N‐phosphinyl ureas: Synthesis,characterization, X‐ray structure,and in vitro evaluation of antitumor activity

A new series of N‐phosphinylureas 5b, 6a–7c was synthesized and characterized by ¹H, ¹³C, ³¹P NMR, IR, and elemental analysis. The three‐dimensional structure of 5b has been determined by X‐ray crystallography. The crystal structure revealed the existence of four independent molecules. All structures form two chains with different arrangements and connect to each other via hydrogen bonds to produce two‐dimensional polymeric chains. The cytotoxicity of cyclophosphamide (a standard antitumor compound) and its nine analogues with formula R¹C₆H₄ NHC(O)NHP(O)XCH₂C(R²)₂ CH₂Y(X = Y = NH, R² = CH₃, R¹ = H ( 5a ), CH₃ ( 5b ), NO₂ ( 5c ), X = O, Y = NH, R² = H, R¹ = H ( 6a , CH₃ ( 6b ), NO₂ ( 6c ), and X = Y = O, R² = CH₃, R¹ = H ( 7a ), CH₃ ( 7b ), NO₂ ( 7c )) as well as phenyl urea were evaluated in vitro against three human tumor cell lines K562, MDA‐MB‐231, and HepG2. The results showed that most of the compounds have significant activity against the selected cell lines. Also, HepG2 cells were more sensitive to all the tested compounds than other cell lines. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 23:74–83, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20754     

RGB pattern of images allows rapid and efficient prediction of antioxidant potential in Calycophyllum spruceanum barks

The use of fast and low-cost methods to optimize the total phenolic compounds (TPC) extraction has been gaining attention in ethnopharmacological research. Extraction conditions of the bioactive compounds from Calycophyllum spruceanum barks were established through multivariate regression models. In this sense, fractional factorial design (FFD) and central rotational composite design (CCRD) were developed using partial least squares regression (PLSR) combined with the information from the color images and spectrophotometry tools to evaluate the antioxidant activity from C. spruceanum barks. In fact, was possible to optimize the extraction of TPC with AA (ethanol 10% v/v, 1 h extraction time at 75 °C temperature). Besides, the precision and performance of generated models were established for the three response variables (TPC, AA by ABTS and FRAP methods) with R² above 0.98 in the PLSR and residual predictive value (RPD) above 3. Thus, the approaches suggested in this study, with emphasis on the use of image analysis, proved to be potential and promising as simple, fast, non-destructive methods for quantifying TPC and antioxidant activity in C. spruceanum barks.     

Determination and quantification of phenolic compounds in methanolic extracts of Solanum ferrugineum (Solanaceae) fruits by HPLC-DAD and HPLC/ESI-MS/TOF

Solanum ferrugineum Jacq. is a wild species that in previous analysis reported a significant antioxidant capacity. The aim of our research was to determine total phenolic content (TPC) and total flavonoid content (TFC), and the phenolic composition by HPLC-DAD and HPLC/ESI-MS/TOF of methanolic extracts of S. ferrugineum fruits, collected from Paredones, Jiquilpan, and Fray Dominguez, Pajuacarán in the Mexican state of Michoacán. TPC and TFC were determined by the spectrophotometric Folin–Ciocalteu reagent and the AlCl₃ method, respectively. TPC in S. ferrugineum fruit [31.41?±?0.91?mg gallic acid equivalent/g dry tissue (DT)] was similar to those reported for Turkey berry (Solanum torvum Sw.) and eggplant (Solanum melongena L.) fruits. The TFC values of S. ferrugineum fruits (29.14?±?4.99?mg catechin equivalent /g DT) corresponded to 80.24% of the TPC. Eight phenolic compounds (PC) were identified by HPLC analysis. The main PC identified in S. ferrugineum fruits were chlorogenic acid, caffeic acid, p-coumaric acid, gallic acid, quercetin, and kaempferol. S. ferrugineum fruits could be used as a starting material for the extraction of high-value PC with potential applications.     

THE PHENOMENON OF CONGLOMERATE CRYSTALLIZATION. PART 54. THE CRYSTALLIZATION MODES OF FIVE NEW COMPLEXES [TRANS-(3,2,3-TET)Co(III)X 2]Y,X=NO− 2, CN−, NCS−

Abstract

A few complexes of formula [trans-Co(N₄)X ₂]Y, where X = a monodentate ligand, N₄ = a tetraamine ligand and Y = a halide or oxy anion have been found to crystallize as conglomerates; however, the majority crystallize as racemates. The complexes are of such variety of composition and packing characteristics that it is difficult to ascertain why they crystallize in one form or the other. We decided to investigate a series of [trans-Co(N₄)X ₂]Y compounds in which the amine was kept constant in order to limit the variables that affect the outcome.

Five different compounds of composition [trans-Co(3,2,3-tet)X ₂]Y (3,2,3-tet = 1,10-diamino-4,7-diaza-decane, X = NO^? ₂, CN^?, SCN^?, and Y = BF^? ₄, Cl^?, Br^?, I^?) were prepared and their crystallization behavior examined by determining their crystal structures. In all cases, when crystallized from deionized water at 21°C, these substances are racemates. Suggestions regarding this crystallization mode are offered in the discussion.     

Changes in Dissociation Efficiency and Kinetics of Peptide Ions Induced by Basic Residues and Their Mechanistic Implication

With matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry, total abundance of product ions formed by dissociation inside (in-source decay, ISD) and outside (post-source decay, PSD) the source was measured for peptide ions [Y ₅ X + H]⁺, [XY ₅ + H]⁺, [Y ₂ XY ₃ + H]⁺, and [XY ₄ X + H]⁺ (X = tyrosine (Y), histidine (H), lysine (K), and arginine (R) with H for the ionizing proton). α-Cyano-4-hydroxycinammic acid was used as matrix. Product abundance became smaller in the presence of basic residues (H, K, and R), in the order Y > H ≈ K > R. In particular, product abundances in ISD of peptide ions with R were smaller than those with H or K by an order of magnitude, which, in turn, were smaller than that for [Y ₆ + H]⁺ by an order of magnitude. Product abundance was affected by the most basic residue when more than one basic residue was present. A kinetic explanation for the data was attempted under the assumption of quasi-thermal equilibrium for peptide ions in MALDI plume which undergoes expansion cooling. Dramatic disparity in product abundance was found to arise from small difference in critical energy and entropy. Results indicate similar transition structures regardless of basic residues present, where the ionizing proton keeps interacting with a basic site. Further implication of the results on the dissociation mechanism along b-y channels is discussed.     

Zum Einfluß der Substituenten R = Ph,NEt2, iPr und tBu in Triphosphanen, (R2P)2P?SiMe3, und Phosphiden,Li(THF)2[(R2P)2P], auf die Bildung und Eigenschaften von Phosphinophosphiniden-Phosphoranen

Concerning the Influence of the Substituents R = Ph, NEt₂, ⁱPr, and ^tBu in Triphosphanes (R₂P)₂P? SiMe₃ and Phosphides Li(THF)₂[(R₂P)₂P] on the Formation and Properties of Phosphino-phosphinidene-phosphoranes The triphosphanes X₂P? P(SiMe₃)? PY₂ 5, 7, 9, 11, 13 and the derived phosphides Li(THF)₂[X₂P? P? PY₂] 6, 8, 10, 12, 14 were synthesized: 5 and 6 with X₂ = ⁱPr₂ and Y₂ = ^tBu₂, 7 and 8 with X₂ = Y₂ = Ph^tBu, 9 and 10 with X₂ = ^tBu₂ and Y₂ = Ph₂, 11 and 12 with X₂ = Y₂ = Ph₂, and 13 and 14 with X₂ = ^tBu₂ and Y₂ = (NEt₂)₂. The silylated triphosphanes at ?70°C in toluene with CBr₄ may yield X₂P? P?P(Br)Y₂ and X₂P? P(Br)? PY₂, and the lithiated phosphides with MeCl may yield X₂P? P?P(Me)Y₂ and X₂P? P(Me)? PY₂ depending on X and Y. The bromiated product of 5 (X₂ = ⁱPr₂, Y₂ = ^tBu₂) is the ylide ⁱPr₂P? P?P(Br)^tBu₂, and the methylated derivatives of 6 are both ⁱPr₂P? P?P(Me)^tBu₂, ^tBu₂P? P?P(Me)ⁱPr and the methylated triphosphane. Ph₂P? P?P(Br)^tBu₂ as well as the brominated triphosphane are obtained from 9 (X₂ = ^tBu₂, Y₂ = Ph₂), and similarly Ph₂P? P?P(Me)^tBu₂ and the methylated triphosphane from 10 . Compound 14 (X₂ = ^tBu₂, Y₂ = (NEt₂)₂ gives rise to the brominated ylide ^tBu₂)P? P?P(Br) · (NEt₂)₂ and to the brominated triphosphane, and on methylation to ^tBu₂P? P?P(Me)(NEt₂)₂ and to ^tBu₂P? P(Me)? P · (NEt₂)₂ (main product). The Br substituted derivatives decompose already on warming to ?30°C, while the methylated compounds are stable up to 20°C.     

Effect of Grinding Process Parameters and Storage Time on Extraction of Antioxidants from Ginger and Nutmeg

The aim of this study was to optimize the grinding process parameters (mesh size of grinder sieve (X₁), the peripheral velocity of the grinding wheels (X₂)), and the storage time (X₃) of ground ginger rhizome and nutmeg to obtain ethanol and ethanol-water extracts with improved antioxidant properties. The optimal conditions were estimated using response surface methodology (RSM) based on a three-variable Box–Behnken design (BBD) in order to maximize the antioxidant capacity (AC) determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) methods, and the total phenolic content (TPC) was determined by the Folin–Ciocalteu (F–C) method in spice extracts. Additionally, the phenolic acid profiles in extracts from optimized conditions were analyzed using ultra-performance liquid chromatography (UPLC). It was found that the optimal preparation conditions for antioxidant extraction were dependent on the spice source and solvent type. The best antioxidant properties in nutmeg extracts were achieved for X₁ = 1.0 mm, X₂ = 40–41 Hz and X₃ = 7 days, whereas the optimized parameters for ginger extracts were more varied (1.0–2.0 mm, 43–50 Hz and 1–9 days, respectively). The ginger extracts contained 1.5–1.8 times more phenolic acids, and vanillic, ferulic, gallic, and p-OH-benzoic acids were dominant. In contrast, the nutmeg extracts were rich in protocatechuic, vanillic, and ferulic acids.     

Optimization of Two Eco-Friendly Extractions of Black Medick (Medicago lupulina L.) Phenols and Their Antioxidant,Cosmeceutical, α-Glucosidase and α-Amylase Inhibitory Properties

Medicago lupulina is an ancient edible plant from the Fabaceae family. In this work, two eco-friendly methods for extraction of bioactive phenolics from M. lupulina were developed using mixtures of water with two non-toxic, skin- and environmentally-friendly polyol solvents: glycerol and polypropylene glycol. Ultrasound-assisted extractions were optimized using a Box–Behnken design. The independent variables were the concentration of organic solvent in water (X₁), extraction temperature (X₂) and time (X₃), while the response was phenolic content. The optimum conditions for extraction of polyphenols were (X₁, X₂, X₃): (45%, 70 °C, 60 min) and (10%, 80 °C, 60 min) for glycerol and polypropylene glycol extraction, respectively. The extracts prepared at optimum conditions were rich in phenolic compounds, mainly derivatives of apigenin, kaempferol, luteolin, quercetin, caffeic and ferulic acid, as well as coumestrol. Their cosmeceutical and antidiabetic activity was tested. Both extracts demonstrated notable antioxidant, anti-lipoxygenase and anti-α-amylase activity. In addition to those activities, the glycerol extract efficiently inhibited protein coagulation, elastase and α-glucosidase activity. Glycerol present in the extract displayed enzyme-inhibiting activity in several assays and supported the action of the bioactive constituents. Thus, the optimized glycerol extract is a desirable candidate for direct incorporation in antidiabetic food supplements and cosmeceutical products.     

Tuning a Single Ligand System to Stabilize Multiple Spin States of Manganese: A First Example of a Hydrazone‐Based Manganese(III) Spin‐Crossover Complex

A series of bis‐chelate pseudo‐octahedral mononuclear coordination complexes of manganese with the chromophore [MnN₄O₂]ⁿ⁺ (n=0, 1) have been generated in all three principal oxidation states of this transition‐metal center under ambient conditions by utilizing a readily tunable, versatile phenolic pyridylhydrazone ligand system (i.e., H₂(3,5‐R¹,R²)‐L; L=ligand). Strategic combinations of the nature and position of a variety of substituent groups afforded selective, spontaneous stabilization of multiple spin states of the manganese center, which, upon close crystallographic scrutiny, appears to be in part due to the occurrence or absence of hydrogen‐bonding interactions that involve the phenolate/phenolic oxygen atom. The divalent complexes are isolable in two forms, namely, molecular [Mn^II{H(3,5‐R¹,R²)‐L}₂] and ionic [Mn^II{H₂(3,5‐R¹,R²)‐L}{H(3,5‐R¹,R²)‐L}]ClO₄, with the latter complex converting easily into the former complex on deprotonation. Accessibility of the higher‐valent states is achievable only when the phenolate oxygen atom is sterically hindered from participation in hydrogen bonding. The [Mn^III{H(3,5‐tBu₂)‐L}₂]ClO₄ complex is the first example of a hydrazone‐based Mn^III complex to exhibit spin crossover. Formation of the tetravalent complexes [Mn^IV{(3,5‐R¹,R²)‐L}₂] (R¹=tBu, R²=H; R¹=R²=tBu) necessitates base‐assisted abstraction of the hydrazinic proton.     

Reversible SO2 Uptake by Tetraalkylammonium Halides: Energetics and Structural Aspects of Adduct Formation Between SO2 and Halide Ions

Contact with SO₂ causes almost immediate dissolution of tetraalkylammonium halides, R₄NX, (R = CH₃ (Me), X = I; R = C₂H₅ (Et), X = Cl, Br, I; R = C₄H₉ (nBu), X = Cl, Br), with the formation of an adduct, [R₄N]⁺[(SO₂)_nX]^– (n = 1–4). Vapor pressure measurements indicate the proclivity for SO₂ uptake follows the order N(CH₃)₄⁺ < N(C₂H₅)₄⁺ < N(C₄H₉)₄⁺. This trend is in accord with the Jenkins–Passmore volume‐based thermodynamic model. Born–Haber cycles, incorporating the lattice energy and gas phase energy terms, are used to evaluate the energetic feasibility of reactions. Density functional theory calculations (B3PW91; 6‐311+G(3df)) have been used to calculate the energetics of (SO₂)_nX^– (X = Cl and Br) anions in the gas phase. The experimental studies show that tetraalkylammonium halides are feasible sorbents for SO₂. In order to correlate the theoretical model, experimental enthalpy, Δ_rH° and entropy, Δ_rS° changes have been determined by the van't Hoff method for the binding of one SO₂ molecule to (C₂H₅)₄NCl, resulting in the liquid adduct (C₂H₅)₄NCl · SO₂. The structure of the analogous 1:1 bromide adduct, (C₂H₅)₄NBr · SO₂, has been determined by single‐crystal X‐ray diffraction (monoclinic, P2₁/c, a = 9.1409(14) Å, b = 12.3790(19) Å, c = 11.3851(17) Å, β = 107.952(2)°, V = 1225.6(3) ų). The structure consists of discrete alkylammonium cations, bromide anions and SO₂ molecules with short contacts between the anion and SO₂ molecules. The (C₂H₅)₄N⁺ cationadopts a transoid conformation with D_2d symmetry, and represents a rare example of a well‐ordered (C₂H₅)₄N⁺ cation in a crystal structure. The Br^– anions and SO₂ molecules forms a chain, (SO₂Br^–)_n, with bifurcated contacts. Non‐bonding electron pairs on the halide anions engage in electrostatic interactions with the sulfur atoms and charge‐transfer interactions with the antibonding S–O orbitals of the bound SO₂ moiety. Raman and ¹⁷O NMR spectra provide compelling evidence for a charge‐transfer interaction between SO₂ molecules and the halide ions.     

Synthese und spektroskopische Charakterisierung einiger Pentacarbonylwolfram(0)‐Komplexe mit monound bicyclischen Phosphiran‐Liganden: Kristallstruktur von [{(Me3Si)2HCPC(H)H–C(H)Ph}W(CO)5]

Synthesis and Spectroscopic Characterisation of some Pentacarbonyltungsten(0) Complexes with Mono‐ and Bicyclic Phosphirane Ligands: Crystal Structure of [{(Me₃Si)₂HCPC(H)H–C(H)Ph}W(CO)₅] The tungsten(0) complex [{(Me₃Si)₂HCPC(Ph)=N}W(CO)₅] ( 1 ) reacts upon heating with alkene derivatives 2 , 6 , 8 , and 10 in toluene to form benzonitrile and the complexes [{(Me₃Si)₂HCPC(R¹,R²)–C(R³,R⁴}W(CO)₅] ( 4 , 7 a , b , 9 a , b , 11 a , b ) ( 4 (trans): R¹,R³ = Ph, R²,R⁴ = H, 7 a , b (cis, meso and rac): R¹,R³ = Ph, R²,R⁴ = H, 9 a , b (RR und SS): R¹ = Ph, R²,R³,R⁴ = H, 11 a , b : R¹=R³ = (CH₂)₄, R²,R⁴ = H). Spectroscopic and mass spectrometric data are discussed. The structure of the complex 9 a was determined by X‐ray single crystal structure analysis showing characteristic data for the phosphirane ring such as a narrow angle at phosphorus (49,2(2)°), different P–C distances (P–C(6) 182,1(5) and P–C(7) 185,2(4) pm) and 152,9(6) pm for the basal C–C bond.     

1:2 Complexes of chloranilic acid with pyrazole and imidazole,and the aceto­nitrile solvate of a 1:1 complex with imidazole

2,5‐Di­chloro‐3,6‐di­hydroxy‐1,4‐benzo­quinone (chloranilic acid) forms X—H?Y (X, Y = N or O) and C—H?Cl hydrogen bonds with pyrazole and imidazole to afford bis­(pyrazolium) di­chloro­anilate and bis­(imidazolium) di­chloro­anilate, (I) and (II), both 2C₃H₅N₂⁺·C₆Cl₂O₄^2?, and imidazolium chloro­anilate aceto­nitrile solvate, C₃H₅N₂⁺·­C₆HCl₂O₄^?·C₂H₃N, (III). Their crystal structures demonstrate three novel supramolecular architectures based on supramolecular synthons to build a ladder, (I), a two‐dimensional network, (II), and a flat ribbon, (III).     

Three Ternary Rare Earth(III) Complexes Based on 3‐[(4,6‐Dimethyl‐2‐pyrimidinyl)thio]‐propanoic Acid and 1,10‐Phenanthroline: Synthesis,Crystal Structure and Antioxidant Activity

Three ternary rare earth [Nd^III ( 1 ), Sm^III ( 2 ) and Y^III ( 3 )] complexes based on 3‐[(4,6‐dimethyl‐2‐pyrimidinyl)thio]‐propanoic acid (HL) and 1,10‐phenanthroline (Phen) were synthesized and characterized by IR and UV/Vis spectroscopy, TGA, and single‐crystal X‐ray diffraction. The crystal structures showed that complexes 1 – 3 contain dinuclear rare earth units bridged by four propionate groups and are of general formula [REL₃(Phen)]₂ · nH₂O (for 1 and 2 : n = 2; for 3 : n = 0). All rare earth ions are nine‐coordinate with distorted mono‐capped square antiprismatic coordination polyhedra. Complex 1 crystallizes in the monoclinic system, space group P2₁/c with a = 16.241(7) Å, b = 16.095(7) Å, c = 19.169(6) Å, β = 121.48(2)°. Complex 2 crystallizes in the monoclinic system, space group P2₁/c with a = 16.187(5) Å, b = 16.045(4) Å, c = 19.001(4) Å, β = 120.956(18)°. Complex 3 crystallizes in the triclinic system, space group P1 with a = 11.390(6) Å, b = 13.636(6) Å, c = 15.958(7) Å, α = 72.310(17)°, β = 77.548(15)°, γ = 78.288(16)°. The antioxidant activity test shows that all complexes own higher antioxidant activity than free ligands.     

Thermal stability of total phenolic compounds and antioxidant activities of jaboticaba peel: Effect of solvents and extraction methods

The objective was to evaluate the effect of temperature on the degradation of total phenolic compounds (TPC) and antioxidant activities (AA), in addition to the effects of solvents (water, ethanol and methanol) and methods of maceration and ultrasound in the extraction of polyphenols from the jaboticaba peel powder (JPP). The thermal stability of the TPC and AA (DPPH, FRAP and ABTS) from JPP at different temperatures (90, 110 and 130 °C) was monitored over time (0–360 min). The effect of solvents (water, ethanol and methanol) and methods of maceration and ultrasound on the extraction of polyphenols from JPP was also evaluated. The best conditions for extracting polyphenols were quantified by HPLC. After extraction, the morphology of the powders was evaluated by scanning electron microscopy (SEM). The study of thermal stability showed that the ABTS radical presented a lower stability with time when compared to the other radicals. In addition, it was observed that the thermal degradation of TPC at the studied temperatures and that there is a positive correlation between TPC and AA. In the ultrasonic extraction using ethanol and methanol in the mass ratio of JPP/volume of solvent 1:20, the maximum TPC amounts were obtained. In the analysis by HPLC, a content of gallic acid (16.28 mg L⁻¹) and hesperidin (9.26 mg L⁻¹) were found for ethanol and methanol, respectively. The SEM images indicated that the changes in the structure favored the formation of pores contributing to the solubilization of TPC and consequently AA.     

Synthesis and Reactivity of Organometallic Intermediates Relevant to Cobalt‐Catalyzed Hydroformylation

Intermediates relevant to cobalt‐catalyzed alkene hydroformylation have been isolated and evaluated in fundamental organometallic transformations relevant to aldehyde formation. The 18‐electron (R,R)‐(^iPrDuPhos)Co(CO)₂H has been structurally characterized, and it promotes exclusive hydrogenation of styrene in the presence of 50 bar of H₂/CO gas (1:1) at 100 °C. Deuterium‐labeling studies established reversible 2,1‐insertion of styrene into the Co?D bond of (R,R)‐(^iPrDuPhos)Co(CO)₂D. Whereas rapid β‐hydrogen elimination from cobalt alkyls occurred under an N₂ atmosphere, alkylation of (R,R)‐(^iPrDuPhos)Co(CO)₂Cl in the presence of CO enabled the interception of (R,R)‐(^iPrDuPhos)Co(CO)₂C(O)CH₂CH₂Ph, which upon hydrogenolysis under 4 atm H₂ produced the corresponding aldehyde and cobalt hydride, demonstrating the feasibility of elementary steps in hydroformylation. Both the hydride and chloride derivatives, (X=H^?, Cl^?), underwent exchange with free ¹³CO. Under reduced pressure, (R,R)‐(^iPrDuPhos)Co(CO)₂Cl underwent CO dissociation to form (R,R)‐(^iPrDuPhos)Co(CO)Cl.     

Hydrophobic ionic liquid‐based ultrasound‐assisted extraction of magnolol and honokiol from cortex Magnoliae officinalis

The hydrophobic ionic liquid of [BMIM][PF₆] was successfully used for the ultrasound‐assisted extraction of hydrophobic magnolol and honokiol from cortex Magnoliae officinalis. To obtain the best extraction efficiencies, some ultrasonic parameters including the concentration of [BMIM][PF₆], pH, ultrasonic power and ultrasonic time were evaluated. The results obtained indicated that the [BMIM][PF₆]‐based ultrasound‐assisted extraction efficiencies of magnolol and honokiol were greater than those of the [BMIM][BF₄]‐based ultrasound‐assisted extraction (from 48.6 to 45.9%) and the traditional ethanol reflux extraction (from 16.2 to 13.3%). Furthermore, the proposed extraction method is validated by the recovery, correlation coefficient (R²) and reproducibility (RSD, n=5), which were 90.8–102.6, 0.9992–0.9998, and 1.6–5.4%, respectively.     

Influence of fluorine substitution on the molecular conformation of 3′‐deoxy‐3′‐fluoro‐5‐methyluridine

Fluorine substitutions on the furanose ring of nucleosides are known to strongly influence the conformational properties of oligonucleotides. In order to assess the effect of fluorine on the conformation of 3′‐deoxy‐3′‐fluoro‐5‐methyluridine (^RT^F), C₁₀H₁₃FN₂O₅, we studied its stereochemistry in the crystalline state using X‐ray crystallography. The compound crystallizes in the chiral orthorhombic space group P2₁2₁2₁ and contains two symmetry‐independent molecules (A and B) in the asymmetric unit. The furanose ring in molecules A and B adopts conformations between envelope (²E, 2′‐endo, P = 162°) and twisted (²T₃, 2′‐endo and 3′exo, P = 180°), with pseudorotation phase angles (P) of 164.3 and 170.2°, respectively. The maximum puckering amplitudes, ν_max, for molecules A and B are 38.8 and 36.1°, respectively. In contrast, for 5‐methyluridine (^RT^OH), the value of P is 21.2°, which is between the ³E (3′‐endo, P = 18.0°) and ³T₄ (3′‐endo and 4′‐exo, P = 36°) conformations. The value of ν_max for ^RT^OH is 41.29°. Molecules A and B of ^RT^F generate respective helical assemblies across the crystallographic 2₁‐screw axis through classical N—H…O aand O—H…O hydrogen bonds supplemented by C—H…O contacts. Adjacent parallel helices of both molecules are linked to each other via O—H…O and O…π interactions.     

Statistical optimization of an RP‐HPLC method for the determination of selected flavonoids in berry juices and evaluation of their antioxidant activities

An isocratic RP‐HPLC method for the separation and identification of selected flavonoids (quercetin, rutin, luteolin‐7‐O‐glucoside, kaempferol and kaempferol‐3‐O‐glucoside) in commercial berry juices (blackcurrant, blueberry, red raspberry and cherry) was developed with the aid of central composite design and response surface methodology. The optimal separation conditions were a mobile phase of 85:15 (% v/v) water–acetonitrile, pH 2.8 (adjusted with formic acid), flow rate 0.5 mL min⁻¹ and column temperature 35°C. The obtained levels of bioflavonoids (mg per 100 mL of juice) were as follows: for quercetin, ca. 0.21–5.12; for kaempferol, ca. 0.05–1.2; for rutin, ca. 0.4–6.5; for luteolin‐7‐O‐glucoside, ca. 5.6–10.2; and for kaempferol‐3‐O‐glucoside, ca. 0.02–0.12. These are considerably lower than the values in fresh fruits. Total phenolic, flavonoid and anthocyanin contents were determined spectrophotometrically. Total flavonoid content varied as follows: blackcurrant > blueberry > red raspberry > cherry. The antioxidant activity of juice extracts (DPPH and ABTS methods) expressed as IC₅₀ values varied from 8.56 to 14.05 mg L⁻¹. These values are ~2.5–3 times lower than quercetin, ascorbic acid and Trolox®, but compared with rutin and butylhydroxytoluene, berries show similar or better antioxidant activity by both the DPPH and ABTS methods.     

Preparation, structures, and properties of niobium chalcogenide halides, NbX2Y2 (X = S, Se; Y = Cl, Br, I)

The preparation of the compounds NbX₂Y₂ (X = S, Se; Y = Cl, Br, I). including that of large single crystals, by chemical transport techniques is reported. Most of these compounds exist in a triclinic low-temperature form and a monoclinic high-temperature form. The crystal structures of triclinic low-temperature NbSe₂Cl₂ and monoclinic NbS₂Cl₂ are reported; both structures consist of cage-shaped units of Nb₂X₄ which are linked together by the Cl atoms to form sheets parallel to the a, b planes. Both the Nb and the X atoms are present in pairs which indicates that the compounds can be formulated as Nb⁴⁺₂(X₂)²⁻₂₂Y⁻₄, in agreement with XPS spectra. The presence of Nb⁴⁺ in pairs explains the observed diamagnetic and semiconducting properties of NbX₂Y₂. The preparation and some properties of MoS₂Cl₂ (orthorhombic) are also given.     

Supercritical Carbon Dioxide Extraction of Four Medicinal Mediterranean Plants: Investigation of Chemical Composition and Antioxidant Activity

With everyday advances in the field of pharmaceuticals, medicinal plants have high priority regarding the introduction of novel synthetic compounds by the usage of environmentally friendly extraction technologies. Herein, a supercritical CO₂ extraction method was implemented in the analysis of four plants (chamomile, St. John’s wort, yarrow, and curry plant) after which the non-targeted analysis of the chemical composition, phenolic content, and antioxidant activity was evaluated. The extraction yield was the highest for the chamomile (5%), while moderate yields were obtained for the other three plants. The chemical composition analyzed by gas chromatography-high-resolution mass spectrometry (GC-HRMS) and liquid chromatography-high-resolution mass spectrometry (LC-HRMS) demonstrated extraction of diverse compounds including terpenes and terpenoids, fatty acids, flavonoids and coumarins, functionalized phytosterols, and polyphenols. Voltammetry of microfilm immobilized on a glassy carbon electrode using square-wave voltammetry (SWV) was applied in the analysis of extracts. It was found that antioxidant activity obtained by SWV correlates well to 1,1-diphenyl-2-picrylhidrazine (DPPH) radical assay (R² = 0.818) and ferric reducing antioxidant power (FRAP) assay (R² = 0.640), but not to the total phenolic content (R² = 0.092). Effective results were obtained in terms of activity showing the potential usage of supercritical CO2 extraction to acquire bioactive compounds of interest.