IC20 Values Research Articles

Application of Artificial Neural Network for Modeling and Prediction of MTT Assay on Human Lung Epithelial Cancer Cell Lines

In this paper, a three-layer artificial neural network (ANN) was investigated to predict the inhibitory concentration (IC) values assessed via MTT cell viability assay on the four types of human lung epithelial cancer cell lines. In order to achieve this purpose, a multilayer perceptron (MLP) neural network trained with back-propagation algorithm was employed for developing the ANN model. To develop the model, the input parameters were concentrations and types of cell lines and the outputs were IC10, IC20, IC30, IC40, IC50, IC60, IC70 and IC80 values in the A549, H157, H460 and H1975 cell lines. The proposed ANN model has achieved good agreement with the experimental data and has a small error between the estimated and experimental values. The obtained results show that the proposed ANN model is a useful, reliable, fast and cheap tool to predict the IC values assessed via MTT cell viability assays.

An investigation of the effects of Cinnamomum cassia bark extracts on oxidative DNA damage and possible cytotoxic and apoptotic activities in transformed/untransformed cell lines from Type 1 diabetic patients, in vitro.

An investigation of the effects of Cinnamomum cassia bark extracts on oxidative DNA damage and possible cytotoxic and apoptotic activities in transformed/untransformed cell lines from Type 1 diabetic patients, in vitro.

Photodegradation of Atrazine on TiO<sub>2</sub>―Products Toxicity Assessment

Toxicity in reaction mixtures of atrazine irradiated on immobilized TiO2 at varying irradiation times was studied using an algal growth test on unicellular green alga Raphidocelis subcapitata and a cytotoxicity test with a RTgill-W1 cell line. The toxicity of atrazine samples to algae decreased exponentially with the time of irradiation on TiO2 up to 3 h for both IC50 and IC20 values calculated for growth rate inhibition and yield. A trend to increasing variability between replicates in atrazine samples irradiated on TiO2 for longer time periods was observed; the trend was particularly pronounced in samples irradiated for 3 and 5 hours, where the atrazine samples caused moderate stimulation in lower concentration treatments (up to 550 μg/l of the initial atrazine concentration). None of the atrazine samples showed significant cytotoxicity to the rainbow trout gill cell line (RTgill-W1).

Quercetin protects human peripheral blood mononuclear cells from OTA-induced oxidative stress, genotoxicity, and inflammation.

Ochratoxin A (OTA) is one of the most abundant food-contaminating mycotoxins world wide, and is detrimental to human and animal health. This study evaluated the protective effect of quercetin against OTA-induced cytotoxicity, genotoxicity, and inflammatory response in lymphocytes. Cytotoxicity determined by MTT assay revealed IC20 value of OTA to be 20 µM, which was restored to near control values by pretreatment with quercetin. Oxidative stress parameters such as antioxidant enzymes, LPO and PCC levels indicated that quercetin exerted a protective effect on OTA-induced oxidative stress. Quercetin exerted an antigenotoxic effect on OTA-induced genotoxicity, by significantly reducing the number of structural aberrations in chromosomes and comet parameters like, % olive tail moment from 2.76 ± 0.02 to 0.56 ± 0.02 and % tail DNA from 56.23 ± 2.56 to 12.36 ± 0.56 as determined by comet assay. OTA-induced NO, TNF-α, IL-6, and IL-8 were significantly reduced in the quercetin pretreated samples indicating its anti-inflammatory role. Our results demonstrate for the first time that quercetin exerts a cytoprotective effect against OTA-induced oxidative stress, genotoxicity, and inflammation in lymphocytes. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 855-865, 2016.

Lead toxicity to Lemna minor predicted using a metal speciation chemistry approach.

In the present study, predictive measures for Pb toxicity and Lemna minor were developed from bioassays with 7 surface waters having varied chemistries (0.5-12.5 mg/L dissolved organic carbon, pH of 5.4-8.3, and water hardness of 8-266 mg/L CaCO3 ). As expected based on water quality, 10%, 20%, and 50% inhibitory concentration (IC10, IC20, and IC50, respectively) values expressed as percent net root elongation (%NRE) varied widely (e.g., IC20s ranging from 306 nM to >6920 nM total dissolved Pb), with unbounded values limited by Pb solubility. In considering chemical speciation, %NRE variability was better explained when both Pb hydroxides and the free lead ion were defined as bioavailable (i.e., f{OH} ) and colloidal Fe(III)(OH)3 precipitates were permitted to form and sorb metals (using FeOx as the binding phase). Although cause and effect could not be established because of covariance with alkalinity (p = 0.08), water hardness correlated strongly (r(2) = 0.998, p < 0.0001) with the concentration of total Pb in true solution ([Pb]T_True solution ). Using these correlations as the basis for predictions (i.e., [Pb]T_True solution vs water hardness and %NRE vs f{OH} ), IC20 and IC50 values produced were within a factor of 2.9 times and 2.2 times those measured, respectively. The results provide much needed effect data for L. minor and highlight the importance of chemical speciation in Pb-based risk assessments for aquatic macrophytes.

In Vitro Interaction of Digestive α-Amylase from Pieris brassicae (Lepidoptera: Pieridae) with a Lectin Extracted from Polygonum persicariae (Polygonaceae)

In the current study, a low weight lectin (19.22 kDa) was extracted from Polygonum persicaria by Sepharose 4B-galactose column and its inhibition was determined against digestive α-amylase of Pieris brassicae larvae. Different concentrations of the purified lectin were prepared and incubated with midgut homogenate of larvae to observe its inhibition. Inhibition study revealed IC10, IC30 and IC50 values of 0.013, 0.104 and 0.422 mg/ml against digestive amylolytic activity of larvae. In zymogram analysis, incubation of midgut homogenates with 0.42 mg/ml of the purified lectin showed decrease in sharpness of band A2 and disappearance of band A1. pH profile of inhibition revealed that the purified lectin caused the highest inhibition at pH 10 and 11 corresponding with control experiment. Time dependency of inhibition demonstrated the highest inhibition after 30 min of post-incubation. Stability of the purified lectin was measured by incubating the molecule at 50, 60 and 70 °C. It was observed that the samples incubated at 60 and 70 °C had no inhibition on amylolytic activity. Finally, Linweaver-Burk analysis revealed significant decrease in Vmax versus control showing non-competitive inhibition.

β-diketone-cobalt complexes inhibit DNA synthesis and induce S-phase arrest in rat C6 glioma cells

β-diketone-cobalt complexes, a family of newly synthesized non-platinum metal compounds, exhibit potential antitumor activity; however, the antitumor mechanism is unclear. The current study investigated the mechanism by which β-diketone-cobalt complexes inhibit rat C6 glioma cell proliferation. It was found that β-diketone-cobalt complexes suppress rat C6 glioma cell viability in a dose-dependent manner (3.125–100 μg/ml). In rat C6 glioma cells, the IC50 value of β-diketone-cobalt complexes was 24.7±3.395 μg/ml and the IC10 value was 4.37±1.53 μg/ml, indicating a strong inhibitory effect. Further investigation suggested that β-diketone-cobalt complexes inhibit rat C6 glioma cell proliferation, which is associated with S-phase arrest and DNA synthesis inhibition. During this process, β-diketone-cobalt complexes decreased cyclin A expression and increased cyclin E and p21 expression. In addition, β-diketone-cobalt complexes exhibit a stronger antitumor capability than the antineoplastic agent, 5-fluorouracil.

English

In view of compliance with increasingly stringent environmental legislation imposed by regional, national and supranational (for example, European Union) authorities, innovative environmental technologies for the treatment of dye-contaminated effluents are necessary in the color industry. In this study, azo (methyl orange (MO) and methyl red (MR)) and triphenylmethanes (malachite green (MG), fushin (F) and crystal violet (CV)) dyes were subjected to distinct treatment strains following an initial qualitative characterization. The effectiveness of their biodegradation using Staphylococcus epidermidis strain was compared with respect to parameters such as residual color, and toxicity on human cells. The Hep-2 cells were exposed to three azo and two triphenylmethane dyes at various concentrations. After 72 h exposure, the protein contents of the samples compared to the protein contents of non-exposed cells were measured. The level of protein content indicates the viability of the cells. The IC20 values show the limiting value of toxicity. The IC50 values before biodegradation show whether samples are clearly toxic. The IC50 value for the azo dyes (MO, MR) were 65 and 10 &mu;g/ml, the IC20 value were 10 and 5 &mu;g/ml. The IC50 for the triphenylmethane dyes (MG, F and CV) were 35, 25 and 30 &mu;g/ml, the IC20 value were 5, 5 and 10 &mu;g/ml. The viability of the cells was good, the protein content of the samples being over 80% compared to the non-exposed cells. The Hep-2 cell test indicated the toxicity of pure dyes before biodegradation; the dyes after decolorization had no adverse effect. The human keratinocyte Hep-2 cells seem to be a useful tool for the study of the purity/toxicity of dyes and other substances applied to textiles. In addition, the initial cytotoxicity of dyes was still present after the biodegradation, while it was completely removed through the bacterial treatment. Our results show that S. epidermidis was a slime-producer developing almost black colonies on Congo red agar plate. A significant increase in azoreductase, lignin peroxidase and laccase activities in the cells were obtained after complete decolorization. &nbsp; Key words: Azo dye, triphenylmethane dye, Staphylococcus epidermidis, cytotoxicity, slime production.

Effects of deltamethrin (pyrethroid insecticide) on growth, reproduction, embryonic development and sex differentiation in two strains of Daphnia magna (Crustacea, Cladocera)

Acute and different chronic ecotoxic effects of deltamethrin have been investigated on two strains (coming from two different laboratories) of Daphnia magna. The effective concentrations immobilizing 50% of daphnids (EC50s) after 24h and 48h were 9.40 and 0.32μgL−1, 8.86 and 0.63μgL−1 for first strain (strain 1) and second strain (strain 2), respectively. Thus, there was an increase of deltamethrin ecotoxicity with time of exposure as confirmed by chronic studies. After 21days of exposure to deltamethrin, daphnids have showed significant effects on survival at deltamethrin concentrations of 0.16μgL−1 and 0.31μgL−1 for strains 1 and 2, respectively. Eleven other endpoints were examined: body length, population growth rate and various reproductive parameters (days to first brood, number of broods, number of cumulative molts and number of neonates), embryotoxicity and appearance of males. IC10 values related to the number of juveniles per live adult were 11 and 46ngL−1 for strains 1 and 2, respectively. Furthermore, an increase in embryo deformities was observed at the highest concentrations tested for both strains. Following deltamethrin exposure, undeveloped second antennae, curved or unextended shell spines, and curved post abdomen spines were observed in live neonates. The production of male juveniles was only registered with strain 1 at 0.16μgL−1. Results suggest that deltamethrin could act as an endocrine disruptor in D. magna as it interferes with sex determination and development abnormality but there is a difference in sensitivity between the two tested strains.

Comparison of five different in vitro assays for assessment of sodium metavanadate cytotoxicity in Chinese hamster ovary cells (CHO-K1 line)

This investigation was undertaken to compare five different in vitro cytotoxicity assays for their power in revealing vanadium-mediated toxicity in Chinese hamster ovary (CHO)-K1 cells. The cells were exposed to sodium metavanadate (NaVO(3)) in the range of 10-1000 µM for 24 h and thereafter the cytotoxic effects of NaVO(3) were measured by colorimetric in vitro assays: the neutral red (NR) test, the 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxyanilide inner salt (XTT) assay, the resazurin assay, the sulforhodamine B (SR-B) assay, and by microscopic assessment of cell viability using the trypan blue (TB) staining method. Among the assays used, the NR test was the most sensitive, since it revealed metavanadate cytotoxicity at the lowest NaVO(3) dose (=50 µM). Also, NaVO(3) cytotoxicity expressed as inhibitory concentration (IC) showed the lowest values for the NR test. Three other tests XTT, resazurin, and SR-B assays showed intermediate sensitivity revealing the cytotoxicity of NaVO(3) at 100 µM. The corresponding IC10 and IC50 values calculated for the XTT, resazurin, and SR-B tests were similar. The TB staining method was the least sensitive, since it recorded metavanadate cytotoxicity at the highest NaVO(3) concentration tested (=600 µM). Based on the cytotoxicity end points measured with the above assays, it can be concluded that lysosomal/Golgi apparatus damage (measured by NR assay) may be the primary effect of NaVO(3) on CHO-K1 cells. The disintegration of mitochondria (assessed with the XTT and resazurin assays) probably follows lysosomal impairment. Plasma membrane permeability (staining with TB) occurs at a late stage of NaVO(3)-induced cytotoxicity on CHO-K1 cells. The results obtained in this research work show that the NR test can be recommended as a very sensitive assay for the assessment of NaVO(3) cytotoxicity in the CHO-K1 cell culture model. Considering the convenience of assay performance along with adequate sensitivity, the XTT and resazurin assays can also be advocated for NaVO(3) cytotoxicity assessment.

A Testosterone Specific Competitive Enzyme Immunoassay for Monitoring Water Quality

Testosterone, an androgen and a primary male sex hormone, migrates through the environment in ways which could pose a threat to water quality and, subsequently, environmental and human health. This paper describes the development of a direct competitive enzyme-linked immunosorbent assay (ELISA) that is capable of measuring testosterone with high specificity. The testosterone ELISA displayed the IC20 (as the limit of detection) and IC50 values of 0.05±0.01μgL(-1) and 0.33±0.18μgL(-1), respectively. In addition, the assay showed <0.1% cross-reactivity against structurally related steroidal compounds. However, this assay was found to be sensitive to environmental matrices such as certain metal ions, pH, and high humic acids, and sample clean-up to remove such interference was necessary before analysis. The analyses of 50 surface water samples collected in rural and urban areas in New South Wales, Australia showed that ELISA results correlated well with the androgenic activity measured by the recombinant yeast-based androgen screen assay.

Cytoprotective effect of epigallocatechin-3-gallate against deoxynivalenol-induced toxicity through anti-oxidative and anti-inflammatory mechanisms in HT-29 cells

Deoxynivalenol (DON) is a mycotoxin produced by Fusarium sp., and is known to elicit pro-inflammatory responses in the cell. The cells exposed to DON undergo apoptosis as a mechanism to shut down the inflammation. In this study, we tested the cytoprotective effect of the green tea polyphenol epigallocatechin 3-gallate (EGCG) on DON-induced toxicity in HT-29 cells. EGCG prevented DON-induced cytotoxicity to HT-29 cells in a dose-response manner. Even the lowest concentration (5 μM) of EGCG showed protection against the highest concentration of DON tried (3.38 μM=1000 ng/ml). Our study also demonstrates that IC20 value of DON in HT 29 cells were 250 ng/ml and pre-treatment with 20 μM EGCG yielded 99% cell viability. EGCG also protected against oxidative stress, up regulation of nuclear factor-kB (NF-κB), cyclooxygenase-2 (COX-2) and caspase-3 activated apoptosis. These results suggest that EGCG acts as cytoprotective agent against DON-induced toxicity.

Multiplex biotoxin surface plasmon resonance method for marine biotoxins in algal and seawater samples

A multiplex surface plasmon resonance (SPR) biosensor method for the detection of paralytic shellfish poisoning (PSP) toxins, okadaic acid (and analogues) and domoic acid was developed. This method was compared to enzyme-linked immunosorbent assay (ELISA) methods. Seawater samples (n=256) from around Europe were collected by the consortia of an EU project MIcroarrays for the Detection of Toxic Algae (MIDTAL) and evaluated using each method. A simple sample preparation procedure was developed which involved lysing and releasing the toxins from the algal cells with glass beads followed by centrifugation and filtering the extract before testing for marine biotoxins by both multi-SPR and ELISA. Method detection limits based on IC20 values for PSP, okadaic acid and domoic acid toxins were 0.82, 0.36 and 1.66 ng/ml, respectively, for the prototype multiplex SPR biosensor. Evaluation by SPR for seawater samples has shown that 47, 59 and 61 % of total seawater samples tested positive (result greater than the IC20) for PSP, okadaic acid (and analogues) and domoic acid toxins, respectively. Toxic samples were received mainly from Spain and Ireland. This work has demonstrated the potential of multiplex analysis for marine biotoxins in algal and seawater samples with results available for 24 samples within a 7 h period for three groups of key marine biotoxins. Multiplex immunological methods could therefore be used as early warning monitoring tools for a variety of marine biotoxins in seawater samples.

Cytotoxic Potency of Mycotoxins in Cultures of V79 Lung Fibroblast Cells

In addition to dietary mycotoxin intake, exposure by inhalation is possible and may result in local effects in the lung. As a first approach to assess the potential local impact of inhaled mycotoxins, the cytotoxicity of 14 different mycotoxins was determined in V79 cell cultures, which served as an in vitro surrogate for lung cells. Cell viability was measured by the neutral red (NR) uptake assay after 48 h of exposure to graded concentrations of structurally diverse compounds: beauvericin, citrinin, enniatin B, moniliformin, ergocornine, ergotamine, fumonisin B1, ochratoxin A, patulin, the trichothecenes deoxynivalenol, HT-2, and T-2 toxin, and zearalenone, and α-zearalenol. The 14 mycotoxins show a wide range of cytotoxic potency, encompassing 7 orders of magnitude, with IC20 values (concentration reducing cell viability by 20%) of 4.3 mM for moniliformin, the least potent mycotoxin, and 2.1 nM for T-2 toxin, the most potent agent. Thus, when inhaled in sufficient quantities, local adverse effects in lung cells cannot be excluded, in particular for highly cytotoxic mycotoxins.

Astemizole Synergizes Calcitriol Antiproliferative Activity by Inhibiting CYP24A1 and Upregulating VDR: A Novel Approach for Breast Cancer Therapy

BackgroundCalcitriol antiproliferative effects include inhibition of the oncogenic ether-à-go-go-1 potassium channel (Eag1) expression, which is necessary for cell cycle progression and tumorigenesis. Astemizole, a new promising antineoplastic drug, targets Eag1 by blocking ion currents. Herein, we characterized the interaction between calcitriol and astemizole as well as their conjoint antiproliferative action in SUM-229PE, T-47D and primary tumor-derived breast cancer cells.Methodology/Principal FindingsMolecular markers were studied by immunocytochemistry, Western blot and real time PCR. Inhibitory concentrations were determined by dose-response curves and metabolic activity assays. At clinically achievable drug concentrations, synergistic antiproliferative interaction was observed between calcitriol and astemizole, as calculated by combination index analysis (CI <1). Astemizole significantly enhanced calcitriol’s growth-inhibitory effects (3–11 folds, P<0.01). Mean IC20 values were 1.82±2.41 nM and 1.62±0.75 µM; for calcitriol (in estrogen receptor negative cells) and astemizole, respectively. Real time PCR showed that both drugs alone downregulated, while simultaneous treatment further reduced Ki-67 and Eag1 gene expression (P<0.05). Astemizole inhibited basal and calcitriol-induced CYP24A1 and CYP3A4 mRNA expression (cytochromes involved in calcitriol and astemizole degradation) in breast and hepatoma cancer cells, respectively, while upregulated vitamin D receptor (VDR) expression.Conclusions/SignificanceAstemizole synergized calcitriol antiproliferative effects by downregulating CYP24A1, upregulating VDR and targeting Eag1. This study provides insight into the molecular mechanisms involved in astemizole-calcitriol combined antineoplastic effect, offering scientific support to test both compounds in combination in further preclinical and clinical studies of neoplasms expressing VDR and Eag1. VDR-negative tumors might also be sensitized to calcitriol antineoplastic effects by the use of astemizole. Herein we suggest a novel combined adjuvant therapy for the management of VDR/Eag1-expressing breast cancer tumors. Since astemizole improves calcitriol bioavailability and activity, decreased calcitriol dosing is advised for conjoint administration.

Epigenetic modifiers enhance the synergistic cytotoxicity of combined nucleoside analog-DNA alkylating agents in lymphoma cell lines

Hematopoietic stem cell transplantation is used for treatment of lymphoma. In an attempt to design an efficacious and safe prehematopoietic stem cell transplantation conditioning regimen, we investigated the cytotoxicity of the combination of busulfan (B), melphalan (M), and gemcitabine (G) in lymphoma cell lines in the absence or presence of drugs that induce epigenetic changes. Cells were exposed to drugs individually or in combination and analyzed by the MTT proliferation assay, flow cytometry, and Western blotting. We used ~IC(10) drug concentrations (57 μM B, 1 μM M and 0.02 μM G), which individually did not have major effects on cell proliferation. Their combination resulted in 50% inhibition of proliferation. Reduction to almost half concentration (20 μM B, 0.7 μM M and 0.01 μM G) did not have significant effects, but addition of the histone deacetylase inhibitor suberoylanilide hydroxamic acid (0.6 μM) to this combination resulted in a marked (~65%) growth inhibition. The cytotoxicity of these combinations correlates with the activation of the ataxia telangiectasia mutated-CHK2 pathway, phosphorylation of KRAB-associated protein-1, epigenetic changes such as methylation and acetylation of histone 3, and activation of apoptosis. The relevance of epigenetic changes is further shown by the induction of DNA methyltransferases in tumor cells with low constitutive levels of DNMT3A and DNMT3B. The addition of 5-aza-2'-deoxycytidine to (BMG+suberoylanilide hydroxamic acid) further enhances cell killing. Overall, BMG combinations are synergistically cytotoxic to lymphoma cells. Epigenetic changes induced by suberoylanilide hydroxamic acid and 5-aza-2'-deoxycytidine further enhance the cytotoxicity. This study provides a rationale for an ongoing clinical trial in our institution using (BMG+suberoylanilide hydroxamic acid) as pre-hematopoietic stem cell transplantation conditioning for lymphoma.

Cytotoxic Effect of Combined Treatment with Ukrain and Methotrexate on Kidney Cells of Green Monkey

Abstract In in vitro study on green monkey kidney (GMK) cell culture, the cytotoxicity of Ukrain, methotrexate (MTX), and their combination was investigated. The effect of these drugs and their combination on viability (MTT test) and apoptosis of the cells was assessed. The IC10 and IC50 values for Ukrain and MTX were also indicated. After 24 h of incubation of GMK cells with Ukrain, IC10 amounted to 84.6 μmol/L and IC50 was 256.3 μmol/L, while MTX IC10 amounted to 7.18 μmol/L and IC50 was 154.8 μmol/l. After 24 h of simultaneous incubation of GMK cells with 50 μmol/L of Ukrain and 5.5 μmol/L of MTX, 15.33 % of cytotoxicity of the drugs in LDH test was found. The most significant increase in the cytotoxicity (42.10 %) was noted after 24 h incubation of GMK cells with 150 μmol/L of Ukrain and 5.5 μmol/L of MTX. Likewise, in the MTT assay the greatest decrease in the cells viability was found after incubation with 150 μmol/L of Ukrain and 5.5 μmol/L of MTX. The evaluation of apoptosis also indicated the adverse effect of combined application of both drugs on GMK cells.

Polysaccharide peptides from Coriolus versicolor competitively inhibit model cytochrome P450 enzyme probe substrates metabolism in human liver microsomes

Polysaccharide peptide (PSP), isolated from COV-1 strain of Coriolus versicolor, is commonly used as an adjunct in cancer chemotherapy or health supplement in China. Previous studies have shown that PSP decreased antipyrine clearance and inhibited rat CYP2C11-mediated tolbutamide 4-hydroxylation and in human CYP2C9. In this study, the effects of the water extractable fraction of PSP on the metabolism of model CYP1A2, CYP2D6, CYP2E1 and CYP3A4 probe substrates were investigated in pooled human liver microsomes. PSP (1.25–20μM) dose-dependently decreased CYP1A2-mediated metabolism of phenacetin to paracetamol (IC50 19.7μM) and CYP3A4-mediated metabolism of testosterone to 6β-hydroxytestosterone (IC20 7.06μM). Enzyme kinetics studies showed the inhibition of CYP1A2 activity was competitive and concentration-dependent (Ki=18.4μM). Inhibition of testosterone to 6β-hydroxytestosterone was also competitive and concentration-dependent (Ki=31.8μM). Metabolism of dextromethorphan to dextrorphan (CYP2D6-mediated) and chlorzoxazone to 6-hydroxychlorzoxazone (CYP2E1-mediated) was only minimally inhibited by PSP, with IC20 values at 15.6μM and 11.9μM, respectively. This study demonstrated that PSP competitively inhibited the CYP1A2- and CYP3A4-mediated metabolism of model probe substrates in human liver microsomes in vitro. The relatively high Ki values for CYP1A2 and CYP3A4 would suggest a low potential for PSP to cause herb–drug interaction related to these CYP isoforms.

Acute and chronic toxicity of four frequently used UV filter substances for Desmodesmus subspicatus and Daphnia magna

As a consequence of growing public concern about UV radiation effects on human health chemical and physical UV filters are increasingly used in personal care and other products. The release of these lipophilic and often persistent compounds into surface waters may pose a risk for aquatic organisms. The aim of the study was to determine effects of four frequently used UV filters on primary aquatic producers and consumers, the green alga Desmodesmus subspicatus and the crustacean Daphnia magna. Exposure to benzophenone 3 (BP3), ethylhexyl methoxycinnamate (EHMC), 3-benzylidene camphor (3-BC) and 3-(4′-methylbenzylidene)-camphor (4-MBC) resulted in growth inhibition of D. subspicatus with 72 h IC10 values of 0.56 mg/L (BP 3), 0.24 mg/L (EHMC), 0.27 mg/L (3-BC) and 0.21 mg/L (4-MBC). EC50 concentrations in the acute test with D. magna were 1.67, 0.57, 3.61 and 0.80 mg/L for BP3, EHMC, 3-BC and 4-MBC, respectively. Chronic exposure of D. magna resulted in NOECs of 0.04 mg/L (EHMC) and 0.1 mg/L (3-BC and 4-MBC). BP 3 showed no effects on neonate production or the length of adults. Rapid dissipation of these substances from the water phase was observed indicating the need for more frequent test medium renewal in chronic tests or the use of flow-through test systems.

Isolation and characterization of α-amylase from thermophilic Geobacillus stearothermophilus

Metabolite formation from radical-based oxidation of the environmental pollutant triclosan (TCS) was compared using an ascomycete (Phoma sp. UHH 5-1-03) and a basidiomycete (Trametes versicolor) laccase, laccase-redox mediator systems, and electrochemical oxidation (EC). Laccase oxidation predominantly yielded TCS di- and trimers, but notably also caused TCS ether bond cleavage. The latter was more prominent during EC-catalysed TCS oxidation, which generally resulted in a broader and more divergent product spectrum. By contrast, only quantitative but not qualitative differences in TCS metabolite formation were observed for the two laccases. Application of the presumable natural laccase redox mediator syringaldehyde (SYD) shifted the TCS-transforming reactions of laccase systems from oligomerization more towards ether bond cleavage. However, the observed rapid removal of SYD from reaction systems caused by predominant adduct formation from SYD and TCS, and concomitant conversion of SYD into 2,6-dimethoxy-1,4-benzoquinone (DMBQ) clearly demonstrates that SYD does not function as a “true” laccase redox mediator in the sense of being recycled during TCS oxidation. Laccase treatment of TCS without SYD decreased the anti-bacterial TCS activity more than treatment employing SYD in addition, indicating that SYD and/or its transformation products contribute to bacterial toxicity. DMBQ was found to be about 80% more active in a bacterial growth inhibition test than its parent compound SYD in terms of IC20 values. These observations establish DMBQ as a potential cause of toxicity effects of SYD-laccase systems. They further illustrate that a natural origin of a redox mediator does not automatically qualify its use as environmentally benign or non-hazardous.