Interaction of metallocene dichlorides with apo-human transferrin: A spectroscopic study and cytotoxic activity against human cancer cell lines.

Metallocene dichlorides (Cp2M(IV)Cl2) are the first class of small and hydrophobic organometallic compounds classified as anticancer agents against numerous cancer cell lines and tumors. In this study, the antiproliferative activities of Cp2VCl2,Cp2NbCl2, Cp2HfCl2 and Cp2ZrCl2were assessed on two human cancer cell lines (HT-29 and MCF-7) using MTT assay. Spectroscopic studies were also conducted using these and other known metallocene dichlorides on apo-human transferrin (apo-hTf) at pH 7.4. UV-Vis and CD showed that their interaction with apo-hTf could induce conformational changes of its secondary structure during binding process. In fluorescence, a decrease in intensity of the emission peak was observed when the apo-hTf:Cp2M(IV)Cl2 complex is being formed, probably due to changes in the microenvironment of its tyrosine and tryptophan residues. Among all metallocene dichlorides studied, Cp2VCl2 has the strong ability to quench the intrinsic fluorescence of apo-hTf through a static quenching mechanism. The association constants for each protein-compound complex were also determined at different temperatures (296 K, 303 K, 310 K, and 317 K) based on fluorescence quenching results. Positive enthalpy changes (ΔH) and entropy changes (ΔS) as well as negative free energies (ΔG) suggest that hydrophobic interactions are the main intermolecular forces involved in the binding process, probably via an endothermic and spontaneous reaction mechanism. The distance, r, between donor (apo-hTf) and acceptor (Cp2M(IV)Cl2) obtained according to Forster's theory of non-radiation energy transfer suggest that the energy transfer from apo-hTf to Cp2M(IV)Cl2 occurs with high probability and distances obtained by FRET with high accuracy.

A molecular docking study of the interactions between human transferrin and seven metallocene dichlorides.

Human Transferrin (hTf) is a metal-binding protein found in blood plasma and is well known for its role in iron delivery. With only a 30% of its capacity for Fe+3 binding, this protein has the potential ability to transport other metal ions or organometallic compounds from the blood stream to all cell tissues. In this perspective, recent studies have described seven metallocene dichlorides (Cp2M(IV)Cl2, M(IV)=V, Mo, W, Nb, Ti, Zr, Hf) suitable as anticancer drugs and less secondary effects than cisplatin. However, these studies have not provided enough data to clearly explain how hTf binds and transports these organometallic compounds into the cells. Thus, a computational docking study with native apo-hTf using Sybyl-X 2.0 program was conducted to explore the binding modes of these seven Cp2M(IV)Cl2 after their optimization and minimization using Gaussian 09. Our model showed that the first three Cp2M(IV)Cl2 (M(IV)=V, Mo, W) can interact with apo-hTf on a common binding site with the amino acid residues Leu-46, Ile-49, Arg-50, Leu-66, Asp-69, Ala-70, Leu-72, Ala-73, Pro-74 and Asn-75, while the next four Cp2M(IV)Cl2 (M(IV)=Nb, Ti, Zr, Hf) showed different binding sites, unknown until now. A decreasing order in the total score (equal to -log Kd) was observed from these docking studies: W (5.4356), Mo (5.2692), Nb (5.1672), V (4.5973), Ti (3.6529), Zr (2.0054) and Hf (1.8811). High and significant correlation between the affinity of these seven ligands (metallocenes) for apo-hTf and their bond angles CpMCp (r=0.94, p<0.01) and Cl-M-Cl (r=0.95, p<0.01) were observed, thus indicating the important role that these bond angles can play in ligand-protein interactions. Fluorescence spectra of apo-hTf, measured at pH 7.4, had a decrease in the fluorescence emission spectrum with increasing concentration of Cp2M(IV)Cl2. Experimental data has a good correlation between KA (r=0.84, p=0.027) and Kd (r=0.94, p=0.0014) values and the calculated total scores obtained from our docking experiments. In conclusion, these results suggest that the seven Cp2M(IV)Cl2 used for this study can interact with apo-hTf, and their affinity was directly and inversely proportional to their bond angles CpMCp and ClMCl, respectively. Our docking studies also suggest that the binding of the first three Cp2M(IV)Cl2 (M(IV)=V, Mo, W) to hTf could abrogate the formation of the hTf-receptor complex, and as a consequence the metallocene-hTf complex might require another transport mechanism in order to get into the cell.

Chemical composition and antioxidant activity of essential oils isolated from Colombian plants / Composição química e atividade antioxidante de óleos essenciais isolados de plantas da Colombia

Treze óleos essenciais de plantas da Colômbia, obtido por hidrodestilação ou hidrodestilação assistida por microondas, da planta inteira, caule, folhas e flores, foram analisados por técnicas de espectrometria de massa acoplada a cromatografia gasosa. Foi avaliada a citotoxicidade de óleos essenciais utilizando o ensaio com Artemia salina e suas atividades antioxidantes medindo seus efeitos sobre os níveis de substâncias reativas ao ácido tiobarbitúrico em microssomas de fígado de rato induzida por Fe2+/H2O2. Cinco óleos apresentaram alta citotoxicidade (LC50<10 µg/mL) sobre o ensaio de Artemia salina. A atividade antioxidante do óleo essencial de Ocotea sp., Tagetes lucida e Lippia alba (quimiotipo geranial) apresentaram os menores valores de Concentração Eficaz (CE50), na ordem de 31,1, 37,9 e 94,9 µg/mL, respectivamente. Os principais componentes desses óleos foram α-pineno (42 por cento), estragol (95,7 por cento) e geranial (30,4 por cento), respectivamente. Elettaria cardamomum e Lippia alba (quimiotipo carvona, Tolima) apresentaram moderada atividade antioxidante com valores de CE50 de 130,5 e 174,4 µg/mL, respectivamente. Os óleos essenciais de mollis Minthostachys mollis, Lippia alba (quimiotipo carvona, Cundinamarca), e Piper sanctifelisis não mostraram atividade antioxidante (CE50>1000 µg/mL).

Thirteen essential oils from Colombian plants, obtained by hydrodistillation or microwave-assisted hydrodistillation of total plant, stem, leaves, and flowers were analyzed by gas-chromatography-mass spectrometry techniques. Cytotoxicity of essential oils was assessed using the brine shrimp assay, and their antioxidant activities measuring their effects on the levels of thiobarbituric acid reactive substances on rat liver microsomes induced by Fe2+/H2O2. Five oils showed high cytotoxicity (LC50<10 µg/mL) on the brine shrimp assay. The antioxidant activity of the essential oil from Ocotea sp., Tagetes lucida and Lippia alba (geranial chemotype) showed the lowest mean effective concentrations (EC50), with values of 31.1, 37.9 and 94.9 µg/mL, respectively. The main components for these oils were α-pinene (42 percent), estragole (95.7 percent) and geranial (30.4 percent), respectively. Elettaria cardamomum and Lippia alba (carvone chemotype, Tolima) presented moderate antioxidant activities with EC50 values of 130.5 and 174.4 µg/mL, respectively. Essential oils from Minthostachys mollis, Lippia alba (carvone chemotype, Cundinamarca), and Piper sanctifelisis did not show antioxidant activity (CE50>1000 µg/mL).

Human and crab exposure to mercury in the Caribbean coastal shoreline of Colombia: impact from an abandoned chlor-alkali plant.

Human hair samples from male and female people aged 6-85 years, as well as muscle of crabs (Callinectes sapidus and Callinectes bocourti) were collected from different fishing places along the Caribbean coastal shoreline of Colombia and analyzed for total mercury (T-Hg) in order to establish the impact of mercury-polluted sediments in Cartagena bay on the ecosystem. Hair T-Hg in inhabitants varied between 0.1 and 21.8 microg/g, with average and median of 1.52 microg/g and 1.1 microg/g, respectively. Differences between sampling locations were significant (P<0.01) and median values decreased in the order: Caño del Oro (1.5 microg/g)

Polycyclic aromatic hydrocarbons and their hydroxylated metabolites in fish bile and sediments from coastal waters of Colombia.

Sediments and fish bile collected from the Atlantic coastal waters of Colombia were analyzed for 16 parent polycyclic aromatic hydrocarbons (PAHs), and 23 hydroxylated PAHs (OH-PAHs), respectively. Sediments contained overall mean SigmaPAH concentrations of 2090, 234 and 170 ng/g, dry wt, for Cartagena Bay, Caimanera Marsh, and Totumo Marsh, respectively. The mean concentration of the summed OH-PAHs in fish bile was 1250, 180 and 64.1 ng/g bile wt for Cartagena Bay, Caimanera Marsh, and Totumo Marsh, respectively. The results suggest that Cartagena Bay is heavily polluted by PAHs, and that exposure to high concentrations of PAHs together with other factors could contribute to the decreased health of fish living in this ecosystem. This is one of the first studies to describe the analysis of 23 individual OH-PAHs in fish bile, using authentic standards.

Contracaecum sp. infection in Hoplias malabaricus (moncholo) from rivers and marshes of Colombia.

Nematode infection indices were recorded in Hoplias malabaricus captured in six different rivers and a marsh belonging to the North Coast Basin of Colombia, and from the Amazon River, during February 2003-December 2004. Preliminary morphological analysis of nematodes indicated the presence of Contracaecum sp. Parasites were mostly found in the intestinal mesenteries and a very low percentage in muscle. Parasite prevalence in all sampling locations at the north of Colombia was 100%, whereas in the Amazon River it was 6.12%. The mean intensity in the different stations were as follows: Magdalena River at the City of Magangué (58.92+/-7.59), Magdalena river at the city of Zambrano (128.9+/-7.08), Sinú River (53.88+/-4.92), Dique Channel (207.3+/-59.52), Cauca River (77.26+/-9.35), Atrato River (21.11+/-2.6), San Jorge River (39.5+/-7.13), and Totumo Marsh (62.5+/-6.38). In average, all specimens of Hoplias malabaricus from the north coast basin of Colombia were infected with a mean intensity of 77.82+/-4.81 (1-466 parasites per host) whereas in fish from the Amazon River this value was significantly lower (intensity 1.0+/-0.0). Size and weight correlated significantly with parasite intensity in fish collected from sampling locations at the north of Colombia (R=0.240, P<0.001 and R=0.199, P=0.008, respectively). Moreover, a significant, but low and negative correlation was found between condition factor and parasite intensity (R=-0.159, P=0.034), suggesting a possible impact of parasites on fish health. These results suggest, for the first time, that the parasitism in Moncholo is a widespread phenomenon in Colombian rivers and could represent a risk factor for human consumers.

Perfluorooctanesulfonate and related fluorochemicals in biological samples from the north coast of Colombia.

Perfluorinated compounds are widespread pollutants of toxicological importance that have been detected in environmental matrices. However, little is known on their distribution in South America. In this study, distribution of perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexanesulfonate (PFHxS), and perfluorooctanesulfonamide (PFOSA) was determined in the bile of mullet, Mugil incilis, and in tissues of pelicans (Pelecanus occidentalis) collected from North Colombia. Analysis was performed by HPLC mass spectrometry after ion-pair extraction. PFOS was found in all bile samples and PFOA and PFHxS were detected at lower frequency. Average concentrations of PFOS, PFOA, and PFHxS in bile of fish from Cartagena Bay, an industrialized site, and Totumo marsh, a reference site, were 3673, 370, 489 and 713, 47.4, 1.27 ng/mL, respectively. PFOS concentrations in pelican organs decreased in the order of spleen>liver>lung>kidney>brain>heart>muscle. These results suggest, for the first time, that perfluorinated compounds are also found in wildlife from Latin American countries.