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Search Results: 1 - 10 of 349389 matches for " Lourivaldo S.;Santos "
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Quantum confinement in PbI2 nanodisks prepared with cucurbit[7]uril
Santos, Erick M. S. dos;Pereira, Lourivaldo S.;Demets, Grégoire J.-F.;
Journal of the Brazilian Chemical Society , 2011, DOI: 10.1590/S0103-50532011000800024
Abstract: this work presents an alternative route for the preparation of heavy metal iodide nanoparticles, particularly lead iodide nanodisks (ca. 50-340 × 7 ?, diameter × thickness), using the macrocycle cucurbit[7]uril as a synthetic template and stabilizing agent. these nanoparticles exhibit an optical-gap blue shift consistent with their small size and 1d quantum confinement. their thicknesses are compatible with an exfoliated single layer of lead iodide, indicating that cucurbit[7]uril, preventing the stacking and formation of tactoids, thus limiting nanoparticles growth in the z direction. the structure, morphology and properties of these disks were analyzed by x-ray powder diffractometry (xrd), uv-visible spectroscopy, atomic force microscopy (afm), scanning electron microscopy with analysis of energy dispersive x-ray fluorescence (sem-eds) and high resolution transmission electron microscopy (hrtem).
Structure-Activity Relationship of Compounds which are Anti-Schistosomiasis Active
Alves, Cláudio Nahum;Barroso, Lúcia Pereira;Santos, Lourivaldo S.;Jardim, Iselino Nogueira;
Journal of the Brazilian Chemical Society , 1998, DOI: 10.1590/S0103-50531998000600010
Abstract: the molecular orbital method am1 was employed to calculate a set of molecular descriptors for twenty synthetic neolignan derivatives with anti-schistosomiasis activity. the pattern recognition method (principal component analysis pca and cluster analysis ca and discriminant analysis methods) have been employed to obtain the relationship between the molecular descriptors and biological activity. the set of molecules was classified into two groups according to their degree of biological activity. these results allow us to rationally project new compounds, potential candidates for synthesis and biological evaluation.
Structure-Activity Relationship of Compounds which are Anti-Schistosomiasis Active
Alves Cláudio Nahum,Barroso Lúcia Pereira,Santos Lourivaldo S.,Jardim Iselino Nogueira
Journal of the Brazilian Chemical Society , 1998,
Abstract: The molecular orbital method AM1 was employed to calculate a set of molecular descriptors for twenty synthetic neolignan derivatives with anti-schistosomiasis activity. The pattern recognition method (principal component analysis PCA and cluster analysis CA and discriminant analysis methods) have been employed to obtain the relationship between the molecular descriptors and biological activity. The set of molecules was classified into two groups according to their degree of biological activity. These results allow us to rationally project new compounds, potential candidates for synthesis and biological evaluation.
Biologically active polyketides produced by Penicillium janthinellum isolated as an endophytic fungus from fruits of Melia azedarach
Marinho, Andrey M. do Rosário;Rodrigues-Filho, Edson;Moitinho, Maria da Luz R.;Santos, Lourivaldo S.;
Journal of the Brazilian Chemical Society , 2005, DOI: 10.1590/S0103-50532005000200023
Abstract: penicillium janthinellum, isolated as an endophytic fungus from fruits of melia azedarach, was cultivated over 20 days on ground and autoclaved white corn, where the known polyketides citrinin, emodin, 1,6,8-trihydroxy-3-hydroxymethylanthraquinone, and a new modified anthraquinone, named janthinone, were produced and isolated by classical chromatographic procedures and identified by ms and 1d and 2d nmr spectroscopic data. the antibacterial properties of these polyketides were investigated. citrinin inhibited 100% of leishmania growth after 48h at a concentration of 40 mg ml-1.
C25 steroid epimers produced by Penicillium janthinellum, a fungus isolated from fruits Melia azedarach
Marinho, Andrey M. do Rosário;Rodrigues-Filho, Edson;Ferreira, Ant?nio Gilberto;Santos, Lourivaldo S.;
Journal of the Brazilian Chemical Society , 2005, DOI: 10.1590/S0103-50532005000800006
Abstract: a plant-derived fungus, penicillium janthinellum, obtained from melia azedarach, produced ergosterol and ergosterol 5a,8a-peroxide along with a mixture of rare c25 steroid epimers. the c25 steroids, named neocyclocitrinols, shows exactly the same tetracyclic ring system present in cyclocitrinol, which was isolated from a sponge-derived penicillium citrinum, with the same bicyclo [4:4:1] skeleton at a/b rings, but showing different side chains. the p. janthinellum was cultivated over white corn and the three steroids were isolated by several silica gel based chromatographic procedures and identified by extensive nmr methods, mainly 1h - 13c correlations and 1h - 1h cosy and tocsy. the biosynthetic origin of the cyclocitrinols is also discussed.
Dihydroflavonols from the leaves of Derris urucu (Leguminosae): structural elucidation and DPPH radical-scavenging activity
L?bo, Lívia T.;Silva, Geilson A. da;Ferreira, Malisson;Silva, Milton N. da;Santos, Alberdan S.;Arruda, Alberto C.;Guilhon, Giselle M. S. P.;Santos, Lourivaldo S.;Borges, Rosivaldo dos Santos;Arruda, Mara Silvia P.;
Journal of the Brazilian Chemical Society , 2009, DOI: 10.1590/S0103-50532009000600013
Abstract: derris urucu is an amazonian plant with insecticide and ichthyotoxic properties. studies with this species show the presence of flavonoids, mainly rotenoids, as well as stilbenes. the ethanol extract of the leaves of derris urucu (leguminosae) afforded three new dihydroflavonols named urucuol a (1), b (2) and c (3), and the dihydroflavonol isotirumalin (4). their structures were elucidated by extensive analysis of 1d and 2d nmr, uv and ir spectra and ms data and comparison with literature data. the isolated compounds (1-4) were evaluated for dpph? radical scavenging activity and showed a relatively lower antioxidant ability compared to the commercial antioxidant trans-resveratrol.
Stilbenes from Deguelia rufescens var. urucu (Ducke) A. M. G. Azevedo leaves: effects on seed germination and plant growth
Lobo, Lívia T.;Silva, Geilson A. da;Freitas, Manolo C. C. de;Souza Filho, Antonio Pedro S.;Silva, Milton N. da;Arruda, Alberto C.;Guilhon, Giselle M. S. P.;Santos, Lourivaldo S.;Santos, Alberdan S.;Arruda, Mara S. P.;
Journal of the Brazilian Chemical Society , 2010, DOI: 10.1590/S0103-50532010001000007
Abstract: the amazon biodiversity may provide plants whose chemical substances are capable of controlling weeds. in this study we report the isolation and identification of five stilbenes from the leaves of "timbó vermelho" (deguelia rufescens var. urucu): 4-methoxylonchocarpene (1); 3,5-dimethoxy-4′-hydroxy-3′-prenyl-trans-stilbene (2), lonchocarpene (3), 3,5-dimethoxy-4′-o-prenyl-trans-stilbene (4) and pterostilbene (5). compounds 2 and 4 are new natural products although 2 has been previously cited as synthesis product. potential allelopathic activity for 1, 2 and 4 was evaluated over seed germination and plant growth of mimosa pudica weed. the observed effects on seed germination did not vary significantly (p > 0.05) when the analysis of phytotoxicity was performed with the substances alone, the maximum inhibition did not exceed 20%. the most intense inhibitions on radicle and hypocotyl development were found for compound 4 (p < 0.05). when tested in pairs, showed antagonism for seed germination and synergism for radicle and hypocotyl development.
Antraquinonas e naftoquinonas do caule de um espécime de reflorestamento de Tectona grandi (Verbenaceae)
Moreira, Rafael Y.O.;Arruda, Mara S.P.;Arruda, Alberto C.;Santos, Lourivaldo S.;Müller, Adolfo H.;Guilhon, Giselle M.S.P.;Santos, Alberdan S.;Terezo, Evaristo;
Revista Brasileira de Farmacognosia , 2006, DOI: 10.1590/S0102-695X2006000300017
Abstract: the hexane extract of the bark of tectona grandis (verbenaceae) afforded two anthraquinones and two naphtoquinones. their caracterizations were obtained through nmr spectroscopic techniques. this is the first phytochemical study of the bark of tectona grandis reforestation specimen in brazil. the main interest in this work is proving the presence of tectoquinone in reforestation specimen.
Synthesis, X-ray crystal structure and theoretical calculations of antileishmanial neolignan analogues
Nascimento, Josenaide P. do;Santos, Lourivaldo S.;Santos, Regina Helena A.;Tozzo, érica;Ferreira, Janaina G.;Carmo, Maria Carolina L. do;Brasil, Davi S. B.;Alves, Cláudio N.;
Journal of the Brazilian Chemical Society , 2010, DOI: 10.1590/S0103-50532010001000006
Abstract: the synthesis and x-ray crystal diffraction structure of two analogues of neolignans, 2-(4-chlorophenyl)-1-phenylethanone (20) and 2-[(4-chlorophenyl)thio]-1-(3,4-dimethoxyphenyl)propan-1-one (12) is described. the compound 12 presents activity against intracellular leishmania donovani and leishmania amazonensis amastigotes that cause cutaneous and visceral leishmaniasis. in addition, the density functional theory (dft) with the b3lyp hybrid functional was employed to calculate a set of molecular descriptors for nineteen synthetic analogues of neolignans with antileishmanial activities. afterwards, the stepwise discriminant analysis was performed to investigate possible relationship between the molecular descriptors and biological activities. through this analysis the compounds were classified into two groups active and inactive according to their degree of biological activities, and the more important properties were charges on some key atoms, electronic affinity and clogp.
Biflavones and triterpenoids isolated from Ouratea castaneifolia (DC.) Engl., Ochnaceae
Nascimento, Luís Adriano S. do;Guilhon, Giselle M. S. P.;Arruda, Mara S. P.;Santos, Lourivaldo S.;Arruda, Alberto C.;Müller, Adolfo H.;Silva, Milton N. da;Rodrigues, Silvane T.;Carvalho, Mário G. de;
Revista Brasileira de Farmacognosia , 2009, DOI: 10.1590/S0102-695X2009000600004
Abstract: this paper presents the chemical investigation of the leaves and stems of ouratea castaneifolia (dc.) engl.. there are no chemical or pharmacological studies with this species. classic phytochemical investigation of the organic extracts together with high pressure liquid chromatography (hplc) procedures lead to the identification of seventeen metabolites: seven triterpenes (friedelin, 3β-friedelinol, α-amyrin, β-amyrin, lupeol, germanicol and taraxerol), four steroids (sitosterol, stigmasterol and the glycosides sitosteryl 3-o-β-d-glucopyranoside and stigmasteryl 3-o-β-d-glucopyranoside), one isoflavone (5,7,4'-trimethoxyisoflavone), one flavone (5,4'-dihydroxy-7,3',5'-trimethoxyflavone) and four biflavones (amenthoflavone, 7,7"-o-dimethylamenthoflavone, heveaflavone and tetramethylamenthoflavone). the structures of the compounds were established by the analysis of 1h, 13c nmr spectra including bidimensional techniques. the classes of the identified metabolites are in agreement with previous studies of the ouratea genus.
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