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.