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Graphene as an optoelectronic material displays unique advantages in the modulation of amplitude and phase of millimeter waves attributed to its high carrier mobility and broadband optoelectronic properties. The electronic properties of graphene are precisely controllable with the screen-printing technique. We herein employed the screen-printed graphene to manipulate the transmission of the guided millimeter waves in a metallic waveguide. The effects of the patterns and sizes of screen-printed graphene on the modulation of guided waves are first investigated and found that the rhombus is the optimal pattern shape in terms of linearly broadband modulation and reflection loss. The advanced screen-printing technique enables tuning the sheet resistance of the graphene from 45 Ω/sq. to 205 Ω/sq. Numerical simulation shows that the maximum transmittance modulation depth of the guided wave is about 20 dB related to the tuning range of the graphene sheet resistance. A millimeter-wave metallic waveguide integrated with screen-printed graphene is fabricated and measured to validate the proposed scenario. The broadband transmittance modulation depth of 4 dB is experimentally observed with reflection loss lower than −15 dB in the full frequency band of 60–75 GHz, which is consistent with simulated results. The guided wave modulation with screen-printed graphene exhibits great opportunities in millimeter wave devices and systems.

Cholesterol (or cholest-5-en-3β-ol) is an essential component of cell membranes and also serves as the precursor for the synthesis of steroid hormones, bile acids, and vitamin D. Its total synthesis was one of the most remarkable achievements of 20th century Chemistry, accomplished almost simultaneously by Robinson in Oxford and Woodward at Harvard. This notable synthetic endeavor is on the basis of the following chapter; in which, the cholesterol structural characterization, the key aspects of its total synthesis as well as the synthesis of its unnatural enantiomer (ent-cholesterol) will be detailed addressed following a chronological perspective. info:eu-repo/semantics/publishedVersion

International audience; Condensation of salicylaldehydes and 2-hydroxynaphthaldehyde with various β−dicarbonyl derivatives 2a-c, in the presence of KF-Al2O3, leads to the synthesis of a series of coumarins 3-8 and benzo[f]coumarins 10 respectively by a solvent free reaction under microwave irradiation. The catalyst is recovered by a simple filtration and reused in subsequent reactions. The structure of all synthesized compounds has been established by using analytical techniques such as IR, 1H and 13C NMR spectroscopic spectra and elemental analysis. Most of the coumarins exhibited significant antibacterial activity against S. aureus Gram-positive bacteria compared to Cefotaxime as positive control. The compounds 4a and 7a demonstrated moderate antimicrobial activity against compound 8a is extremely sensitive. In addition, the compounds showed moderate to good antiradical (DPPH) activity. Theoretical calculations let us to confirm the reaction mechanism. Parameters drug-likeness and physicochemical properties including pharmacokinetic analysis of the synthesized compounds was performed using DruliTo program.

The aim of this study was to evaluate the morphological, physico-chemical characteristics and in vitro antioxidant activity (DPPH, FRAP, total antioxidant activity, Fe2+-chelating activity and CUPRAC) of five date cultivars (Phoenix dactylifera L.) growing in Algeria. The fruits are characterized as being economically important via their PH values, weight and quality. The highest level of total phenolic and condensed tannins contents was found in 80% methanol extracts. This level ranged from 20.38–69.85 mg GAE/100 g DW and between 3.58 and 60.05 mg CE/100 g DW. The highest total flavonoid contents were found in acetonic extracts. The fruits exerted different antioxidant activities and they were influenced by the extraction solvent. Although they have low phenolic contents, 70% acetone extracts gave the highest antioxidant activities. Using UHPLC-DAD-ESI-MSn analysis, 19 compounds were identified, most detected compounds were found in 70% acetonic extracts. Thus, 70% acetone was found to be the best solvent to run such investigation. Due to date-pathogen, infected Tinnaser date synthesized more or new polyphenols such as O-p-coumaroylshikimic acid and apigenin pentosyl hexoside. Keywords: Antioxidant activity, Date fruit, Morphological, Physico-chemical, UHPLC-DAD-ESI-MSn, Solvent

Calendula officinalis is an edible and medicinal plant with recognised economic value. What about the other Calendula species? This work aims to provide in-depth information about the UHPLC-MS/MS profile of other Portuguese Calendula species and in doing so contribute to answer that question. The knowledge on the metabolic machinery from C. arvensis, C. suffruticosa subsp. algarbiensis and lusitanica growing in Portugal is herein broadened using UHPLC-MS/MS. Phenolic acids, flavonoids and saponins were identified, some being firstly reported both in the species and genus. The antimicrobial potential of these species was assessed against several fungus and bacteria, strong activity against dermatophytes was observed. C. suffruticosa subsp. algarbiensis showed the best results especially against the two strains of Microsporum. The demonstrated antimicrobial activity and the richness in phenolic compounds reinforces that other Calendula species can be regarded as interesting ingredients to be included on the formulation of smart foods and/or natural medicines.

Salicornia ramosissima J. Woods is a salt tolerant plant currently used in the human diet, whose genus not only displays great potential as a crop plant in deserts and highly saline soils, but also has value in traditional medicine and exhibits promising biological activities. The present study was designed to evaluate the effect of S. ramosissima ethanolic extract on carbon tetrachloride (CCl 4 )-induced testicular damage in a mouse model and identify secondary metabolites present in the tested extract. The histopathological analysis showed that the treatment with the ethanolic extract prior to CCl 4 administration prevented significantly the architectural disorder of seminiferous epithelium and germ cell exfoliation. The phytochemical study allowed the identification of known phenolic and aliphatic compounds [ethyl linolenoate ( 1 ), sitostanol ( 2 ), octadecyl ( 3 ) and eicosanyl ( 4 ) ( E )-ferulates, ethyl ( E )-2-hydroxycinnamate ( 5 ), scopoletin ( 6 ), a triacylglycerol of tetracosanoic acid ( 7 )], and three new compounds: saliramoester, a long chain triester ( 8 ), saliramophenone, a propiophenone derivative ( 9 ) and saliramopyrrole a pyrrole-3-carbaldehyde derivative ( 10 ). Their chemical structures were elucidated using detailed spectroscopic studies (1D and 2D NMR and MS). These results enhance the value of S. ramosissima as an excellent source of structurally interesting phytochemicals and as protective agent against testicular toxicity.

Aplysia sea hares are harmless to humans and good materials for producing compounds with pharmacological properties. Aplysia species have been investigated for their human nutritional value. The knowledge on the metabolic machinery from edible Aplysia depilans Gmelin is herein broadened by identifying chlorophylls, phenolic acids, terpenes, including xanthophylls, and alkaloids, some being reported for the first time both in the species and genus. The anti-inflammatory potential was assessed using RAW 264.7 macrophages challenged with lipopolysaccharide, revealing that A. depilans ethyl acetate partionated fraction interfered with cellular NO levels, mainly due to a decrease on inducible nitric oxide synthase expression. A strong capacity to inhibit phospholipase A 2 and 5-lipoxygenase was also evidenced. Morphological studies with SH-SY5Y neuroblastoma cells demonstrated chromatin condensation compatible with apoptosis, confirmed by the activation of caspase 3/7. The anti-inflammatory and pro-apoptotic effects reinforce A. depilans as an interesting ingredient to be included on the formulation of smart foods and/or nutraceuticals.

Optimal reaction pathways for the conversion of renewable feedstocks are often examined by reaction network flux analysis. An alternative modelling approach for reaction networks is a Petri net. These explicitly take the reaction sequence into account. In the optimisation of a network, this can allow the implementation of constraints on circular reaction structures, which are common substructures in chemical reaction networks. In this study, we compare the performance of the models in an illustrative minimal working example of a circular reaction substructure. The reaction network flux analysis is shown to be a relaxation of the Petri net formulation. Most notable, this work contributes to well-reasoned model choices for reaction networks.

Global optimization is desirable for the design of chemical and energy processes as design decisions have a significant influence on the economics. A relevant challenge for global flowsheet optimization is the incorporation of accurate thermodynamic models. A promising alternative to conventional thermodynamic property models is the integration of data-driven surrogate models into mechanistic process models and deterministic global optimization in a reduced space. In our previous works, we trained artificial neural networks (ANNs) on thermodynamic data and included the surrogate models in the global flowsheet optimization of subcritical organic Rankine cycles (ORC). In this work, we extend the framework to the optimization of transcritical ORCs operating at a supercritical high pressure level and subcritical low pressure level. We train separate ANNs for supercritical and subcritical thermodynamic properties. ANNs with a small number of neurons can learn the thermodynamic properties to sufficient accuracy. We identify the optimal working fluid among 122 available fluids in the thermodynamic library CoolProp via a deterministic global optimization of the hybrid process model using the solver MAiNGO. The results show that the process can be optimized efficiently and that transcritical operation can enable high power generation.

Nanoparticles (NP) bioactivity is under deep scrutiny. In this work, the antioxidant response to TiO2-NP in wheat (Triticum aestivum) was determined. For that, enzymatic and the non-enzymatic antioxidants were evaluated in plants exposed to the P25 anatase:rutile material composed of TiO2-NP and under environmentally realistic doses (0; 5; 50; 150 mg/L for 20 days). Shoot but not root growth was reduced. In leaves, thiol metabolism and ascorbate accumulation were the preferred route whereas in roots the pre-existing antioxidant capacity was preferentially utilized. Both leaves and roots showed increased glutathione reductase and dehydroascorbate reductase activities and decreased ascorbate peroxidase activity. Roots, nevertheless, presented higher enzymatic basal levels than leaves. On the other hand, when examining non-enzymatic antioxidants, the ratio of reduced-to-oxidized glutathione (GSH/GSSG) increased in leaves and decreased in roots. Exposed leaves also presented higher total ascorbate accumulation compared to roots. TiO2-NP exposure down regulated, with more prominence in roots, antioxidant enzyme genes encoding catalase, ascorbate peroxidase, monodehydroascorbate reductase and dehydroascorbate reductase. In leaves, superoxide dismutase gene expression was increased. All data pinpoint to TiO2-NP toxicity above 5 mg/L, with aerial parts being more susceptible, which draws concerns on the safety doses for the use of these NPs in agricultural practices. published

We recently demonstrated the potential of deterministic global optimization in a reduced-space formulation for flowsheet optimization. However, the consideration of implicit unit operations such as flash calculations is still challenging and the solution of complex flowsheets incorporating such operations can be intractable. We show that the solution of flash equations can be integrated in global optimization via artificial neural networks (ANNs). Thus, flash calculations are no longer performed within the flowsheet optimization. Instead, flash equations are solved offline and then learned using ANNs. ANNs have been used successfully in the literature to learn flash equilibria but have not yet been included in deterministic global optimization for this task. We embed the ANNs in a hybrid model and use deterministic global optimization to solve it. In addition, we utilize deterministic global optimization to calculate a guaranteed worst-case accuracy of ANNs compared to a rigorous model. We demonstrate the proposed approach on an illustrative five-component vapor-liquid equilibrium flash using our in-house solver MAiNGO.

Deterministic global optimization of process flowsheets has so far mostly been limited to simplified thermodynamic models. Herein, we demonstrate a way to integrate accurate thermodynamic models for the optimal process design of an organic Rankine cycle (ORC) via the use of artificial neural networks (ANNs). We generate training data using the thermodynamic library Coolprop and learn thermodynamic properties. The ANNs are subsequently embedded in the process design optimization problem in a reduced-space, which is solved to global optimality using our in-house optimization software MAiNGO. The importance of accurate thermodynamics is illustrated for the design of an ORC for geothermal power generation. We show that the use of an accurate thermodynamic model leads to different design decisions in comparison to a simplified model. Furthermore, we investigate the influence of the network architecture and complexity on accuracy, optimization results and computational performance.

Tetrakis(1H-pyrazol-1-yl)methanes are very rare compounds of which only two are known: the unsubstituted 1 obtained classically by Hückel in 1937 from carbon tetrachloride and prepared again several times and the 3,5-dimethyl substituted 2 obtained serendipitously by Pombeiro in 2009. We have now extended this group to include four new derivatives 8, 9, 11 and 12 bearing methyl groups. The X-ray crystal structure of the four compounds has been determined. They have been studied by NMR both in solution (H, C, N) and in the solid state (C and N). DFT calculations of the six compounds (geometries, energies and absolute shieldings) have been used to discuss the experimental observations., We thank Dr. Duane Choquesillo-Lazarte (LEC, IACT-CSIC) for compound 12 X-ray data collection. This work was carried out with financial support from the Ministerio de Ciencia, Innovación y Universidades (Project PGC2018-094644-B-C22) and Direccion General de Investigacion en Innovacion de la Comunidad de Madrid (PS2018/EMT-4329 AIRTEC-CM). Computer, storage and other resources from the CTI (CSIC) are gratefully acknowledged. Thanks are also due to University of Aveiro and FCT/MEC for the financial support of the QOPNA research unit (FCTUID/QUI/00062/2019) through national founds and, where applicable, co-financed by the FEDER, within the PT2020 Partnership, and also to the Portuguese NMR network. Support from the UNED is also greatly acknowledged

The search of new antioxidants, as drugs candidates, is an active field of medicinal chemistry. The synthesis of compounds with antioxidant potential has increased in recent years and a high number of structurally diverse compounds have been published. This review aims to show the current state-of-the-art on the development of antioxidant compounds incorporating the pyrazole pharmacophore. It is a well-timed review driven by the increasing number of papers, on this issue, that have been published since the beginning of the 21st century (from 2000 to 2017). The aim is to look deeper into the structures already published in the literature containing the pyrazole core as the unique pharmacophore or combined with other pharmacophores and see the relationship between the presence of this five-membered nitrogen heterocycle and the behaviour of the compounds as potential antioxidant agents. An attempt was made to whenever possible establish structure-activity relationships that could help the design of new and more potent antioxidant agents containing this important pharmacophore., Thanks are due to the Integrated Programme of SR&TD “pAGE e Protein aggregation Across the Lifespan” (reference CENTRO-01- 0145FEDER-000003), co-funded by Centro (2020) program, Portugal 2020, European Union, through the European Regional Development Fund as well as to the University of Aveiro and FCT/ MEC for the financial support to the QOPNA research project (FCT UID/QUI/00062/2013), financed by national funds and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement.

Dynamic modeling is an important tool to gain better understanding of complex bioprocesses and to determine optimal operating conditions for process control. Currently, two modeling methodologies have been applied to biosystems: kinetic modeling, which necessitates deep mechanistic knowledge, and artificial neural networks (ANN), which in most cases cannot incorporate process uncertainty. The goal of this study is to introduce an alternative modeling strategy, namely Gaussian processes (GP), which incorporates uncertainty but does not require complicated kinetic information. To test the performance of this strategy, GPs were applied to model microalgae growth and lutein production based on existing experimental datasets and compared against the results of previous ANNs. Furthermore, a dynamic optimization under uncertainty is performed, avoiding over-optimistic optimization outside of the model’s validity. The results show that GPs possess comparable prediction capabilities to ANNs for long-term dynamic bioprocess modeling, while accounting for model uncertainty. This strongly suggests their potential applications in bioprocess systems engineering.

This work focuses on the prediction of research and motor octane numbers of gasolines throughout multivariate statistical analysis, which may significantly increase the celerity of the quality control process. The aim of this work is to compare the performance of two different multivariate models, based on partial least squares regression and artificial networks. The results show that both models predict octane numbers with accuracy, presenting coefficients of determination above 0.95 for the calibration data set. For the test data set, partial least squares model is more accurate, which might indicate the existence of linear correlations between spectral data and octane numbers. The statistical parameters also show that the research octane number prediction is more accurate than the motor octane number.

This study investigates the structural composition and major sources of water-soluble organic matter (WSOM) from PM2.5 collected, in parallel, during summer and winter, in two contrasting suburban sites at Iberian Peninsula Coast: Aveiro (Portugal) and Coruña (Spain). PM10 samples were also collected at Coruña for comparison. Ambient concentrations of PM2.5, total nitrogen (TN), and WSOM were higher in Aveiro than in Coruña, with the highest levels found in winter at both locations. In Coruña, concentrations of PM10, TN, and WSOM were higher than those from PM2.5. Regardless of the season, stable isotopic δ13C and δ15N in PM2.5 suggested important contributions of anthropogenic fresh organic aerosols (OAs) at Aveiro. In Coruña, δ13C and δ15N of PM2.5 and PM10 suggests decreased anthropogenic input during summer. Although excitation-emission fluorescence profiles were similar for all WSOM samples, multi-dimensional nuclear magnetic resonance (NMR) spectroscopy confirmed differences in their structural composition, reflecting differences in aging processes and/or local sources between the two locations. In PM2.5 WSOM in Aveiro, the relative distribution of non-exchangeable proton functional groups was in the order: H-C (40-43%) > H-C-C= (31-39%) > H-C-O (12-15%) > Ar-H (5.0-13%). However, in PM2.5 and PM10 WSOM in Coruña, the relative contribution of H-C-O groups (24-30% and 23-29%, respectively) equals and/or surpasses that of H-C-C= (25-26% and 25-29%, respectively), being also higher than those of Aveiro. In both locations, the highest aromatic contents were observed during winter due to biomass burning emissions. The structural composition of PM2.5 and PM10 WSOM in Coruña is dominated by oxygenated aliphatic compounds, reflecting the contribution of secondary OAs from biogenic, soil dust, and minor influence of anthropogenic emissions. In contrast, the composition of PM2.5 WSOM in Aveiro appears to be significantly impacted by fresh and secondary anthropogenic OAs. Marine and biomass burning OAs are important contributors, common to both sites. Xunta de Galicia ( Programa de Consolidación y Estructuración de Unidades de Investigación Competitivas Refs. GRC2013-047 and ED431C 2017/28) published

Viscose and wool fabrics were modified by the insertion of the metal organic framework copper(II) benzene-1,3,5-tricarboxylate (Cu-BTC MOF) through two different techniques, ex situ (ex-Cu-BTC@fabric) and in situ (Cu-BTC@fabric), and the obtained new materials used to remove phenol from petroleum fractions. The copper and MOF contents were, respectively, 32.3-34.5 mg g(-1) and 102.1-110.0 mg g(-1) for in situ, and 15.6-17.3 mg g-1 and 50.0-55.2 mg g(-1), for ex situ modified fabrics. The efficiency of phenol removal from n-octane was followed the order of fabric < ex-Cu-BTC@fabric < Cu-BTC@fabric and viscose fabric exhibited much higher affinity. The highest phenol removal percentage (90%) was attained after 12 h contact time. The maximum adsorption capacity was 333 mg g(-1) for Cu-BTC@viscose and 306 mg g(-1) after 6 successive recovering cycles. The adsorption was pseudo-second order and well fitted to the Langmuir isotherm. The adsorption mechanism may occur via the (i) physical deposition into the Cu-BTC pores, (ii) hydrogen bonding between the phenol by droxy groups and those of cellulose, and (iii) Cu(II) phenol chelation. The results showed that the insertion of Cu-BTC MOF into natural fabrics is a promising way to effectively remove phenols from fuel. published

Sesquiterpene lactones (SL) are secondary metabolites common in several families of plants, most prevalent in the Asteraceae but also found in fungi and invertebrates. These compounds have a 15-carbon skeleton biogenetically formed from three isoprenoid units and present a lactone moiety. They also constitute a large and diverse group of biologically active compounds that exhibit a broad spectrum of biological properties, ranging from anti-inflammatory, phytotoxic, antibacterial, and antifungal to cytotoxic/anticancer activities. Parthenolide-like compounds belong to the germacranolide subclass of SL and are chemically characterized by a 10-membered ring with a 5-membered fused lactone, the presence of a α-methylene group and a C4-C5 epoxide ring are also characteristic in their structure. In the past few years, an increasing interest in this SL type compounds was observed, mainly due to its most noticeable member parthenolide, a natural compound that possess different biological effects and can act through several mechanisms of action, and it was also used in cancer clinical trials. Therefore, more and more research has been published on parthenolide and its analogs aiming to improved and/or discover new biological activities. The information that will be presented herein was collected by searching the term parthenolide on Scopus, Web of Science, and PubMed databases on papers published in the last 3 years. Around 256 entries appear in our bibliographic search, from which the most relevant were selected to understand the current state of art and to give suggestions that can be used to conduct future research in the development of more effective and selective parthenolide-like drugs. This chapter will provide a comprehensive overview of the advances on synthesis, potential therapeutic applications, structure–activity relationships, mechanism of action evidences, and pharmacology of parthenolide and parthenolide-like SL that were published in the last 3 years. Anticancer and anti-inflammatory effects will be highlighted but other important activities recently reported will also be discussed. Topics where the knowledge on parthenolide-like SL is more limited (toxicity, delivery systems, and synergistic effects) will be also mentioned. The broadest conclusion is that parthenolide and parthenolide-like SL are biologically active compounds that can become very promising drugs, especially if their use to treat human health problems, such as cancer, inflammation, bone loss, septic shock, parasite infections, just to highlight a few, turn out to be a fact. The recent results in new forms of parthenolide delivery and its synergistic effects showed that it is possible to overcome its weaknesses and its medical application seems to be plausible.

Flavonoids are a subclass of phenolic compounds that occur ubiquitously in food plants and vegetables. This class of compounds shares a common 15-carbon structure represented by a benzene ring (A) condensed with a heterocyclic six-membered pyran or pyranone ring (C) that carries a phenyl ring (B) in the 2-, 3-, or 4-position. These compounds are known to modulate important cellular signaling processes including those associated with inflammatory diseases, hence rendering them a clinical potential in this area. In general, the antiinflammatory properties of flavonoids involve the inhibition of the activity of several proinflammatory biochemical mediators (cytokines, adhesion molecules, NO ) and enzymes (COX-2, LOX, iNOS). In addition, these compounds may also interact with important transcription factors and signaling pathways, including nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) thus regulating the proinflammatory genes’ expression. Importantly, the capacity of flavonoids to interact with these cellular markers is dependent on specific structural features. In general, the hydroxyl substitutions at the 3′-, 4′-, 5-, and 7-positions, the unsaturated C2 C3 function and the 4-keto group of the C-ring are the main structural requirements to provide efficient inhibition of signaling molecules. This manuscript revises relevant studies focusing the structure–affinity relationship between flavonoids and key inflammatory markers, underlying the specific structural features involved in these interactions, as well as an approach to some synthetic strategies aiming the enhancement of flavonoids antiinflammatory properties.

Solution-state H-1 NMR spectroscopy was applied to characterize the structural features of water- and alkaline-soluble organic matter (WSOM and ASOM, respectively) sequentially extracted from fine urban atmospheric aerosols collected over different seasons. The objectives of this study were twofold: (i) to compare the functional characteristics of fine aerosol WSOM and the yet unknown ASOM, and (ii) to assess the sources of WSOM and ASOM at an urban location. The H-1 NMR analysis confirmed that the WSOM and ASOM fractions hold similar 1H functional groups; however, they differ in terms of their relative distribution throughout the seasons. The winter and autumn samples have a less aliphatic and oxidized character and higher contributions from aromatic groups than those of warmer conditions. The urban aerosol WSOM and ASOM fractions do not fit the established H-1 NMR source apportionment fingerprints of marine, secondary, and biomass burning organic aerosols (OAs), exhibiting a smaller relative contribution of carbon-oxygen double bonds, which is indicative of a less oxidized character. These results confirm that the boundaries of the pre-established source categories, especially for secondary and biomass burning OAs, might be different at urban locations, suggesting the need to improve the H-1 NMR source apportionment model for including a new fingerprint for urban OAs. (C) 2015 Elsevier Ltd. All rights reserved.

Salicornia ramosissima J. Woods is considered, in the Iberian Peninsula and France, a gourmet product. Nevertheless, is one of the less studied Salicornia species. In this work, GC-MS was employed to, for the first time; fully characterise the lipophilic profile of S. ramosissima and to assess the effect of natural and extra irrigation in that profile. The obtained data showed esterified and free fatty acids, fatty alcohol, sterols, alkanes and aromatic acid derivatives, being palmitic acid, tetracosanol and octacosanol the most abundant compounds. The extra irrigation increases significantly (P < 0.001) the content of esterified lipophilic compounds. Stigmastanol, 24-ethyl-δ(22)-coprostenol, several secondary fatty alcohols and dicarboxylic acids were identified for the first time in Salicornia genus. Several of the detected compounds are known to have health benefits and our results suggest that S. ramosissima should be considered as an important dietary source of lipophilic phytochemicals. Fundação para a Ciência e a Tecnologia (FCT, Portugal), the European Union, QREN, FEDER, COMPETE, for funding the Organic Chemistry Research Unit (QOPNA) (Project PEst-C/QUI/UI0062/2013; FCOMP-01-0124-FEDER-037296), Centre for Environmental and Marine Studies (CESAM) and the Portuguese National NMR Network (RNRMN). info:eu-repo/semantics/publishedVersion

The review covers work published in the calendar year 2011. Novel reaction chemistry and new ring synthetic methods for pyrans, [1]benzopyrans, dihydro[1]benzopyrans (chromenes, chromans), [2]benzopyrans, dihydro[2]benzopyrans (isochromenes, isochromans), pyranones, coumarins, chromones, xanthenes, xanthones, thiopyrans, dioxins, dioxanes, trioxanes, tetraoxanes, dithianes, trithianes, and oxathianes are reviewed.

The structural assignment of a new natural product molecule is not only to establish the 3D structure of a compound, but potentially to provide the basis for research in a multitude of disciplines, ultimately generating new therapeutic agents and/or new understanding of disease biology. The development of modern spectroscopic techniques has transformed the structure assignment process, which previously was essentially based on chemical degradation or derivatization followed by partial or total synthesis. Notably, it was only in the specialization era of the spectroscopic structural assignment of natural products that the field of marine natural products chemistry took shape. Today the processes of marine and terrestrial natural product isolation and structural determination are frequently streamlined and expeditious due to the spectacular advances in chromatographic and spectroscopic technologies as well as chemical synthesis. The NMR spectroscopy is a powerful tool in structure elucidation because the properties it displays can be related to the molecular structure. The chemical environment of a particular nucleus is associated with the chemical shift (d, ppm), and the area of a resonance, usually presented as its relative integral, is related to the number of nuclei giving rise to the NMR signal. The interactions between individual nuclei, mediated by electrons in a chemical bond, determine the coupling constant (J, Hz). In this chapter we will present the techniques commonly used, basic concepts, and how they are useful for chemists in the structural elucidation of mainly bioactive marine natural products. Its complex planar structure is determined by 1H and 13C NMR analysis strongly supported by other 1D (DEPT) and 2D (COSY, TOCSY, HSQC/HMQC, HMBC) NMR techniques. The stereochemistry is generally based on NOE experiments (NOE difference, NOESY, and ROESY), 1H–1H and 1H–13C coupling constants, chiral derivatizing agents, and also in empirical procedures comparing the chemical shifts of unknown vicinal and proximal centers with libraries of configurationally known stereomodels. However, the most reliable option to assign all the 3D structure of a marine natural product still is their total synthesis. The use of NMR hyphenated with other chromatographic and spectroscopic techniques and microcoil probes and narrow diameter tube probes for the structural elucidation of bioactive marine natural products, mainly associated with the quantitative NMR determinations, will be also briefly described. The chapter will finish with a description of the structural characterization of several types of marine natural products using all the referred NMR techniques followed by a small reference to the misassignments that still are very common.

Copyright © 2013 Phytochemical Society of Europe. Published by Elsevier B.V. All rights reserved. Two new meronorsesquiterpenes (cystoazorones A and B) and two new meroditerpenes (cystoazorols A and B), along with benzoic acid were isolated from the brown macroalga Cystoseira abies-marina. The structures of the new compounds were established by 1D and 2D NMR as well as HRMS spectral analysis. The in vitro cytotoxicity and antioxidant activity of the isolated compounds were also evaluated. Cystoazorones A and B, and cystoazorol A exhibited in vitro growth inhibitory activity against HeLa cells. The HeLa cell line in log phase was found to be more sensitive to cystoazorol A than when it was in lag phase. Cystoazorol A also showed a selectivity index higher than taxol, which was used as a positive control. Cystoazorols A and B were found to be the strongest antioxidants among the compounds tested.

An efficient two step synthetic methodology of new 5(4)-aryl-4(5)-[3(5)-(2- hydroxyphenyl)-1H-pyrazol-5(3)-yl]-1H-1,2,3-triazole dyads was established. The reaction of (E)-2-styryl-4H-chromen-4-ones, used as building blocks, with sodium azide, gave 4(5)-aryl-5(4)-(chromon-2-yl)-1H-1,2,3-triazoles bearing either electron-donating or electron-withdrawing substituents in their styryl moiety which upon reaction with hydrazine hydrate afforded the expected pyrazoles in moderate to very good yields. © 2013 Elsevier Ltd. All rights reserved.

The present study reports the electrochemical behavior of several phenolic and catecholic-substituted 2,3-diarylxanthones on a glassy carbon electrode, challenged by cyclic voltammetry at different pH values (4.0, 7.4, and 11.0). Higher pH values required lower anodic and cathodic peak voltages. The oxidation of catecholic groups occurred at lower peak potentials in a reversible and pH dependent manner. Anodic peak potentials appeared at higher pH values and were attributed to the electrochemically irreversible oxidation of the phenolic groups. The number and position of hydroxyl substituents were the determinants for the electrochemical behavior and found to correlate with the scavenging activity for reactive oxygen (ROS) and nitrogen species (RNS). A xanthone with two catechol units presented the lowest anodic potential voltage (Epa = 0.15 V) and proved to be the most effective ROS and RNS scavenger. Faculdade de Farmácia da Universidade do Porto, Universidade de Aveiro, Fundação para a Ciência e a Tecnologia (Portugal) and FEDER for funding the Organic Chemistry Research Unit (project PEst-C/QUI/UI0062/2011) and also to the Portuguese National NMR Network (RNRMN).

article i nfo Lamium album L. is an edible plant which is consumed raw or cooked, in particular in the Mediterranean and sur- rounding areas. It is also consumed as tea infusions and as a main component of food supplements, because of its pharmacological effects. Despite being consumed by humans for centuries, the chemical composition of L. album L. is far from being understood. In this study, a purified ethanolic extract (PEEL) was prepared and further analyzed by high performance liquid chromatography and electrospray mass spectrometry. Overall, verbascoside accounted for approximately half of the phenolic content of the extract, but this also contained other bioactive phenolic com- pounds herein detected for the first time in the genus, namely isoscutellarein derivatives. The latter included isoscutellarein-7-O-allosyl(1 →2)glucoside, its O-methyl derivative, three acetyl derivatives of isoscutellarein-O- allosyl glucoside and one acetylated form of O-methylisoscutellarein-7-O-allosyl(1 →2)glucoside. From those, the main isoscutellarein derivative was assigned to isoscutellarein-7-O-(6-O-acetyl-β-allosyl)(1→2)-β-glucoside, as confirmed by NMR. Altogether, isoscutellarein derivatives accounted for almost 30% of PEEL phenolics. Since verbascoside and isoscutellareinderivativesare main components ofL. albumL.ethanolicextract,theirpossibleas- sociation to the health benefits of the plant is discussed.

A new natural spiro compound 3,4-dehydrotheaspirone 1 and the known arctiol [1β,6α-dihydroxy-4(14)-eudesmene] 2 were isolated from Juniperus brevifolia . Arctiol is reported for the first time in the Juniperus genus. Their structures were established by 1D, and 2D NMR and MS spectra. Antimicrobial and cytotoxic activities of 1 and several secondary metabolites 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 previously isolated by our group from J. brevifolia were evaluated and some SAR has been established. The 18-hydroxydehydroabietane ( 4 ) displayed great antiproliferative activity against cancer cell lines tested, namely HeLa, A-549 and MCF-7. Compound 4 also presented a significant bactericidal effect against Bacillus cereus at different concentrations tested.

The present review aims to show the state of the art on the oxidation mechanisms occurring in wines, as well as the methods to monitor, classify and diagnose wine oxidation. Wine oxidation can be divided in enzymatic oxidation and non-enzymatic oxidation. Enzymatic oxidation almost entirely occurs in grape must and is largely correlated with the content of hydroxycinnamates, such as caffeoyltartaric acid and para-coumaroyltartaric acid, and flavan-3-ols. Non-enzymatic oxidation, also called chemical oxidation of wine, prevails in fermented wine and begin by the oxidation of polyphenols containing a catechol or a galloyl group. These phenolic. reactions, both enzymatic and non-enzymatic, result in by-products named quinones. However, in non-enzymatic oxidation, oxygen does not react directly with phenolic compounds. The limitation on the reactivity of triplet oxygen is overcome by the stepwise addition of a single electron, which can be provided by reduced transition metal ions, essentially iron(II) and copper(I). The sequential electron transfer leads to the formation of hydroperoxide radical (HOO center dot), hydrogen peroxide (H2O2), and hydroxyl radical (HO center dot). The later radical will oxidize almost any organic molecule found in wine and will react with the first species it encounters, depending on their concentration. Sulfur dioxide (SO2) and ascorbic acid, when added to wine, are able to reduce the quinones. Alternative options have been assessed for the prevention of oxidation during wine storage; nevertheless, these are not fully understood or commonly accepted. During aging, aldehydes are important intermediates in the chemical transformations occurring in wines, leading to color and flavor changes. In the same way, a range of off-flavors can be formed from wine oxidation. At low concentrations these flavors may add to the complexity of a wine, but as these increase they begin to detract from wine quality. In addition to the major chemical browning involving wine phenols, the main oxidation reactions occurring during grape juice heating or storage are caramelization and Maillard reaction, which are temperature dependent. Different methods have been proposed in the literature, addressing the complexity and multi-scale related with the oxidation process, to attempt the quantification of antioxidant activity in wines. These methods can be broadly divided in: i) methods based on chemical reactions and ii) methods based on the chemical-physical properties of antioxidants.

Tetravalent metal phosphates and phosphonates form highly insoluble inorganic polymers and can act as good catalysts in some oxidative reactions. In the present work, zirconium phosphate amorphous (ZrPA), scandium exchanged zirconium phosphate amorphous (ScZrPA), sodium exchanged zirconium phosphate amorphous (NaZrPA), potassium exchanged zirconium phosphate amorphous (KZrPA), zirconium phenylphosphonate amorphous (ZrPPA) and zirconium phenylphosphonate phosphate amorphous (ZrPA/ZrPPA), were prepared and evaluated as catalysts for the oxidation of 3,7,7-trimethylbicyclo[4.1.0]hept-3-ene [(+)-3-carene)] by hydrogen peroxide, in different solvents. It was found that the oxidation reaction of (+)-3-carene yielded three major products, namely α-3,4-epoxycarane, carane-3β,4α-diol and 3β-acetoxycaran-4α-ol, depending on the catalyst and solvent conditions. No β-3,4-epoxycarane was detected in the studied conditions.