Navegando por Autor "Demuner, Antônio J."
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Item An optimized and validated 1H NMR method for the quantification of α-pinene in essentials oils(Talanta, 2015-10-31) Cerceau, Cristiane I.; Barbosa, Luiz C.A.; Filomeno, Claudinei A.; Alvarenga, Elson S.; Demuner, Antônio J.; Fidencio, Paulo H.The authenticity and composition of commercial essential oils requires strict quality control. Due to the importance of α-pinene containing essential oils, a rapid and efficient method for quantification of this terpene in oils of eucalyptus, pink pepper and turpentine using 1H NMR was developed and validated. All evaluated parameters (selectivity, linearity, accuracy/precision, repeatability, robustness, stability of analyte and internal standard in solutions) showed satisfactory results. The limit of detection (LOD) and limit of quantification (LOQ) were 0.1 and 2.5 mg respectively. These values indicated that α-pinene was detected in 35 mg samples containing at least 0.3% of this compound. In addition, a minimum of 8% of α-pinene in the sample was required for quantification. Furthermore, the standard deviations found in the 1H NMR methodology were less than 1% and were lower than those obtained by gas chromatographic analysis. Statistical tests have shown that the results obtained by 1H NMR methodology are similar to those obtained by GC-FID technique using external and internal standardization and normalization within 95% confidence. R&R values lower than 10% have shown that all the methods are appropriate and the 1H NMR method is suitable for quantification of α-pinene in samples of essential oils since this method possessed the smallest R&R (1.81) value.Item Phytotoxic constituents from Nimbya alternantherae(Biochemical Systematics and Ecology, 2006-11) Demuner, Antônio J.; Barbosa, Luiz C. A.; Veiga, Thiago A. M.; Barreto, Robert W.; King-Diaz, Beatriz; Lotina-Hennsen, BlasA phytotoxic compound identified as 6-(3,3-dimethylallyloxy)-4-methoxy-5-methylphthalide (1), was isolated from the phytopathogenic fungus Nimbya alternantherae, cultivated on solid media. Catalytic hydrogenation of 1 resulted in the quantitative formation of second compound (2). Both compounds (1, 2) act by inhibiting the ATP synthesis in spinach thylakoids. A detailed investigation on the mechanism of action indicates that compound 1 acts as a Hill reaction inhibitor and uncoupler of photosynthesis.Item Síntese de novas fitotoxinas derivadas do 8- oxabiciclo[ 3. 2. 1] oct- 6- en- 3- ona(Química Nova, 2005-05) Barbosa, Luiz C. A.; Maltha, Célia R. A.; Demuner, Antônio J.; Ganen, Flávia R.; Silva, Antônio A. daThe [4+3] cycloaddition was utilized in order to prepare 8-oxabicyclo[3.2.1]oct-6-en-3-one (1) derivatives. The correspondent acetonide 6 was converted into several alcohols (11-16). Addition of aryllithium reagents to 6 resulted in 3-(2-fluorophenyl)-6,7-exo-isopropylidenedioxy -8-oxabicyclo[3.2.1]octan-3a-ol (11, 72%) and 3-(2,4-dimethoxyphenyl)-6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan -3a-ol (16, 20%). The 3-butyl-6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3 a-ol (15, 56%) was obtained through a Grignard reaction. Reduction of 6 resulted in 6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3 b-ol (7, 62%) and 6,7-exo-isopropylidenedioxy-8-oxabicyclo[3.2.1]octan-3 a-ol (8, 20%). The alcohols were treated with thionyl chloride in pyridine, and the corresponding alkenes were obtained with 31-80% yield. The effect of these compounds on the development of radicle and aerial parts of Sorghum bicolor was evaluated.Item Síntese e atividade fitotóxica de 2- fenil- 6, 7- exo- isopropilidenodioxi- 8- oxabiciclo [ 3. 2. 1] oct- 2- eno(Química Nova, 2000-07) Barbosa, Luiz Cláudio A.; Demuner, Antônio J.; Costa, Adilson V.; Borges, Eduardo E. L.; Mann, JohnSynthesis and phytotoxic activity of 2-Phenyl-6,7-exo isopropylidenedioxi-8-oxabicyclo[3.2.1]oct-2-ene.The [3+4] cycloaddition between furan and the oxyallyl cation generated from 1-bromo-1-phenylpropan-2-one (4), resulted in the formation of 2-phenyl-8-oxabicyclo[3.2.1]oct-6-en-3-one (5) in 30% yield. This compound was further converted into 2-phenyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]oct-2-ene (13) in 35.4% yield. The selective effect of compound (13) and its isomer 3-phenyl-6,7-exo-isopropylidenedioxi-8-oxabicyclo[3.2.1]oct -2-ene (1a) on the radicle growth of Sorghum bicolor L. (sorghum) and Cucumis sativus L. (cucumber) were evaluated. For both plants, compound 13 showed to be more potent than its isomer 1a.Item Síntese e avaliação da atividade antimicrobiana de furanonas halogenadas e de compostos análogos aos nostoclídeos(Química Nova, 2010) Barbosa, Luiz C. A.; Maltha, Célia R. A.; Demuner, Antônio J.; Pinheiro, Patrícia F.; Varejão, Jodieh O. S.; Montanari, Ricardo M.; Andrade, Nélio J.Considering the broad spectrum of biological activity of gamma-butyrolactone derivatives, we presented the synthesis of 3,4-dihalo-5-arylidenefuran-2(5H)-ones (17-21) and analogues (24-28) of the natural product nostoclide (7,8). Furanones 17-21 were synthesized from the condensation of aromatic aldehydes with lactones 14 and 15, that were obtained from mucobromic and mucochloric acids. Lactone 15 was converted into the intermediate 23 in 36% overall yield. Compound 23 was then transformed into the nostoclide analogues 24-28. Some of the compounds prepared showed antimicrobial activities against Escherichia coli, Staphylococcus aureus and Bacillus cereus comparable to commercial antibiotics.Item Síntese e avaliação da atividade fitotóxica de derivados da α-Santonina(Química Nova, 2009) Alvarenga, Elson S.; Barbosa, Luiz C. A.; Saliba, William A.; Arantes, Francisco F. P.; Demuner, Antônio J.; Silva, Antônio A.Mixtures of α-Santonin and various solvents were irradiated by either high or low pressure mercury lamps. The photochemical reactions afforded lumisantonin (11) (76% in acetonitrile), (3S,3aS,9bS)-3,6,6-trimethyl-3,3a,4,5-tetrahydronafto[1,2-b]furan-2,7(6H,9bH)dione (12) (100% in acetonitrile), 10α-acetoxy-3-oxo-1,7αH,6,11βH-guaia-4-en-6,12-olide (8) (26% in acetic acid), 10α-hydroxy-3-oxo-1,7αH,6,11βH-guaia-4-en-6,12-olide (10) (32%) and (E)-3-((3S,3aS,7aS)-3-methyl-2-oxo-6-(propan-2-ylidene)hexahydrobenzofuran-7-(7aH)-ylidene)propanoic acid (9) (44%) (in water/ acetic acid 1:1, v/v). Lactone 12 was also prepared by irradiation of lumisantonin in diethyl ether. Lactones 8 and 10 were converted, respectively, into the 10α-acetoxy-3β-hydroxy-1,7αH,6,11βH-guaia-4-en-6,12-olide (13) (87%) and 3β,10α-dihydroxy-1,7αH,6,11βH-guaia-4-en-6,12-olide (14) (75%) by sodium borohydride reduction. The effects of the compounds on the development of radicle of Sorghum bicolor and Cucumis sativus were evaluated.Item Synthesis of novel α-santonin derivatives as potential cytotoxic agents(European Journal of Medicinal Chemistry, 2010-10-23) Arantes, Francisco F.P.; Barbosa, Luiz C.A.; Maltha, Célia R.A.; Demuner, Antônio J.; Costa, PatriciaMarçal da; Ferreira, José R.O.; Costa-Lotufo, Letícia V.; Moraes, Manoel O.; Pessoa, CláudiaTen novel a -santonin derivatives have been synthesized as cytotoxic agents. The in vitro antitumor activity of these compounds has been evaluated against cancer cells lines. Structure-activity relationships indicate that a -methylene- g -lactone and endoperoxide functionalities play important roles in conferring cytotoxicity. The compounds 2e4, possessing the a -methylene- g -lactone group showed IC 50 values between 5.70 and 16.40 m M. Mixture of isomers 5 and 6, with the a -methylene- g -lactone and endoperoxide functionalities, displayed the greatest activity, with IC 50 values between 1.45 and 4.35 m M. The biological assays conducted with normal cells revealed that the compounds 2, 5 and 6 are selective against cancer cells lines tested. Bioactive lactones described herein and in our previous report did not cause disruption of the cell membrane in mouse erythrocytes.Item Synthesis, molecular properties and DFT studies of new phosphoramidates as potential urease inhibitors(Medicinal Chemistry Research, 2014-06-28) Oliveira, Fabricio M.; Barbosa, Luiz C. A.; Demuner, Antônio J.; Maltha, Célia R. A.; Pereira, Silvana R.; Horta, Lı́via P.; Modolo, Luzia V.In this work, new phosphoramidates were prepared and screened for their putative urease inhibitory activity. The importance of this class of compounds is related to the wide range of biological activities which they exhibit. Consequently, higher activity shown by phosphoramidates 3a, 4b, 5a, 5b, 5c, and 9a suggests that they could serve as lead substances for the development of novel synthetic compounds with enhanced inhibitory ureolitic activity. Their predicted ADMET properties are also in accordance with the general requirements for drug-like compounds. Structure–activity relationship analyses suggest that the presence of cyclohexylamine group is an important structural feature associated with enhanced activities. DFT calculations were performed to obtain the energy values of HOMO and LUMO, and dipole moment.