2009-20013
Publicação 34
“Photophysical properties and photodynamic activity of a novel menthol–zinc phthalocyanine conjugate incorporated in micelles”
Romero, M. P. ; Gobo, N. R .S. ; de Oliveira, K. T. ; Iamamoto, Y. ; Serra, O. A. ; Louro, S. R.W. J. Photoch Photobio A 2013, 253, 22-29.
DOI: 10.1016/j.jphotochem.2012.12.009
Abstract
The synthesis, photophysical properties, and photodynamic activity of the lipophilic tetra-menthyl-substituted zinc phthalocyanine (ZnMintPc, main regioisomer {2,9,16,23-tetrakis{[(1S,2R,5S)-5-methyl-2-(1-methylethyl)cyclohexyl]oxy}-phthalocyaninato}zinc(II)) are described. This compound was synthesized under cyclotetramerization conditions by reaction of substituted phthalonitrile prepared from 4-nitrophthalonitrile with natural l-menthol. This new phthalocyanine presented remarkable structural and photophysical features with potential application in photodynamic therapy (PDT) involving hydrophobic membrane regions. This photosensitizer was incorporated in micelles of 12 different surfactants, namely ionic detergents SDS, CTAB, and HPS, the non-ionic detergents Tween® 20, Tween® 80, C12E9, Brij® 30, Brij® 35, Brij® 97, and Brij® 98, and the triblock copolymers Pluronic F-68 and Pluronic F-127. Solubilization or aggregation in the lipophilic compartment of the micelles was assessed by UV–vis absorption and photoluminescence spectroscopies. Singlet oxygen was produced by irradiation of the micelles with light from red LEDs, peaked at 635 nm, and the quantum yields were obtained using 1,3-diphenylisobenzofuran (DPBF) as probe. Two micellar systems, more specifically Brij® 30 and Pluronic® F-127, displayed excellent ability to generate singlet oxygen. Photobleaching rates of the ZnMintPc incorporated into the micelles were also obtained. The results demonstrated the lipophilic ZnMintPc is suitable for PDT applications and suggest the use of Pluronic® F-127 in the formulation of adequate drug delivery systems for this photosensitizer.
Publicação 33
“Tetrabenzoporphyrins: synthetic developments and applications”
Carvalho, C. M. B. ; Brocksom, T. J. ; de Oliveira, K. T. Chem. Soc. Rev. 2013, 42, 3302-3317.
Abstract
Tetrabenzoporphyrins have attracted considerable worldwide attention over the last few decades. Since the discovery of these pigments, chemists, biologists, medical professionals and material scientists have devoted pronounced efforts in order to develop synthetic methods and discover useful applications for these compounds. Nowadays, tetrabenzoporphyrins occupy a prominent position in porphyrin chemistry, and this review is intended to cover the main synthetic methods and applications of these compounds.
Publicação 32
“Synthesis and photophysical studies of a chlorin sterically designed to prevent self-aggregation”
de Assis, F. F. ; de Souza, J. M. ; Assis, B. H.K. ; Brocksom, T. J. ; de Oliveira, K. T.
Dyes. Pigments. 2013, 98, 153-159.
DOI: 10.1016/j.dyepig.2013.02.011
Abstract
Synthesis and photophysical evaluations of a new non-aggregating chlorin derivative are described. A β-octa(carboxyethyl)porphyrin 3 was synthesized in 2 steps starting from pyrrole-3,4-dicarboxylic acid diethyl ester (2). The new chlorin derivative 6 was obtained through a 1,3-dipolar cycloaddition using benzyl azomethine ylide. Chlorin 6 presents a molecular scaffold in an “L” shape avoiding aggregation in solutions at 1–27 mM. Photophysical properties were measured, and indicate that this new compound can be considered a useful candidate for PDT studies.
Publicação 31
“Synthesis of functionalized chlorins sterically-prevented from self-aggregation”
dos Santos, F. A. B. ; Uchoa, A. F. ; Baptista, M. S. ; Iamamoto, Y. ; Serra, O. A. ; Brocksom, T. J. ; de Oliveira, K. T.
Dyes. Pigments. 2013, 99, 402-411.
DOI: 10.1016/j.dyepig.2013.05.024
Abstract
The synthesis of six new regioisomeric chlorin derivatives sterically-prevented from self-aggregation is described. The compounds were prepared by the Diels–Alder reaction between protoporphyrin IX dimethyl ester, and N-[p-(1,3-dithiolan)phenyl]maleimide and N-(p-formylphenyl)maleimide. The protopophyrin IX dimethyl ester was synthesized in 2 steps from natural hematoporphyrin using a modified procedure from literature, and the substituted maleimides were conveniently synthesized, aiming at producing formyl-chlorins for subsequent functionalization with amphiphilic groups. The Diels–Alder reactions were systematically studied in order to establish optimized conditions for the cycloadditions.
The regioisomers were fully characterized and the aggregation studies were performed by NMR, UV–Vis spectroscopy, and also HRMS (ESI-TOF and MALDI-TOF). Preliminary evaluations on the photosensitizing activities and amphiphilicity were carried out indicating that these new compounds are potential candidates, to be studied in more advanced tests of Photodynamic Therapy (PDT). This work represents on advance on our previous study, with respect to these new structures, their photophysical properties and amphiphilicity.
Publicação 30
“Nanoparticles of Lyotropic Liquid Crystals: A Novel Strategy for the Topical Delivery of a Chlorin Derivative for Photodynamic Therapy of Skin Cancer”
Petrilli, R. ; Praca, F. ; Carollo, A. R. ; Medina, W. ; Oliveira, K. T. ; Fantini, M. ; Neves, M. d. G. ; Cavaleiro, J. ; Serra, O. ; Iamamoto, Y. ; Bentley, M. V.
Curr. Nanosci. 2013, 9, 434-441.
DOI: 10.2174/1573413711309040003
Abstract:
Nanoparticles of lyotropic liquid crystals loaded with a new photosensitizer (a chlorin derivative) were developed for use in photodynamic therapy (PDT). These systems were characterized by spectrofluorimetric, dynamic light scattering, and small angle X-ray diffraction (SAXRD) analyses. In vitro and in vivo penetration studies in animal models were performed using animal model membranes. The systems had a particle size of 161 ± 4 nm and a polydispersity index of 0.175 ± 0.027. Furthermore, SAXRD studies demonstrated that the preparations remained in the liquid crystalline phase type hexagonal after drug loading. The encapsulation rate was higher than 50%, and cell viability studies revealed that the nanodispersion is not harmful for L929 skin cells. In vitro and in vivo penetration studies confirmed that the nanodispersion of hexagonal phase enabled a higher drug skin uptake compared to the control. Additionally, a fluorescence microscopy study demonstrated a higher biodistribution of the chlorin derivative in the skin layers of hairless mice compared to the control. Taken together, the results show the potential of this nanodispersion for the delivery of the photosensitizer into the skin, which is a crucial condition for successful topical PDT.
Publicação 29
“Synthesis of an Octa-tert-butylphthalocyanine: A Low-Aggregating and Photochemically Stable Photosensitizer”
Gobo, N. R. S. ; Brocksom, T. J. ; Zukerman-Schpector, J. ; de Oliveira, K. T..
Eur. J. Org. Chem. 2013, 23, 5028–5031.
Abstract
The synthesis of a new octa-tert-butylphthalocyanine is described. First, the 4,5-di-tert-butylphthalonitrile building block was synthesized in a six-step approach, in which the last step is a three reaction domino sequence. Then, this phthalonitrile was cyclotetramerized to furnish a new phthalocyanine dye, which presented no aggregation in solution and good photophysical properties.
Publicação 28
“Synthesis and photophysical evaluations of ß-fused uracil-porphyrin derivatives”
Carvalho, C. M. B. ; Fujita, M. A. ; Brocksom, T. J. ; de Oliveira, K. T. .
Tetrahedron. 2013, 69, 9986-9993.
DOI: 10.1016/j.tet.2013.09.069
Abstract
New β-fused uracil-porphyrin conjugates were synthesized by the tetramerization of uracil-pyrroles under acidic conditions. Two different synthetic approaches were systematically studied in order to evaluate their efficiency, as well as the possibility to obtain a single regioisomer. Metallation effects were studied for aggregation in solution, and preliminary photophysical experiments were also performed in order to evaluate the potential of these new compounds.
Publicação 27
“Oxidative Potential of Some Endophytic Fungi Using 1-Indanone as a Substrate”
Fill, T. P. ; da Silva, J. V. ; de Oliveira, K. T. ; da Silva, B. S. ; Rodrigues Filho, E..
J Microbiol. Biotechn. 2012, 22, 832-837.
Abstract
The oxidative potential of the fungus Penicillium brasilianum, a strain isolated as an endophyte from a Meliaceae plant (Melia azedarach), was investigated using 1-indanone as a substrate to track the production of monooxygenases. The fungus produced the dihydrocoumarin from 1-indanone with the classical Baeyer-Villiger reaction regiochemistry, and (-)-(R)-3-hydroxy-1-indanone with 78% ee. Minor compounds resulting from lipase and SAM activities were also detected. The biotransformation procedures were also applied to a collection of Penicillium and Aspergillus fungi obtained from M. azedarach and Murraya paniculata. The results showed that Baeyer-Villiger were mostly active in fungi isolated from M. azedarach. Almost all of the fungi tested produced 3-hydroxy-1-indanone.
Publicação 26
“Real-time mechanistic monitoring of an acetal hydrolysis using ultrafast 2D NMR”
Queiroz J. L. H. K. ; Giraudeau, P ; Santos, F. A. B. ; de Oliveira, K. T. ; Ferreira, A. G. .
Magn. Reson. Chem. 2012, 50, 496-501.
Abstract
Ultrafast (UF) 2D NMR makes it possible to obtain a 2D NMR spectrum in less than a second. Here, UF-HSQC experiments are used for the real-time mechanistic study of an acetal hydrolysis at ¹³C natural abundance, and it is possible to characterize the presence of the hemiacetal, an intermediate with a well-known short lifetime. The assignments are confirmed and rationalized by quantum calculations of ¹H and ¹³C NMR chemical shifts and natural bonding orbital analysis. Copyright © 2012 John Wiley & Sons, Ltd.
Publicação 25
“Linker for Activation of T-cell Family Member2 (LAT2) a Lipid Raft Adaptor Protein for AKT Signaling, Is an Early Mediator of Alkylphospholipid Anti-leukemic Activity”
Thome, C. H. ; dos Santos, G. A. ; Ferreira, G. A. ; Scheucher, P. S. ; Izumi, C. ; Leopoldino, A. M. ; Simao, A. M. ; Ciancaglini, P. ; Oliveira, K. T. ; Chin, A. ; Hanash, S. M. ; Falcao, R. P. ; Rego, E. M. ; Greene, L. J. ; Faca, V. M. .
Mol. Cell. Proteomics. 2012, 11, 1898-1912.
Abstract
Lipid rafts are highly ordered membrane domains rich in cholesterol and sphingolipids that provide a scaffold for signal transduction proteins; altered raft structure has also been implicated in cancer progression. We have shown that 25 μM 10-(octyloxy) decyl-2-(trimethylammonium) ethyl phosphate (ODPC), an alkylphospholipid, targets high cholesterol domains in model membranes and induces apoptosis in leukemia cells but spares normal hematopoietic and epithelial cells under the same conditions. We performed a quantitative (SILAC) proteomic screening of ODPC targets in a lipid-raft-enriched fraction of leukemic cells to identify early events prior to the initiation of apoptosis. Six proteins, three with demonstrated palmitoylation sites, were reduced in abundance. One, the linker for activation of T-cell family member 2 (LAT2), is an adaptor protein associated with lipid rafts in its palmitoylated form and is specifically expressed in B lymphocytes and myeloid cells. Interestingly, LAT2 is not expressed in K562, a cell line more resistant to ODPC-induced apoptosis. There was an early loss of LAT2 in the lipid-raft-enriched fraction of NB4 cells within 3 h following treatment with 25 μM ODPC. Subsequent degradation of LAT2 by proteasomes was observed. Twenty-five μM ODPC inhibited AKT activation via myeloid growth factors, and LAT2 knockdown in NB4 cells by shRNA reproduced this effect. LAT2 knockdown in NB4 cells also decreased cell proliferation and increased cell sensitivity to ODPC (7.5×), perifosine (3×), and arsenic trioxide (8.5×). Taken together, these data indicate that LAT2 is an early mediator of the anti-leukemic activity of alkylphospholipids and arsenic trioxide. Thus, LAT2 may be used as a target for the design of drugs for cancer therapy.
Publicação 24
“New Columnar Zn-Phthalocyanine Designed for Electronic Applications”
Bechtold, I. H. ; Eccher, J. ; Faria, G. C. ; Gallardo, H. ; Molin, F.; Gobo, N. R. S. ; de Oliveira, K. T. ; Von S., H. .
The Journal of Physical Chemistry. B (1997 : Online) 2012, 116, 13554-13560.
Abstract
Columnar liquid crystals are composed of disk-shaped aromatic molecules surrounded by flexible side chains, where molecules self-assemble in columns and thereby form large surface-oriented domains. These systems are known for their good charge and exciton transport along the columns, with mobilities approaching those of aromatic single crystals. Such semiconducting materials are promising for devices applications, since the output efficiency can be tuned by properly aligning columns. In the work presented here, the synthesis and characterization of a new Zn-phthalocyanine (ZnPc) is described which exhibits remarkable properties, such as hexagonal columnar order, achieved by cooling down from the isotropic phase to room temperature. Such order was confirmed by optical microscopy and X-ray diffraction experiments. Diodes were constructed using spin-coated films, and the conductive properties were investigated by current versus voltage analysis, where mobilities of 10–3 and 10–2 cm2/(V s) were obtained for the nonannealed and annealed films, respectively.
Publicação 23
“Selective photoinactivation of C. albicans and C. dubliniensis with hypericin”
Bernal, C. ; Rodrigues, J. A. O. ; Guimarães, A. P. P. ; Ribeiro, A. O. ; de Oliveira, K, T. ; Imasato, H. ; Perussi, J. R. .
Laser. Phys. 2011, 21, 245-249.
Abstract
The genus Candida includes different species that have the potential to invade and colonize the human body and C. albicans is the most common cause of skin, nail and mucous infections. The increasing resistance against antifungal drugs has renewed the search for new treatment procedures and antimicrobial photodynamic inactivation (PDI) is a propitious candidate. Hypericin (HY) has several wanted properties to be used as a photosensitizer in this technique including a high quantum yield of singlet oxygen generation, a high extinction coefficient near 600 nm, and a relatively low dark toxicity. Although the phototoxicity of HY on several tumor cells has been reported, the data concerning its photoactivity on microorganisms are scarce. The aim of this study was to obtain the experimental parameters to achieve an acceptable selective hypericinphotoinactivation of two species of Candida comparing with fibroblasts and epithelial cells which are the constituents of some potential host tissues, such mucosas, skin and cavities. Microorganisms and cells were incubated with the same HY concentrations and short incubation time followed by irradiation with equal dose of light. The best conditions to kill just Candida were very low HY concentration (0.1–0.4 μg ml−1) incubated by 10 min and irradiated with LED 590 nm with 6 J cm−2.
Publicação 22
“New porphyrins tailored as biodiesel fluorescent markers”
Figueira, A. C. B. ; de Oliveira, K. T. ; Serra, O. A. .
Dyes. Pigments. 2011, 383-388.
Doi 10.1016/j.dyepig.2011.05.020
Abstract
This work reports the synthesis, characterization, and evaluation of new porphyrins tailored to become biodiesel fluorescent markers. The compounds were obtained by the synthetic modification of the commercially available porphyrin 5,10,15,20-meso-tetrakis(pentafluorophenyl)porphyrin (TPPF20) using ethanol and hexadecan-1-ol (cetylic alcohol) as nucleophilic reagents.
The stability of the marked biodiesel fuel solutions was investigated every 15 days for a total period of 3 months, and under different storage temperature and light exposure condition, simulating the conventional stock conditions. The influence of the different substituents of the porphyrins on the fluorescence properties of the biodiesel fuel markers was also assessed.
The resulting porphyrins were highly soluble in biodiesel fuel and displayed strong fluorescence characterized by two strong emission bands. The fluorescent markers did not affect the biodiesel physical properties and were stable in storage conditions for at least 3 months at a concentration of 4 ppm.
The best storage condition was found to be absence of light and 6 °C; the limit of detection by photoluminescence technique had magnitude of 10−13 mol L−1.
The synthesized porphyrins were characterized by nuclear magnetic resonance (1H-NMR and 19F-NMR), mass spectrometry (HRMS), ultraviolet visible absorption spectroscopy, and photoluminescence spectroscopy.
Publicação 21
“Tandem reduction + cyclization of ortho-substituted cinnamic esters”
Sass, D. C. ; de Lucca, E. C. ; da Silva B., J. ; de Oliveira, K. T. ; Constantino, M. G. .
Tetrahedron. Lett. 2011, 52, 5371-5374.
Doi 10.1016/j.tetlet.2011.08.039
Abstract
Conjugate reduction of ortho-substituted cinnamic esters by Stryker’s reagent to form copper enolates, followed by intramolecular aldol-type cyclization, successfully generated indane and tetralin rings in one pot efficiently. This tandem reaction is generally diastereoselective and provides good yields.
Publicação 20
“Chlorin Photosensitizers Sterically Designed To Prevent Self-Aggregation”
Uchoa, A. F. ; de Oliveira, K. T. ; Baptista, M. S. ; Bortoluzzi, A. J. ; Iamamoto, Y. ; Serra, O. A,J Org. Chem. 2011, 76, 8824-8832.
Abstract
The synthesis and photophysical evaluation of new chlorin derivatives are described. The Diels–Alder reaction between protoporphyrin IX dimethyl ester and substituted maleimides furnishes endo-adducts that completely prevent the self-aggregation of the chlorins. Fluorescence, resonant light scattering (RLS) and 1H NMR experiments, as well as X-ray crystallographic have demonstrated that the configurational arrangement of the synthesized chlorins prevent π-stacking interactions between macrocycles, thus indicating that it is a nonaggregating photosensitizer with high singlet oxygen (ΦΔ) and fluorescence (Φf) quantum yields. Our results show that this type of synthetic strategy may provide the lead to a new generation of PDT photosensitizers.
Publicação 19
“Revisiting the stability of endo/exo Diels-Alder adducts between cyclopentadiene and 1,4-benzoquinone”
Tormena, C. F. ; Lacerda Jr., Valdemar ; de Oliveira, K.T.,J Brazil Chem Soc. 2010, 21, 112-118.
Doi 10.1590/S0103-50532010000100017
Abstract
In this work it is presented a detailed theoretical analysis of the relative stability of endo/exo Diels-Alder adducts formed by the reaction between cyclopentadiene (1) and 1,4-benzoquinone (2). The intrinsic reaction coordinate (IRC) showed the existence of only one transition state for the reaction studied, for both endo 3 and exo 4adducts. The energies of both adducts were obtained at high level of theory (CBS-Q) confirming that the endoadduct is more stable than exo, which is in the opposite way to the observed in reactions that usually follow Alder’s rule. An electronic structure analysis was performed through NBO methodology, indicating that the attractive delocalization interaction predominates over the steric repulsive interaction in the endo adducts. In summary, for the studied cycloaddition reaction the endo adduct is the thermodynamic and kinetic product, which can be also confirmed by experimental data mentioned in this work.
Publicação 18
“Interaction of 10-(octyloxy) decyl-2-(trimethylammonium) ethyl phosphate with mimetic membranes and cytotoxic effect on leukemic cells”
dos Santos, G.A. ; Thomé, C.H. ; Ferreira, G.A. ; Yoneda, J.S. ; Nobre, T.M. ; Daghastanli, K.R.P. ; Scheucher, P.S. ; Gimenes-Teixeira, H.L. ; Constantino, M.G. ; de Oliveira, K.T. ; Faca, V. M. ; Falcao, R. P. ; Greene, J. L. ; Ciancaglini, P. BBA-Biomembranes. 2010, 1714-1723.
Doi 10.1016/j.bbamem.2010.05.013
Abstract
10-(Octyloxy) decyl-2-(trimethylammonium) ethyl phosphate (ODPC) is an alkylphospholipid that can interact with cell membranes because of its amphiphilic character. We describe here the interaction of ODPC with liposomes and its toxicity to leukemic cells with an ED-50 of 5.4, 5.6 and 2.9 μM for 72 h of treatment for inhibition of proliferation of NB4, U937 and K562 cell lines, respectively, and lack of toxicity to normal hematopoietic progenitor cells at concentrations up to 25 μM. The ED-50 for the non-malignant HEK-293 and primary human umbilical vein endothelial cells (HUVEC) was 63.4 and 60.7 μM, respectively. The critical micellar concentration (CMC) of ODPC was 200 μM. Dynamic light scattering indicated that dipalmitoylphosphatidylcholine (DPPC) liposome size was affected only above the CMC of ODPC. Differential calorimetric scanning (DCS) of liposomes indicated a critical transition temperature (Tc) of 41.5 °C and an enthalpy (∆H) variation of 7.3 kcal mol−1. The presence of 25 μM ODPC decreased Tc and ∆H to 39.3 °C and 4.7 kcal mol−1, respectively. ODPC at 250 μM destabilized the liposomes (36.3 °C, 0.46 kcal mol−1). Kinetics of 5(6)-carboxyfluorescein (CF) leakage from different liposome systems indicated that the rate and extent of CF release depended on liposome composition and ODPC concentration and that above the CMC it was instantaneous. Overall, the data indicate that ODPC acts on in vitro membrane systems and leukemia cell lines at concentrations below its CMC, suggesting that it does not act as a detergent and that this effect is dependent on membrane composition.
Publicação 17
“Photoluminescence studies in rare earth ions coordinated by a carbazolic derivative”
Martins, R. F. ; Neri, C. . ; Sousa Filho, P. C. ; Serra, O. A. ; de Oliveira, K.T. QuimNova, 2010, 33, 2118-2123.
Doi 10.1590/S0100-40422010001000022
Abstract
[RE(czb)3(H2O)2] complexes (where RE = Eu3+, Tb3+, Gd3+; and czb = 4-(9H-carbazol-9-yl)benzoato) have been synthesized and characterized. The Gd3+ complex was used to determine the triplet state energy of the czb ligand. Photoluminescence measurements of the complexes have been carried out under UV excitation. The Tb3+complex exhibited a strong green luminescence indicating an efficient antenna effect, whereas the Eu3+ complex showed low red luminescence and the Gd3+ complex a blue-green luminescence from the ligand. The luminescence lifetimes and quantum yields have also been measured for the evaluation of the spectroscopic behavior of the complexes.
Publicação 16
O Prêmio Nobel de Química em 2010: União direta de carbonos sp2 e sp
Brocksom, T. J. ; Alves, L. C ; WULF, G. D. ; Desiderá, A. L. ; de Oliveira, K.T. . O Prêmio Nobel de Química em 2010: União direta de carbonos sp2 e sp. Quím Nova Esc , v. 32, p. 233-239, 2010.
Publicação 15
“Amphiphilic cerium(III) ß-diketonate as a catalyst for reducing diesel/biodiesel soot emissions”
de Sousa Filho, P.. C. ; Gomes, L. F. ; de Oliveira, K. T. ; Neri, C. R. ; Serra, O. A. .
Appl. Catal. A-Gen 2009, 360, 210-217.
Doi 10.1016/j.apcata.2009.03.024
Abstract
This work reports on the synthesis, characterization and applications of the new cerium(III) β-diketonate Ce(hdacac)3(Hhdacac)3·2H2O (where hdacac and Hhdacac denote, respectively, the hexadecylpentane-2,4-dionate and hexadecylpentane-2,4-dione ligands) as catalyst for the reduction of automotive emissions. Due to its amphiphilic character, this complex can be solubilized in non-polar fuels, thus generating cerium(IV) oxide particles, which efficiently catalyze the oxidation of diesel/biodiesel soot.
The synthesized complex was characterized by microanalysis (C, H), thermal analysis, and infrared spectroscopy. Scanning electron microscopy, X-ray diffractometry, and specific surface area measurements attested that the complex can act as a soluble precursor of homogeneous CeO2 spherical nanoparticles. The efficiency of this compound as catalyst for the reduction of soot emission was evaluated through static studies (comprising carbon black oxidation), which confirmed that increasing concentrations of the complex result in lower carbon black oxidation temperatures and lower activation Gibbs free energies. Dynamic studies, which embraced the combustion of diesel/biodiesel blends containing different amounts of the solubilized complex in a stationary motor, allowed a comparative evaluation of the soot emission through diffuse reflectance spectroscopy. These analyses provided very emphatic evidences of the efficiency of this new cerium complex for the control of soot emission in diesel/biodiesel motors.
Publicação 14
“Extraction and purification of chlorophyll A isolated from Spirulina maxima: an experiment for the chemistry courses”
Maestrin, A. P. J. ; Neri, C. R. ; de Oliveira, K. T. ; Serra, O. A. ; Iamamoto, Y. .
Quim Nova, 2009, 32, 1670-1672.
Doi 10.1590/S0100-40422009000600054
Abstract
This work describes a simple and economical experiment for the extraction and purification of chlorophyll a fromSpirulina maxima. Extraction and purification of natural compounds can be considered one of the most illustrative experiments that can be performed in Organic Chemistry courses. Particularly, the chromatography of dyes and pigments allows students to have a better comprehension of the chromatography separations. These compounds represent an important class of organic pigments applied in pharmaceutical, cosmetic, detergent compositions, and various other fields and can be extracted from plants and algae. To extract, separate and purify chlorophyll afrom associated pigments such as xanthophylls, carotenes, and pheophytins, very costly processes are reported. The present approach is perfectly adequate for use in Chemistry experiments for undergraduate students.
Publicação 13
“Synthesis of Phthalocyanines-ALA Conjugates: Water-Soluble Compounds with Low Aggregation”
de Oliveira, K. T. ; de Assis, F. F. ; Ribeiro, A. O. ; Neri, C. R. ; Fernandes, A. U. ; Baptista, M. S. ; Lopes, N. P. ; Serra, O. A. ; Iamamoto, Y.
J Org. Chem. 2009, 74, 7962-7965.
Abstract
Syntheses of two water-soluble phthalocyanines (Pc) containing 5-aminolevulinic acid (ALA) linked to the core structure are described. These compounds were prepared by using original functionalizations, and they present remarkable structural and photophysical features, indicating that they could be applied to photodynamic therapy (PDT).
Publicação 12
“Aromaticity: historical evolution of the concept and quantitative criteria”
Caramori, G. F. ; de Oliveira, K. T. . Quim Nova, 2009, 32, 1871-1884.
Doi 10.1590/S0100-40422009000700034
Abstract
In this paper the evolution of the concept of aromaticity is discussed. It considers not only historical aspects of the aromaticity concept but also the different criteria (theoretical and experimental) that have appeared to explain the properties of the aromatic compounds. The topics range from the isolation of benzene by Faraday (1825) until the modern criteria based on geometries, magnetic properties, resonance energy (RE), aromatic stabilization energy (ASE), topological analyses, and others. A chronological separation of issues concerning aromaticity was made, splitting the definitions before and after the appearance of the quantum chemistry. This work reviews the concept of aromaticity.