The guanidine and benzoic acid (1:1) complex. The polarized vibrational studies and theoretical investigations

The structure of guanidinium benzoate was discovered by Silva et al. On the basis of these X-ray crystallographic studies the detailed DFT investigation are performed. According to this result the infrared spectrum for one theoretical molecule was calculated. On the basis of potential energy distribution (PED) analysis the clear-cut assignments of observed bands were performed. For the calculated molecule with energy minimum the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were obtained. The energy difference between HOMO and LUMO was analyzed. According to theoretical calculations the direction of dipole moments (TDM) for bands observed in infrared spectra are analyzed. Verification of theoretical TDM behaviors is performed on the basis of experimental polarized specular reflection infrared spectra. The detailed assignments of observed bands is presented. Both theoretical and experimental spectra are compared. Crucial role of three different hydrogen bonds is studied in detail. Additionally, on the basis of differential scanning calorimetric study no phase transition was found in investigated crystal in the range 100-400K.

[Analysis of functionalized arene degradation pathways in model water-organic media]

The degradation of functionalized arenes exposed to a mixed culture of chemoorganoaeroheterotrophic microorganisms has been shown to predominantly occur through oxidative intradiol decyclization of the aromatic ring. The spatial structure of the catalytic center of intradiol dioxygenase and its complexes with catechol and protocatechuic acid has been characterized using quantum chemical modeling procedures. The dependence of the total energy of the enzyme-substrate complex on the length of the bond between the iron atom and the hydroxyl group of the substrate (Fe-4-OH and Fe-1-OH) before and after the separation of water and a tyrosine residue (Tyr) from the catalytic center has been demonstrated for the first time.

Theoretical study on molecular structure and vibrational analysis included FT-IR, FT-Raman and UV techniques of 2,4,5-trimethylbenzoic acid (monomer and dimer structures)

Theoretical study on the structural and vibrational analysis of monomer and dimer structures of 2,4,5-trimethylbenzoic acid (2,4,5-TMBA, C₁₀H₁₂O₂) were presented. The geometry of the molecule was fully optimized. The Fourier transform infrared (FT-IR) and the Fourier transform Raman (FT-Raman) spectra of the title molecule in solid phase were recorded in the region 4000-400 cm(-1) and 4000-50 cm(-1), respectively. The geometrical parameters and energies were investigated with the help of Density Functional Theory (DFT) employing B3LYP method and 6-311++G(d,p) basis set. The spectroscopic data of the molecule in the ground state were calculated by using DFT/B3LYP method with the 6-311++G(d,p) basis set. The vibrational spectra were calculated and fundamental vibrations were assigned on the basis of the potential energy distribution (PED) of the vibrational modes. The geometric parameters were compared with experimental data of the title molecule. The UV absorption spectrum of the studied compound was computed and recorded in the range of 190-400 nm dissolved in water and ethanol. Besides, charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap, molecular electrostatic potential (MEP) were calculated and presented. In addition these, thermodynamic properties and Mulliken atomic charges were performed.

Fenton-like oxidation of small aromatic acids from biomass burning in water and in the absence of light: implications for atmospheric chemistry

The oxidation of organic compounds from biomass burning in the troposphere is worthy of concern due to the uncertainty of chemical transformations that occur during the reactions and to the possibility of such compounds producing others more aggressive to the environment in general. In this work was studied the oxidation of relevant atmospheric organic compounds resulting from biomass burning, three small aromatic acids with similar molecular structures (benzoic, 4-hydroxybenzoic and 3,5-dihydroxybenzoic acids), in aqueous phase and in the absence of light. The oxidation process used was the Fenton-like reaction and it was evaluated by ultraviolet-visible and molecular fluorescence spectroscopies. The extent of oxidation of the acids depended on the pH of the solution, and the rate of reaction increased as the pH decreased from neutral (5) to acid (4) in atmospheric waters. Even in the absence of light, Fenton-like oxidation of the three acids originated new chromophoric compounds, which tended to be more complex than the reactants. However, after the formation of new compounds they were totally oxidized for 3,5-dihydroxybenzoic acid and only partially degraded for benzoic and 4-hydroxybenzoic acids, at least after 48 h of reaction at pH 4.5. Furthermore, the night period may be sufficient for a full degradation of the 3,5-dihydroxybenzoic acid and of their oxidation products in atmospheric waters. Thus, the results obtained in this study highlight that organic compounds from biomass burning with similar molecular structures may have different behavior regarding to their reactivity and persistence in atmospheric waters, even without light.

Intramolecular [3 + 2]-cycloadditions of azomethine ylides derived from secondary amines via redox-neutral C-H functionalization

Azomethine ylides are accessed under mild conditions via benzoic acid catalyzed condensations of 1,2,3,4-tetrahydroisoquinolines or tryptolines with aldehydes bearing a pendent dipolarophile. These intermediates undergo intramolecular [3 + 2]-cycloadditions in a highly diastereoselective fashion to form polycyclic amines with four new stereogenic centers. Challenging substrates such as piperidine, morpholine, and thiomorpholine undergo the corresponding reactions at elevated temperatures.

Electrochemical and spectroscopic characteristics of p-acryloyloxybenzoyl chloride and p-acryloyloxybenzoic acid and antimicrobial activity of organic compounds

The purpose of this multidisciplinary work is to characterize title compounds, p-acryloyloxybenzoyl chloride (ABC) and p-acryloyloxybenzoic acid (ABA) by means of experimental and theoretical evidences. As experimental research, Fourier transformation-infrared spectra (in the region 400-4000 cm(-1)) and nuclear magnetic resonance (NMR) chemical shifts (with a frequency of 400 MHz) are examined for spectroscopic properties belonging to the new synthesized compounds. Moreover, the compounds are investigated for antimicrobial activity against various microorganisms (Gram-positive and Gram-negative) by means of the visual inhibition zone technique on the agar media. The experimental results observed indicate that ABA exhibits more powerful inhibitors of microorganisms due to the presence of the hydroxyl group leading to higher reactive system, one of the most striking features of the paper. As for the theoretical studies, the optimized molecular structures, vibrational frequencies, corresponding vibrational spectra interpreted with the aid of normal coordinate analysis based on scaled density functional force field, atomic charges, thermodynamic properties at different temperature, 1H NMR chemical shifts by way of density functional theory (DFT) with the standard (B3LYP) methods at 6-311G++(d,p) basis set combination for the first time. According to findings, the 1H NMR chemical shifts and vibrational frequencies are obtained to be in good agreement with the suitable experimental results. Thus, it would be more precise to say that the calculation level chosen is powerful approach for understanding in the identification of the molecules investigated. At the same time, we determine the electrochemical characteristics belonging to the samples via the simulation of translation energy (HOMO-LUMO), molecular electrostatic potential (MEP) and electrostatic potential (ESP) investigations. It is observed that the strong intra-molecular charge transfer (ICT) appears between the donor and acceptor in the both compounds (especially ABA) due to the existence of the strong electronic donating groups and effective π-π* conjugated segments with high electronic donor ability for the electrophilic attack (intermolecular interactions).

Characterization of a dielectric phantom for high-field magnetic resonance imaging applications

PURPOSE

In this work, a generic recipe for an inexpensive and nontoxic phantom was developed within a range of biologically relevant dielectric properties from 150 MHz to 4.5 GHz.

METHODS

The recipe includes deionized water as the solvent, NaCl to primarily control conductivity, sucrose to primarily control permittivity, agar-agar to gel the solution and reduce heat diffusivity, and benzoic acid to preserve the gel. Two hundred and seventeen samples were prepared to cover the feasible range of NaCl and sucrose concentrations. Their dielectric properties were measured using a commercial dielectric probe and were fitted to a 3D polynomial to generate a recipe describing the properties as a function of NaCl concentration, sucrose concentration, and frequency.

RESULTS

Results indicated that the intuitive linear and independent relationships between NaCl and conductivity and between sucrose and permittivity are not valid. A generic polynomial recipe was developed to characterize the complex relationship between the solutes and the resulting dielectric values and has been made publicly available as a web application. In representative mixtures developed to mimic brain and muscle tissue, less than 2% difference was observed between the predicted and measured conductivity and permittivity values.

CONCLUSIONS

It is expected that the recipe will be useful for generating dielectric phantoms for general magnetic resonance imaging (MRI) coil development at high magnetic field strength, including coil safety evaluation as well as pulse sequence evaluation (including B₁(+) mapping, B₁(+) shimming, and selective excitation pulse design), and other non-MRI applications which require biologically equivalent dielectric properties.

Distributed feedback imprinted electrospun fiber lasers

Imprinted, distributed feedback lasers are demonstrated on individual, active electrospun polymer nanofibers. In addition to advantages related to miniaturization, optical confinement and grating nanopatterning lead to a significant threshold reduction compared to conventional thin-film lasers. The possibility of imprinting arbitrary photonic crystal geometries on electrospun lasing nanofibers opens new opportunities for realizing optical circuits and chips.

Study of inclusion complex between 2,6-dinitrobenzoic acid and β-cyclodextrin by 1H NMR, 2D 1H NMR (ROESY), FT-IR, XRD, SEM and photophysical methods

The formation of host-guest inclusion complex of 2,6-dinitrobenzoic acid (2,6-DNB) with nano-hydrophobic cavity of β-cyclodextrin (β-CD) in solution phase has been studied by UV-visible spectroscopy and electrochemical analysis (cyclic voltammetry, CV). The effect of acid-base concentrations of 2,6-DNB has been studied in presence and absence of β-CD to determination for the ground state acidity constant (pKa). The binding constant of inclusion complex at 303 K was calculated using Benesi-Hildebrand plot and thermodynamic parameter (ΔG) was also calculated. The solid inclusion complex formation between β-CD and 2,6-DNB was confirmed by 1H NMR, 2D 1H NMR (ROESY), FT-IR, XRD and SEM analysis. A schematic representation of this inclusion process was proposed by molecular docking studies using patch dock server.

A highly sensitive nanoscale pH-sensor using Au nanoparticles linked by a multifunctional Raman-active reporter molecule

Chemical sensing on the nanoscale has been breaking new ground since the discovery of surface enhanced Raman scattering (SERS). For nanoparticles, controlled particle aggregation is necessary to achieve the largest SERS enhancements. Therefore, aggregating agents such as salts or linker molecules are used in conjunction with chemically sensitive reporters in order to develop robust environmentally sensitive SERS probes. While salt-induced colloidal nanosphere aggregates have produced robust SERS signals, their variability in aggregate size contributes significantly to poor SERS signal reproducibility, which can complicate their use in in vitro cellular studies. Such systems often also lack reproducibility in spectral measurements between different nanoparticle clusters. Preaggregation of colloids via linkers followed by surface functionalization with reporter molecules results in the linker occupying valuable SERS hotspot volume which could otherwise be utilized by additional reporter molecules. Ideally, both functionalities should be obtained from a single molecule. Here, we report the use of 3,5-dimercaptobenzoic acid, a single multifunctional molecule that creates SERS hotspots via the controlled aggregation of nanoparticles, and also reports pH values. We show that 3,5-dimercaptobenzoic acid bound to Au nanospheres results in an excellent pH nanoprobe, producing very robust, and highly reproducible SERS signals that can report pH across the entire physiological range with excellent pH resolution. To demonstrate the efficacy of our novel pH reporters, these probes were also used to image both the particle and pH distribution in the cytoplasm of human induced pluripotent stem cells (hiPSCs).

Synthesis of new compounds with promising antiviral properties against group A and B Human Rhinoviruses

The human common cold, which is a benign disease caused by the Rhinoviruses, generally receives palliative symptomatic treatments, since no specific therapy against any of these viruses currently exists. In this work, some original synthetic compounds were produced and tested, in order to find non-toxic substances with an improved protection index (PI) for infected cells, as compared to reference drugs such as Pirodavir. We designed a series of novel molecules with a double oxygen in the central hydrocarbon chain and some modifications of the lateral methylisoxazole and propoxybenzoate moieties of lead compound 6602 (ethyl 4-{3-[2-(3-methyl-1,2-isoxazol-5-yl)ethoxy]propoxy}benzoate). It was found that most of these substances were actually less toxic than Pirodavir; in addition, the new molecule indicated as 8c was more than 30 times less toxic than Pirodavir, about twice as active on the group A strain of Rhinovirus HRV14, and even four times more effective on the group B strain HRV39, as compared to Pirodavir's PI.

The redox-Mannich reaction

A complement to the classic three-component Mannich reaction, the redox-Mannich reaction, utilizes the same starting materials but incorporates an isomerization step that enables the facile preparation of ring-substituted β-amino ketones. Reactions occur under relatively mild conditions and are facilitated by benzoic acid.

Novel triphenylantimony(V) and triphenylbismuth(V) complexes with benzoic acid derivatives: structural characterization, in vitro antileishmanial and antibacterial activities and cytotoxicity against macrophages

Two novel organoantimony(V) and two organobismuth(V) complexes of the type ML₂ were synthesized, with L = acetylsalicylic acid (HL1) or 3-acetoxybenzoic acid (HL2) and M = triphenylantimony(V) (M1) or triphenylbismuth(V) (M2). Complexes, [M1(L1)₂] (1), [M1(L2)₂]∙CHCl₃ (2), [M2(L1)₂], (3) and [M2(L2)₂] (4), were characterized by elemental analysis, IR and NMR. Crystal structures of triphenylantimony(V) dicarboxylate complexes 1 and 2 were determined by single crystal X-ray diffraction. Structural analyses revealed that 1 and 2 adopt five-coordinated extremely distorted trigonal bipyramidal geometries, binding with three phenyl groups in the equatorial position and two deprotonated organic ligands (L) in the axial sites. The metal complexes, their metal salts and ligands were evaluated in vitro for their activities against Leishmania infantum and amazonensis promastigotes and Staphylococcus aureus and Pseudomonas aeruginosa bacteria. Both the metal complexes showed antileishmanial and antibacterial activities but the bismuth complexes were the most active. Intriguingly, complexation of organobismuth(V) salt reduced its activity against Leishmania, but increased it against bacteria. In vitro cytotoxic test of these complexes against murine macrophages showed that antimony(V) complexes were the least toxic. Considering the selectivity indexes, organoantimony(V) complexes emerge as the most promising antileishmanial agents and organobismuth(V) complex 3 as the best antibacterial agent.

Steric hindrance of 2,6-disubstituted benzoic acid derivatives on the uptake via monocarboxylic acid transporters from the apical membranes of Caco-2 cells

Benzoic acid is a typical substrate for monocarboxylic acid transporters (MCTs), and easily taken up from the apical membranes of Caco-2 cells by MCTs. However, some benzoic acid derivatives were sparingly taken up by Caco-2 cells. To elucidate the mechanism of lower uptake of the derivatives, we investigated the effect of substitution of benzene ring on the uptake by MCTs using Caco-2 cells. Among the benzoic acid derivatives tested, the uptake of 2,6-disubstituted benzoic acids was markedly lower than that of other benzoic acids. Co-incubation of the 2,6-disubstituted derivatives with benzoic acid did not decrease the uptake of benzoic acid, while co-incubation with other derivatives significantly decreased the uptake of benzoic acid. Kinetic analyses elucidated that the uptake of 2,6-dichlorobenzoic acid and 2,3,6-trichlorobenzoic acid did not involve the carrier-mediated process. The 2,6-disubstitution of benzoic acid may prevent the access of carboxylic acid group to MCTs expressed on the apical membranes of Caco-2 cells.

A benzoic acid derivative and flavokawains from Piper species as schistosomiasis vector controls

The search of alternative compounds to control tropical diseases such as schistosomiasis has pointed to secondary metabolites derived from natural sources. Piper species are candidates in strategies to control the transmission of schistosomiasis due to their production of molluscicidal compounds. A new benzoic acid derivative and three flavokawains from Piper diospyrifolium, P. cumanense and P. gaudichaudianum displayed significant activities against Biomphalaria glabrata snails. Additionally, "in silico" studies were performed using docking assays and Molecular Interaction Fields to evaluate the physical-chemical differences among the compounds in order to characterize the observed activities of the test compounds against Biomphalaria glabrata snails.

Experimental and theoretical investigation of p-n alkoxy benzoic acid based liquid crystals - a DFT approach

In the present study structural effects of alkoxy chain lengths and mesogen properties of hydrogen bonded (nOBASA) complexes (n=5, 6, 7) have been studied by density functional theory (DFT) calculations and Fourier Transform Infrared (FT-IR) spectrum. The B3LYP/6-311G(d,p) level of theory has been adopted for all the computations. The experimental FT-IR (400-4000cm(-1)) spectrum was recorded on the solid phase of the molecule. The intermolecular hydrogen bond formation has been conformed from the optimized geometry. The vibrational assignments, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies were calculated. The stability of molecule arising from hyper-conjugative interactions and charge delocalization were analyzed using natural bond orbital (NBO) analysis. The electron density (ED) in the σ(*) and π(*) anti-bonding orbital and second order delocalization energies confirmed the occurrence of intermolecular charge transfer. The energetic behavior of the title compounds in solvent phase is examined using the B3LYP/6-311G(d,p) method by applying the Onsager and polarizable continuum model. The molecular electrostatic potential (MEP) surface was generated over the optimized geometry of the molecule to obtain the chemical reactivity of the molecule. The charge distribution of the mesogen molecules has been calculated. The reliability of the methods used has been assessed by comparing the theoretical results obtained from the experimental findings. Moreover, the mesomorphic behavior and the nematic phase stabilities for each molecule have been predicted using calculated local charge distribution. The simulated FT-IR spectrum of 5OBASA was agreed with experimentally observed spectrum.

Behavior-selective apoptotic capacity of 4-(3,4,5-Trimethoxyphenoxy) benzoic acid and its methyl derivatives on two breast cancer cell lines

Breast cancer is one of the most common tumors in females. The therapeutic resistance of breast cancer has motivated the development of new agents for prevention and treatment. For the present study, several compounds were designed and analyzed for their antitumor activity in many cancer cell lines. 4-(3,4,5-Trimethoxyphenoxy) benzoic acid (compound 1) and its derivatives were selected for studying the anti-proliferative and cytotoxic effects on five human cancer cell lines. Results indicated that compounds 1 and 2 significantly suppressed the cell viability of MCF-7 and MDA-MB-468 cancer cells. However, compounds 1 and 2 had only minor effects on HepG2, Huh-7, and Hela cells. Moreover, compounds 1 and 2 exhibited a novel anti-tumor activity through the induction of cell-cycle arrest at G2/M and apoptosis in MCF-7 and MDA-MB-486 breast cancer cells. Both compounds reduced colony-forming ability in MCF-7 cells. Flow cytometric analysis indicated that caspase-3 activity was increased in response to treatment with compounds 1 and 2. Taken together, these findings suggest that the novel compounds 1 and 2 are potential anticancer agents with clinical promise for breast cancer therapy.

Comparison of halide impacts on the efficiency of contaminant degradation by sulfate and hydroxyl radical-based advanced oxidation processes (AOPs)

The effect of halides on organic contaminant destruction efficiency was compared for UV/H2O2 and UV/S2O8(2-) AOP treatments of saline waters; benzoic acid, 3-cyclohexene-1-carboxylic acid, and cyclohexanecarboxylic acid were used as models for aromatic, alkene, and alkane constituents of naphthenic acids in oil-field waters. In model freshwater, contaminant degradation was higher by UV/S2O8(2-) because of the higher quantum efficiency for S2O8(2-) than H2O2 photolysis. The conversion of (•)OH and SO4(•-) radicals to less reactive halogen radicals in the presence of seawater halides reduced the degradation efficiency of benzoic acid and cyclohexanecarboxylic acid. The UV/S2O8(2-) AOP was more affected by Cl(-) than the UV/H2O2 AOP because oxidation of Cl(-) is more favorable by SO4(•-) than (•)OH at pH 7. Degradation of 3-cyclohexene-1-carboxylic acid, was not affected by halides, likely because of the high reactivity of halogen radicals with alkenes. Despite its relatively low concentration in saline waters compared to Cl(-), Br(-) was particularly important. Br(-) promoted halogen radical formation for both AOPs resulting in ClBr(•-), Br2(•-), and CO3(•-) concentrations orders of magnitude higher than (•)OH and SO4(•-) concentrations and reducing differences in halide impacts between the two AOPs. Kinetic modeling of the UV/H2O2 AOP indicated a synergism between Br(-) and Cl(-), with Br(-) scavenging of (•)OH leading to BrOH(•-), and further reactions of Cl(-) with this and other brominated radicals promoting halogen radical concentrations. In contaminant mixtures, the conversion of (•)OH and SO4(•-) radicals to more selective CO3(•-) and halogen radicals favored attack on highly reactive reaction centers represented by the alkene group of 3-cyclohexene-1-carboxylic acid and the aromatic group of the model compound, 2,4-dihydroxybenzoic acid, at the expense of less reactive reaction centers such as aromatic rings and alkane groups represented in benzoic acid and cyclohexanecarboxylic acid. This effect was more pronounced for the UV/S2O8(2-) AOP.

Fluorescence enhancement of europium(III) perchlorate by benzoic acid on bis(benzylsulfinyl)methane complex and its binding characteristics with the bovine serum albumin (BSA)

A novel ligand with double sulfinyl groups, bis(benzylsulfinyl)methane L, was synthesized by a new method. Its novel ternary complex, EuL2.5⋅L'·(ClO4)2⋅5H2O, has been synthesized [using L as the first ligand, and benzoic acid L' as the second ligand], and characterized by elemental analysis, molar conductivity, coordination titration analysis, FTIR, TG-DSC, (1)H NMR and UV-vis. In order to study the effect of the second ligand on the fluorescence properties of rare-earth sulfoxide complex, a novel binary complex EuL2.5·(ClO4)3·3H2O has been synthesized. Photoluminescent measurement showed that the first ligand L could efficiently transfer the energy to Eu(3+) ions in the complex. Furthermore, the detailed luminescence analyses on the rare earth complexes indicated that the ternary Eu (III) complex manifested stronger fluorescence intensities, longer lifetimes, and higher fluorescence quantum efficiencies than the binary Eu (III) materials. After introducing the second ligand L', the fluorescence emission intensities and fluorescence lifetimes of the ternary complex enhanced more obviously than the binary complex. This illustrated that the presence of both the first ligand L and the second ligand L' could sensitize fluorescence intensities of Eu (III) ions. The fluorescence spectra, fluorescence lifetime and phosphorescence spectra were also discussed. To explore the potential biological value of Eu (III) complexes, the binding interaction among Eu (III) complexes and bovine serum albumin (BSA) was studied by fluorescence spectrum. The result indicated that the reaction between Eu (III) complexes and BSA was a static quenching procedure. The binding site number, n, of 0.60 and 0.78, and binding constant, Ka, of 0.499 and 4.46 were calculated according to the double logarithm regression equation, respectively for EuL2.5⋅L'⋅(ClO4)2⋅5H2O and EuL2.5⋅(ClO4)3⋅3H2O systems.

Novel, fast and efficient one-pot sonochemical synthesis of 2-aryl-1,3,4-oxadiazoles

Ultrasound promoted synthesis of 2-aryl-1,3,4-oxadiazoles at ambient temperature is reported. The remarkable features of the new procedure are shorter reaction time, excellent yields, cleaner reaction profile and simple experimental and workup procedure.

The roles of reactive species in micropollutant degradation in the UV/free chlorine system

The UV/free chlorine process forms reactive species such as hydroxyl radicals (HO(•)), chlorine atoms (Cl(•)), Cl2(•-), and O(•-). The specific roles of these reactive species in aqueous micropollutant degradation in the UV/chlorine process under different conditions were investigated using a steady-state kinetic model. Benzoic acid (BA) was chosen as the model micropollutant. The steady-state kinetic model developed fitted the experimental data well. The results showed that HO(•) and Cl(•) contributed substantially to BA degradation, while the roles of the other reactive species such as Cl2(•-) and O(•-) were negligible. The overall degradation rate of BA decreased as the pH increased from 6 to 9. In particular, the relative contributions of HO(•) and Cl(•) to the degradation changed from 34.7% and 65.3% respectively at pH 6 to 37.9% and 62% respectively at pH 9 under the conditions evaluated. Their relative contributions also changed slightly with variations in chlorine dosage, BA concentration and chloride concentration. The scavenging effect of natural organic matter (NOM) on Cl(•) was relatively small compared to that on HO(•), while bicarbonate preferentially reduced the contribution of Cl(•). This study is the first to demonstrate the contributions of different reactive species to the micropollutant degradation in the UV/chlorine system under environmentally relevant conditions.

A novel substance with allelopathic activity in Ginkgo biloba

Ginkgo (Ginkgo biloba) is one of the oldest living tree species and has been widely used in traditional medicine. Leaf extracts of ginkgo, such as the standardized extract EGb761, have become one of the best-selling herbal products. However, no bioactive compound directed at plants has been reported in this species. Therefore, we investigated possible allelopathic activity and searched for allelopathically active substances in ginkgo leaves. An aqueous methanol leaf extract inhibited the growth of roots and shoots of garden cress (Lepidium sativum), lettuce (Lactuca sativa), timothy (Phleum pratense) and ryegrass (Lolium multiflorum) seedlings. The extract was purified by several chromatographic runs and an allelopathically active substance was isolated and identified by spectral analysis to be the novel compound 2-hydroxy-6-(10-hydroxypentadec-11-enyl)benzoic acid. The compound inhibited root and shoot growth of garden cress and timothy at concentrations greater than 3 μM. The activity of the compound was 10- to 52-fold that of nonanoic acid. These results suggest that 2-hydroxy-6-(10-hydroxypentadec-11-enyl)benzoic acid may contribute to the allelopathic effect caused by ginkgo leaf extract. The compound may also have potential as a template for the development of new plant control substances.

Bisphenol A treatment by the hot persulfate process: oxidation products and acute toxicity

In this study, a thermally activated persulfate oxidation process was investigated to treat aqueous Bisphenol A (BPA) solution. The effect of temperature (40-50-60-70°C), initial pH (pH=3.0, 6.5, 9.0 and 11.0) and persulfate concentration (0-20mM) on bisphenol A (BPA) and TOC removals was examined. The activation energy for hot persulfate oxidation of BPA was calculated as 184 ± 12 kJ/mol. Acidic and neutral pH values were more favorable for BPA oxidation than basic pH values. TOC removals did not exhibit a specific pattern with varying initial pHs. Gas chromatography/mass spectrometry was employed to identify oxidation products. Several aromatic and a few aliphatic compounds could be detected including benzaldehyde, p-isopropenyl phenol, 2,3-dimethyl benzoic acid, 3-hydroxy-4-methyl-benzoic acid, ethylene glycol monoformate and succinic acid. Acute toxicity tests conducted with Vibrio fischeri indicated that the inhibitory effect of 88 μM BPA solution originally being 58%, increased to 84% after 30 min and decreased to 22% after 90 min hot persulfate treatment that could be attributed to the formation and subsequent disappearance of oxidation products.

Stereochemical assignment of the fungal metabolites pestalotiopsones D and E through enantiopure synthesis

The pestalotiopsones are fungal metabolites isolated from an endophytic fungus Pestalotiopsis sp. found in the mangrove Rhizophora mucronata, used in traditional Chinese medicine to treat symptoms of dysentery. The absolute configurations of pestalotiopsones D (4) and E (5) were elucidated through total synthesis of both the R and S enantiomers, allowing for the assignment of the stereochemistry of the natural compounds as the (+)-S enantiomers. The key steps include homologation of a substituted benzoic acid to the appropriate phenylacetate derivative using Birch reductive alkylation, an oxa-Michael cyclization induced by microwave irradiation to form the chromanone substructure, and an IBX-mediated dehydrogenation yielding the chromone skeleton. Assessment of the synthetic compounds against clinical pathogens was performed.