Exhaustive extraction of phenolics and tannins from some sun-exposed forbs and shrubs of the tropical Andes

Monomeric and polymeric phenolic derivatives have attracted renewed attention due to novel discoveries and applications in the pharmaceutical and food industries. Although lower and higher plants generally synthesize these compounds as allomones, antioxidants, ultraviolet (UV) radiation filters, and for other purposes, relatively few species accumulate them in sufficient quantity to be of interest for industrial applications. For the most part these plants are woody perennials with long-lived leaves. Assuming that the metabolic investment of plants growing in high elevation regions is greater than that of lower areas due to the need to protect sun-exposed tissue to excess UV-B radiation and avoid the associated damage to DNA and free radical-mediated redox processes, we anticipated to find useful amounts of these materials in Andean forbs of low-mid stature and limited leaf longevity in western Venezuela where the UV-B contribution to solar radiation is high. Therefore the aims of this investigation were: 1) Select a group of representative Andean species of mid altitude flora in sun-exposed meadows. 2) Devise appropriate extraction methods to obtain the highest possible yield of phenolic and condensed tannins. 3) Compare the response of phenolic material during extraction depending on plant species. Eight plant species (Alnus acuminata, Clidemia ciliata, C. flexuosa, C. hirta, Miconia tuberculata, Monochaetum meridensis, and Psamisia penducifolia) of three distantly related dicotiledoneous families (Betulaceae, Ericaceae, Melastomataceae) and a fern (Pteridium arachnoideum) (Dennstaedtiaceae) growing at 2200 m above sea level and commonly found across the Andes were selected for study during the rainy season. Repeated sequential treatment of vacuum dried plant leaves and blending in 70% aqueous acetone at room temperature followed by sonication at 4-6°C was employed to obtain the phenolic-condensed tannin enriched extract. The monomeric and polymeric fractions were separated by exclusion chromatography and quantified by the modified Prussian Blue specrophotometric method. These species were found to contain elevated levels of phenolics (30-123 mg salicylic acid eq. g”“1 dw of leaf) and tannins (20-521 mg quebracho tannin eq g”“1 dw of leaf ) and to require between four and five consecutive extractions before a negative Prussian blue test of the extracted material could be attained. Single solvent treatments yielded only 21.1-80.3% of monomeric phenolics and 25.1-84.8% of condensed tannins, depending on plant species, although time of extraction did not improve yields. However, better yields were obtained by raising the volume/sample weight ratio from 70/5 (mL/g) to 140/5 although no further increments could be procured at higher ratios presumably because of inefficient blending of leaf particles suspended in the solvent. Surprisingly, C. flexuosa and M. meridensis furnished a higher yield of phenolics and tannins in the second extraction batch than in the first. To the competitive contribution of other more soluble solutes that are discharged in the first batch was attributed this odd behavior. We conclude that 1) plants growing in open areas at mid altitude in the tropical Andes contain a large proportion of phenolic/condensed tannin material. 2) These compounds need at least three and occasionally more sequential extractions for adequate removal from plant tissue and is strongly species dependent. 3) Solubility in aqueous acetone, adequate particle blending and competition by other components in the plant all contribute to extraction efficiency. 4) The high contents of phenolics and tannins found for the first time in some of these fast growing plants opens the possibility of their exploitation as new sources of these compounds

Detection of paramagnetic spins with an ultrathin van der Waals quantum sensor

Detecting magnetic noise from small quantities of paramagnetic spins is a powerful capability for chemical, biochemical, and medical analysis. Quantum sensors based on optically addressable spin defects in bulk semiconductors are typically employed for such purposes, but the 3D crystal structure of the sensor inhibits the sensitivity by limiting the proximity of the defects to the target spins. Here we demonstrate the detection of paramagnetic spins using spin defects hosted in hexagonal boron nitride (hBN), a van der Waals material which can be exfoliated into the 2D regime. We first create negatively charged boron vacancy (V$_{\rm B}^-$) defects in a powder of ultrathin hBN nanoflakes ($<10$~atomic monolayers thick on average) and measure the longitudinal spin relaxation time ($T_1$) of this system. We then decorate the dry hBN nanopowder with paramagnetic Gd$^{3+}$ ions and observe a clear $T_1$ quenching, under ambient conditions, consistent with the added magnetic noise. Finally, we demonstrate the possibility of performing spin measurements including $T_1$ relaxometry using solution-suspended hBN nanopowder. Our results highlight the potential and versatility of the hBN quantum sensor for a range of sensing applications, and pave the way towards the realisation of a truly 2D, ultrasensitive quantum sensor.Comment: 19 pages, 11 figure

Modeling of Gold Cyanidation

The chemistry of gold dissolution in alkaline cyanide solution has continually received attention and new rate equations expressing the gold leaching are still developed. The effect of leaching parameters on gold gold cyanidation is studied in this work in order to optimize the leaching process. A gold leaching model, based on the well-known shrinking-core model, is presented in this work. It is proposed that the reaction takes place at the reacting particle surface which is continuously reduced as the reaction proceeds. The model parameters are estimated by comparing experimental data and simulations. The experimental data used in this work was obtained from Ling et al. (1996) and de Andrade Lima and Hodouin (2005). Two different rate equations, where the unreacted amount of gold is considered in one equation, are investigated. In this work, it is presented that the reaction at the surface is the rate controlling step since there is no internal diffusion limitation. The model considering the effect of non-reacting gold shows that the reaction orders are consistent with the experimental observations reported by Ling et al. (1996) and de Andrade Lima and Hodouin (2005). However, it should be noted that the model obtained in this work is based on assumptions of no side reactions, no solid-liquid mass transfer resistances and no effect from temperature

Stability

After manufacturing or preparation and during use, medicines are subject to changes. Examples are a decline of the content, formation of degradation products, changes in appearance and microbiological contamination. In this chapter, physical degradation, chemical degradation and microbiological aspects of the stability of pharmaceutical preparations are discussed. The section on chemical stability not only concerns hydrolysis, oxidation, isomerisation and photolysis but also structural changes of proteins. This basic knowledge leads to a general advice on how to improve the stability of pharmacy preparations. This is not only relevant for the formulation of medicines, but also for reconstitution and for the storage in the pharmacy of licensed pharmaceutical preparations. If degradation reactions are sufficiently understood, the pharmacist may be able to solve every day’s stability problems and to illustrate this, examples are given. When performing stability studies on medicines to determine shelf life and usage periods, it is shown that chemical degradation may be fairly predictable but shelf life and usage periods may be influenced by less predictable causes. Changes that can be observed by the patient, offer another perspective. The last section of the chapter provides advice on storage conditions, shelf life and usage periods of pharmacy preparations.</p

Electrospun Nanofibers for Label-Free Sensor Applications

Electrospinning is a simple, low-cost and versatile method for fabricating submicron and nano size fibers. Due to their large surface area, high aspect ratio and porous structure, electrospun nanofibers can be employed in wide range of applications. Biomedical, environmental, protective clothing and sensors are just few. The latter has attracted a great deal of attention, because for biosensor application, nanofibers have several advantages over traditional sensors, including a high surface-to-volume ratio and ease of functionalization. This review provides a short overview of several electrospun nanofibers applications, with an emphasis on biosensor applications. With respect to this area, focus is placed on label-free sensors, pertaining to both recent advances and fundamental research. Here, label-free sensor properties of sensitivity, selectivity, and detection are critically evaluated. Current challenges in this area and prospective future work is also discussed

Measuring chloride binding in cementitious materials: A review by RILEM TC 298-EBD

The phase assemblage evolution of binders with novel supplementary cementitious materials (SCMS) during exposure to adverse environments needs to be quantified to accelerate their adoption, and further optimize binder formulation. As such, the interaction between chloride and cementitious matrices with novel SCMs needs to be quantified. The goal of workgroup 2 of RILEM TC EBD-298 is to assess the methods used to quantify chloride binding. This state-of-the-art report reviews the standardized and novel methods to measure chloride binding through an average content (acid/water soluble) or a specific bound content per phase (XRD, TGA, SEM–EDS, …). Each method is presented with respect to our current understanding of chloride binding and speciation in cementitious materials. The discussion around the purpose, use and reporting of each method highlights the gaps limiting the comparison between studies, in particular the lack of standard protocol, and complementary characterization. This review is the groundwork for a “cookbook” of experimental workflows to investigate chloride binding in modern cementitious binders

Measuring chloride binding in cementitious materials: A review by RILEM TC 298-EBD

The phase assemblage evolution of binders with novel supplementary cementitious materials (SCMS) during exposure to adverse environments needs to be quantified to accelerate their adoption, and further optimize binder formulation. As such, the interaction between chloride and cementitious matrices with novel SCMs needs to be quantified. The goal of workgroup 2 of RILEM TC EBD-298 is to assess the methods used to quantify chloride binding. This state-of-the-art report reviews the standardized and novel methods to measure chloride binding through an average content (acid/water soluble) or a specific bound content per phase (XRD, TGA, SEM–EDS, …). Each method is presented with respect to our current understanding of chloride binding and speciation in cementitious materials. The discussion around the purpose, use and reporting of each method highlights the gaps limiting the comparison between studies, in particular the lack of standard protocol, and complementary characterization. This review is the groundwork for a “cookbook” of experimental workflows to investigate chloride binding in modern cementitious binders

Investigations of some energy transfer processes associated with acetylacetonate complexes of the lanthanoid and groups I and II metal ions

Intermolecular energy transfer occurs between Tb(aa)₃.3H₂0 and Ln(aa)₃.3H₂O complexes (Ln = Pr, Nd, Sm, Eu, Dy, Ho or Er; aa = acetylacetonate) in n-butanol solution at 293K. Measurement of the decay time of the Tb³⁺ ⁵D₄level indicates that transfer occurs from this level to excited levels of the Ln³⁺ ions with bimolecular rate constants within the range 0.5 - 4.9 x 10⁵ dm³ mol s ⁻¹. Data from similar measurements on a mixed crystal EuxTb(1-x)(aa)₃.3H₂O and other considerations indicate that this is a very short range electron-exchange transfer. Similar measurements of the Tb³⁺ ion phosphorescence yield indicate the presence of a further intermolecular transfer process between a higher excited state of the Tb³⁺ complex and the added Ln³⁺ complexes. The Stern-Volmer Quenching constants vary from 11 dm³ mol⁻¹ for Ho and Sm to 110 dm³ mol⁻¹ for Pr. It is concluded that this transfer is unlikely to occur from either the ligand singlet or triplet levels and it is proposed that a higher Tb³⁺ level such as the ⁵D₃ may be involved in both inter- and intramolecular energy transfer. Intermolecular energy transfer between excited state Tb³⁺ ions in Tb(aa)₃.3H₂O and Ln³⁺ ions in Ln(aa)₃.3H₂O, where Ln = Eu and Sm, is shown to be markedly solvent dependent. It is proposed that the Tb³⁺ → Ln³⁺ energy transfer occurs in mixed metal dimers where the Tb-Ln distance is likely to be ca. 0.4 nm. The solvent dependent behaviour is related to the relative concentrations of monomeric and dimeric species in the various solvents. The rate controlling step in the intermolecular energy transfer is probably that, of monomer-dimer reaction which at 273K is of the order of 10⁵ dm³ mol⁻¹ s⁻¹. The activation energy of this reaction between Tb, Eu and Sm acetylacetonates is estimated to be ca. 23 kJ mol⁻¹. ¹H NMR spectra of Lu(aa)3.2H2O in several solvents are reported. The spectral profiles are temperature dependent in benzene and toluene solutions and the multiplicity of ligand methyl resonances is attributed to slow exchange between non-equivalent methyl groups in a dimeric structure. The temperature dependence in acetone solution is consistent with the presence of a monomer-dimer equilibrium with △H° = -28.2 ± 1.5 kJ mol⁻¹ and △S° = -74.5 ± 4.5 J K ⁻¹ mol⁻¹. The single ligand-methyland 3-H resonances in the' strongly coordinating solvents dimethyl sulphoxide and pyridine indicate the sole presence of solvated monomers. Previous proposals about the anomalous spectrum of Mg(aa)₂ in CDCl₃ are also discussed. The extremely low efficiency of the intermolecular enrgy transfer process in europium acetylacetonate compared with the corresponding terbium acetylacetonate is attributed to the presence of a charge-transfer excited state lying below the ligand singlet states. This is supported by the anomalous absorption spectrum of the Eu³⁺complex and the effects of added anions in other ligand systems. The phosphorescence spectra of the Group I and Group II metal acetylacetonates (Metal = Li, Na, K, Rb, Gs, Mg, Ca, Sr and Ba) have all been measured in solid Ethanol glass solutions at 77K and found to have profiles similar to that of Al(aa)₃. The phosphorescence decays are non-exponential and this behaviour is attributed to the presence of both coordinated and free acetylacetonate anion. Time resolved spectroscopy and other considerations indicate that the energies of the lowest excited ligand singlet and triplet states of the aa⁻ ion are, unlike the triplet state lifetime, little affected by coordination. Solvolysis is reported in ethanol solution which invalidates some previously-reported spectral parameters

溶液内化学過程についての系統的理解

京都大学0048新制・課程博士博士(工学)甲第16875号工博第3596号新制||工||1543(附属図書館)29550京都大学大学院工学研究科分子工学専攻(主査)教授 佐藤 啓文, 教授 田中 一義, 教授 梶 弘典学位規則第4条第1項該当Doctor of Philosophy (Engineering)Kyoto UniversityDFA