Novel vanadyl complexes with quinoxaline N1,N4-dioxide derivatives as potent in vitro insulin-mimetic compounds

Design of novel iron compounds as potential therapeutic agents against tuberculosis

“…This is in accordance with the presence of a secondary amine formed by deprotonation of the primary amine as a consequence of the coordination with iron ion. This behavior was previously observed for vanadyl, palladium and copper complexes with this family of ligands, and for metal chelates with aromatic ligands involving the amino group in ortho position to the N-oxide [5][6][7][8][9][10]17,28]. Besides, the strong ν(N → O) band for the free ligands turned weak upon complexation indicating the coordination of one N → O group per ligand molecule keeping the other uncoordinated as shown in Fig.…”

“…Both newly developed iron complexes showed significantly higher activity than the other complexes and the free ligands. As previously reported for related copper, vanadyl and palladium complexes [5][6][7][8][9][10], the change of the substituents on the quinoxaline moiety produced significant differences in biological activity. The MIC values of L3 and L4 iron complexes (0.78 μg/mL) are comparable or better than those of some "second-line" drugs in clinical use as streptomycin (MIC = 1.00 μg/mL), ciprofloxacin (MIC = 6 μM, 2.00 μg/mL), p-aminosalicylic acid (MIC = 3.3-13.1 μM, 0.5-2.0 μg/mL), ethionamide (MIC = 3.8-7.…”

“…Unfortunately, it was impossible to obtain single crystals adequate for a crystallographic study. Nevertheless, complexes could be adequately characterized in the same way as previously done for the reported copper, vanadium, palladium and iron compounds of this family of ligands by using a combination of several physicochemical methods [5][6][7][8][9][10]. Both complexes are neutral non conducting compounds in DMSO.…”

“…The IR spectra of both new complexes were compared with those of the free ligands and the previously reported Cu, V, Pd and Fe complexes [5][6][7][8][9][10]17]. So, taking into account our previous knowledge on vibrational behavior of 3-aminoquinoxaline-2-carbonitrile N 1 ,N 4 -dioxide derivatives metal complexes, vibration bands related with the ligand's coordination mode were tentatively assigned.…”

“…Part of our group has been involved in the synthesis and biological assessment of a large amount of quinoxaline 1,4-di-N-oxide derivatives, including some of their metal complexes [5][6][7][8][9][10]. Some of these organic derivatives have shown excellent M. tuberculosis growth inhibition values.…”