Nanci C. de Lucas

C−H Functionalization of 1,4-Naphthoquinone by Oxidative Coupling with Anilines in the Presence of a Catalytic Quantity of Copper(II) Acetate

The oxidative addition of anilines (2) with 1,4-naphthoquinone (3) to give N-aryl-2-amino-1,4-naphthoquinones (1) was found to be catalyzed by copper(II) acetate. In the absence of the catalyst, the reactions are slower and give lower yields with the formation of many colateral products. In the presence of 10 mol % hydrated copper(II) acetate, the reactions are generally more efficient in that they are cleaner, higher yielding, and faster.

Laser flash photolysis study of the phenolic hydrogen abstraction by 1,2-aceanthrylenedione triplet

The nanosecond laser flash photolysis technique has been used to study the reactivity of 1,2-aceanthrylenedione (1) triplet towards phenols. Using acetonitrile as solvent, the quenching rate constant kq ranged from 3.3 x 105 L mol-1s-1 (phenol) to 1.3 x 107 L mol-1s-1 (4hydroxyphenol). Phenols with electron donating substituents were more reactive. The kinetic isotope effect (kH/kD) observed for the quenching of 1 with 4-methoxyphenol was 1.5. The Hammett plot for the reaction of the triplet of 1 with phenols gave a reaction constant r = 1.04 in acetonitrile solution. The low value for the quenching rate constant measured for this triplet with 1,3-cyclohexadiene (kq=2.0 x 104 L mol-1s-1) and the diffusion controlled quenching rate constant obtained for b-carotene suggest that the energy of the lowest triplet state for 1,2-aceanthrylenedione is located between 88 and 219 kJ mol-1.

Raman spectroscopic study of antioxidant pigments from cup corals Tubastraea spp.

Chemical investigation of nonindigenous Tubastraea coccinea and T. tagusensis by Raman spectroscopy resulted in the identification of carotenoids and indolic alkaloids. Comparison of Raman data obtained for the in situ and crude extracts has shown the potential of the technique for characterizing samples which are metabolic fingerprints, by means of band analysis. Raman bands at ca. 1520, 1160, and 1005 cm(-1) assigned to ν1(C═C), ν2(C-C), and ρ3(C-CH3) modes were attributed to astaxanthin, and the band at 1665 cm(-1) could be assigned to the ν(C-N), ν(C-O), and ν(C-C) coupled mode of the iminoimidazolinone from aplysinopsin. The antioxidant activity of the crude extracts has also been demonstrated, suggesting a possible role of these classes of compounds in the studied corals.

Singlet oxygen production by pyrano and furano 1,4-naphthoquinones in non-aqueous medium.

The influence of ring size on the photobehaviour of condensed 1,4-naphthoquinone systems, such as pyrano- and furano-derivatives (1 and 2, respectively) has been investigated. The absorption spectra for both families of naphthoquinones reveal clear differences; in the case of 2 they extend to longer wavelengths. A solvatochromic red shift in polar solvents is consistent with the π,π* character of the S(0)→ S(1) electronic transition in all cases. Theoretical (B3LYP) analysis of the HOMO and LUMO Kohn-Sham molecular orbitals of the S(0) state indicates that they are π and π* in nature, consistent with the experimental observation. A systematic study on the efficiency of singlet oxygen generation by these 1,4-naphthoquinones is presented, and values larger than 0.7 were found in every case. In accordance with these results, laser flash photolysis of deoxygenated acetonitrile solutions led to the formation of detectable triplet transient species with absorptions at 390 and 450 nm (1) and at 370 nm (2), with φ(ISC) close to 1. Additionally, the calculated energies for the T(1) states relative to the S(0) states at UB3LYP/6-311++G** are ca. 47 kcal mol(-1) for 1 and 43 kcal mol(-1) for 2. A comparison of the geometrical parameters for the S(0) and T(1) states reveals a marked difference with respect to the arrangement of the exocyclic phenyl ring whilst a comparison of electronic parameters revealed the change from a quinone structure to a di-dehydroquinone diradical structure.

Evaluation of antimicrobial, antioxidant and phototoxic activities of extracts and isolated compounds from Stachytarpheta cayennensis (Rich.) Vahl, Verbenaceae

Stachytarpheta cayennensis (Rich.) Vahl, Verbenaceae, plant extract, is a Brazilian medicinal plant externally used in folk medicine for purulent ulcers, skin lesions and internally for inflammations, fever, renal disorders and atherosclerosis. S. cayennesis was studied to identify potential bioactive compounds that may justify their therapeutic use against skin lesions and atherosclerosis. The antioxidant, antimicrobial and phototoxicity capacities of the crude ethanolic extract, fractions and isolated compounds from roots of S. cayennesis were evaluated through in vivo and in vitro tests. Strains of Saccharomyces cerevisiae, an eukaryotic cell model, were used to assess both the phototoxicity and the capacity to protect against the lethal oxidative stress caused by menadione and hydrogen peroxide. The extract, fractions and the two major isolated compounds, verbascoside and betulinic acid, of S. cayennensis were able to increase the tolerance and decrease the lipid peroxidation of S. cerevisiae to reactive oxygen species (ROS). The antioxidant activity was also evaluated by scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH•). Verbascoside exhibited a moderate antimicrobial activity against Streptococcus pyogenes, S.epidermidis and Staphylococcus aureus. Neither the ethanolic extract nor fractions showed phototoxicity, indicating that the S. cayennensis extract is safe for use in the treatment of skin lesions and as an active cosmetic ingredient.

Silica nanoparticles doped with anthraquinone for lung cancer phototherapy.

In the present study, SiO2 nanoparticles functionalized with 3-(2-aminoethylamino)propyl group (SiNP-AAP) were used, for the first time, to covalently bond rose bengal (SiNP-AAP-RB) or 9,10-anthraquinone-2-carboxylic acid (SiNP-AAP-OCAq). The functionalized SiNP were characterized by: Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM); elemental analysis (CHN) for determination of the dye concentration; FTIR and UV-vis diffuse reflectance (DR-UV-vis) and a surface area study (BET). The functionalized SiNPs were applied in photodynamic therapy (PDT) against lung cancer cell lines. The evaluated cytotoxicity revealed 20-30% cell survival after 15min of PDT for both materials but the OCAq concentration was half of the RB nanomaterial. The phototoxicity was mainly related to oxidative stress generated in the cellular environment by singlet oxygen and by hydrogen abstraction as confirmed by the laser flash photolysis technique. The unprecedented results indicate that SiNP-AAP-OCAq is a possible system for promoting cell apoptosis by both type I and type II mechanisms.

Theoretical study of photochemical hydrogen abstraction by triplet aliphatic carbonyls by using density functional theory.

The density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) have been used to study the lowest lying spin states of the photochemical hydrogen abstraction reaction by formaldehyde, acetaldehyde, and acetone in the presence of different hydrogen donors: propane, 2-propanol, and methylamine. Calculations of all the critical points on the PES of these reactions were performed at uB3LYP/6-311++G(d,p). Methylamine is the best hydrogen donor, in thermodynamic and kinetic terms, followed by 2-propanol and finally propane. Secondary C-H hydrogen abstraction in 2-propanol and C-H abstraction in methylamine is thermodynamically and kinetically favored with respect to hydrogen abstraction from the OH and NH functional groups. Charge transfer takes place before the transition state when methylamine is the hydrogen donor, and for other hydrogen donors, charge transfer begins only in the transition state. The extent of the charge transfer in the transition states corresponds to about 50% of the total change in electron density of the oxygen atom of the T(1) carbonyl compounds during the course of the hydrogen abstraction reactions. The effect of solvent was investigated using the continuum solvation model for the reaction of triplet acetaldehyde in acetonitrile, which resulted in a barrierless transition state for hydrogen abstraction from methylamine.

Antioxidant activity of natural compounds of Stachytarpheta cayennensis (Rich.) Vahl, Verbenaceae, by scavenger of mitochondrial reactive oxygen species

The etiology of a range of diseases is associated with an excessive generation of reactive oxygen species (ROS). Exacerbated ROS production leads to mitochondrial dysfunction, cellular damage and apoptosis. Nowadays, many strategies are being developed for the targeted delivery of antioxidants compounds to mitochondria, trying to minimize the damages. Production of ROS was investigated by the molecular probes CM-H2DCFDA and Amplex Red. The purpose of this work is to evaluate the antioxidant capacity of verbascoside, martinoside, betulinic acid from the Stachytarpheta cayennensis and quercetin by an in vitro assay with isolated mitochondria from mices brain The results showed that all compounds tested exhibited a scavenger effect on the ROS generated by the isolated mitochondria, which displayed a dependent dose increase.

A reatividade do estado excitado triplete de 1,3-indanodiona em benzeno

Rate constants for the quenching of 1,3-indandione (1) triplet by olefins and by hydrogen and electron donors were obtained employing the laser flash photolysis technique in benzene solution. These rate constants ranged from 2.5x105 Lmol-1s-1 (for 2-propanol) to 5.9x109 Lmol-1s-1 (for DABCO). From the quenching rate constants by 1,3-cyclohexadiene, trans- and cis-stilbene a value between 49.3 and 52.4 kcal/mol was estimated for the energy of the triplet state of 1,3-indandione. The np* character of this triplet state was evidenced by the quenching rate constants obtained when typical hydrogen donors were employed as quenchers. For 2-phenyl-1,3-indandione (2, R=phenyl) a fast Norrish type I reaction is operating which prevents the determination of kinetic and spectroscopic data of its triplet state.

SÍNTESE DE DERIVADOS DE FENANTRIDINONAS POR ARILAÇÃO DIRETA. CARACTERIZAÇÃO DOS ESPECTROS DE ABSORÇÃO E EMISSÃO DE EXEMPLOS REPRESENTATIVOS

The phenanthridinone heterocyclic system has attracted considerable attention in recent years due to the diverse array of physical, chemical and pharmacological properties demonstrated by natural and synthetic derivatives. As a consequence there has been considerable development of synthetic methodology for the synthesis of this and related heterocyclic ring systems. The synthetic literature is discussed and is compared with a direct arylation methodology for the intramolecular cyclization of tertiary (2-iodo)benzoylamides to generate the biaryl bond of these compounds. The efficient methodology allowed the synthesis of a number of previously unknown phenanthridinone products. The photoluminescent properties of representative examples were characterized and it is proposed that the previously unknown compound 1s reveals dual fluorescence in a manner similar to the known compound 1r.