The complex chemical functionalization of the aldehyde group was elucidated in copper and cobalt complexes for 4- and 3-pyridinecarboxaldehyde ligands.
Based on the known antioxidant effect of flavonoids, baicalin (baic) found in roots of Scutellaria has been selected. Its coordination complex with the oxidovanadium(IV) cation, Na[VO(baic)].6HO (VO(baic)), was synthesized at pH9 in ethanol and characterized by physicochemical methods. Spectrophotometric studies at pH9 showed a ligand: metal stoichiometry of 2:1. By vibrational spectroscopy a coordination mode through the cis 5-OH and 6-OH deprotonated groups is inferred. EPR spectroscopy shows an environment of four aryloxide (ArO) groups in the equatorial plane of the VO moiety, both in solution and in the solid complex. The antioxidant capacity against superoxide and peroxyl radicals of VO(baic) resulted greater than for baicalin and correlated with previous results obtained for other VOflavonoid complexes. The coordination mode produces delocalization of the electron density and the stabilization of the radical formed by interaction with external radicals. The complex and the ligand displayed no toxic (Artemia salina test) and no mutagenic (Ames test) effects. The complex improved the ability of the ligand to reduce cell viability of human lung cancer cell lines (A549) generating reactive oxygen species (ROS) in cells, being this effect reversed by pre-incubation of the cells with antioxidants such as vitamins C and E. The addition of NAC (N-acetyl-l-cysteine, a sequestering agent of free radicals) suppresses the anticancer effect, confirming the oxidative stress mechanism. The complex interacted with bovine serum albumin (BSA) with stronger binding than baicalin and the mechanisms involved H bonding and van der Waals interactions.
Continuing and expanding our previous work on flavonoid oxidovanadium(IV) (VO) metal complexes as possible anti-cancer agents, the VOapigenin compound was synthesized and characterized. An "acetylacetone-like" coordination through the C¼O and OÀ À moieties of the ligand to the metal center with one apigenin ligand per metal ion was assumed using different spectroscopies and elemental analysis as well as thermal measurements. The vibrational experimental spectrum of VOapigenin was supported by theoretical calculations. According to the structure of the flavonoid it exerted mild antioxidant properties that were enhanced by metal coordination. The compounds showed moderate anticancer activity on lung A549 and cervix HeLa cancer cell lines, displaying an incubation time dependent behavior. Cellular increase of reactive oxygen species (ROS) and glutathione depletion have been measured upon incubation with the compounds. These cell killing activities were reverted when natural antioxidants were incubated with the compounds and the addition of the antioxidant agent Nacetylcysteine generated depletion of the cellular ROS levels. Therefore, a stress oxidative mechanism of action has been assumed. Moreover, the compounds showed no toxicity against Artemia salina and were not mutagenic. Both apigenin and the complex could be transported and stored by bovine serum albumin with similar binding constants and mechanisms than other VOflavonoid complexes.
Iron modified ZSM-11 zeolites were tested as heterogeneous catalysts in the photodegradation of Dichlorvos water solutions. ZSM-11 zeolite matrixes were synthesized by the hydrothermal method and iron was incorporated by the wet impregnation method in four different concentrations. Catalysts samples were characterized by several techniques (XRD, BET, UV-vis DRS, ICP-OES, TPR, EPR) in order to confirm structure, crystallinity and iron species present. a-Fe 2 O 3 was detected by XRD in higher iron content samples and it presence was confirmed by EPR, TPR and UV-vis DRS. Band gap energies for Fe/ZSM-11 samples were closer to that reported for pure a-Fe 2 O 3 . The materials so far characterized were tested as heterogeneous catalyst in Dichlorvos photodegradation. Fe/ZSM-11 with a 6 wt% of iron incorporation showed the best catalytic behavior. Higher iron loadings showed lower degradation efficiencies. This material is reusable for at least six catalytic cycles without considerable differences among the DDVP amount degraded.
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