946 resultados para Chitosan derivatives
Resumo:
This paper reports the synthesis of Au nanoparticles by 30-fs pulses irradiation of a sample containing HAuCl4 and chitosan, a biopolymer used as reducing agent and stabilizer. We observed that it is a multi-photon induced process, with a threshold irradiance of 3.8 x 10(11) W/cm(2) at 790 nm. By transmission electron microscopy we observed nanoparticles from 8 to 50 nm with distinct shapes. Infrared spectroscopy indicated that the reduction of gold and consequent production of nanoparticles is related to the fs-pulse induced oxidation of hydroxyl to carbonyl groups in chitosan. (C) 2011 Optical Society of America
Resumo:
Credneramides A (1) and B (2), two vinyl chloride-containing metabolites, were isolated from a Papua New Guinea collection of cf. Trichodesmium sp. nov. and expand a recently described class of vinyl chloride-containing natural products. The precursor fatty acid, credneric acid (3), was isolated from both the aqueous and organic fractions of the parent fraction as well as from another geographically and phylogenetically distinct cyanobacterial collection (Panama). Credneramides A and B inhibited spontaneous calcium oscillations in murine cerebrocortical neurons at low micro-molar concentrations (1, IC50 4.0 mu M; 2, IC50 3.8 mu M).
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A set of benzofuroxan derivatives was tested in vitro against Trypanosoma cruzi epimastigote forms. The influence of physicochemical properties on these benzofuroxan derivatives' activity was observed, and the presence of electron-withdrawing and hydrophobic groups attached to the benzene ring seems to make a favorable contribution at lower concentrations.
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A series of 2,5-diaryl substituted furans functionalized with several amino acids were synthesized and evaluated as the cyclooxygenases COX-1 and COX-2 enzymes inhibitors. The proline-substituted compound inhibited PGE(2) secretion by LPS-stimulated neutrophils, suggesting selectivity for COX-2. Molecular docking studies in the binding site of COX-2 were performed. (C) 2011 Elsevier Masson SAS. All rights reserved.
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Essential oils of ripe fruits from Schinus terebinthifolius (Anacardiaceae), obtained using a pilot extractor and a Clevenger apparatus were chemically characterized. Due the high amount of (-)-alpha-pinene in both oils, this monoterpene was tested against the protozoan parasite Trypanosoma cruzi, showing a moderate potential (IC50 63.56 mu g/mL) when compared to benznidazole (IC50 43.14 mu g/mL). Otherwise, (-)-alpha-pinene oxide did not showed anti-trypanosomal activity (IC50 > 400 mu g/mL) while (-)-pinane showed an IC50 of 56.50 mu g/mL. The obtained results indicated that the epoxydation of a-pinene results to the loss of the anti-parasitic activity while its hydrogenation product, contributed slightly to the increased activity.
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An antioxidant structure-activity study is carried out in this work with ten flavonoid compounds using quantum chemistry calculations with the functional of density theory method. According to the geometry obtained by using the B3LYP/6-31G(d) method, the HOMO, ionization potential, stabilization energies, and spin density distribution showed that the flavonol is the more antioxidant nucleus. The spin density contribution is determinant for the stability of the free radical. The number of resonance structures is related to the pi-type electron system. 3-hydroxyflavone is the basic antioxidant structure for the simplified flavonoids studied here. The electron abstraction is more favored in the molecules where ether group and 3-hydroxyl are present, nonetheless 2,3-double bond and carbonyl moiety are facultative.
Resumo:
Aims: Guided tissue regeneration (GTR) and enamel matrix derivatives (EMD) are two popular regenerative treatments for periodontal infrabony lesions. Both have been used in conjunction with other regenerative materials. We conducted a Bayesian network meta-analysis of randomized controlled trials on treatment effects of GTR, EMD and their combination therapies. Material and Methods: A systematic literature search was conducted using the Medline, EMBASE, LILACS and CENTRAL databases up to and including June 2011. Treatment outcomes were changes in probing pocket depth (PPD), clinical attachment level (CAL) and infrabony defect depth. Different types of bone grafts were treated as one group and so were barrier membranes. Results: A total of 53 studies were included in this review, and we found small differences between regenerative therapies which were non-significant statistically and clinically. GTR and GTR-related combination therapies achieved greater PPD reduction than EMD and EMD-related combination therapies. Combination therapies achieved slightly greater CAL gain than the use of EMD or GTR alone. GTR with BG achieved greatest defect fill. Conclusion: Combination therapies performed better than single therapies, but the additional benefits were small. Bayesian network meta-analysis is a promising technique to compare multiple treatments. Further analysis of methodological characteristics will be required prior to clinical recommendations.
Benefits of Combinations of Vitamin A, C and E Derivatives in the Stability of Cosmetic Formulations
Resumo:
Chemically stable ester derivatives of vitamins A, C and E have become a focus of interest for their role in the satisfactory results in skin aging treatments. Accordingly, the aim of this study was to evaluate the physical and chemical stability of a cosmetic formulation containing 1% retinyl palmitate, ascorbyl tetraisopalmitate and tocopheryl acetate, alone or in combination. In the studies of physical stability, a Brookfield rheometer was used to determine rheological behavior of formulations containing the vitamins. Chemical stability was determined by HPLC on a Shimadzu system with UV detection. Results showed that formulations had pseudoplastic behavior and that vitamins did not alter their apparent viscosity and thixotropy. In the chemical stability studies, first-order reaction equations were used for determinations of the shelf-life of vitamins derivatives considering a remaining concentration of 85%. Combined vitamins in a single formulation had a slightly lower degradation rate as compared to different preparations containing only one of the vitamins. Considering that many cosmetic formulations contain vitamin combinations it is suggested that the present study may contribute to the development of more stable formulations containing liposoluble vitamins.
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The present study reports the identification of two new staurosporine derivatives, 2-hydroxy-7-oxostaurosporine (1) and 3-hydroxy-7-oxostaurosporine (2), obtained from mid-polar fractions of an aqueous methanol extract of the tunicate Eudistoma vannamei, endemic to the northeast coast of Brazil. The mixture of 1 and 2 displayed IC50 values in the nM range and was up to 14 times more cytotoxic than staurosporine across a panel of tumor cell lines, as evaluated using the MTT assay.
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Two new epimeric chlorinated withaphysalins, rel-(4 beta,5 beta,6 alpha,18S,22R)- and rel-(4 beta,5 beta,6 alpha,18R,22R)-6-chloro-18,20-epoxy-18-ethoxy-4,5-dihydroxy-1- oxowitha-2,24-diene-26,22-lactone (1 and 2 resp.), together with the new rel-(4 beta,5 beta,6a,18R,22R)-6-chloro-18,20-epoxy-4,5-dihydroxy-18-methoxy-1-oxowitha-2,24-diene-26,22-lactone (3) and rel-(3 beta,4 beta,5 beta,6 beta,18R,22R)-5,6:18,20-diepoxy-3,18-diethoxy-4-hydroxy-1-oxowith-24-ene-26,22-lactone (4) were isolated from the leaves of Acnistus arborescens and named withaphysalins TW, respectively. The final structures and the complete 1H- and 13C-NMR assignments of the three chlorowithaphysalins 13 were performed by means of HR-ESI-MS and 1D- and 2D-NMR experiments, including COSY, HSQC, and HMBC, beside comparison with spectral data of analogous compounds from the literature. The structure of 4 was also confirmed by means of a single-crystal X-ray diffraction analysis.
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Tuberculosis (TB) is a major infectious disease caused by Mycobacterium tuberculosis (Mtb). According to the World Health Organization (WHO), about 1.8 million people die from TB and 10 million new cases are recorded each year. Recently, a new series of naphthylchalcones has been identified as inhibitors of Mtb protein tyrosine phosphatases (PTPs). In this work, 100 chalcones were designed, synthesized, and investigated for their inhibitory properties against MtbPtps. Structure-activity relationships (SAR) were developed, leading to the discovery of new potent inhibitors with IC50 values in the low-micromolar range. Kinetic studies revealed competitive inhibition and high selectivity toward the Mtb enzymes. Molecular modeling investigations were carried out with the aim of revealing the most relevant structural requirements underlying the binding affinity and selectivity of this series of inhibitors as potential anti-TB drugs.
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Celecoxib (Cx) shows high efficacy in the treatment of osteoarthritis and rheumatoid arthritis as a result of its high specificity for COX-2, without gastrolesivity or interference with platelet function at therapeutic concentrations. Besides of anti-inflammatory effects, Cx also has a potential role for oral cancer chemoprevention. For these conditions, oral administration in long-term treatment is a concern due to its systemic side effects. However, local application at the site of injury (e.g., buccal inflammation conditions or chemoprevention of oral cancer) is a promising way to reduce its toxicity. In this study, the in vitro characterization of mucoadhesive chitosan (CHT) gels associated to AzoneA (R) was assessed to explore the potential buccal mucosal administration of Cx in this tissue. Rheological properties of gels were analyzed by a rheometer with cone-plate geometry. In vitro Cx release and permeability studies used artificial membranes and pig cheek mucosa, respectively. Mucoadhesion were measured with a universal test machine. CHT gels (3.0%) containing 2.0% or 3.0% Az showed more appropriate characteristics compared to the others: pH values, rheology, higher amount of Cx retained in the mucosa, and minimal permeation through mucosa, besides the highest mucoadhesion values, ideal for buccal application. Moreover, the flux (J) and amounts of drug released decreased with increased CHT and Az concentrations. CHT gels (3.0%) associated with 2.0% or 3.0% Az may be considered potential delivery systems for buccal administration of Cx.
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Several studies on polythiophene gas sensors, based mainly on electrochemical and gravimetric principles can be found in the literature. However, other principles of gas detection, such as optical and thermal, are still little studied. Optical sensing is suitable for remote detection and offers great versatility at low cost. Here,we report on the use of thin films of seven polythiophene derivatives as active layer in optical sensors for the detection of six volatile organic compounds (n-hexane, toluene, tetrahydrofuran, chloroform, dichloromethane and methanol) and water vapor, in concentration range of 500-30,000 ppm. The results showed that it is possible to use different polythiophene derivatives to differentiate VOCs by optical sensing. Differentiation can be performed based on the presence or not of response to an analyte and the sensitivity value of the sensors for the analytes. Another important feature is the lack of the effect of humidity on the response of most films, which could be a major drawback in the application of these sensors. (C) 2011 Elsevier B.V. All rights reserved.
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Phytochemical studies of Hortia brasiliana and Hortia oreadica (Rutaceae) have led to the identification of three novel dihydrocinnamic acids: 5-methoxy-2,2-dimethyl-2H-1-benzopyran-8-propanoic acid, 5,6-dimethoxy-2,2-dimethyl-2H-1-benzopyran-8-propanoic acid and erythro-2-hydroxy-4-methoxy-3-(1,2,3-trihydroxy-3-methylbutyl) benzenepropanoic acid from H. brasiliana and the second compound and six known dihydrocinnamic acids from H. oreadica. Engler included Hortia as the single Neotropical genus in the Toddalioideae subtribe Toddaliinae. However, the range of dihydrocinnamic acid derivatives found in H. brasiliana and H. oreadica show that they contain similar compounds to other species of Hortia and clearly point to their phytochemical affinities with other Rutoideae species. (C) 2012 Elsevier Ltd. All rights reserved.
Resumo:
Plasticized natural macromolecules-based polymer electrolyte samples were prepared and characterized. The plasticization of chitosonium acetate with glycerol increased the ionic conductivity value from 3.0 x 10(-7) S/cm to 1.1 x 10(-5) S/cm. The conductivity temperature relationship of the samples exhibits either VTF or Arrhenius type depending on the glycerol concentration in the sample. The dielectric studies evidencing the relaxation process in the plasticized sample at low frequency region are due to the electric polarization effect. Moreover, the samples were transparent in the Vis region, showed thermal stability up to 160 degrees C and good surface uniformity.