Paludolactone: a new eudesmanolide lactone from Wedelia paludosa DC. (Acmela brasiliensis)

Phytochemical investigation of the whole plant of Wedelia paludosa (Acmela brasiliensis) furnished a new eudesmanolide lactone, named paludolactone (2), in addition to the known eudesmanolide (1), stigmasterol, kaurenoic and oleanolic acids. 1H- and 13C-NMR, and MS spectroscopic and elemental analyses were used for the structural elucidation of these compounds.     

Thermal stability of ferrocene derivatives and ferrocene-containing polyamides

Thermogravimetric data and the kinetic interpretation of the curves of mass loss for ferrocene, ferrocenecarboxylic and ferrocenedicarboxylic acids and a series of ferrocene-containing polyamides are presented. The results indicate that the degradation process occurred with more than one stage of thermal degradation. The apparent activation energy values and the FTIR spectra of the degradation products suggest that the degradation mechanism occurred by either scission of weak links or by random scission of the chain. Apparently, the N-vicinal methylene group was the primary site of attack of oxygen on the polymer chain. This revised version was published online in August 2006 with corrections to the Cover Date.     

Thermal degradation of biodegradable edible films based on xanthan and starches from different sources

Films based on xanthan/wheat starch and xanthan/maize starch were prepared in different proportions and analysed in terms of thermal stability in relation to the degradation reaction in an inert atmosphere. The main gaseous decomposition products were identified by infrared spectroscopy. Xanthan was found to be less thermally stable than starch from different sources. The starch addition to xanthan induced an increase in the film thermal stabilities. The thermal degradation mechanism of xanthan starts with scission of the side chain groups with subsequent scission of the main chain. Starches from maize and wheat presented a constant mechanism of thermal degradation. The proportion of xanthan/starch (50/50) presented a synergistic behaviour which may be associated with changes in the mechanism of the thermal degradation process. The FTIR spectra of the gaseous products during thermal degradation of xanthan showed a broad absorption in the 2750–3300 cm⁻¹ region, probably indicating decomposition of β-d-mannopyranosyl groups, present in xanthan side chains. For pure starches, absorptions related to alcohol O–H stretching (3500–3750 cm⁻¹), CO stretching of CO₂, CO and carbonyl compounds (2361, 2177 and 1743 cm⁻¹, respectively) were observed. For xanthan/starch mixtures (50/50) the same compounds as those for the pure polymer degradation were evolved. However, a shift of the CO to higher wavenumber values indicates that new carbonyl compounds are being formed due to changes in the thermal degradation mechanism.     

Dynamical relativistic effects in quasielastic 1p-shell proton knockout from 16O

We have measured the cross section for quasielastic 1p-shell proton knockout in the 16O(e,e(')p) reaction at omega = 0.439 GeV and Q2 = 0.8 (GeV/c)(2) for missing momentum P(miss)相似文献   

Simultaneous electrochemical determination of three sunscreens using cetyltrimethylammonium bromide

This paper proposes a methodology based on electrochemical reduction for the simultaneous determination of three sunscreen agents, namely 4-methylbenzylidene camphor (MBC), benzophenone-3 (BENZO) and 2-ethylhexyl-4-methoxycinnamate (EHMC) by differential-pulse polarography (DPP). The highest peak currents and optimal separation of reduction peaks were obtained by using a supporting electrolyte consisted of Britton-Robinson buffer-methanol (8:2) solution at pH 4.0 and cationic surfactant 3.0 x 10(-4)mol L(-1) cetyltrimethylammonium bromide (CTAB). The methodology was validated using four commercial sunscreen preparation as a sample and the results showed high recovery rates. The efficiency of the proposed methodology was demonstrated by comparing the results obtained by DPP with those obtained by the high-performance liquid chromatography (HPLC) method.     

Phytochemistry and Biological Activities of Amburana cearensis (Allemão) ACSm

Amburana cearensis (Allemão) ACSm. belongs to the Fabaceae family and occurs in the Brazilian semiarid, Argentina, Paraguay, Bolivia, and Peru. Numerous studies that portray its ethnobotany, use in popular medicine, chemical composition, and biological activities exist in the literature. This review aimed to provide an overview of the chemical composition, ethnopharmacology, and biological activities associated with A. cearensis and its isolated constituents. Information was collected from internet searches in the Scopus, Medline, PubMed, Google Scholar, and ScienceDirect databases were performed covering publications from 1997–2020. An ethnopharmacological literature analysis revealed that A. cearensis is used to treat a wide range of respiratory disorders in addition to intestinal, circulatory, and inflammatory problems. Coumarins, flavonoids, phenolic glycosides, phenolic acids, phenylpropanoid derivatives, and triterpenoids, among others, have been reported as active compounds, with High-Performance Liquid Chromatography (HPLC) being the main analytical technique used. The A. cearensis extracts and compounds presented several biological activities, including antimicrobial, antinociceptive, anti-inflammatory, antioxidant, neuroprotective, and myorelaxant activities, among others. This review provides a useful bibliography for future investigations and A. cearensis applications; however, future studies should focus on its toxic effects and the mechanisms of action of its extracts and isolated constituents to guide clinical applications.     

Use of Natural Monomer in the Synthesis of Nano- and Microparticles of Polyurethane by Suspension-Polyaddition Technique

Summary: Polyurethane nano- and microparticles were synthesized by suspension-polyaddition technique, using aqueous polymerization medium. Castor oil, a vegetable triglyceride possessing hydroxyl groups was used as natural polyol and methylene diphenyl diisocyanate (MDI) as isocyanate. The levofloxacin, an antibacterial drug was used as model drug to measure the particles encapsulation efficiency. The effect of the addition of a second polyol, the poly(ethylene glycol) (PEG), and the stirring rate on the mean diameter and morphology of particles was also investigated. The poly(ethylene glycol) has an important effect in the reduction of particles size and their porosity. On the other hand, the poly(ethylene glycol) reduced the yield of encapsulation from 70% for the formulation without PEG to 20% for formulations with PEG. FTIR analysis confirmed the polyurethane formation. Dynamic light scattering study, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to determine the nanoparticles size and shape. Spectrofluorimetric analysis was used to detect the levofloxacin.     

Soy Protein Isolate Based Films: Influence of Sodium Dodecyl Sulfate and Polycaprolactone-triol on Their Properties

Summary: We report on the preparation and properties of soy protein isolate (SPI)-sodium dodecyl sulfate (SDS)-polycaprolactone-triol (PCL-T) films obtained by solvent casting from solutions containing variable amounts of SDS or SDS/PCL-T. It is shown that the mechanical and thermal properties, and the morphology of SPI-based biofilms can be easily controlled by changing SDS, PCL-T, and moisture contents, enabling the fabrication of rigid and flexible materials as pure SPI films [Young's modulus ∼ 1 400 MPa, elongation at break (E) ∼ 2%, and glass transition temperature (T_g) ∼ 150 °C] and SPI/SDS/PCL-T films with [PCL-T] ≥ 18% (Young's modulus ∼ 50 MPa, E ∼ 90%, and T_g ∼ 135 °C), respectively. Micrographs taken at the cross-section of biofilms whose [PCL-T] ≥ 18% revealed the occurrence of a porous matrix, whereas a dense bulk phase was otherwise observed (pure SPI, SPI/SDS, and SPI/SDS/PCL-T films with [PCL-T] < 18%).     

Rapid and inexpensive method for the simple fabrication of PDMS‐based electrochemical sensors for detection in microfluidic devices

The fabrication of PDMS microfluidic structures through soft lithography is widely reported. While this well‐established method gives high precision microstructures and has been successfully used for many researchers, it often requires sophisticated instrumentation and expensive materials such as clean room facilities and photoresists. Thus, we present here a simple protocol that allows the rapid molding of simple linear microchannels in PDMS substrates aiming microfluidics‐based applications. It might serve as an alternative to researchers that do not have access to sophisticated facilities such as clean rooms. The method developed here consists on the use of pencil graphite leads as template for the molding of PDMS channels. It yields structures that can be used for several applications, such as housing support for electrochemical sensors or channels for flow devices. Here, the microdevices produced through this protocol were employed for the accommodation of carbon black paste, which was utilized for the first time as amperometric sensor in microchip electrophoresis. This platform was successfully used for the separation and detection of model analytes. Ascorbic acid and iodide were separated within 45 s with peak resolution of 1.2 and sensitivities of 198 and 492 pA/μM, respectively. The background noise was ca. 84 pA. The analytical usefulness of the system developed was successfully tested through the quantification of iodide in commercial pharmaceutical formulations. It demonstrates good efficiency of the microfabrication protocol developed and enables its use for the easy and rapid prototyping of PDMS structures over a low fabrication cost.     

An extension of Mercer’s theory to L p

Let X be a topological space, either locally compact or first countable, endowed with a strictly positive measure ?? and ${\mathcal{K}:L^2(X,\nu)\to L^2(X,\nu)}$ an integral operator generated by a Mercer like kernel K. In this paper we extend Mercer??s theory for K and ${\mathcal{K}}$ under the assumption that the function ${x\in X\to K(x,x)}$ belongs to some L ^p/2(X, ??), p??? 1. In particular, we obtain series representations for K and some powers of ${\mathcal{K}}$ , with convergence in the p-mean, and show that the range of certain powers of ${\mathcal{K}}$ contains continuous functions only. These results are used to estimate the approximation numbers of a modified version of ${\mathcal{K}}$ acting on L ^p (X, ??).