Artigos
URI permanente para esta coleçãohttps://locus.ufv.br/handle/123456789/11800
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Item New rubrolide analogues as inhibitors of photosynthesis light reactions(Journal of Photochemistry and Photobiology B:, 2015-03-01) Varejão, Jodieh O.S.; Barbosa, Luiz C.A.; Ramos, Gabriela Álvarez; Varejão, Eduardo V.V.; King-Díaz, Beatriz; Lotina-Hennsen, BlasNatural products called rubrolides have been investigated as a model for the development of new herbi- cides that act on the photosynthesis apparatus. This study comprises a comprehensive analysis of the photosynthesis inhibitory ability of 27 new structurally diverse rubrolide analogues. In general, the results revealed that the compounds exhibited efficient inhibition of the photosynthetic process, but in some cases low water solubility may be a limiting factor. To elucidate their mode of action, the effects of the compounds on PSII and PSI, as well as their partial reaction on chloroplasts and the chlorophyll a fluorescence transients were measured. Our results showed that some of the most active rubrolide ana- logues act as a Hill reaction inhibitors at the QB level by interacting with the D1 protein at the reducing side of PSII. All of the active analogues follow Tice’s rule of 5, which indicates that these compounds pre- sent physicochemical properties suitable for herbicides.Item Novel hederagenin–triazolyl derivatives as potential anti-cancer agents(European Journal of Medicinal Chemistry, 2016-06-10) Rodríguez-Hernández, Diego; Demuner, Antonio J.; Barbosa, Luiz C.A.; Heller, Lucie; Csuk, RenéA series of novel aryl-1H-1,2,3-triazol-4-yl methylester and amide derivatives of the natural product hederagenin was synthesized aiming to develop new antitumor agents, using Huisgen 1,3-dipolar cycloaddition reactions, with yields between 35% and 95%. The structures of all derivatives (2–31) were confirmed by MS, IR, ^1H NMR and ^13C NMR spectroscopic data. The cytotoxic activities of all compounds were screened against a panel of six human cancer cell lines using SRB assay. It was found that most of the compounds displayed higher levels of antitumor activities as compared to parent hederagenin. Compounds 4, 8 and 15 were the most potent against all human cancer cell lines. Furthermore, compound 11 was the most cytotoxic against cell HT29 showing EC50 = 1.6 μM and a selectivity index of 5.4.Item Highly potent anti-leishmanial derivatives of hederagenin, a triperpenoid from Sapindus saponaria L.(European Journal of Medicinal Chemistry, 2016-11-29) Rodríguez-Hernández, Diego; Barbosa, Luiz C.A.; Demuner, Antonio J.; Almeida, Raquel M.de; Fujiwara, Ricardo T.; Ferreira, Sebastião R.Leishmaniasis is a neglected tropical disease (NTDs), endemic in 88 countries that affect more than 12 million people. Current drugs are limited due to their toxicity, development of biological resistance, length of treatment and high cost. Thus, the search for new effective and less toxic treatments is an urgent need. In this study, we report the synthesis of 3 new amide derivatives of hederagenin (22–24) with yields between 70% and 90%, along with 57 other derivatives of hederagenin (1–21, 25–60) carrying different groups at C-28 previously reported by our group, and the results of their in vitro ability to inhibit the growth of Leishmania infantum. Some derivatives (3, 4, 44, 49 and 52), showed activity at micromolar level and low toxicity against BGM and HepG2 cells. Moreover, the ability of hederagenin derivatives 3 (IC50 = 9.7 μM), 4 (12 μM), 44 (11 μM) and 49 (2 μM), to prevent proliferation of intracellular amastigote forms of L. infantum and their higher selectivity index and low toxicity compared to commercial positive drug control of choice (potassium antimonyl tartrate trihydrate) (IC50 = 80 μM, SI = 0.1), make these compounds promising candidates for the treatment of leishmaniasis.Item Hederagenin as a triterpene template for the development of new antitumor compounds(European Journal of Medicinal Chemistry, 2015-11-13) Rodríguez-Hernández, Diego; Demuner, Antonio J.; Barbosa, Luiz C.A.; Csuk, René; Heller, LucieIn this study, a series of novel C-28 esters and amides derivatives of hederagenin (He) were designed and synthesized in attempt to develop potent antitumor 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. Although most of the compounds displayed moderate to high levels of cytotoxic activity they were all more potent than the natural product He. The most active compounds had either an ethylpyrimidinyl (27) or an ethylpyrrolidinyl (28) substituent, with EC50 in the range of 1.1–6.5 μM for six human cancer cell lines. Notably, this corresponds to an approximately 30-fold times greater potency than He.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 A validated 1 H NMR method for quantitative analysis of α -bisabolol in essential oils of Eremanthus erythropappus(Talanta, 2016-08-10) Cerceau, Cristiane I.; Barbosa, Luiz C.A.; Alvarenga, Elson S.; Ferreira, Antonio G.; Thomasi, Sérgio S.α-Bisabolol is a natural terpene produced by Eremanthus erythropappus and is widely used in cosmetics and pharmaceuticals due to its anti-inflammatory, antibacterial and antimycotic properties. Due to these applications, a control of composition and authenticity of commercial oils rich in this terpene is required, resulting in a demand for new methodologies for quality control. In this work a rapid and efficient method for quantification of α-bisabolol in the essential oil of E. erythropappus (candeia) using 1H NMR was developed, validated and compared to gas chromatography (GC) method. The quantification of α-bisabolol by 1H NMR was successfully achieved for most of the essential oil samples of E. erythropappus evaluated, except for those with a more complex composition. To circumvent this limitation a 2D NMR COSY contour map was used. This method proved to be a fast and efficient alternative, providing results with standard deviations SD<0.3%. All evaluated parameters (selectivity, linearity, accuracy/precision, repeatability, robustness and stability of analyte and internal standard in solution) gave satisfactory results. Using the 1H NMR signals at 5.36 and 5.13 ppm, the limit of detection (LOD) and limit of quantification (LOQ) were 0.26 and 2.59 mg, respectively. The results obtained by the 1H NMR method presented SD=0.59%, smaller than the value found for GC (SD=1.18%). Tukey tests have shown that the results obtained by 1H NMR and COSY methodology are similar to the obtained by the traditional GC-FID technique using external and internal standardization and normalization with 95% confidence.