Bioactivity of Phenanthrenes from Juncus acutus on Selenastrum capricornutum

Twenty-five 9,10-dihydrophenanthrenes, four phenanthrenes, a dihydrodibenzoxepin, and a pyrene, isolated from the wetland plant Juncus acutus, were tested to detect their effects on the green alga Selenastrum capricornutum. Nine of the compounds were isolated and identified for the first time. Most of the compounds caused inhibition of algal growth. The 9,10-dihydrophenanthrenes 1, 5, 21, and 22 were the most active.     

Short-term algal toxicity test based on phosphate uptake

In order to develop a short-term algal toxicity test, the growth of and the phosphate uptake by the green alga Selenastrum capricornutum during batch culture were observed. In the control medium, S. capricornutum took up phosphate earlier than it grew. It was also observed that the phosphate uptake was inhibited by the presence of a toxicant. From these results, phosphate uptake was considered as one of the useful effect parameters for a short-term algal toxicity test. As the removal rate of phosphate from the medium is a function of the amount of algal cell initially inoculated, the test period is variable. The relationship between the amount of inoculation and phosphate uptake was examined and the test conditions suitable for a 3-h toxicity test were established as one example. According to this test procedure, the inhibitory effect of some toxicants on the phosphate uptake was determined. For comparison, a conventional algal assay based on algal growth was also performed. The EC50s for both tests were close. This indicated that the algal toxicity test method proposed in this paper would be useful for the uses where rapidity is required.     

Toxicity and Degradation Study of Clofibric Acid by Treatment with Ozone in Water

This article presents the results of the degradation of clofibric acid by ozonation. Furthermore, results of the toxic effect of clofibric acid and its intermediate compound, 4-chlorophene generated during the oxidation process, to alga Selenastrum capricornium, are also discussed. The degradation and mineralization of the compound are studied according to the optimized operating conditions. These variables include pH, conductivity, hydraulic retention time and the use of a mixing maze. All the trials are conducted in a purpose-built pilot-scale reactor. Working under the optimal operating conditions (pH = 9, HRT = 12.5 min and ozone dose = 14 ± 2 gN/m³), a degradation value of 98% was obtained, although mineralization of the compound did not occur. Results show that clofibric acid and its intermediate are toxic during the first 10 min of treatment for concentrations equal to or greater than 1 mg/L. Under optimal conditions toxicity is not observed for any concentrations.     

Toxicological and chemical characterization of organic micropollutants in river po waters (Italy)

River Po waters were collected at the end of the drainage basin, extracted by means of XAD-2 resins and tested for toxicity on aquatic organisms (Daphnia magna and Selenastrum capricornutum) and for mutagenicity with a modified Ames test. The extracts were analyzed by HRGC/FID and selective detectors for the determination of the most common classes of toxic compounds. The relationships between toxicological responses and analytical results are discussed.     

Action of antialgal compounds fromJuncus effusus L. onSelenastrum capricornutum

Twenty-nine free and glucosylated dihydrophenanthrenes and tetrahydropyrenes isolated fromJuncus effusus have been tested against the unicellular green algaSelenastrum capricornutum. The free compounds showed a strong inhibitory activity, while the glucosides were inactive or had a slight stimulating effect on growth. Tetrahydropyrene33, obtained by hydrolysis of the natural-glucosides29 and30 or by hemisynthesis from1, is the most active compound, causing 90% inhibition of the growth at 2.5 × 10^–5 M concentration. Synthetic -glucosides28, 31, and32 showed comparable activity to those of29 and30.     

Dihydrophenanthrene and Phenanthrene Mimics of Natural Compounds—Synthesis and Antialgal Activity

9,10-Dihydrophenanthrenes and phenanthrenes, mimics of natural compounds with strong antialgal activity, have been synthesized through cross-coupling of 1-(2-iodo-5-methoxy)-phenylethanol with variously substituted iodobenzenes. The synthetic compounds, bearing a hydroxyl or a methoxyl group at C-2 and a methyl in the C ring, were tested against the green alga Selenastrum capricornutum. All compounds, except 2-methoxy-7-methylphenanthrene, caused inhibition of algal growth by more than 70% at 10^–4 M, and many of them retained this strong activity at 10^–5 M.     

Ecotoxicological Assessment of Mixtures of Ether Carboxylic Derivative and Amine-Oxide-Based Non-ionic Surfactants on the Aquatic Environment

The purpose of this study was to discuss the effect of the chemical structure of anionic and non-ionic surfactants and surface activity on toxicity. Single and binary mixtures of three ether carboxylic derivative surfactants and three amine-oxide-based non-ionic surfactants were used. Toxicity was determined using three test organisms: freshwater crustaceans (Daphnia magna), luminescent bacteria (Vibrio fischeri), and microalgae (Selenastrum capricornutum). The toxicity of surfactants is related to the hydrophobic alkyl chain, the degree of ethoxylation, and the critical micelle concentration of surfactants. Relationships found agreed with the fact that the lower toxicity is shown by the shorter alkyl chain. There is a strong relation between surface activity and toxicity: the toxicity increased as the CMC of the surfactant or mixtures of surfactants decreased. Commercial products are formulated using surfactants mixtures, so it is important to know their behavior using an easily measured property: the least toxic mixtures were formed by the surfactants having lower individual toxicity. Around the CMC, our data show a synergism for the binary mixtures. The results have given rise to a classification of the different surfactants and their mixtures according to the organism test, as safe, harmful or toxic. V. fischeri was in general the most sensitive microorganism to the toxic effect of the surfactants, followed by Daphnia magna, while Selenastrum capricornutum was more tolerant. These results can be useful for selecting technically efficient surfactants and their mixtures with a lower ecotoxicity on the aquatic environment.     

Sorption of organics by Selenastrum capricornutum

The sorption of eight organic compounds by a representative green alga, Selenastrum capricornutum, was determined by gas-liquid chromatography using a series of linear model experiments. The log₁₀ bioconcentration factors (BCF), defined as the ratio of the concentration on in the algae to the concentration in the aqueous medium, are as follows: benzene, 3.32; toluene, 3.18; chlorobenzene, 3.69; 1,2-dichlorobenzene, 4.17; naphthalene, 4.10; phenanthrene, 4.38; di-n-butylphthalate, 4.36 and pyrene, 4.56. The relation of log₁₀ BCF correlation with log₁₀ octanol-water partition coefficient was determined as log₁₀ BCF = 0.46 log₁₀ P + 2.36.     

Synthesis and Antialgal Activity of Dihydrophenanthrenes and Phenanthrenes II: Mimics of Naturally Occurring Compounds in Juncus effusus

9,10-Dihydrophenanthrenes and phenanthrenes, mimics of natural compounds with strong antialgal activity, have been synthesized through cross-coupling by zerovalent Ni of 1-(2-iodo-5-methoxy)-phenylethanol or 2-iodo-5-methoxyacetophenone with iodoxylenes. The synthetic compounds had a hydroxyl or a methoxyl group at C-2 and two methyls in the C ring. Assays on the green alga Selenastrum capricornutum showed that all the compounds, except 2-methoxy-5,7-dimethylphenanthrene, caused strong inhibition of algal growth at 10^–4 M. 2-Hydroxy-7,8-dimethyl-9,10-dihydrophenanthrene and 2-methoxy-5,6-dimethylphenanthrene fully inhibited growth at 10^–5 M.     

The growth inhibition of planktonic algae due to surfactants used in washing agents

A survey of inhibitory effects of nonionic and anionic surfactants, including a soap, used in washing agents, on the growth on three species of freshwater phytoplankton, Selenastrum capricornutum, Nitzschia fonticola and Microcystis aeruginosa was conducted. Based on the specific growth rate, μu estimated from a short period (2 or 3 days) cultivation of test algae, the growth inhibition was determined using EC₅₀ values where μu in the culture medium with surfactant decreased 50% of that without surfactant.The EC₅₀ values of nonionic and anionic surfactants tested here for S. capricornutum ranged from 2 to 50 mg l⁻¹ and from 10 to 100 mg l⁻¹, respectively. The tolerances of three species of algae tested with three surfactants, LAS, AE (EO:9) and soap, were different and the inhibitory effects were species specific. EC₅₀ values of LAS, AE (EO:9) and soap for S. capricornutum were 50–100, 4–8 and 10–50 mg l⁻¹, respectively. Those for N. fonticola were 20–50, 5–10 and 20–50 mg l⁻¹, and those for M. aeruginosa were 10–20, 10–50 and 10–20 mg l⁻¹, respectively.