Abstract: In this work, an alkaloids extract from Annona squamosa plant have been studied as possible corrosion inhibitor for C38 steel in molar hydrochloric acid (1 M HCl). Potentiodynamic polarization and AC impedance methods have been used. The corrosion inhibition efficiency increases on increasing plant extract concentration. Polarisation studies showed that Annona squamosa extract was mixed-type inhibitor in 1 M HCl. The inhibition efficiency of Annona squamosa extract was temperature-dependent and its addition led to an increase of the activation corrosion energy revealing a physical adsorption between the extract and the metal surface. The adsorption of the Annona squamosa extract followed Langmuir's adsorption isotherm. The inhibitive effect of Annona squamosa is ascribed to the presence of organic compounds in the extract. The examined extract is considered as non-cytotoxic substance.

Abstract: The corrosion rates in the presence of some indole derivates, namely, 9H-pyrido[3,4-b]indole (norharmane) and 1-methyl-9H-pyrido[3,4-b]indole (harmane), as inhibitors of C38 steel corrosion inhibitor in 1 M HCl solution, were measured by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques, in the range of temperatures from 25 to 55 °C. Results obtained revealed that the organic compounds investigated have inhibiting properties for all temperatures. The inhibition was assumed to occur via adsorption of the indole molecules on the metal surface. Adsorption of indole derivates was found to follow the Langmuir isotherm. The apparent activation energies, enthalpies, and entropies of the dissolution process and the free energies and enthalpies for the adsorption process were determined by potentiodynamic polarization and electrochemical impedance. The fundamental thermodynamic functions were used to collect important information about indole inhibitory behaviour. © 2013 M. Lebrini et al.

Abstract: The effect of alkaloids extracted from Isertia coccinea plant (AEIC) on the corrosion of C38 steel in 1 M hydrochloric acid was investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. Potentiodynamic polarization curves indicated that the extract behave as mixed-type inhibitor. The experimental data obtained from EIS method show a frequency distribution and therefore a modelling element with frequency dispersion behaviour, a constant phase element (CPE) has been used. The inhibition efficiencies of the extract calculated by three methods show the same tendency. Inhibition was found to increase with increasing concentration of the plant extract. The results obtained show that the extract solution of the plant could serve as an effective inhibitor for the corrosion of C38 steel in hydrochloric acid solution. The apparent activation energy of the process taking place in inhibitor presence was determined on the ground of four temperature values in the range from 25 degrees C to 55 degrees C using the data obtained by two independent methods. Theoretical fitting of different isotherms, Langmuir, Temkin and Frunkin, were tested to clarify the nature of adsorption.

Abstract: The search for safe antimalarial compounds acting against asexual symptom-responsible stages and sexual transmission-responsible forms of Plasmodium species is one of the major challenges in malaria elimination programs. So far, among current drugs approved for human use, only primaquine has transmission-blocking activity. The discovery of small molecules targeting different Plasmodium falciparum life stages remains a priority in antimalarial drug research. In this context, several independent studies have recently reported antiplasmodial and transmission-blocking activities of commonly used stains, dyes and fluorescent probes against P. falciparum including chloroquine-resistant isolates. Herein we have studied the antimalarial activities of dyes with different scaffold and we report that the triarylmethane dye (TRAM) Brilliant green inhibits the growth of asexual stages (IC50 ≤ 2 μM) and has exflagellation-blocking activity (IC50 ≤ 800 nM) against P. falciparum reference strains (3D7, 7G8) and chloroquine-resistant clinical isolate (Q206). In a second step we have investigated the antiplasmodial activities of two polysulfonated triarylmethane food dyes. Green S (E142) is weakly active against P. falciparum asexual stage (IC50 ≃ 17 μM) whereas Patent Blue V (E131) is inactive in both antimalarial assays. By applying liquid chromatography techniques for the culture supernatant analysis after cell washings and lysis, we report the detection of Brilliant green in erythrocytes, the selective uptake of Green S (E142) by infected erythrocytes, whereas Patent Blue V (E131) could not be detected within non-infected and 3D7-infected erythrocytes. Overall, our results suggest that two polysulfonated food dyes might display different affinity with transporters or channels on infected RBC membrane. © 2017 The Authors

Abstract: Climatic changes result in an increased in mean temperature and in a higher incidence of extreme weather events such as heat and cold waves. For ectotherms, such as insect parasitoids, the ability to remain active under extreme climatic conditions is a significant key to fitness. The body size of individuals, and in particular their surface to volume ratio, may play a role in their resistance to thermal conditions. The thermal tolerances are investigated of two closely-related sympatric parasitoid species [Aphidius avenae Haliday and Aphidius rhopalosiphi De Stefani-Perez (Hymenoptera: Aphidiinae)] that have a similar ecology but differ in body size and phenologies. The critical thermal limits of individuals are assessed in both sexes of each parasitoid species and the influence of surface volume ratios on their thermal tolerances. Aphidius avenae is less resistant to low temperatures and more resistant to high temperatures than A. rhopalosiphi. The lower surface to volume ratio of A. avenae individuals may help them to remain active in summer when experiencing heat waves. However, body size is not the sole factor that plays a role in differences of thermal tolerance between species and body size may not be an adaptation to extreme temperatures but rather a by-product of developmental regulation. Closely-related sympatric species from the same ecological guild can have different thermal tolerances that may allow them to occur within the same habitat. The present study also highlights the importance of clearly defining how to measure critical thermal limits to determine the thermal tolerance of a species.