Kinetics and mechanism of dissolved organic phosphorus (DOP) digestion by the UV/O3 process

In this study, the kinetics and mechanism of UV/O₃ synergistic oxidative digestion of dissolved organic phosphorus (DOP) were investigated, focusing on the ozone direct oxidation and hydroxyl radical oxidation parts of glufosinate and triphenyl phosphate (TPhP). The p-chlorobenzoic acid (p-CBA) was selected as the probe compound, and two kinds of reaction kinetic models were proposed by competitive kinetic method with R_ct according to the different scale of rate constants of hydroxyl radical oxidation. Under the condition of weakly alkaline (pH = 9.0) and weakly acidic environment (pH = 5.0), the second-order rate constants of glufosinate and TPhP was determined indirectly to be ko_{3/glufosinate} = (2.903 ± 0.247)M⁻¹s⁻¹ and ko_3/TPhP = (3.307 ± 0.204) M⁻¹s⁻¹ by ozone direct oxidation, and k_{·OH/glufosinate} = (1.257 ± 1.031) × 10⁹ M⁻¹s⁻¹ and k_·OH/TPhP = (7.120 × 10⁸ ± 0.963) M⁻¹s⁻¹ by hydroxyl radical oxidation, respectively. The comparison of the contribution levels of the two parts to the digestion process showed that the contribution levels in the digestion of glufosinate and TPhP processes both the contribution of ·OH were higher than those of ozone, 86.3% and 72.6%, respectively.     

ESI activity of Br−, BF4−, ClO4− and BPh4− anions in the presence of Li+ and NBu4+ counter‐ions

To improve our understanding of the electrospray ionization (ESI) process, we have subjected equimolar mixtures of salts A⁺X⁻ (A⁺ = Li⁺, NBu₄⁺; X⁻ = Br⁻, ClO₄⁻, BF₄⁻, BPh₄⁻) in different solvents (CH₃CN, tetrahydrofuran, CH₃OH, H₂O) to negative‐ion mode ESI and analyzed the relative ESI activity of the different anionic model analytes. The ESI activity of the large and hydrophobic BPh₄⁻ ion greatly exceeds that of the smaller and more hydrophilic anions Br⁻, ClO₄⁻ and BF₄⁻, which we ascribe to its higher surface activity. Moreover, the ESI activity of the anions is modulated by the action of the counter‐ions and their different tendency toward ion pairing. The tendency toward ion pairing can be reduced by the addition of the chelating ligands 12‐crown‐4 and 2.2.1 cryptand and is, although to a smaller degree, further influenced by the variation of the solvent. Complementary electrical conductivity measurements afford additional information on the interactions of the ionic constituents of the sample solutions. Copyright © 2017 John Wiley & Sons, Ltd.     

Three New Dimeric Orcinol Glucosides from Curculigo orchioides

Three new phenolic glucosides named orcinosides A, B, and C ( 1, 2 , and 3 , resp.) were isolated in low yields (4.0×10⁻⁶, 11.5×10⁻⁶, 4.5×10⁻⁶%, resp.) from the rhizomes of Curculigo orchioides. Their structures were elucidated by comprehensive spectroscopic analyses including FAB‐MS, HR‐ESI‐MS, IR, and 1D‐ and 2D‐NMR (HSQC, HMBC) data. Compounds 1 – 3 contained two orcinol‐glucoside moieties linked through a CH₂ group.     

The unusual fragmentation of long‐chain feruloyl esters under negative ion electrospray conditions

Long‐chain ferulic acid esters, such as eicosyl ferulate ( 1 ), show a complex and analytically valuable fragmentation behavior under negative ion electrospay collision‐induced dissociation ((?)‐ESI‐CID) mass spectrometry, as studied by use of a high‐resolution (Orbitrap) mass spectrometer. In a strong contrast to the very simple fragmentation of the [M + H]⁺ ion, which is discussed briefly, the deprotonated molecule, [M – H]^?, exhibits a rich secondary fragmentation chemistry. It first loses a methyl radical (MS²) and the ortho‐quinoid [M – H – Me]^‐? radical anion thus formed then dissociates by loss of an extended series of neutral radicals, C_nH_2n + 1^? (n = 0–16) from the long alkyl chain, in competition with the expulsion of CO and CO₂ (MS³). The further fragmentation (MS⁴) of the [M – H – Me – C₃H₇]^? ion, discussed as an example, and the highly specific losses of alkyl radicals from the [M – H – Me – CO]^‐? and [M – H – Me – CO₂]^‐? ions provide some mechanistic and structural insights.     

Synthesis of cobalt A2B triaryl corroles bearing methoxy or hydroxyl groups and their activity in electrocatalytic hydrogen evolution

Four A₂B cobalt corrole complexes 1 – 4 appending two methoxy or hydroxyl groups on the 10-meso phenyl group had been synthesized. Four cobalt corroles showed high electrocatalytic activity for hydrogen evolution reaction (HER) in the organic phase and in the aqueous phase. The hydrogen evolution pathway was EECEC when using acetic acid as proton source. When trifluoroacetic acid was used as proton source, the hydrogen evolution route via EECEC or EECC depending on the concentration of trifluoroacetic acid. Cobalt corrole 4 showed the best HER performance with the k_obs of 122.68 s⁻¹ in organic phase and the TOF of 832.2 h⁻¹ in aqueous phase respectively. The results suggested the phenyl hydroxyl group at the cobalt corrole peripheral may act as the proton relay group in HER and the o-hydroxyl of phenyl was better than m- hydroxyl for proton relay.     

Novel cytotoxic oxovanadium(IV) complexes: Influence of pyrazole‐incorporated heterocyclic scaffolds on their biological response

Homoleptic VO^IV complexes with bidentate heterocycles, namely bipyrazole/pyrimidin‐2‐amine/triazolopyrimidine derivatives, are novel square pyramidal oxovanadium(IV) complexes. Their identities have been established using physicochemical techniques, namely elemental and spectral (ESI‐MS, IR, UV–visible) analyses. The in vitro antibacterial activities against Gram‐negative and Gram‐positive microorganisms have been studied for all compounds, exhibiting good inhibition as compared to the ligands. In addition, all compounds exhibit significant cytotoxicity towards brine shrimp with LD₅₀ values obtained in the range 8–24 μg ml⁻¹. Cellular level cytotoxicity has been investigated using bioassay of Schizosaccharomyces pombe , the complexes showing inevitable viability as concentration increases. Notably, UV absorption spectral titrations of the synthesized complexes with DNA reveal that the complexes bind to calf thymus DNA (CT‐DNA) through intercalation mode (K _b = 10⁴–10⁵ M⁻¹). Molecular docking reveals that the compounds are stacked between the base pairs of DNA. The results suggest that the complexes show promising binding affinity compared to the ligands towards CT‐DNA.     

Characterization of phenolic compounds in green and red oak‐leaf lettuce cultivars by UHPLC‐DAD‐ESI‐QToF/MS using MSE scan mode

Lettuce (Lactuca sativa ) is one of the most popular leafy vegetables in the world and constitutes a major dietary source of phenolic compounds with health‐promoting properties. In particular, the demand for green and red oak‐leaf lettuces has considerably increased in the last years but few data on their polyphenol composition are available. Moreover, the usage of analytical edge technology can provide new structural information and allow the identification of unknown polyphenols. In the present study, the phenolic profiles of green and red oak‐leaf lettuce cultivars were exhaustively characterized by ultrahigh‐performance liquid chromatography (UHPLC) coupled online to diode array detection (DAD), electrospray ionization (ESI), and quadrupole time‐of‐flight mass spectrometry (QToF/MS), using the MS^E instrument acquisition mode for recording simultaneously exact masses of precursor and fragment ions. One hundred fifteen phenolic compounds were identified in the acidified hydromethanolic extract of freeze‐dried lettuce leaves. Forty‐eight of these compounds were tentatively identified for the first time in lettuce, and only 20 of them have been previously reported in oak‐leaf lettuce cultivars in literature. Both oak‐leaf lettuce cultivars presented similar phenolic composition, except for apigenin‐glucuronide and dihydroxybenzoic acid, only detected in the green cultivar; and for luteolin‐hydroxymalonylhexoside, an apigenin conjugate with molecular formula C₄₀H₅₄O₁₉ (monoisotopic MW = 838.3259 u ), cyanidin‐3‐O ‐glucoside, cyanidin‐3‐O ‐(3″‐O ‐malonyl)glucoside, cyanidin‐3‐O ‐(6″‐O ‐malonyl)glucoside, and cyanidin‐3‐O ‐(6″‐O ‐acetyl)glucoside, only found in the red cultivar. The UHPLC‐DAD‐ESI‐QToF/MS^E approach demonstrated to be a useful tool for the characterization of phenolic compounds in complex plant matrices.     

Organotin(IV) complexes derived from proteinogenic amino acid: synthesis,structure and evaluation of larvicidal efficacy on Anopheles stephensi mosquito larvae

Five new organotin(IV) complexes of composition [Bz₂SnL¹]_n ( 1 ), [Bz₃SnL¹H⋅H₂O] ( 2 ), [Me₂SnL²⋅H₂O] ( 3 ), [Me₂SnL³] ( 4 ) and [Bz₃SnL³H]_n ( 5 ) (where L¹ = (2S )‐2‐{[(E )‐(4‐hydroxypentan‐2‐ylidene)]amino}‐4‐methylpentanoate, L² = (rac )‐2‐{[(E )‐1‐(2‐hydroxyphenyl)methylidene]amino}‐4‐methylpentanoate and L³ = (2S )‐ or (rac )‐2‐{[(E )‐1‐(2‐hydroxyphenyl)ethylidene]amino}‐4‐methylpentanoate) were synthesized and characterized using ¹H NMR, ¹³C NMR, ¹¹⁹Sn NMR and infrared spectroscopic techniques. The crystal structure of 2 reveals a distorted trigonal‐bipyramidal geometry around the tin atom where the oxygen atoms of the carboxylate ligand and a water ligand occupy the axial positions, while the three benzyl ligands are located at the equatorial positions. On the other hand, the analogous derivative of enantiopure L³H ( 5 ) consists of polymeric chains, in which the ligand‐bridged tin atoms adopt the same trans ‐Bz₃SnO₂ trigonal‐bipyramidal configuration and are now coordinated to a phenolic oxygen atom instead of H₂O. In 2 , the OH hydrogen of the ketoimine substituent has moved to the nearby nitrogen atom while in the salicylidene derivative 5 , the OH is located almost midway between the phenolic oxygen atom and the nitrogen atom of the CN group. For the dibenzyltin derivative 1 , a polymeric chain structure is observed as a result of a long intermolecular Sn⋅⋅⋅O bond involving the exocyclic carbonyl oxygen atom from the tridentate ligand of a neighbouring tin‐complex unit. The tin atom in this complex has distorted octahedral coordination geometry. In contrast, the racemic dimethyltin(IV) complexes 3 and 4 display discrete monomeric structures with a distorted octahedral‐ and trigonal‐bipyramidal geometry, respectively. The structures show that the coordination mode of the Schiff base ligand depends primarily on the number of bulky benzyl ligands (R) at the tin atom, as indeed found in the structures of related complexes where R = phenyl. With three bulky R groups, the tridentate chelating O,N,O coordination mode is preferred, whereas with fewer or less bulky R ligands, only the carboxylate and hydroxy groups are involved, which leads to polymers. Larvicidal efficacies of two of the new tribenzyltin(IV) complexes ( 2 and 5 ) were assessed on the second larval instar of Anopheles stephensi mosquito larvae and compared with two triphenyltin(IV) analogues, [Ph₃SnL¹H]_n and [Ph₃SnL³H]_n . The results demonstrate that the compounds containing Sn–Ph ligands are more effective than those with Sn–Bz ligands. Copyright © 2016 John Wiley & Sons, Ltd.     

Identification and fragmentation pathways of caffeine metabolites in urine samples via liquid chromatography with positive electrospray ionization coupled to a hybrid quadrupole linear ion trap (LTQ) and Fourier transform ion cyclotron resonance mass spectrometry and tandem mass spectrometry

Liquid chromatography (LC) with positive ion electrospray ionization (ESI+) coupled to a hybrid quadrupole linear ion trap (LTQ) and Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) was employed for the simultaneous determination of caffeine and its metabolites in human urine within a single chromatographic run. LC/ESI‐FTICRMS led to the unambiguous determination of the molecular masses of the studied compounds without interference from other biomolecules. A systematic and comprehensive study of the mass spectral behaviour of caffeine and its fourteen metabolites by tandem mass spectrometry (MS/MS) was performed, through in‐source ion trap collision‐induced dissociation (CID) of the protonated molecules, [M+H]⁺. A retro‐Diels‐Alder (RDA) process along with ring‐contraction reactions were the major fragmentation pathways observed during CID. The base peak of xanthine precursors originates from the loss of methyl isocyanate (CH₃NCO, 57 Da) or isocyanic acid (HNCO, 43 Da), which in turn lose a CO unit. Also uric acid derivatives shared a RDA rearrangement as a common fragmentation process and a successive loss of CO₂ or CO. The uracil derivatives showed a loss of a ketene unit (CH₂CO, 42 Da) from the protonated molecule along with the loss of H₂O or CO. To assess the potential of the present method three established metabolite ratios to measure P450 CYP1A2, N‐acetyltransferase and xanthine oxidase activities were evaluated by a number of identified metabolites from healthy human urine samples after caffeine intake. Copyright © 2009 John Wiley & Sons, Ltd.     

Poly(styrene‐b‐isobutylene) multiarm star‐block copolymers

Multiarm star‐branched polymers based on poly(styrene‐b‐isobutylene) (PS‐PIB) block copolymer arms were synthesized under controlled/living cationic polymerization conditions using the 2‐chloro‐2‐propylbenzene (CCl)/TiCl₄/pyridine (Py) initiating system and divinylbenzene (DVB) as gel‐core‐forming comonomer. To optimize the timing of isobutylene (IB) addition to living PS⊕, the kinetics of styrene (St) polymerization at −80°C were measured in both 60 : 40 (v : v) methyl cyclohexane (MCHx) : MeCl and 60 : 40 hexane : MeCl cosolvents. For either cosolvent system, it was found that the polymerizations followed first‐order kinetics with respect to the monomer and the number of actively growing chains remained invariant. The rate of polymerization was slower in MCHx : MeCl (k_app = 2.5 × 10⁻³ s⁻¹) compared with hexane : MeCl (k_app = 5.6 × 10⁻³ s⁻¹) ([CCl]_o = [TiCl₄]/15 = 3.64 × 10⁻³M; [Py] = 4 × 10⁻³M; [St]_o = 0.35M). Intermolecular alkylation reactions were observed at [St]_o = 0.93M but could be suppressed by avoiding very high St conversion and by setting [St]_o ≤ 0.35M. For St polymerization, k_app = 1.1 × 10⁻³ s⁻¹ ([CCl]_o = [TiCl₄]/15 = 1.82 × 10⁻³M; [Py] = 4 × 10⁻³M; [St]_o = 0.35M); this was significantly higher than that observed for IB polymerization (k_app = 3.0 × 10⁻⁴ s⁻¹; [CCl]_o = [Py] = [TiCl₄]/15 = 1.86 × 10⁻³M; [IB]_o = 1.0M). Blocking efficiencies were higher in hexane : MeCl compared with MCHx : MeCl cosolvent system. Star formation was faster with PS‐PIB arms compared with PIB homopolymer arms under similar conditions. Using [DVB] = 5.6 × 10⁻²M = 10 times chain end concentration, 92% of PS‐PIB arms (M_n,PS = 2600 and M_n,PIB = 13,400 g/mol) were linked within 1 h at −80°C with negligible star–star coupling. It was difficult to achieve complete linking of all the arms prior to the onset of star–star coupling. Apparently, the presence of the St block allows the PS‐PIB block copolymer arms to be incorporated into growing star polymers by an additional mechanism, namely, electrophilic aromatic substitution (EAS), which leads to increased rates of star formation and greater tendency toward star–star coupling. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1629–1641, 1999     

Novel aluminium compounds derived from Schiff bases: Synthesis,characterization and catalytic performance in hydroboration

Seven novel aluminium complexes supported by Schiff base ligands derived from o‐diaminobenzene or o‐aminothiophenol were synthesized and characterized. The reactions of AlMe₃ with L¹ (N,N′‐bis(benzylidine)‐o‐phenylenediamine) and L² (N,N′‐bis(2‐thienylmethylene)‐o‐phenylenediamine) gave the complexes L¹AlMe₃ ( 1 ) and L²AlMe₂ ( 2 ), respectively, which involved two types of reaction mechanisms: one was proton transfer and ring closure, and the other was alkyl transfer. Complexes L³AlMe₂ (HL³ = 4‐chlorobenzylidene‐o‐aminothiophenol) ( 3 ), L⁴AlMe₂ (HL⁴ = 2‐thiophenecarboxaldehyde‐o‐aminothiophenol) ( 4 ), L³AlH(NMe₃) ( 5 ), L⁴AlH(NMe₃) ( 6 ) and L⁵AlH(NMe₃) (HL⁵ = 4‐methylbenzylidene‐o‐aminothiophenol) ( 7 ) were prepared by reacting HL^3–5 with equimolar AlMe₃ or H₃Al?NMe₃, respectively. Compounds 3 – 7 feature an organic–inorganic hybrid containing CNAlSC five‐membered ring. All complexes were characterized using ¹H NMR and ¹³C NMR spectroscopy, X‐ray crystal structure analysis and elemental analysis. The efficient catalytic performances of 1 – 7 for the hydroboration of carbonyl groups were investigated, with compound 4 exhibiting the highest catalytic activity among all the complexes.     

Nonaqueous Solution Studies on the Protonation Equilibria of some Phenolic Acids

The protonation equilibria for some phenolic acids in nonaqueous solutions have been studied by pH-potentiometry. The dissociation constants, pK _a, of these phenolic acids and the thermodynamic functions, ΔG ^o,ΔH ^o and ΔS ^o, for the successive and overall protonation processes of these phenolic acids have been derived at different temperatures in three different mixtures of water and dioxane (mole fractions of dioxane were 0.083, 0.174 and 0.33). Titrations were also carried out in (water + dioxane) with ionic strengths of 0.15, 0.20 and 0.25 mol⋅dm⁻³ NaNO₃, and the resulting dissociation constants are reported. A detailed thermodynamic analysis of the effects of organic solvent, dioxane, temperature and ionic strength on the protonation processes of phenolic acids is presented and discussed to determine the factors which control these processes. Ahmed E. Fazary; previous address: Egyptian Organization for Biological Products and Vaccines, 51 Wezaret El-Zeraa Street, Agouza, Giza, Egypt. Tel. +2010-3017357.     

Surface‐initiated atom transfer radical polymerization of a new rhodanine‐based monomer for rapid magnetic removal of Co(II) ions from aqueous solutions

The present study reports synthesis and characterization of a new acrylamide‐based monomer containing rhodanine moiety, N‐3‐amino‐thiazolidine‐4‐one‐acrylamide (ATA). Poly(ATA)‐grafted magnetite nanoparticles (poly(ATA)‐g‐MNPs) were prepared using surface‐initiated atom transfer radical polymerization of the monomer on Fe₃O₄ nanoparticles. The grafted nanoparticles were characterized by Fourier transform infrared analysis, scanning electron microscopy, X‐ray diffraction, and vibrating sample magnetometry. The amount of the grafted polymer was 209 mg g⁻¹, as calculated from thermogravimetric analysis experiment. The capability of poly(ATA)‐g‐MNPs to remove Co(II) cations was shown under optimal conditions of contact time, pH, adsorbent dosage, and initial Co(II) concentration. About 86% of the Co(II) cations were removed over 7 minutes. The adsorption kinetics obeyed the pseudo–second‐order kinetic equation, and the Langmuir isotherm model best described the adsorption isotherm with a maximum adsorption capacity of 3.62 mg g⁻¹. The thermodynamic investigation showed spontaneous nature of the adsorption process (ΔG = −2.90 kJ mol⁻¹ at 25°C ± 1°C). In addition, the poly(ATA)‐g‐MNPs were regenerated by simply washing with an aqueous 0.1M HCl solution. The study of the reusability of the prepared magnetic sorbent revealed that the sorbent can be reused without a significant decrease in the extraction efficiency and be recovered by 95.4% after 7 cycles. These findings suggest that the grafted nanoparticles are stable and reusable adsorbent and can be potentially applied to water treatment in efficient removal of Co(II) cations.     

(2,2′‐Bipyridyl‐κ2N,N′)­bis­(salicyl­ato‐κ2O,O′)­zinc(II)

The asymmetric unit of the title compound, [Zn(C₇H₅O₃)₂(C₁₀H₈N₂)], contains one monomeric zinc complex. The Zn atom is coordinated to one 2,2′‐bipyridyl ligand via both N atoms and to two salicyl­ate anions (Hsal⁻) in a bidentate chelating manner involving carboxyl­ate O‐atom coordination. The complex exhibits a distorted octahedral geometry about the Zn^II atom, with the `apical' positions occupied by one of the two N atoms of the bipyridyl ligand and an O atom from one Hsal<sup>−</sup> ligand; the Zn atom is 0.168 (1) Å out of the `basal' plane. Two intramolecular six‐membered hydrogen‐bonded rings are present, generated from interactions between the carboxyl and hydroxyl groups of the salicyl­ate ligands. The crystal packing is governed by weak C—H⋯O and C—H⋯π interactions.     

Steric and electronic evaluations of P(o‐tol)R2, where R is phenyl or cyclohexyl: crystal structures of SeP(o‐tol)R2

The crystal structures of SeP(o‐tol)R₂, where o‐tol is ortho‐tolyl (2‐methylphenyl) and R is Ph (phenyl), namely (2‐methylphenyl)diphenylphosphane selenide, C₁₉H₁₇PSe, or Cy (cyclohexyl), namely dicyclohexyl(2‐methylphenyl)phosphane selenide, C₁₉H₂₉PSe, were determined to aid in the evaluation of the steric and electronic behaviour of these analogous phosphane compounds. The compounds crystallized in similar monoclinic crystal systems, but are differentiated in their unit cells by a doubling of the number of independent molecules for R = Cy (Z′ = 2) and the choice of glide plane by convention. The preferred orientation for the o‐tolyl substituent obtained from the X‐ray structural analysis is gauche for R = Ph and anti for R = Cy (using the Se—P—C_ipso—C_ortho torsion angles as reference). Density functional theory (DFT) calculations showed both conformations to be equally probable and indicate that the preferred solid‐state conformer is probably due to the minimization of repulsion energies, resulting in a packing arrangement primarily featuring weak C—H…Se interactions and additional C—H…π interactions in the R = Ph structure. A detailed electronic and steric analysis was conducted on both phosphanes using Se—P bond lengths, multinuclear NMR ¹J_Se–P coupling constants, theoretical topological evaluation and crystallographic and solid‐angle calculations, and compared to selected literature examples. The results indicate that the use of the o‐tolyl substituent increases both the electron‐donating capability and the steric size, but is also dependent on whether the o‐tolyl group adopts a gauche or anti conformation. The single‐crystal geometrical data are unable to detect electronic differences between these two structures due to the somewhat large displacement parameters observed for the Se atom in the R = Cy structure.     

Rapid and Selective Detection of Cyanide Anion by Enhanced Fluorescent Emission and Colorimetric Color Changes at Micromole Levels in Aqueous Medium

One main source of cyanide (CN⁻) exposure for mammals is through the plant consumption; thus, the sensitive and selective cyanide detection in plant tissue is a significant and urgent work. Here, a simple sensor N′‐(2,4‐dihydroxybenzylidene)naphtha[2,1‐b]furan‐2‐carbohydrazide ( Q1‐3 ) was designed and synthesized for selective and sensitive dual‐channel detection of cyanide in aqueous medium (DMSO/H₂O, 1:9, v/v). Acylhydrazone and phenolic hydroxyl groups on Q1‐3 are the recognition sites, and naphthofuran group is the signal report group. The intramolecular charge transfer between the benzene group and naphthofuran group was impeded because of the electron‐withdrawing groups (hydroxyl) on sensor Q1‐3 . Interestingly, the sensor Q1‐3 exhibited an intramolecular charge transfer absorption band at 400 nm and emission band at 500 nm, respectively, directly realizing an “OFF–ON” response after the deprotonation process induced by cyanide anions in aqueous medium (DMSO/H₂O, 1:9, v/v). Notably, this sensor was successfully applied to detect cyanide anions in food samples, which proves a very simple and selective platform for on‐site monitoring of cyanide in agriculture samples. In addition, the test strips and silica gel plates based on Q1‐3 were also fabricated, which could act as test kits and silica gel plates for convenient and efficient detection of cyanide anions.     

Identification of bioactive compounds in Shaoyao‐Gancao decoction using β2‐adrenoceptor affinity chromatography

Shaoyao‐Gancao decoction, a Chinese herbal formula, is composed of Paeoniae Radix alba and Glycyrrhiza Radix et rhizoma . It has been widely used to treat muscle spasms and asthma. However, little is known about the bioactive components of Shaoyao‐Gancao decoction. In the present study, the bioactive compounds in water‐extract of Shaoyao‐Gancao decoction were separated by the immobilized β₂‐adrenoceptor affinity column and identified using quadrupole time‐of‐flight mass spectrometry. The affinity constants of the separated compounds that bind to β₂‐adrenoceptor were determined by frontal analysis. Compound bioactivity was tested in a rat tracheal smooth muscle relaxation assay. We identified the bioactive compounds in the water extract of Shaoyao‐Gancao decoction that bound to the β₂‐adrenoceptor as paeoniflorin and liquiritin. Paeoniflorin and liquiritin had only one binding site on the immobilized β₂‐adrenoceptor, and the affinity constants were (2.16 ± 0.10) × 10⁴ M⁻¹ and (2.95 ± 0.15) × 10⁴ M⁻¹, respectively. Both compounds induced a concentration‐dependent relaxation of tracheal smooth muscle following K⁺‐stimulated contraction, and the relaxation effects were abrogated by the β₂‐adrenoceptor antagonist, ICI 118551. Therefore, paeoniflorin and liquiritin are bioactive compounds in Shaoyao‐Gancao decoction and the β₂‐adrenoceptor affinity chromatography is a useful tool for identifying potential β₂‐adrenoceptor ligands in natural products used in traditional Chinese medicine.     

Changes in Carcinogenic Heterocyclic Amines during in vitro Digestion

The high amounts of heterocyclic amines (HCAs) in overcooked foods are known carcinogens. However, the quantitative changes in carcinogenic substances, such as HCAs, caused by human digestion, have not been studied. This study was performed to evaluate the effects of digestive enzymes and the enterobacteria, Escherichia coli (E. coli) and Lactobacillus casei (L. casei), on the quantitative changes in four HCAs: 2‐amino‐3,4,8‐trimethylimidazo[4,5‐f]quinoxaline (4,8‐DiMeIQx), 2‐amino‐3,7,8‐trimethylimidazo[4,5‐f]quinoxaline (7,8‐DiMeIQx), 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ), and 2‐amino‐3,8‐dimethylimidazo[4,5‐f]quinoxaline (MeIQx). Digestive enzymes gradually reduced the amount of four HCAs during in vitro experiments (p < 0.05). The concentration of all HCAs rapidly decreased after digestion in the mouth and stomach. L. casei dramatically reduced the amount of HCAs during in vitro digestion (p < 0.05). From the results of this study, we hypothesize that the amount of HCAs in overcooked food could be decreased, and their risk could be reduced during human digestion by digestive enzymes and enterobacteria.     

Electrospray ionization tandem mass spectrometric analysis of ent‐6,7‐seco‐kaurane diterpenoids from the Isodon species

Electrospray ionization tandem mass spectrometry (ESI‐MSⁿ) using an ion trap instrument and accurate mass measurement on a quadrupole time‐of‐flight (Q‐TOF) mass spectrometer has aided the structural characterization and differentiation of the enmein and spiro‐lactone types of ent‐6,7‐seco‐kaurane diterpenoids from Isodon species. The mass spectral fragmentation data from both techniques was compared to obtain the mass spectrometric fragmentation pathways of the ent‐6,7‐seco‐kaurane diterpenoids with high confidence. The analysis revealed that losses of CH₂O and CO₂ are the predominant process for the enmein type of ent‐kauranes in negative ion mode, and the loss of CO₂ is typical for the spiro‐lactone type in positive ion mode. In addition, compounds of the spiro‐lactone type with a conserved core structure but different substituent groups, such as acetyl, hydroxyl, and aldehyde moiety, resulted in diagnostic product ions by means of successive losses of AcOH, H₂O, and CO, respectively. The fragmentation knowledge will facilitate the analysis and identification of the ent‐6,7‐seco‐kauranes in future plant research. Copyright © 2008 John Wiley & Sons, Ltd.