Ecotoxicity of the nonsteroidal ecdysone mimic RH-5849 to Daphnia magna

Determination of 12 insect growth regulator residues in foods of different matrixes by modified QuEChERS and UPLC-MS/MS

An analytical method was developed and validated for the simultaneous determination of 12 insect growth regulators (IGRs) (buprofezin, cyantraniliprole, flubendiamide, flonicamid, tolfenpyrad, chlorantraniliprole, RH-5849, methoxyfenozide, chromafenozide, tebufenozide, pyriproxyfen and fenoxycarb) in foods collected from different matrixes by modified QuEChERS and ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The samples were ultrasonically extracted with acetonitrile containing 0.5% formic acid, and different QuEChERS purification conditions were optimized for different matrixes (vegetable oil, fruit and tea). 12 IGRs were separated on a Plus C18 column, and detected by MS/MS under multiple reaction monitoring (MRM) mode. The developed method was validated in terms of linearity, matrix effect, accuracy and precision. Acceptable recoveries of IGRs in three different substrates (vegetable oil, tea and fruit) at three spiked levels were in the range of 65.47-95.17%, 80.55-110.15%, and 62.02-96.50%, respectively, with RSDs less than 11.58%. The method showed a good linearity (R 2 ≥ 0.9994) for all analytes in the range of 0.2-200 μg L-1. The LODs (S/N = 3) and LOQs (S/N = 10) of the method were 0.04-0.40 μg kg-1, and 0.13-1.24 μg kg-1, respectively. Owing to the advantages of simple operation, high accuracy and sensitivity, this method is suitable for the rapid and simultaneous detection of 12 IGRs in vegetable oil, tea and fruit.

Ecotoxicity profile of heavily contaminated surface water of two rivers in Tunisia

Persistent organic and inorganic contaminants generated by industrial effluent wastes poses a threat to the maintenance of aquatic ecosystems and public health. The Khniss and Hamdoun rivers, located in the central-east of Tunisia, receive regularly domestic and textile wastewater load. The present study aimed to survey the water quality of these rivers using physicochemical, analytical and toxicological approaches. In the physicochemical analysis, the recorded levels of COD and TSS in both samples exceed the Tunisian standards. Using the analytical approach, several metals and some textile dyes were detected. Indeed, 17 metals were detected in both samples in varying concentrations, which do not exceed the Tunisian standards. The sources of metals pollution can be of natural and anthropogenic origin. Three textile disperse dyes were detected with high levels compared to other studies: the disperse orange 37 was detected in the Khniss river with a concentration of 6.438 μg/L and the disperse red 1 and the disperse yellow 3 were detected in the Hamdoun river with concentrations of 3.873 μg/L and 1895 μg/L, respectively. Textile activities were the major sources of disperse dyes. For both samples, acute and chronic ecotoxicity was observed in all the studied organisms, however, no genotoxic activity was detected. The presence of metals and textile disperse dyes could be associated with the ecotoxicological effects observed in the river waters, in particular due to the industrial activity, a fact that could deteriorate the ecosystem and therefore threaten the human health of the population living in the study areas. Combining chemical and biological approaches, allowed the detection of water ecotoxicity in testing organisms and the identification of possible contributors to the toxicity observed in these multi-stressed water reservoirs.

20-Hydroxyecdysone (20E) signaling as a promising target for the chemical control of malaria vectors

With the rapid development and spread of resistance to insecticides among anopheline malaria vectors, the efficacy of current World Health Organization (WHO)-approved insecticides targeting these vectors is under threat. This has led to the development of novel interventions, including improved and enhanced insecticide formulations with new targets or synergists or with added sterilants and/or antimalarials, among others. To date, several studies in mosquitoes have revealed that the 20-hydroxyecdysone (20E) signaling pathway regulates both vector abundance and competence, two parameters that influence malaria transmission. Therefore, insecticides which target 20E signaling (e.g. methoxyfenozide and halofenozide) may be an asset for malaria vector control. While such insecticides are already commercially available for lepidopteran and coleopteran pests, they still need to be approved by the WHO for malaria vector control programs. Until recently, chemicals targeting 20E signaling were considered to be insect growth regulators, and their effect was mostly studied against immature mosquito stages. However, in the last few years, promising results have been obtained by applying methoxyfenozide or halofenozide (two compounds that boost 20E signaling) to Anopheles populations at different phases of their life-cycle. In addition, preliminary studies suggest that methoxyfenozide resistance is unstable, causing the insects substantial fitness costs, thereby potentially circumventing one of the biggest challenges faced by current vector control efforts. In this review, we first describe the 20E signaling pathway in mosquitoes and then summarize the mechanisms whereby 20E signaling regulates the physiological processes associated with vector competence and vector abundance. Finally, we discuss the potential of using chemicals targeting 20E signaling to control malaria vectors.

Ecotoxicological assessment of synthetic and biogenic surfactants using freshwater cladoceran species

Surfactants have been continuously detected within aquatic environments as a consequence of their use on a global scale. Lipopeptides are biosurfactants naturally produced by Bacillus subtilis that have been explored as green alternatives. The assessment of ecotoxicological parameters of synthetic and biogenic surfactants are required for evaluating toxicity values and to verify the eco-friendly behaviour of the biological compounds. This study aimed to conduct toxicity testing for different surfactants - sodium dodecyl sulphate and Triton X-100 - and biosurfactants - surfactin, iturin and fengycin - at different concentrations using Daphnia magna as model organism and Dendrocephalus brasiliensis as alternative test species for monitoring of pollutants in tropical freshwaters. According results, both species showed high sensitivity for the anionic compound SDS concerning the recommended dosage use, exhibiting EC_50-48h values of 24.1 and 15.4 mg/L for D. magna and D. brasiliensis, respectively. Although the biological source, surfactin showed the lower safety behaviour among the biogenic surfactants, while iturin and fengycin revealed very low toxicity effects on both organisms. Besides, data exhibited a higher responsiveness of D. brasiliensis for all tested compounds in comparison to D. magna, highlighting the importance of this species for monitoring of pollutants in tropical and subtropical environments.