Centro de Ciências Exatas e Tecnológicas
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/9791
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9 resultados
Resultados da Pesquisa
Item Caracterização química do “pitch” em indústria de celulose e papel de Eucalyptus(Química Nova, 2006-05) Cruz, Mariluze P.; Barbosa, Luiz C. A.; Maltha, Célia R. A.; Gomide, José L.; Milanez, Augusto F.The chemical analysis of the acetone, chloroform, toluene and methanol extracts of a pitch sample was carried out by IR and GC-MS, leading to the identification of sixty nine compounds, including fatty acids, alcohols and hydrocarbons. Analysis of the acetone extractive of a eucalyptus wood used in Brazil for pulp production was also carried out, resulting in identification of fifty nine compounds, including mainly fatty acids, phenolic compounds, b-sitosterol and other steroids. This analysis showed that pitch formation had a contribution from wood extractives and other sources of contamination. The results obtained and the methodology applied can be used by the pulp industry to develop new methods of pitch control.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 Constituintes químicos de Melaleuca alternifolia (Myrtaceae)(Química Nova, 2004-07) Vieira, Tatiana R.; Barbosa, Luiz C. A.; Maltha, Célia R. A.; Paula, Vanderlúcia F.; Nascimento, Evandro A.he first chemical study of non-volatile constituents from the bark and stem of Melaleuca alternifolia (Myrtaceae) led to the isolation and identification of 3,3’-O- dimethylellagic acid (1) and five pentacyclic triterpenes: 2α,3β,23-trihydroxyolean-12-en-28-oic acid (arjunolic acid, 2), 3β- hydroxylup-20(29)-en-27,28-dioic acid (melaleucic acid, 3), betulinic acid (4), betuline (5), 3β-O-acetylurs-12-en-28-oic acid (6), a mixture of fatty acids and esters, and several hydrocarbons. For 2α,3β,23-trihydroxyolean-12-en-28-oic acid (2) and 3β-O- acetylurs-12-en-28-oic acid (6) a first detailed assignment of 1 H NMR is presented.Item Determinação da relação siringila/guaiacila da lignina em madeiras de eucalipto por pirólise acoplada à cromatografia gasosa e espectrometria de massas ( PI - CG/ EM)(Química Nova, 2008) Barbosa, Luiz C. A.; Maltha, Célia R. A.; Silva, Vanessa Lopes; Colodette, Jorge LuizThe use of analytical pyrolysis combined with gas chromatography/mass spectrometry (Py-GC/MS) to determine the syringyl/guaiacyl ratio (S/G) in lignins from Eucalyptus spp woods was investigated. Sample of E. grandis and "E. urograndis" wood, with and without extractives, were subjected to pyrolysis from 300 ºC to 600 ºC. The products that results from pyrolysis were identified by mass spectrometry and the S/G ratio was determined based on the areas of the peaks corresponding to the guaiacyl and syringyl derivatives. The best S/G estimation is achieved when pyrolysis is carried out at 550 ºC. Extractives and carbohydrate present in the woods do not interfere with the results.Item Atividade antiinflamatória de carboidrato produzido por fermentação aquosa de grãos de quefir(Química Nova, 2008) Moreira, Maria E. C.; Santos, Marcelo H.; Pereira, Ivan O.; Ferraz, Vany; Barbosa, Luiz C. A.; Schneedorf, José M.Kefir, a symbiont microorganism suspension, presents benefic effects to health. Some kefir grains were cultivated in brown sugar, allowing to isolate a substance named CSQ. This was evaluated on a biologic essay of mouse foot edema, presenting an inhibitory activity of 30+4 % against carrageenan after the stimulus. It was observed that a cultivation mean containing sucrose, and not the milky mean, lead to the production of different sugar polymeric chains of kefir. The results in vivo suggest that the CSQ exerted an anti-inflammatory activity.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 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 Antioxidant activity of Maytenus imbricata Mart., Celastraceae(Revista Brasileira de Farmacognosia, 2008-11-29) Barbosa, Luiz C. A.; Ribeiro, Sonia M. R.; Queiroz, José H.; Oliveira, Márcio L. R.; Silva, Grácia D. F.; Silva, Silvia R. S.; Duarte, Lucienir P.; Vieira Filho, Sidney A.The free radical scavenging activity (FRS) using 2,2-diphenyl-1-picrylhydrazyl (DPPH), the reducer power and the total phenolic concentration of extracts and compounds isolated from leaves, branches and roots of Maytenus imbricata Mart. (Celastraceae) were evaluated. Some extracts, a mixture of phenolic compounds (MPC) and epicatechin showed higher RP and FRS (DPPH) activities in comparison with the standard butylhydroxyanisole (BHA) and galic acid (GA) used in assays. The ethyl acetate extract from leaves showed higher total phenolic content and also higher RP and FRS (DPPH) than the other extracts. These facts indicate that there are some relations between phenolic concentration in the extract and the antioxidant activity and the reducer power. The solvent used in the extraction process influences the chemical composition of the extracts and consequently its antioxidant and reducer power activities.Item Influência da temperatura do ar de secagem sobre o teor e a composição química do óleo essencial de Lippia alba (Mill) N. E. Brown(Química Nova, 2006-06-14) Barbosa, Fabrizio da F.; Barbosa, Luiz C. A.; Melo, Evandro C.; Botelho, Fernando Mendes; Santos, Ricardo H. S.Leaves of Lippia alba were submitted to six different drying treatments, using air at ambient temperature and heated up to 80 °C. The essential oil was extracted by steam distillation and analyzed by GC-MS. For the dried leaves, the oil content was reduced by 12 to 17% when compared with the fresh plant (0.66%). The major oil component was citral, representing 76% for the fresh plant, and varying from 82 to 84% for the dried material. These results showed that L. alba can be submitted to a drying process of up to 80 ºC without degradation and/or loss of the major, [LC1] active component.