MDHB) is the by-product of chlorination disinfection of paraben and frequently detected in the aquatic environments, which exhibited higher persistence and toxicity than paraben itself. In this paper, the combined irradiation and biological treatment process was employed to investigate the removal of MDHB from aqueous solution. The results showed that the removal efficiency of MDHB and total organic carbon (TOC) by irradiation process increased with radiation dose no matter what the initial concentration of MDHB was. The maximum removal efficiency of MDHB was 100%, 91.1%, 93%, respectively, for the initial concentration of MDHB of 1 mg/L, 5 mg/L and 10 mg/L with the radiation dose of 800 Gy. However, the maximum removal efficiency of TOC among all the experimental groups was only 15.3% obtained with the initial concentration of 1 mg/L at dose of 800 Gy. The subsequent biological treatment enhanced the mineralization of MDHB. The suitable radiation dose for the subsequent biological treatment was determined to be 600 Gy. In this case the removal efficiency of TOC increased to about 70%. Compared to the single biological treatment, the integrated irradiation and biological treatment significantly increase the degradation and mineralization of MDHB. Moreover, the dechlorination efficiency reached 77.4% during the integrated irradiation and biological treatment process. In addition, eight intermediates were identified during the combined process and the possible degradation pathway was proposed.