Centro de Ciências Exatas e Tecnológicas
URI permanente desta comunidadehttps://locus.ufv.br/handle/123456789/9791
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18 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 de 2-( 2- piridil) quinolinas promovida por micro- ondas e suas atividades antifúngicas(Química Nova, 2017-09) Borel, Carmindo R.; Barbosa, Luiz C. A.; Maltha, Célia R. A.; Fernandes, Sergio A.; Santos, Larissa B.; Takahashi, Jacqueline A.In this work a series of 2-(2- pyridyl)quinolines were prepared via a Povarov reaction between anilines, 2-pyridinocarbadehyde and ethyl vinyl ether under microwaves heating conditions. The optimized conditions herein reported allowed the preparation of several pyridylquinolines in yields in the range of 30-83%, some of them not previously accessible by this multicomponent process. The reported methodology has advantage over previous report due to its larger scope and short reaction time (2 hours). All quinolines obtained were assayed against five species of clinically important yeasts Candida sp and against Cryptococcus neoformans. Some of them possessed a broad spectrum of action including 2-(2-pyridyl)quinoline (20) and 6,8-dimethoxy-2-(pyridin-2-yl)quinolone (22) that were highly effective in inhibiting Candida species (IC50 < 1.95 µg/mL against C. tropicalis and C. krusei). Some compounds were more potent than commercial drugs Nistatin and Miconazole.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 Hederagenin amide derivatives as potential antiproliferative agents(European Journal of Medicinal Chemistry, 2019-04-15) Barbosa, Luiz C. A.; Demuner, Antonio J.; Rodríguez-Hernández, Diego; Martins, João Paulo Ataide; Csuk, René; Fischer (nee Heller), LucieIn this study, a series of C-28 amides derivatives of hederagenin with or without the presence of an acetyl group at positions 3 and 23 in ring A, were synthetized aiming to develop potent cytotoxic agents. Their structures were confirmed by MS, IR, 1H NMR and 13C NMR spectroscopic analyses and their cytotoxic activities were screened in SRB assays using a panel of six human cancer cell lines. The majority of the amide derivatives were cytotoxic for a variety of human tumor cell lines. In general, the hydroxylated derivatives (1a-1d; EC50 in the range 1.2–22.5 μM) were less active than the acetylated derivatives (2a-2n; EC50 in the range 0.4–9.0 μM). Hydroxylated derivative bearing pyrrolidinyl substituent 1c, was the most active for HT29 human line cells (EC50 = 1.2 μM), however their acetylated derivative 2c was the most potent and selective against A2780, FaDu, SW1736 cells, showing EC50 values between 0.4 and 1.7 μM and SI between 5.6 and 24. Staining experiments combined with fluorescence microscopy indicate that the cell membrane became permeable, and finally a process of secondary necrosis was observed. In addition, the docking results showed that acetylated compounds display more affinity to HER2 than to USP7, indicating that HER2 is a most probable receptor, both proteins found in tumor cell line A2780.Item Synthesis and evaluation of cadiolide analogues as inhibitors of bacterial biofilm formation(Medicinal Chemistry Research, 2018-12) Mairink, Simone Z.; Barbosa, Luiz C. A.; Boukouvalas, John; Pedroso, Silvia H. S. P.; Magalhães, Paula P.; Farias, Luiz M.; Santos, Simone G.Bacterial biofilm infections pose a major clinical challenge due to the ability of biofilms to resist high levels of conventional antibiotics. In the present study, we describe the synthesis and biofilm inhibiting properties of nine new butenolides related to the cadiolide family of marine antibiotics. Eight new cadiolide analogues were synthesized using oxazole−ynone Diels−Alder cycloaddition/cycloreversion as the key step. Their effects on bacterial growth and biofilm formation were investigated against a range of Gram-positive and Gram-negative bacteria, namely Staphylococcus aureus, Enterococcus faecalis, Acinetobacter baumannii, Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. The cadiolide analogues strongly inhibited biofilm formation of the two Gram-positive bacteria (S. aureus and E. faecalis) at concentrations as low as 0.3 μg mL−1 and 0.5 μg mL−1, respectively. The identification of synthetic cadiolides with potent biofilm-inhibiting capabilities opens a new avenue for therapeutic interventions and highlights the potential of this class of compounds for antimicrobial drug development.