Mononuclear and Tetranuclear Copper(II) Complexes Bearing Amino Acid Schiff Base Ligands: Structural Characterization and Catalytic Applications.

Two new glycine-Schiff base copper(II) complexes were synthesized. Single crystal X-ray diffraction (SCXRD) allowed us to establish the structure of both complexes in the solid state. The glycine-Schiff base copper(II) complex derived from 2'-hydroxy-5'-nitroacetophenone showed a mononuclear hydrated structure, in which the Schiff base acted as a tridentate ligand, and the glycine-Schiff base copper(II) complex derived from 2'-hydroxy-5'-methylacetophenone showed a less common tetranuclear anhydrous metallocyclic structure, in which the Schiff base acted as a tetradentate ligand. In both compounds, copper(II) had a tetracoordinated square planar geometry. The results of vibrational, electronic, and paramagnetic spectroscopies, as well as thermal analysis, were consistent with the crystal structures. Both complexes were evaluated as catalysts in the olefin cyclopropanation by carbene transference, and both led to very high diastereoselectivity (greater than 98%).

Synthesis, characterization and biological evaluation of octyltrimethylammonium tetrathiotungstate.

Octyltrimethylammonium tetrathiotungstate salt (ATT-C8) was synthesized and its ability to chelate copper was evaluated. The biological and toxic aspects were evaluated by in vitro and in vivo assays, using bovine aorta endothelial cells (BAEC) and zebrafish (Danio rerio) embryos. The obtained results suggest that ATT-C8 has better biocompatibility, showing a significantly lower lethal concentration 50 (LC50) value in comparison to ammonium tetrathiotungstate (ATT). Zebrafish embryos assay results indicate that both tetrathiotungstate salts at the studied concentrations increase the hatching time. Even more, an in vivo assay showed that synthesized materials behave as copper antagonists and have the ability to inhibit its toxicological effects. Also, both materials were found to be active for the in vitro 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The characterization of the materials was carried out using the following spectroscopic techniques: Ultraviolet-Visible (UV-Vis), Fourier Transform Infrared (FTIR) and proton nuclear magnetic resonance (1H-NRM).

Chemical Tools of Octopus maya during Crab Predation Are Also Active on Conspecifics.

Octopus maya is a major socio-economic resource from the Yucatán Peninsula in Mexico. In this study we report for the first time the chemical composition of the saliva of O. maya and its effect on natural prey, i.e. the blue crab (Callinectes sapidus), the crown conch snail (Melongena corona bispinosa), as well as conspecifics. Salivary posterior glands were collected from octopus caught by local fishers and extracted with water; this extract paralyzed and predigested crabs when it was injected into the third pereiopod. The water extract was fractionated by membrane ultrafiltration with a molecular weight cut-off of 3 kDa leading to a metabolic phase (>3 kDa) and a neurotoxic fraction (<3 kDa). The neurotoxic fraction injected in the crabs caused paralysis and postural changes. Crabs recovered to their initial condition within two hours, which suggests that the effects of the neurotoxic fraction were reversible. The neurotoxic fraction was also active on O. maya conspecifics, partly paralyzing and sedating them; this suggests that octopus saliva might be used among conspecifics for defense and for reduction of competition. Bioguided separation of the neurotoxic fraction by chromatography led to a paralysis fraction and a relaxing fraction. The paralyzing activity of the saliva was exerted by amino acids, while the relaxing activity was due to the presence of serotonin. Prey-handling studies revealed that O. maya punctures the eye or arthrodial membrane when predating blue crabs and uses the radula to bore through crown conch shells; these differing strategies may help O. maya to reduce the time needed to handle its prey.