Flávia C.S. de Paula

A synthetic dinuclear copper(II) hydrolase and its potential as antitumoral: Cytotoxicity, cellular uptake, and DNA cleavage

We have studied the protonation equilibria of a dicopper(II) complex [Cu(2)(micro-OH)(C(21)H(33)ON(6))](ClO(4))(2).H(2)O, (1), in aqueous solution, its interactions with DNA, its cytotoxic activity, and its uptake in tumoral cells. C(21)H(33)ON(6) corresponds to the ligand 4-methyl-2,6-bis[(6-methyl-1,4-diazepan-6-yl)iminomethyl]phenol. From spectrophotometric data the following pKa values were calculated 3.27, 4.80 and 6.10. Complex 1 effectively promotes the hydrolytic cleavage of double-strand plasmid DNA under anaerobic and aerobic conditions. The following kinetic parameters were calculated k(cat) of 2.73 x 10(-4)s(-1), K(M) of 1.36 x 10(-4)M and catalytic efficiency of 2.01 s(-1)M(-1), a 2.73 x 10(7) fold increase in the rate of the reaction compared to the uncatalyzed hydrolysis rate of DNA. Competition assays with distamycin reveal minor groove binding. Complex 1 inhibited the growth of two tumoral cell lines, GLC4 and K562, with the IC(50) values of 14.83 microM and 34.21 microM, respectively. There is a good correlation between cell growth inhibition and intracellular copper content. When treated with 1, cells accumulate approximately twice as much copper as with CuCl(2). Copper-DNA adducts are formed inside cells when they are exposed to the complex. In addition, at concentrations that compound 1 inhibits tumoral cell growth it does not affect macrophage viability. These results show that complex 1 has a good therapeutic prospect.

A PHYSICOCHEMICAL STUDY OF THE TETRACYCLINE COORDINATION TO OXOVANADIUM(IV)

The interaction of tetracycline and oxovanadium(IV) in aqueous solution was studied by potentiometric and spectrophotometric methods. Oxovanadium(IV) ions form both a positively charged 1:1 and a neutral 2:1 metal-ligand complex with tetracycline. When a 1:1 ligand-to-metal ratio mixture is used at about pH 4.5 the 1:1 species predominates, being replaced at pH 6 by the binuclear complex. The binuclear complex has been isolated and fully characterised. Infrared and EPR studies suggest the existence of two distinct vanadyl binding sites. Our results indicate that the first vanadium coordinates to the BCD-ring system and the second one to the A-ring. Biological implications of the existence of a neutral complex at physiological pH are briefly discussed.

Impact of the carbon chain length of novel platinum complexes derived from N-alkyl-propanediamines on their cytotoxic activity and cellular uptake.

This work describes the synthesis and characterization of four new ligands derived from 1,3-propanediamine in addition to the preparation and characterization of their respective platinum(II) complexes by reaction with K(2)PtCl(4). These ligands were obtained by the reaction of the corresponding alkyl mesylate with 1,3-propanediamine. We have prepared compounds having different carbon chains lengths in an attempt to correlate this factor, which influences the lipophilicity of the compounds, with cytotoxic activity. Octanol/water partition coefficients, the effect of the four complexes on the growth of two tumoral cell lines, and their cellular uptake were investigated. Increasing lipophilicity enhances the rate of cellular uptake and, consequently, the cytotoxic activity.

Avaliação do ácido trans, trans-mucônico urinário como biomarcador de exposição ao benzeno

OBJECTIVE To assess the use of trans, trans-muconic acid as a biomarker of occupational exposure to benzene. METHODS Trans, trans-muconic acid in urine samples of exposed (exposed group, n=36) and non-exposed (non-exposed group, n=116) workers to benzene. Urinary levels of trans, trans-muconic acid were quantified by high-performance liquid chromatography. The study sample consisted of subjects exposed to benzene in an oil refinery in Belo Horizonte, Brazil. Non-parametric statistical analysis was carried out using Kruskall-Wallis test, Mann-Whitney test and Spearman correlation at p<0.05. RESULTS Workers were exposed on average to benzene levels of 0.15 +/- 0.05 mg/m3 (0.05 ppm) and they showed a urinary trans, trans-muconic acid mean value of 0.19 +/- 0.04 mg/g of creatinine. The reference value range of trans, trans-muconic acid in non-exposed subjects was 0.03 to 0.26 mg/g of creatinine (mean 0.10 +/- 0.08 mg/g of creatinine). There was seen a statistical difference between trans, trans-muconic acid levels in urine samples from exposed and non-exposed groups. There was no correlation between urinary trans, trans-muconic acid and air benzene levels. There was no correlation between urinary trans, trans-muconic acid levels in the exposed group and smoking. Alcohol consumption up to 48 hours before sampling procedure showed no effect on trans, trans-muconic acid levels in both exposed and non-exposed groups. There was however a correlation between age (range 18 to 25 years) and urinary metabolite levels in the latter group. CONCLUSIONS The results show that it is important to evaluate the effect of age and smoking habits on urinary trans, trans-muconic acid levels.OBJETIVO: Avaliar o uso do acido trans, trans-muconico urinario como biomarcador na monitorizacao da exposicao ocupacional ao benzeno. METODOS: Foi estudado o comportamento do acido trans, trans-muconico em amostras de urina de individuos expostos (N=36) e nao expostos (N=116) ocupacionalmente ao solvente. A concentracao urinaria do acido foi determinada por Cromatografia Liquida de Alta Eficiencia. A amostra foi constituida de individuos expostos ao benzeno em uma refinaria de petroleo localizada em Belo Horizonte, MG. Foram empregados os testes estatisticos nao-parametricos de Kruskall-Wallis, Mann Witney e de correlacao de Spearman, ao nivel de significância de 0,05%. RESULTADOS: A exposicao media ao benzeno dos trabalhadores selecionados foi de 0,15±0,05 mg/m³ (0,05 ppm) o que resultou em um valor medio do metabolito urinario de 0,19±0,04 mg/g de creatinina. A faixa de referencia do acido trans, trans-muconico no grupo nao exposto variou de 0,03 a 0,26 mg/g de creatinina (media de 0,10±0,08 mg/g de creatinina). Foi encontrada uma diferenca significativa entre os niveis de acido trans, trans-muconico do grupo exposto e nao exposto. Entretanto, nao houve correlacao entre os niveis do metabolito urinario e do benzeno no ar. Foi observada a correlacao entre acido trans, trans-muconico e habito de fumar no grupo de individuos expostos. A ingestao de alcool num periodo de ate 48 horas antes da coleta das amostras nao mostrou interferir nos niveis do metabolito nos dois grupos estudados. Foi observada a correlacao entre acido trans, trans-muconico e idade (faixa etaria de 18 a 25 anos) no grupo de nao expostos. CONCLUSOES: Os resultados obtidos evidenciaram a importância de ser mais bem avaliada a influencia do habito de fumar e da faixa etaria do trabalhador nos niveis urinarios do acido trans, trans-muconico.

Cytotoxicity and Cellular Accumulation of Palladium(II) Complexes of Tetracyclines

We studied the cytotoxic effect and the uptake of PdII complexes of doxycycline (Dox), [Pd(Dox)Cl2] (1), and tetracycline (Tc), [Pd(Tc)Cl2] (2), in chronic myelogenous leukemia cells. The effect of the compounds on macrophage viability was also investigated. Compound 1 is more effective than compound 2 in inhibiting the growth of K562 cells with the IC50 values of 14.44 and 34.54 μM, respectively. There is a good correlation between cell‐growth inhibition and intracellular metal concentrations, determined by inductively coupled plasma atomic emission spectroscopy (ICP‐AES). Incubation of the cells with equitoxic concentrations of both compounds yields approximately the same intracellular Pd concentration. At the IC50 doses, intracellular concentration is ca. 33×10−16 mol/cell for both compounds 1 and 2. This suggests that more [Pd(Tc)Cl2] is needed to produce a cytotoxic effect, because it enters cells more slowly. Both compounds up to 16 μM did not affect the viability of mouse peritoneal macrophages after a 48‐h incubation. After 72 h of incubation, the IC50 values are 22 for [Pd(Dox)Cl2] and 40 μM for [Pd(Tc)Cl2]. Therefore, the cytotoxic effect in cancer cells exhibited by both compounds is higher than their effect in macrophages.

Validação do método de Ducos modificado para a determinação do ácido trans,trans-mucônico urinário

O presente trabalho foi realizado objetivando validar um metodo analitico para a determinacao do acido trans,trans-muconico (ATTM) urinario empregando-se cromatografia liquida de alta eficiencia com deteccao UV. O ATTM foi previamente extraido das amostras biologicas, utilizando-se colunas de troca ionica e identificado por cromatografia liquida de alta eficiencia (CLAE). O cromatografo foi equipado com coluna de fase reversa Lichrosorb RP 18, 5 µm (250 x 4,2 mm). A temperatura da coluna foi mantida a 40 oC. A fase movel utilizada foi acido acetico 1% - metanol (90-10 v/v), pH = 2,72 a um fluxo de 1 mL/min e deteccao UV em comprimento de onda de 264 nm. O metodo apresentou linearidade instrumental (0,006 a 10,0 µg/mL), limites de deteccao (0,006 µg/mL) e quantificacao (0,03 µg/mL), precisao (CV intra-ensaio: 9,57%, CV interensaio: 11,15%) e recuperacao (86,45%) adequados a determinacao da concentracao urinaria de ATTM em trabalhadores expostos ao benzeno.