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Natural flavonoids such as quercetin, (+)catechin and rutin as well as four methoxylated derivatives of quercetin used as models were investigated to elucidate their impact on the oxidant and antioxidant status of human red blood cells (RBCs). The impact of these compounds against metal toxicity was studied as well as their antiradical activities with DPPH assay. Antihemolytic experiments were conducted on quercetin, (+)catechin and rutin with excess of Fe, Cu and Zn (400 μM), and the oxidant (malondialdehyde, carbonyl proteins) and antioxidant (reduced glutathione, catalase activity) markers were evaluated. The results showed that Fe and Zn have the highest prooxidant effect (37 and 33% of hemolysis, respectively). Quercetin, rutin and (+)catechin exhibited strong antioxidant properties toward Fe, but this effect was decreased with respect to Zn ions. However, the Cu showed a weak antioxidant effect at the highest flavonoid concentration (200 μM), while a prooxidant effect was observed at the lowest flavonoid concentration (100 μM). These results are in agreement with the physico-chemical and antiradical data which demonstrated that binding of the metal ions (for FeNTA: (+)Catechin, KLFeNTA = 1.6(1) × 106 M-1 > Rutin, KLFeNTA = 2.0(9) × 105 M-1 > Quercetin, KLFeNTA = 1.0(7) × 105 M-1 > Q35OH, KLFeNTA = 6.3(8.7) × 104 M-1 > Quercetin3'4'OH and Quercetin 3OH, KLFeNTA ~ 2 × 104 M-1) reflects the (anti)oxidant status of the RBCs. This study reveals that flavonoids have both prooxidant and antioxidant activity depending on the nature and concentration of the flavonoids and metal ions., Competing Interests: The authors have declared that no competing interests exist.

The syntheses of two new ligands based on a calix[4]arene scaffold in the cone conformation functionalized on the phenolic positions 1 and 3 by diethylthiophosphonates (L1) or tetra(tri)thioethyleneglycol (L2) crowns are described. Together with ligand L3, the parent calix[4]arene substituted by a penta(tetra)thioethyleneglycol crown, the spectroscopic properties of the ligands were determined by means of UV-Vis absorption spectroscopy and steady-state and time-resolved fluorescence spectroscopy, showing that the ligands display modest but non-negligible intrinsic fluorescence properties (ϕ fluo = 0.023; 0.026 and 0.029 for L1, L2 and L3 in CH 2 Cl 2 , respectively). The X-ray crystal structures of ligand L1, and of its synthetic precursor were determined and analyzed for their capacity to accommodate the incoming cationic species. The ligands were further investigated for their complexation properties of divalent cations such as Cu 2+ , Zn 2+ , Hg 2+ and Cd 2+ (under their nitrate salts) in 1 : 1 CH 3 CN/CH 2 Cl 2 solutions (I = 0.01 M Et 4 NNO 3 , T = 25.0(2) °C), in which the additions of cations were monitored by absorption and steady-state fluorescence spectrophotometries. The stoichiometries of the corresponding complexes were assessed by ESI-MS, while insights into the structures of the complexes in solution were obtained with density functional theory (DFT) calculations. The influence of the sulphur and phenol coordinating moieties was addressed to show that the thiocrown compounds L2 and L3 displayed a marked affinity towards the soft mercuric cation (Δlog K ≥ 2), with no particular size selectivity effect, whereas ligand L1 can accommodate both the thio and phenol units to coordinate with Cu(ii). Altogether, these results point to the use of L3 as a selective fluoroionophore for detection of Hg 2+ .

Obesity is characterized by iron deficiency, carbohydrate and fat alterations as well as oxidative stress. Iron status monitoring is recommended because of the conventional oral iron preparations that frequently exacerbate the already present oxidative stress. Iron complexation by natural antioxidants can be exploited. We herein investigated the metabolic effects of quercetin (25 mg/kg/day), iron (2.5 mg Fe/kg/day) or quercetin-iron complexes (molar ratio 5:1; 25 mg/2.5 mg/kg/day) in animal models of obesity. Our results emphasized that obese rats displayed metabolic alterations that were worsened by iron supplementation. In contrast, quercetin used alone or as iron complex clearly prevented adipose fat accumulation and alleviated the hyperglycemia, hyperlipidemia, liver steatosis and oxidative stress. In addition, it induced a modulation of lipase activities in obese rats. Interestingly, quercetin-iron complexes showed enhanced beneficial effects such as a corrected iron deficiency in obese rats when compared to quercetin alone. In conclusion, antianemic, hypoglycemic, hypolipidemic and antioxidative effects of the quercetin-iron complexes shed a light on their beneficial use against obesity-related metabolic alterations., (Copyright © 2015 Elsevier Inc. All rights reserved.)

In this contribution we present two ligands based on a do3a platform containing a picolinate group attached to the fourth nitrogen atom of the cyclen unit, which are designed for stable lanthanide complexation in aqueous solutions. Potentiometric measurements reveal that the thermodynamic stability of the complexes is very high (log K = 21.2-23.5), being comparable to that of the dota analogues. Luminescence lifetime measurements performed on solutions of the Eu(III) and Tb(III) complexes indicate that the complexes are nine coordinate with no inner-sphere water molecules. A combination of density functional theory (DFT) calculations and NMR measurements shows that for the complexes of the heaviest lanthanides there is a major isomer in solution consisting of the enantiomeric pair Λ(δδδδ) and Δ(λλλλ), which provides square antiprismatic coordination (SAP) around the metal ion. Analysis of the Yb(III)-induced paramagnetic shifts unambiguously confirms that these complexes have SAP coordination in aqueous solution. For the light lanthanide ions however both the SAP and twisted-square antiprismatic (TSAP) isomers are present in solution. Inversion of the cyclen ring appears to be the rate-determining step for the Λ(δδδδ) ↔ Δ(λλλλ) enantiomerization process observed in the Lu(III) complexes. The energy barriers obtained from NMR measurements for this dynamic process are in excellent agreement with those predicted by DFT calculations. The energy barriers calculated for the arm-rotation process are considerably lower than those obtained for the ring-inversion path. Kinetic studies show that replacement of an acetate arm of dota by a picolinate pendant results in a 3-fold increase in the formation rate of the corresponding Eu(III) complexes and a significant increase of the rates of acid-catalyzed dissociation of the complexes. However, these rates are 1-2 orders of magnitude lower than those of do3a analogues, which shows that the complexes reported herein are remarkably inert with respect to metal ion dissociation., (© 2011 American Chemical Society)