Secondary Metabolites from the Fruiting Bodies of Coriolopsis aspera in Vietnam and their Bioactivities

Chemistry of Natural Compounds -     

Extraction of cellulose fibers from flax and hemp: a review

Cellulose - The paper is a review on the extraction processes of cellulosic fibers from flax and hemp. The two lignocellulosic crops have a long history of use by humans for extraction of the bast...     

Mechanistic Insights into the Interface‐Directed Transformation of Thiols into Disulfides and Molecular Hydrogen by Visible‐Light Irradiation of Quantum Dots

Quantum dots (QDs) offer new and versatile ways to harvest light energy. However, there are few examples involving the utilization of QDs in organic synthesis. Visible‐light irradiation of CdSe QDs was found to result in virtually quantitative coupling of a variety of thiols to give disulfides and H₂ without the need for sacrificial reagents or external oxidants. The addition of small amounts of nickel(II) salts dramatically improved the efficiency and conversion through facilitating the formation of hydrogen atoms, thereby leading to faster regeneration of the ground‐state QDs. Mechanistic studies reveal that the coupling reaction occurs on the QD surfaces rather than in solution and offer a blueprint for how these QDs may be used in other photocatalytic applications. Because no sacrificial agent or oxidant is necessary and the catalyst is reusable, this method may be useful for the formation of disulfide bonds in proteins as well as in other systems sensitive to the presence of oxidants.     

Simple Synthetic Receptors for Aspirin

Shallow methylene‐bridged cavitands appended with simple H‐bond donor/acceptor groups are shown to bind aspirin. The structural features needed in a synthetic receptor for aspirin binding are defined.     

From Enantiopure Hydroxyaldehydes to Complex Heterocyclic Scaffolds: Development of Domino Petasis/Diels–Alder and Cross‐Metathesis/Michael Addition Reactions

One‐step assembly of hexahydroisoindole scaffolds by a sequence that combines the Petasis (borono‐Mannich) and Diels–Alder reactions is described. The unique selectivity observed experimentally was confirmed by quantum calculations. The current method is applicable to a broad range of substrates, including free sugars, and holds significant potential to efficiently and stereoselectively build new heterocyclic structures. This easy and fast entry to functionalized polycyclic compounds can be pursued by further transformations, for example, additional ring closure by a cross‐metathesis/Michael addition domino sequence.     

Elemental Sulfur Disproportionation in the Redox Condensation Reaction between o‐Halonitrobenzenes and Benzylamines

The disproportionation of elemental sulfur at moderate temperatures is investigated in the redox condensation involving o‐halonitrobenzenes 1 and benzylamines 2 . As a redox moderator, elemental sulfur plays the dual role of both electron donor and acceptor, generating its lowest and highest oxidation states: S^?2 (sulfide equivalent) in benzothiazole 3 and S⁺⁶ (sulfate equivalent) in sulfamate 4 , and filling the electron gap of the global redox condensation process. Along with this process, a cascade of reactions of reduction of the nitro group of 1 , oxidation of the aminomethyl group of 2 , metal‐free aromatic halogen substitution, and condensation finally led to 2‐arylbenzothiazoles 3 .     

Investigation of Growth Conditions for the Expansion of Porcine Mesenchymal Stem Cells on Microcarriers in Stirred Cultures

The extensive use of mesenchymal stem cells (MCS) in tissue engineering and cell therapy increases the necessity to improve their expansion. Among these, porcine MCS are valuable models for tissue engineering and are classically expanded in static T-flasks. In this work, different processes of stirred cultures were evaluated and compared. First, the effect of glucose, glutamine, antioxidant, and growth factors concentrations on porcine MSC expansion were analyzed in a suitable medium by performing kinetic studies. Results showed that a lower glucose concentration (5.5 mM) enabled to increase maximal cell concentration by 40 % compared with a higher one (25 mM), while addition of 2 to 6 mM of glutamine increased maximal cell concentration by more than 25 % compared with no glutamine supplementation. Moreover, supplementation with 1 μM thioctic acid increased maximal cell concentration by 40 % compared with no supplementation. Using this adapted medium, microcarriers cultures were performed and compared with T-flasks expansion. Porcine MSC were shown to be able to proliferate on the five types of microcarriers tested. Moreover, cultures on Cytodex 1, Cytopore 2, and Cultispher G exhibited a MSC growth rate more than 40 % higher compared with expansion in T-flasks, while MSC metabolism was similar.     

Multiple-State Emissions from Neat,Single-Component Molecular Solids: Suppression of Kasha's Rule

Three rigid and structurally simple heterocyclic stilbene derivatives, (E)-3H,3′H-[1,1′-biisobenzofuranylidene]-3,3′-dione, (E)-3-(3-oxobenzo[c] thiophen-1(3H)-ylidene)isobenzofuran-1(3H)-one, and (E)-3H,3′H-[1,1′-bibenzo[c] thiophenylidene]-3,3′-dione, are found to fluoresce in their neat solid phases, from upper (S₂) and lowest (S₁) singlet excited states, even at room temperature in air. Photophysical studies, single-crystal structures, and theoretical calculations indicate that large energy gaps between S₂ and S₁ states (T₂ and T₁ states) as well as an abundance of intra and intermolecular hydrogen bonds suppress internal conversions of the upper excited states in the solids and make possible the fluorescence from S₂ excited states (phosphorescence from T₂ excited states). These results, including unprecedented fluorescence quantum yields (2.3–9.6 %) from the S₂ states in the neat solids, establish a unique molecular skeleton for achieving multi-colored emissions from upper excited states by “suppressing” Kasha's rule.     

Monochromophore-Based Phosphorescence and Fluorescence from Pure Organic Assemblies for Ratiometric Hypoxia Detection

Hypoxia is a parameter related to many diseases. Ratiometric hypoxia probes often rely on a combination of an O₂-insensitive fluorophore and an O₂-sensitive phosphor in a polymer matrix, which require high cost and multi-step synthesis of transition metal complexes. The two-chromophore hypoxia probes encounter unfavorable energy transfer processes and different stabilities of the chromophores. Reported herein is a pure organic ratiometric hypoxia nanoprobe, assembled by a monochromophore, naphthalimide ureidopyrimidinone (BrNpA-UPy), bridged by a bis-UPy-functionalized benzyl skeleton. The joint factors of quadruple hydrogen bonding, the rigid backbone of UPy, and bromine substitution of the naphthalimide derivative facilitate bright phosphorescence (Φ_P=7.7 %, τ_P=3.2 ms) and fluorescence of the resultant nanoparticles (SNPs) at room temperature, which enable accurate, ratiometric, sensitive oxygen detection (K_sv=189.6 kPa⁻¹) in aqueous solution as well as in living HeLa cells.     

Analysis of trace elements in the fingernails of breast cancer patients using instrumental neutron activation analysis

Journal of Radioanalytical and Nuclear Chemistry - The aim of this study was to find trace elements that increase risk of breast cancer based on the deviation of the concentration of trace elements...