Pressurized hot water extraction (PHWE)

Pressurized hot water extraction (PHWE) has become a popular green extraction method for different classes of compounds present in numerous kinds of matrices such as environmental, food and botanical samples. PHWE is also used in sample preparation to extract organic contaminants from foodstuff for food safety analysis and soils/sediments for environmental monitoring purposes. The main parameters which influence its extraction efficiency are namely the temperature, extraction time, flow rates and addition of modifiers/additives. Among these different parameters studied, temperature is described as the most important one. It is reported that the extraction of certain compounds is rather dependent on pressurized water with different applied temperature. Thus, the stability and reduced solubilities of certain compounds at elevated temperatures are highlighted in this review. With some modifications, a scaled-up PHWE could extract a higher amount of desirable compounds from solid and powdered samples such as plant and food materials. The PHWE extracts from plants are rich in chemical compounds or metabolites which can be a potential lead for drug discovery or development of disease-resistant food crops.     

Stability of T. Chan＇s Preconditioner from Numerical Range

A matrix is said to be stable if the real parts of all the eigenvalues are negative. In this paper, for any matrix An, we discuss the stability properties of T. Chan＇s preconditioner cU（An） from the viewpoint of the numerical range. An application in numerical ODEs is also given.     

Two-phase flow distribution of air–water annular flow in a parallel flow heat exchanger

The air and water flow distribution are experimentally studied for a round header – flat tube geometry simulating a parallel flow heat exchanger. The number of branch flat tube is 30. The effects of tube outlet direction, tube protrusion depth as well as mass flux, and quality are investigated. The flow at the header inlet is identified as annular. For the downward flow configuration, the water flow distribution is significantly affected by the tube protrusion depth. For flush-mounted configuration, most of the water flows through frontal part of the header. As the protrusion depth increases, more water is forced to the rear part of the header. The effect of mass flux or quality is qualitatively the same as that of the protrusion depth. Increase of the mass flux or quality forces the water to rear part of the header. For the upward flow configuration, however, most of the water flows through rear part of the header. The protrusion depth, mass flux, or quality does not significantly alter the flow pattern. Possible explanations are provided based on the flow visualization results. Negligible difference on the water flow distribution was observed between the parallel and the reverse flow configuration.     

Coordination assembly and characterization of red-emitting europium (III) organic/inorganic polymeric hybrids

Novel luminescent ternary organic-inorganic-polymeric hybrid material has been assembled by Eu(3+) complex incorporating into poly (methyl methacrylate) (PMMA) matrix. The functionalized silylated precursor PDC-Si derived from PDC (2,6-pyridinedicarboxylic acid chloride) behaves as the coordination units of Eu(3+) ion. The organic polymer was introduced into the system by directly dissolving PMMA in solution of Eu(PDC-Si)(3) complex and N-N-Dimethyl Formamide (DMF) with subsequent addition of tetraethoxysilane to promote hydrolysis and condensation. The structure and photophysical properties of the resulting hybrids are characterized by Fourier transform infrared spectra, X-ray diffraction (XRD), scanning electronic microscopy and photoluminescence spectra. The luminescence quantum yield was calculated based on the emission spectra and luminescence lifetimes. XRD reveals its amorphous structure. Efficient energy transfer process occurs between PMMA and Eu(3+), and replacement of water molecule by PMMA in the first coordination sphere was confirmed by comparing with the binary hybrid.     

Determination of metabolites in Uncaria sinensis by HPLC and GC-MS after green solvent microwave-assisted extraction

Uncaria sinensis (Oliv.) Havil (Rubiaceae) has been used as an important Traditional Chinese Medicine (TCM) herb for the treatment of fevers and various nervous disorders. The major bioactive secondary metabolites from different classes of chemical compounds, i.e. organic acid, flavonoid and alkaloid, present in this TCM herb, namely catechin, caffeic acid, epicatechin and rhynchophylline, were extracted by microwave-assisted extraction (MAE) method with ultra-pure water as the extraction solvent. The optimal extraction conditions for this green solvent MAE method were found to be 100 °C for 20 min. The recoveries of the compounds were found to be comparable to that of heating under reflux using ultra-pure water for 60 min. The method precision (RSD, n = 6) was found to vary from 0.19% to 5.60% for the proposed method on different days for the secondary metabolites. Simultaneously, the key primary metabolites such as sucrose and phenylalanine for the biosynthesis of bioactive secondary metabolites were successfully characterized by GC-MS. Furthermore, an approach using the combination of primary and secondary metabolite profiling based on their chemical fingerprints with Principal Component Analysis (PCA) was successfully developed to evaluate the quality of U. sinensis obtained from different sources. This approach was shown to be feasible in discriminating U. sinensis from different origins and thus a potential application for the quality control of other medicinal herbs.     

Bruceines K and L from the Ripe Fruits of Brucea javanica

Bruceine K ( 1 ), a pentacyclic C₂₀‐quassinoid bearing a unique 12,20‐epoxy moiety, and bruceine L ( 2 ), along with the ten known compounds (6S,7E)‐6,9,10‐trihydroxy‐ and (6S,7E)‐6,9‐dihydroxymegastigma‐4,7‐dien‐3‐one ( 3 and 4 , resp.), cleomiscosins A–C, luteoline, quercetine, bruceantinol, pinoresinol, and thevetiaflavone, were isolated from the ripe fruits of Brucea javanica. Bruceines K ( 1 ) and L ( 2 ) were determined to be (1β,2α,11β,12β,14ξ,15β)‐12,20‐epoxy‐1,2,11,13,14,15‐hexahydroxypicras‐3‐en‐16‐one and (1β,2α,11β,12β,15β)‐13,20‐epoxy‐1,2,11,12‐tetrahydroxy‐16‐oxo‐15‐(senecioyloxy)picras‐3‐en‐21‐oic acid methyl ester (senecioic acid=3‐methylbut‐2‐enoic acid), respectively, on the basis of NMR (¹H‐ and ¹³C‐NMR, DEPT, ¹H,¹H‐COSY, NOESY, HMQC, and HMBC) and ESI‐MS data. Among the known compounds, (6S,7E)‐6,9,10‐trihydroxy‐ and (6S,7E)‐6,9‐dihydroxymegastigma‐4,7‐dien‐3‐one ( 3 and 4 , resp.), cleomiscosin C, luteoline, quercetine, and thevetiaflavone were isolated for the first time from the Brucea plants.     

Soulamarin, a new coumarin from stem bark of Calophyllum soulattri

The extracts of the stem bark of Calophyllum soulattri gave a new pyranocoumarin, soulamarin (1), together with five other xanthones caloxanthone B (2), caloxanthone C (3), macluraxanthone (4), trapezifolixanthone (5) and brasixanthone B (6) one common triterpene, friedelin (7), and the steroidal triterpene stigmasterol (8). The structures of these compounds were established based on spectral evidence (1D and 2D NMR).     

Bis(5,7‐dimethyl‐8‐hydroxyquinolinato)platinum(II) Complex for Efficient Organic Heterojunction Solar Cells

Organic photovoltaic (OPV) cells using metal(II) (Pt, Pd, Cu, and Ni) chelates of 8‐hydroxyquinoline (Hq) or 5,7‐dimethyl‐8‐hydroxy‐quinoline (HMe₂q) as an electron donor were fabricated by vacuum deposition. The bis(5,7‐dimethyl‐8‐hydroxyquinolinato)platinum(II) [Pt(Me₂q)₂]‐based OPVs showed the best performance with an open voltage (V_OC) of 0.42 V, a short circuit current density (J_SC) of 14.8 mA cm^?2, and a maximum power conversion efficiency (η_P) of 2.4 %. The X‐ray single‐crystal structures together with the grazing incidence X‐ray diffraction (GIXRD) data of thin film samples reveal that the peripheral methyl substituent(s) and platinum(II) ion are essential for the high degree of film crystallinity resulting in improved performance of the as‐fabricated field‐effect transistors (FETs) and OPV cells.     

Organo‐ and Hydrogelators Based on Luminescent Monocationic Terpyridyl Platinum(II) Complexes with Biphenylacetylide Ligands

A series of phosphorescent terpyridyl platinum(II) complexes with ancillary biphenylacetylide ligands, namely, [(R₃tpy)PtC≡C(biphenyl)]X (R=tBu, H, or Et₂N; tpy=2,2′;6′,2′′‐terpyridyl; X is an anion) were synthesized and structurally characterized by various spectroscopic techniques and X‐ray diffraction methods. Despite a lack of long alkyl chain(s) or hydrogen‐bonding motif(s), complexes [(tpy)PtC≡C(biphenyl)]Cl and [(tBu₃tpy)PtC≡C(biphenyl)]X (X=Cl, ClO₄, PF₆, or BF₄) were found to gelate water and organic solvents, respectively. The self‐aggregation of these complexes in solutions and the resulting gels were investigated with variable‐temperature (VT) ¹H NMR spectroscopy, polarized optical microscopy, and absorption/emission spectroscopy. SEM micrographs on dry gels revealed entangled nanofibers with diameters of 20–40 nm and lengths of tens of micrometers. Powder X‐ray diffraction (PXRD) study revealed various degrees of crystallinity of these fibrillar nanostructures. The substituents on both the terpyridyl and acetylide ligands and counterion of these complexes play a profound but concerted role in tuning the intermolecular metal???metal and/or π–π interactions, and hence the gelation properties.