Growth Inhibition Bioassay Research Articles

Specialized Metabolites from the Allelopathic Plant Retama raetam as Potential Biopesticides.

To cope with the rising food demand, modern agriculture practices are based on the indiscriminate use of agrochemicals. Although this strategy leads to a temporary solution, it also severely damages the environment, representing a risk to human health. A sustainable alternative to agrochemicals is the use of plant metabolites and plant-based pesticides, known to have minimal environmental impact compared to synthetic pesticides. Retama raetam is a shrub growing in Algeria’s desert areas, where it is commonly used in traditional medicine because of its antiseptic and antipyretic properties. Furthermore, its allelopathic features can be exploited to effectively control phytopathogens in the agricultural field. In this study, six compounds belonging to isoflavones and flavones subgroups have been isolated from the R. raetam dichloromethane extract and identified using spectroscopic and optical methods as alpinumisoflavone, hydroxyalpinumisoflavone, laburnetin, licoflavone C, retamasin B, and ephedroidin. Their antifungal activity was evaluated against the fungal phytopathogen Stemphylium vesicarium using a growth inhibition bioassay on PDA plates. Interestingly, the flavonoid laburnetin, the most active metabolite, displayed an inhibitory activity comparable to that exerted by the synthetic fungicide pentachloronitrobenzene, in a ten-fold lower concentration. The allelopathic activity of R. raetam metabolites against parasitic weeds was also investigated using two independent parasitic weed bioassays to discover potential activities on either suicidal stimulation or radicle growth inhibition of broomrapes. In this latter bioassay, ephedroidin strongly inhibited the growth of Orobanche cumana radicles and, therefore, can be proposed as a natural herbicide.

Lovastatin production by an oleaginous fungus, Aspergillus terreus KPR12 using sago processing wastewater (SWW)

BackgroundLovastatin is one of the first statins to be extensively used for its cholesterol-lowering ability. It is commercially produced by fermentation. Species belonging to the genus Aspergillus are well-studied fungi that have been widely used for lovastatin production. In the present study, we produced lovastatin from sago processing wastewater (SWW) under submerged fermentation using oleaginous fungal strains, A. terreus KPR12 and A. caespitosus ASEF14.ResultsThe intra- and extracellular concentrations of lovastatin produced by A. terreus KPR12 and A. caespitosus ASEF14 were lactonized. Because A. caespitosus ASEF14 produced a negligible amount of lovastatin, further kinetics of lovastatin production in SWW was studied using the KPR12 strain for 9 days. Lovastatin concentrations in the intra- and extracellular fractions of the A. terreus KPR12 cultured in a synthetic medium (SM) were 117.93 and 883.28 mg L–1, respectively. However, these concentrations in SWW were 142.23 and 429.98 mg L–1, respectively. The yeast growth inhibition bioassay confirmed the antifungal property of fungal extracts. A. terreus KPR12 showed a higher inhibition zone of 14 mm than the ASEF14 strain. The two-way analysis of variance (ANOVA; p < 0.01) showed significant differences in the localization pattern, fungal strains, growth medium, and their respective interactions. The lovastatin yield coefficient values were 0.153 g g–1 on biomass (YLOV/X) and 0.043 g g–1 on the substrate, starch (YLOV/S). The pollutant level of treated SWW exhibited a reduction in total solids (TS, 59%), total dissolved solids (TDS, 68%), biological oxygen demand (BOD, 79.5%), chemical oxygen demand (COD, 57.1%), phosphate (88%), cyanide (65.4%), and void of nutrients such as nitrate (100%), and ammonia (100%).ConclusionThe starch-rich wastewater serves as a suitable medium for A. terreus KPR12 for the production of lovastatin. It simultaneously decontaminates the sago processing wastewater, enabling its reuse for irrigation/recreation.Graphical

Individual and Binary Mixture Toxicity of Five Nanoparticles in Marine Microalga Heterosigma akashiwo.

The investigation of the combined toxic action of different types of nanoparticles (NPs) and their interaction between each other and with aquatic organisms is an important problem of modern ecotoxicology. In this study, we assessed the individual and mixture toxicities of cadmium and zinc sulfides (CdS and ZnS), titanium dioxide (TiO2), and two types of mesoporous silicon dioxide (with no inclusions (SMB3) and with metal inclusions (SMB24)) by a microalga growth inhibition bioassay. The counting and size measurement of microalga cells and NPs were performed by flow cytometry. The biochemical endpoints were measured by a UV-VIS microplate spectrophotometer. The highest toxicity was observed for SMB24 (EC50, 3.6 mg/L) and CdS (EC50, 21.3 mg/L). A combined toxicity bioassay demonstrated that TiO2 and the SMB3 NPs had a synergistic toxic effect in combinations with all the tested samples except SMB24, probably caused by a “Trojan horse effect”. Sample SMB24 had antagonistic toxic action with CdS and ZnS, which was probably caused by metal ion scavenging.

Effect of Dissolved Organic Matter Concentration and Source on the Chronic Toxicity of Copper and Nickel Mixtures to Chlorella sp.

There have been limited studies on the effects of toxicity-modifying factors, such as dissolved organic matter (DOM), on the toxicity of metal mixtures to aquatic biota. The present study investigated the effects of DOM concentration (low, 2.8 ± 0.1 mg C/L; high, 11 ± 1.0 mg C/L) and DOM source (predominantly terrestrial or microbial) on the chronic toxicity of copper (Cu) and nickel (Ni) binary mixtures to the green freshwater microalga Chlorella sp. This was assessed by using a full factorial design of 72-h growth inhibition bioassays. Measured algal growth rate was compared with growth predicted by the concentration addition and independent action reference models. Model predictions were based on concentrations of dissolved metals, labile metals (measured by diffusive gradients in thin films [DGT]), and calculated free metal ions (determined by the Windermere Humic Aqueous Model). Copper/Ni mixture toxicity was synergistic to Chlorella sp. in the absence of added DOM, with evidence of metal concentration-dependent toxicity at low effect concentrations. As DOM concentration increased, the mixture interaction changed from synergism to noninteraction or antagonism depending on the metal speciation method used. The DOM source had no significant effect on mixture interaction when based on dissolved and free metal ion concentrations but was significantly different when based on DGT-labile metal concentrations. Ratio-dependent mixture interaction was observed in all treatments, with increased deviation from the reference model predictions as the mixture changed from Ni- to Cu-dominated. The present study demonstrated that both DOM concentration and source can significantly change metal mixture toxicity interactions and that these interactions can be interpreted differently depending on the metal speciation method used. Environ Toxicol Chem 2021;40:1908-1918. © 2021 SETAC.

Potential of arsenic bioremediation by a cyanobacterium isolated from the Salado River in the Atacama Desert

AbstractCyanobacteria and microalgae are recognized as excellent metal(loid)s-bioremediators of aquatic systems. We isolated a cyanobacterium from the Salado River in the Atacama Desert, northern Chile, which was identified as Cyanobium sp. Growth inhibition bioassays were conducted with arsenic and cadmium, and tolerance of Cyanobium to these metals was estimated. Removal of arsenic was assessed under different pH conditions and over time. We showed that the Cyanobium strain isolated from the Salado River has a greater tolerance to the arsenic and cadmium compounds than other species commonly used in metal(loid)s-bioremediation. Removal of up to 90% of arsenic was obtained in alkaline conditions, within the first 3 hours of exposure suggesting that Cyanobium sp. isolated from the Atacama Desert could be further studied with biotechnological purposes and to understand the evolutionary mechanisms of adaption to arid environments.

Streptomyces sp. M54: an actinobacteria associated with a neotropical social wasp with high potential for antibiotic production.

Streptomyces symbionts in insects have shown to be a valuable source of new antibiotics. Here, we report the genome sequence and the potential for antibiotic production of "Streptomyces sp. M54", an Actinobacteria associated with the eusocial wasp, Polybia plebeja. The Streptomyces sp. M54 genome is composed of a chromosome (7.96Mb), and a plasmid (1.91Kb) and harbors 30 biosynthetic gene clusters for secondary metabolites, of which only one third has been previously characterized. Growth inhibition bioassays show that this bacterium produces antimicrobial compounds that are active against Hirsutella citriformis, a natural fungal enemy of its host, and the human pathogens Staphylococcus aureus and Candida albicans. Analyses through TLC-bioautography, LC-MS/MS and NMR allowed the identification of five macrocyclic ionophore antibiotics, with previously reported antibacterial, antitumor and antiviral properties. Phylogenetic analyses placed Streptomyces sp. M54 in a clade of other host-associated strains taxonomically related to Streptomyces griseus. Pangenomic and ANI analyses confirm the identity of one of its closest relatives as Streptomyces sp. LaPpAH-199, a strain isolated from an ant-plant symbiosis in Africa. In summary, our results suggest an insect-microbe association in distant geographic areas and showcase the potential of Streptomyces sp. M54 and related strains for the discovery of novel antibiotics.

Amoxicillin in Water: Insights into Relative Reactivity, Byproduct Formation, and Toxicological Interactions during Chlorination

In recent years, many studies have highlighted the consistent finding of amoxicillin in waters destined for wastewater treatment plants, in addition to superficial waters of rivers and lakes in both Europe and North America. In this paper, the amoxicillin degradation pathway was investigated by simulating the chlorination process normally used in a wastewater treatment plant to reduce similar emerging pollutants at three different pH values. The structures of 16 isolated degradation byproducts (DPs), one of which was isolated for the first time, were separated on a C-18 column via a gradient HPLC method. Combining mass spectrometry and nuclear magnetic resonance, we then compared commercial standards and justified a proposed formation mechanism beginning from the parent drug. Microbial growth inhibition bioassays with Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus were performed to determine the potential loss of antibacterial activity in isolated degradation byproducts. An increase of antibacterial activity in the DPs was observed compared to the parent compound.

Bioprospecting medicinal plants for the isolation and screening of lovastatin producing endophytic fungi

Endophytic fungi reside within the plant tissues asymptomatically and produce various secondary metabolites of pharmaceutical interest. The current study aims to bio-prospect medicinal plants for the isolation and screening of lovastatin producing endophytic fungi. Endophytic population in the leaf, stem, root and flower (as applicable) of ten medicinal plants has been studied and their potential to produce the anti-hypercholesterolemia drug, lovastatin has been evaluated. A total of 98 fungal isolates were obtained from the plant tissues and lovastatin yield from them was quantified to be within the range of 5 mg/L to 71.5 mg/L in the first round of submerged fermentation. The subsequent levels of screening witnessed a great change in the yield which could be attributed to gene attenuation, a usual phenomenon in endophytes. A novel lovastatin producer, designated as HL1, belonging to candida sp. residing within the leaves of Hibiscus rosa-sinensis was found to consistently yield higher amounts of lovastatin i.e., 40 mg/L through all rounds of screening, alongside two strains of Aspergillus sp., designated as HL4 and HL5, from the same tissue with a yield of 21.5 and 18 mg/L respectively. Preliminary confirmation of lovastatin presence in the fungal extract was done by Thin Layer Chromatography (TLC) and yeast growth inhibition bioassay.

In-vivo antiproliferative activity of Morus latifolia leaf and bark extracts against Ehrlich's ascites carcinoma.

Cancer is the second death causing disease all over the world and until today 100 different types of cancer have been identified whose treatment methods consist of serious side effects on human body. To reduce the frequency of adverse effects of cancer treatment, nowadays plant derived natural components are getting priority. The plant Morus latifolia is widely available in northern part of Bangladesh. The earlier researches suggested that popular varieties of some Morus sp. like Morus alba, Morus indica etc. have good anti-proliferative activity. Hence, this study was designed to evaluate the anti-proliferative activity of leaf and bark extracts of M. latifolia against Ehrlich's ascites carcinoma (EAC) in vivo. The leaf and bark extracts of M. latifolia were used in severalbioassays including Brine shrimp lethalitytest, hemagglutination activitytest, antioxidant activity test,and cell growth inhibitiontest. Besides, fluorescence microscopy was performed to study apoptotic features in EAC cells, and molecular analysis like real-time PCR were also conducted. The results of Brine shrimp lethality test, hemagglutination activity test, and antioxidant activity assay supported the cell growth inhibition capability of leaf and bark extracts which was confirmed by in vivo cell growth inhibition bioassay. Moreover, the experimental extracts were able to inducecell apoptotis through altering the expression pattern of Bcl-2 and Bax genes. All of the results of this study suggest that several noble compounds are present in M. latifolia plant extracts which are capable for healing cancer cells.

Bioactivity of cardanol against the rust red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae)

AbstractCashew nut shell liquid (CNSL) is an economically important by-product obtained from the cashew nut Anacardium occidentale L. The liquid has been found to be versatile with a wide range of uses, including as a raw material in the polymer industry, in the development of drugs (antioxidants) and in pest control. One important chemical component of CNSL known for its bioactivity is cardanol. We isolated (8Z,11Z)-3-(8,11,14-pentadecatrienyl)phenol, a cardanol from CNSL, and determined its insecticidal and progeny growth and development inhibition activities against Tribolium castaneum Hebst. We used a bioassay-guided approach for the isolation. Exposure to cardanol produced 80% mortality of adult T. castaneum in the insecticidal bioassay. In the progeny growth and development inhibition bioassay, 46.7% of larvae were killed, and only 20.7% of adults emerged without deformities after the cardanol treatment. The amount of isolated cardanol from the 1 g equivalent/ml extracted CNSL was found to be 36.55 mg with LC50 value of 47.88 mg/ml and 13.28 mg/ml against adult T. castaneum and its larvae, respectively. We conclude that cardanol can potentially be useful in managing stored product insect pests, especially T. castaneum, but with the prerequisite that one should take much care when handling and when applying the compound.

Oxidation of fluoroquinolone antibiotics by peroxymonosulfate without activation: Kinetics, products, and antibacterial deactivation

While fluoroquinolone (FQ) antibiotics are susceptible to degradation by sulfate and/or hydroxyl radicals formed in peroxymonosulfate (PMS) based advanced oxidation processes, here we report that unactivated PMS itself exhibits a specific high reactivity toward FQs for the first time. Reaction kinetics of PMS with two model FQs, ciprofloxacin (CF) and enrofloxacin (EF), showed a strong pH dependency with apparent second-order rate constants of 0.10–13.05 M−1s−1 for CF and 0.51–33.17 M−1s−1 for EF at pH 5–10. This pH dependency was well described by species-specific parallel reactions. On the basis of reaction kinetics and structure–activity assessment, the tertiary and secondary aliphatic N4 amines on the FQs’ piperazine ring were proposed to be the main reaction sites. High performance liquid chromatography/electrospray ionization tandem mass analysis showed the formation of hydroxylated, N-oxide, and dealkylated products. Bacterial growth inhibition bioassays using Escherichia coli showed that oxidation products of FQs by PMS retained negligible antibacterial potency in comparison to parent FQs. Kinetic modeling using the rate constants estimated from pure water well predicted the oxidation kinetics of low levels of CF and EF by PMS in surface water. The degradation efficiency of FQs by PMS in surface water was slightly lower than that by ozone, comparable to that by ferrate, and much higher than that by permanganate. These results suggest that PMS is a promising oxidant for the treatment of FQs in water.

Potential of synthetic chalcone derivatives to prevent marine biofouling

Biofouling represents a major economic, environmental and health concern for which new eco-friendly solutions are needed. International legislation has restricted the use of biocidal-based antifouling coatings, and increasing efforts have been applied in the search for environmentally friendly antifouling agents. This research work deals with the assessment of the interest of a series of synthetic chalcone derivatives for antifouling applications. Sixteen chalcone derivatives were synthesized with moderate yields (38–85%). Antifouling bioactivity of these compounds was assessed at different levels of biological organization using both anti-macrofouling and anti-microfouling bioassays, namely an anti-settlement assay using mussel (Mytilus galloprovincialis) larvae, as well as marine bacteria and microalgal biofilms growth inhibition bioassays. Results showed that three compounds (11, 12, and 16) were particularly active against the settlement of mussel larvae (EC50 7.24–34.63 μM), being compounds 12 and 16 also able to inhibit the growth of microfouling species (EC50 4.09–20.31 μM). Moreover, the most potent compounds 12 and 16 were found to be non-toxic to the non-target species Artemia salina (<10% mortality at 25 μM). A quantitative structure-activity relationship model predicted that descriptors describing the ability of molecules to form hydrogen bonds and encoding the shape, branching ratio and constitutional diversity of the molecule were implied in the antifouling activity against the settlement of mussel larvae. This work elucidates for the first time the relevance of synthesizing chalcone derivatives to generate new non-toxic products to prevent marine biofouling.

Degradation of ciprofloxacin by manganese(III) intermediate: Insight into the potential application of permanganate/bisulfite process

Permanganate could be activated by bisulfite to generate soluble Mn(III) which can oxidize organic contaminants rapidly. However, a lot of concerns need to be addressed for the application of permanganate/bisulfite (PM/BS) process. Taking ciprofloxacin as a target contaminant, the influence of pH, temperature and co-existing solutes on the degradation of organic contaminant in PM/BS process was systematically investigated. The PM/BS process oxidized ciprofloxacin with kobs 2.18–6.27 orders of magnitude larger than other oxidation processes under various reaction conditions and thus stood out. Ciprofloxacin present in real waters can be degraded effectively in the PM/BS process and the co-existing solutes have less inhibiting effect at lower pH and lower ciprofloxacin concentration. Bromate less than 5 µg/L was generated in PM/BS process even in the presence of 1000 µg/L bromide and thus bromate generation in PM/BS process was not a concern. The residual manganese species could be easily removed by aeration from real waters. The degradation products of ciprofloxacin in PM/BS process were identified and the plausible reaction pathways were proposed. Although the quinolone core structure in degradation products remained unattacked, bacterial growth inhibition bioassays and genotoxic experiments showed that the PM/BS treated ciprofloxacin samples displayed negligible cytotoxic and genotoxic potency.

Improved large-scale prediction of growth inhibition patterns using the NCI60 cancer cell line panel.

Motivation: Recent large-scale omics initiatives have catalogued the somatic alterations of cancer cell line panels along with their pharmacological response to hundreds of compounds. In this study, we have explored these data to advance computational approaches that enable more effective and targeted use of current and future anticancer therapeutics.Results: We modelled the 50% growth inhibition bioassay end-point (GI50) of 17 142 compounds screened against 59 cancer cell lines from the NCI60 panel (941 831 data-points, matrix 93.08% complete) by integrating the chemical and biological (cell line) information. We determine that the protein, gene transcript and miRNA abundance provide the highest predictive signal when modelling the GI50 endpoint, which significantly outperformed the DNA copy-number variation or exome sequencing data (Tukey’s Honestly Significant Difference, P <0.05). We demonstrate that, within the limits of the data, our approach exhibits the ability to both interpolate and extrapolate compound bioactivities to new cell lines and tissues and, although to a lesser extent, to dissimilar compounds. Moreover, our approach outperforms previous models generated on the GDSC dataset. Finally, we determine that in the cases investigated in more detail, the predicted drug-pathway associations and growth inhibition patterns are mostly consistent with the experimental data, which also suggests the possibility of identifying genomic markers of drug sensitivity for novel compounds on novel cell lines.Contact: terez@pasteur.fr; ab454@ac.cam.ukSupplementary information: Supplementary data are available at Bioinformatics online.

UVC based advanced oxidation for decolourization and mineralization of calconcarboxylic acid in aqueous solution: Eco‐toxicological effect of post treated solutions and its remedy

The present study reports two important aspects of wastewater treatment by UVC light (λ = 254 nm) in the presence of hydrogen peroxide (HP) and ammonium persulphate (APS) taking Calconcarboxylic acid (CCA) as a model pollutant. The first part deals with the effect of various operational parameters on the decolourization and mineralization of CCA. Most importantly, the eco-toxicological effect of the treated solutions was examined on the basis of E. coli growth inhibition bioassay and the remedy for the same has been suggested in the second part. Although both oxidants show higher mineralization at pH 1, APS is preferred over HP for having higher mineralization, biodetoxification, and electrical energy efficiency. The presence of –COOH group in CCA has detrimental effect on its mineralization and biodetoxification, as well as on the electrical energy efficiency. Although a rise in mineralization at all pH is observed by the removal of the –COOH group, it is significant in alkaline media. Since treatment at pH 1 is not ideal for real scale applications, it is advisable to remove the –COOH group before treatment, so as to make treatment possible in alkaline media. Removal of –COOH group also leads to higher biodetoxification in a shorter treatment period.

Toxicity of arsenic species to three freshwater organisms and biotransformation of inorganic arsenic by freshwater phytoplankton (Chlorella sp. CE-35)

In the environment, arsenic (As) exists in a number of chemical species, and arsenite (AsIII) and arsenate (AsV) dominate in freshwater systems. Toxicity of As species to aquatic organisms is complicated by their interaction with chemicals in water such as phosphate that can influence the bioavailability and uptake of AsV. In the present study, the toxicities of AsIII, AsV and dimethylarsinic acid (DMA) to three freshwater organisms representing three phylogenetic groups: a phytoplankton (Chlorella sp. strain CE-35), a floating macrophyte (Lemna disperma) and a cladoceran grazer (Ceriodaphnia cf. dubia), were determined using acute and growth inhibition bioassays (EC50) at a range of total phosphate (TP) concentrations in OECD medium. The EC50 values of AsIII, AsV and DMA were 27±10, 1.15±0.04 and 19±3mg L−1 for Chlorella sp. CE-35; 0.57±0.16, 2.3±0.2 and 56±15mgL−1 for L. disperma, and 1.58±0.05, 1.72±0.01 and 5.9±0.1mgL−1 for C. cf. dubia, respectively. The results showed that AsIII was more toxic than AsV to L. disperma; however, AsV was more toxic than AsIII to Chlorella sp. CE-35. The toxicities of AsIII and AsV to C. cf. dubia were statistically similar (p>0.05). DMA was less toxic than iAs species to L. disperma and C. cf. dubia, but more toxic than AsIII to Chlorella sp. CE-35. The toxicity of AsV to Chlorella sp. CE-35 and L. disperma decreased with increasing TP concentrations in the growth medium. Phosphate concentrations did not influence the toxicity of AsIII to either organism. Chlorella sp. CE-35 showed the ability to reduce AsV to AsIII, indicating a substantial influence of phytoplankton on As biogeochemistry in freshwater aquatic systems.

Influence of the carbon source on Gordonia alkanivorans strain 1B resistance to 2-hydroxybiphenyl toxicity.

The viability of bacteria plays a critical role in the enhancement of fossil fuels biodesulfurization efficiency since cells are exposed to toxic compounds such as 2-hydroxybiphenyl (2-HBP), the end product of dibenzothiophene (DBT) biodesulfurization. The goal of this work was to study the influence of the carbon source on the resistance of Gordonia alkanivorans strain 1B to 2-HBP. The physiological response of this bacterium, pre-grown in glucose or fructose, to 2-HBP was evaluated using two approaches: a growth inhibition toxicity test and flow cytometry. The results obtained from the growth inhibition bioassays showed that the carbon source has an influence on the sensitivity of strain 1B growing cells to 2-HBP. The highest IC50 value was obtained for the assay using fructose as carbon source in both inoculum growth and test medium (IC50-48h = 0.464mM). Relatively to the evaluation of 2-HBP effect on the physiological state of resting cells by flow cytometry, the results showed that concentrations of 2-HBP >1mM generated significant loss of cell viability. The higher the 2-HBP concentration, the higher the toxicity effect on cells and the faster the loss of cell viability. In overall, the flow cytometry results highlighted that strain 1B resting cells grown in glucose-SO4 or glucose-DBT are physiologically less resistant to 2-HBP than resting cells grown in fructose-SO4 or fructose-DBT, respectively.

Occurrence and potential combined toxicity of dissolved organic contaminants in the Forth estuary and Firth of Forth, Scotland assessed using passive samplers and an algal toxicity test

As an alternative procedure to conventional water quality assessment, the presence and combined toxicity of dissolved organic contaminants in water at five sites in the Forth estuary and the Firth of Forth, Scotland, United Kingdom was investigated using silicone rubber passive sampling devices (SR-PSDs) and an algal growth inhibition bioassay. SR-PSDs were deployed in water at the five sites for ~2months. Following retrieval, extracts from the deployed SR-PSDs were assessed for both algal growth inhibition and the occurrence of a wide range of organic contaminants, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and a variety of plant protection products (PPPs; commonly referred to collectively as ‘pesticides’). The 72h algal growth inhibition test was performed using a native marine phytoplankton (Diacronema lutheri) in 24 well microplates. Freely dissolved (e.g. bioavailable) concentrations of PAHs and PCBs were determined using performance reference compounds (PRCs). The algal toxicity tests exhibited varied effects at the five sites indicating the presence of, and exposure to, phytotoxic compounds and their potential toxicity in the Forth. The individual and total dissolved concentrations of 40 PAHs and 32 PCBs measured in the study were relatively low and showed input of petrogenic, atmospheric and sewage related sources. Several pesticides of diverse polarities were identified in the water suggesting sources from both riverine input and direct discharges. The study thus illustrates the value of combining bioassays and chemical analysis (with effective sampling technique) for a realistic and rapid assessment of organic contaminants in the aquatic environment.

Transition metal catalyzed mineralization of Calcon and bioassay of the mineralized solutions by Escherichia coli colony forming unit assay

Mineralization of Calcon was studied by Fenton and Fenton like processes in a wide range of pH with hydrogen peroxide (HP) and ammonium persulphate (APS) as oxidants and catalyzed by transition metal catalysts such as Fe2+, Ag+ and Co2+. Maximum mineralization for Fenton and other processes was achieved at pH 3 and 1, respectively. Although mineralization was negligible in alkaline media, the catalytic activity of metal ions on HP is found to be similar, while that on APS was in the order: Fe2+>Co2+>Ag+. The study reveals that Calcon resisted mineralization by Fenton process (35.6% in 120min) and the efficiency of other systems followed the order: Fe2+/APS>Ag+/APS≈Ag+/HP>Co2+/HP>Co2+/APS and a maximum of 91.1% and 73.7% mineralization were achieved with Fe2+/APS and Ag+/APS systems, respectively, at pH 1. To understand the impact of these processes operating at low pH, biotoxicity of the treated solutions was evaluated on the basis of Escherichia coli (E. coli) growth inhibition bioassay. It was observed that the treated solutions were still more toxic to E. coli than the original dye solution. Thus, metal catalyzed Fenton and Fenton like processes are not environmentally benign under the specified conditions of our study.

Rational design and efficient synthesis of a fluorescent-labeled jasmonate

A fluorescent-labeled jasmonate was rationally designed based on examination of the model of interaction between the jasmonate and its receptor. An efficient synthetic route has been developed for this molecule. The biological activity of this fluorescent probe was retained which was similar to that of the methyl jasmonate as examined by root growth inhibition bioassay. This fluorescent probe will greatly facilitate biological studies of jasmonates through fluorescent imaging.