Determination of quinolizidine alkaloids in Sophora medicinal plants by capillary electrophoresis

A new capillary electrophoresis (CE) method for the determination of quinolizidine alkaloids in Sophora medicinal plants was developed. A total of seven alkaloid components (cytisine, sophocarpine, matrine, lehmannine, sophoranol, oxymatrine and oxysophocarpine) were separated within 15 min. The running buffer was a 50 mM phosphate buffer containing 1%HP-β-CD and 3.3% isopropanol. The linear calibration ranges were 5.50-88.0 μg ml⁻¹ for cytisine and lehmannine, 5.00-88.0 μg ml⁻¹ for sophocarpine and sophoranol, 5.60-89.6 μg ml⁻¹ for matrine and oxysophocarpine, and 24.0-384 μg ml⁻¹ for oxymatrine. The recoveries of the seven alkaloids were 96.0-102.9% with relative standard deviations from 1.50 to 3.00% (n = 5). The method was successfully applied to different Sophora medicinal plants including Sophora flavescens, Sophora tonkinensis and Sophora alopecuroides.     

Fluorescence detection of total count of Escherichia coli and Staphylococcus aureus on water-soluble CdSe quantum dots coupled with bacteria

The aim of this paper was to demonstrate a fluorescence measurement method for rapid detection of two bacterial count by using water-soluble quantum dots (QDs) as a fluorescence marker, and spectrofluorometer acted as detection apparatus, while Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were as detection target bacteria. Highly luminescent water-soluble CdSe QDs were first prepared by using thioglycolic acid (TGA) as a ligand, and were then covalently coupled with target bacteria. The bacterial cell images were obtained using fluorescence microscopy. Our results showed that CdSe QDs prepared in water phase were highly luminescent, stable, and successfully conjugated with E. coli and S. aureus. The fluorescence method could detect 10²-10⁷ CFU/mL total count of E. coli and S. aureus in 1-2 h and the low detection limit is 10² CFU/mL. A linear relationship of the fluorescence peak intensity and log total count of E. coli and S. aureus have been established using the equation Y = 118.68X − 141.75 (r = 0.9907).     

Distribution and accumulation of antimony in plants in the super-large Sb deposit areas, China

Antimony (Sb) distribution and accumulation in plants in Xikuangshan Sb deposit area, the only one super-large Sb deposit in the world, Hunan, China were investigated. Results show that soils were severely polluted with the average Sb concentrations up to 5949.20 mg kg^− 1. Sb widely occurred in 34 plants with various concentrations ranging from 3.92 mg kg⁻¹ to 143.69 mg kg^− 1, Equisetaceae family has the highest concentration (98.23 mg kg^− 1) while Dryopteridacea family has the lowest one (6.43 mg kg^− 1). H. ramosissima species of Equisetaceae family had the highest Sb average concentration of 98.23 mg kg^− 1 and P. vittata species of Pteridaceae family showed advantage of accumulating Sb from the contaminated environment (Biological Accumulation Coefficient, BAC = 0.08). Almost all species enriched Sb in their upground part such as shoot, leaf and flower (Biological Transfer Coefficient, BTC > 1), which may attribute to the high acropetal coefficient and Sb transformation from the atmosphere to the plants. P. phaseoloides and D. indicum showed predominantly accumulation of Sb in the upground part with BTC of 6.65 and 5.47, respectively.From the low bioavailable fraction in soils and weak relationship between total soil concentrations in soils and plants, it seems that the Sb bioavailability was limited and varied with different soil sites as well as plant species. Those observations would be significant to the phytoaccumulation and phytoremediation of plants and ecological and environmental risk assessment in Sb contaminated areas.     

A xanthone and a polyketide derivative from the leaves of Cassia obtusifolia (Leguminosae)

A new xanthone, 1,8-dihydroxy-3-methoxy-6-methylxantone and a new polyketide derivative, (4R^∗,5S^∗,6E,8Z)-ethyl-4-((E)-but-1-enyl)-5-hydroxypentdeca-6,8-dienoate, together with 20 known secondary metabolites, including 2 steroids, 4 xanthones, 10 anthraquinones, 2 triterpenoids, 1 fatty ester, and (E)-eicos-14-enoic acid, were isolated from the leaves of Cassia obtusifolia. To the best of our knowledge, the last compound was isolated from a natural source for the first time. The structures of all the compounds were elucidated on the basis of 1D and 2D NMR experiments. Some of the compounds were tested against Salmonella typhi, Staphylococcus aureus, Candida albicans ATCC 9002, and Candida tropicalis, they did not show any activity.     

Dual-color upconversion fluorescence and aptamer-functionalized magnetic nanoparticles-based bioassay for the simultaneous detection of Salmonella Typhimurium and Staphylococcus aureus

A sensitive luminescent bioassay for the simultaneous detection of Salmonella Typhimurium and Staphylococcus aureus was developed using aptamer-conjugated magnetic nanoparticles (MNPs) for both recognition and concentration elements and using upconversion nanoparticles (UCNPs) as highly sensitive dual-color labels. The bioassay system was fabricated by immobilizing aptamer 1 and aptamer 2 onto the surface of MNPs, which were employed to capture and concentrate S. Typhimurium and S. aureus. NaY_0.78F₄:Yb_0.2,Tm_0.02 UCNPs modified aptamer 1 and NaY_0.28F₄:Yb_0.70,Er_0.02 UCNPs modified aptamer 2 further were bond onto the captured bacteria surface to form sandwich-type complexes. Under optimal conditions, the correlation between the concentration of S. Typhimurium and the luminescent signal was found to be linear within the range of 10¹–10⁵ cfu mL⁻¹ (R² = 0.9964), and the signal was in the range of 10¹–10⁵ cfu mL⁻¹ (R² = 0.9936) for S. aureus. The limits of detection of the developed method were found to be 5 and 8 cfu mL⁻¹ for S. Typhimurium and S. aureus, respectively. The ability of the bioassay to detect S. Typhimurium and S. aureus in real water samples was also investigated, and the results were compared to the experimental results from the plate-counting methods. Improved by the magnetic separation and concentration effect of MNPs, the high sensitivity of UCNPs, and the different emission lines of Yb/Er- and Yb/Tm-doped NaYF₄ UCNPs excited by a 980 nm laser, the present method performs with both high sensitivity and selectivity for the two different types of bacteria.     

Fluorimetric detection of pathogenic bacteria using magnetic carbon dots

A novel and facile approach of pathogenic bacteria detection, which utilizes fluorescent sensing and bacteria capture with Magnetic carbon dots (Mag-CDs), was proposed in this work. Magnetic nanoparticles were synthesized and then decorated with C-dots, and further functionalized with amine groups (chitosan). In this way, bacteria were strongly anchored on the hybrid material Mag-CDs for highly sensitive fluorescent detection. The Mag-CDs were characterized by UV–vis, FT-IR spectra, TEM images, XRD, and EDX. The characterizations validate the fabrication of amine-Mag-CDs and the promising applications of this material. Fluorescence spectroscope and MALDI-MS were used for the detection and identification of bacterial strains, respectively. The limit of detection for Staphylococcus aureus and Escherichia coli was found to be 3 × 10² and 3.5 × 10² cfu mL⁻¹, respectively. With these encouraging results, it is expected that it would open revenues for promising applications of Mag-CDs nanomaterial.     

Calorimetric investigation of the effect of hydroxyanthraquinones in Rheum officinale Baill on Staphylococcus aureus growth

The inhibitory effects of five hydroxyanthraquinones (HAQs) from root and rhizoma of Rheum officinale Baill, a traditional Chinese medicinal (TCM) herb, on Staphylococcus aureus growth were investigated by calorimetry. The power-time curves of S.aureus with and without HAQ were acquired and the extent and duration of inhibitory effects on the metabolism evaluated by growth rate constants (k₁, k₂), half inhibitory ratio (IC₅₀), maximum heat output (P_max) and peak time (t_p). The value of k₁ and k₂ of S. aureus in the presence of the five HAQs decreased with the increasing concentrations of HAQs. Moreover, P_max was reduced and the value of t_p increased with increasing concentrations of the five drugs. The inhibitory activity varied for different drugs. IC₅₀ of the five HAQs was 4 μg ml⁻¹ for emodin, 3.5 μg ml⁻¹ for rhein, 10 μg ml⁻¹ for aloe-emodin, 1000 μg ml⁻¹ for chrysophanol, 1600 μg ml⁻¹ for physcion. The sequence of antimicrobial activity of the five HAQs: rhein > emodin > aloe-emodin > chrysophanol > physicion.     

Non-chromatographic screening method for the determination of mercury species. Application to the monitoring of mercury levels in Antarctic samples

A simple non-chromatographic method for the determination of mercury (Hg²⁺), methylmercury (MeHg⁺), dimethylmercury (Me₂Hg), and phenylmercury (PhHg⁺) employing atomic fluorescence spectrometry (AFS) as detection technique was developed. Mercury species showed a particular behavior in the presence of several reagents. In a first stage SnCl₂ was employed for Hg²⁺ determination; in a second step, [Hg²⁺ + PhHg⁺] concentration was determined using SnCl₂ and UV radiation. MeHg⁺ decomposition was prevented adding 2-mercaptoethanol. In a third stage, [Hg²⁺ + PhHg⁺ + MeHg⁺] concentration was determined using K₂S₂O₈. Finally, the four species were determined employing NaBH₄. Reagents concentration and flow rates were optimized. The extraction technique of mercury species involved the use of 2-mercaptoethanol as ion-pair reagent. The limits of detection for Hg²⁺, PhHg⁺, MeHg⁺, and Me₂Hg were 1, 40, 68, and 99 ng L⁻¹ with a relative standard deviation of 1.5, 3.1, 4.7 and 5.8%, respectively. Calibration curve was linear with a correlation factor equal to 0.9995. The method was successfully applied to the determination of the mercury species in two Antarctic materials: IRMM 813 (Adamussium colbecki) and MURST-ISS-A2 (Antarctic Krill).     

A general method for the synthesis of oligosaccharides consisting of α-(1→2)- and α-(1→3)-linked rhamnan backbones and GlcNAc side chains

A general method has been developed for the synthesis of oligosaccharides consisting of (1→2)- and (1→3)-linked rhamnans with GlcNAc side chains. As examples, highly effective and convergent syntheses of two decasaccharides in the O polysaccharide moiety of the lipopolysaccharide of the phytopathogenic bacterium Pseudomonas syringae pv. ribicola NCPPB 1010 were achieved. The two decasaccharides consist of O polysaccharide repeating units I+II and II+I, respectively. Allyl 3-O-acetyl-4-O-benzoyl-α-l-rhamnopyranoside, allyl 2-O-benzoyl-3-O-chloroacetyl-α-l-rhamnopyranoside, 2,4-di-O-benzoyl-3-O-chloroacetyl-α-l-rhamnopyranosyl trichloroacetimidate, and 3-O-acetyl-2,4-di-O-benzoyl-α-l-rhamnopyranosyl trichloroacetimidate, which were obtained by highly regioselective 3-O-acylations, were used as the key synthons to obtain the required α-(1→2)- and α-(1→3)-linked rhamnoocta saccharide acceptors with 3³- and 3⁷-free hydroxyl groups. Therefore, several disaccharides were synthesized, from which tetrasaccharides and hexasaccharides were then synthesized. Coupling of the hexasaccharide donors with the disaccharide acceptors gave the octasaccharide acceptors. Finally, the coupling of 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-d-glucopyranosyl trichloroacetimidate with the octasaccharide acceptors, followed by deprotection, afforded the two target decasaccharides. A repeating hexasaccharide unit of the cell wall polysaccharide of β-hemolytic Streptococci Group A was also synthesized in a similar way.     

High dielectric constant PrYxOy sensing films electrolyte-insulator-semiconductor pH-sensor for the detection of urea

In this paper, we describe the structural and sensing properties of high-k PrY_xO_y sensing films deposited on Si substrates through reactive co-sputtering. Secondary ion mass spectrometry and atomic force microscopy were employed to analyze the compositional and morphological features of these films after annealing at various temperatures. The electrolyte-insulator-semiconductor (EIS) device incorporating a PrY_xO_y sensing membrane that had been annealed at 800 °C exhibited good sensing characteristics, including a high sensitivity (59.07 mV pH⁻¹ in solutions from pH 2 to 12), a low hysteresis voltage (2.4 mV in the pH loop 7 → 4 → 7 → 10 → 7), and a small drift rate (0.62 mV h⁻¹ in the buffer solution at pH 7). The PrY_xO_y EIS device also showed a high selective response towards H⁺. This improvement can be attributed to the small number of crystal defects and the large surface roughness. In addition, the enzymatic EIS-based urea biosensor incorporating a high-k PrY_xO_y sensing film annealed at 800 °C allowed the potentiometric analysis of urea, at concentrations ranging from 1 to 16 mM, with a sensitivity of 9.59 mV mM⁻¹.     

Apteniols A-F, oxyneolignans from the leaves of Aptenia cordifolia

Investigation of the organic extract of Aptenia cordifolia leaves revealed six new oxyneolignans named apteniols A-F. The structures were determined by means of spectroscopic methods. The C₆C₃ units are linked by an oxygen atom at C4-C4′ or C4-C2′ and they are dihydrophenylpropanoid acid units. Their effects on germination and growth of Lactuca sativa L. have been studied in the range concentration 10⁻⁴-10⁻⁷ M.     

Coordination to copper(II) strongly enhances the in vitro antimicrobial activity of pyridine-derived N(4)-tolyl thiosemicarbazones

Five copper(II) complexes with N(4)-ortho, N(4)-meta and N(4)-para-tolyl thiosemicarbazones derived from 2-formyl and 2-acetylpyridine were obtained and thoroughly characterized. The crystal structure of N(4)-meta-tolyl-2-acetylpyridine thiosemicarbazone (H2Ac4mT) was determined, as well as that of its copper(II) complex [Cu(2Ac4mT)Cl], which contains an anionic ligand and a chloride in the coordination sphere of the metal. The in vitro antimicrobial activities of all thiosemicarbazones and their copper(II) complexes were tested against Salmonella typhimurium and Candida albicans. Upon coordination a substantial decrease in the minimum inhibitory concentration, from 225 to 1478 μmol L⁻¹ for the thiosemicarbazones to 5–30 μmol L⁻¹ for the complexes was observe against the growth of Salmonella typhimurium and from 0.7–26 to 0.3–7 μmol L⁻¹ against the growth of C. albicans, suggesting that complexation to copper(II) could be an interesting strategy of dose reduction.     

Polyhydroxylated macrolide isolated from the endophytic fungus Pestalotiopsis mangiferae

A new polyhydroxylated macrolide, named mangiferaelactone (1) was isolated from a solid culture of the endophytic fungus Pestalotiopsis manguiferae, together with ten known compounds [(6S,1′S)-LL-P880α; (6S,1′S,2′R)-LL-P880β; (1′S,2′R)-LL-880γ; (1′R)-dehydropestalotin; (−)-5-carboxylmellein; (−)-5-methylmellein; (−)-5-hydroxylmethylmellein; arabenoic acid; 5,6-dihydro-4-methoxy-2H-pyran-2-one; and the (−)-2-hexylidene-3-methylsuccinic acid]. P. manguiferae was isolated from Hyptis dilatata, a small shrub common in the central region of Panama. The structure of compound 1 was elucidated by a combination of spectroscopic methods (IR, MS, optical rotation, 1D and 2D NMR spectroscopy). The absolute configuration of 1 was established as 4R,7R,8R,9S by application of vibrational circular dichroism (VCD). Compound 1 showed a minimum inhibitory concentration (MIC) of 1.6863 mg/mL against Listeria monocytogenes, and 0.5529 mg/mL against Bacillus cereus. No activity was observed for compound 1 against Plasmodium falciparum or Trypanosoma cruzi; likewise, no cytotoxic activity was observed against A2058 and H522-T1 cells.     

Luminescence of NaGdFPO4:Ln after VUV excitation: A comparison with GdPO4:Ln (Ln=Ce, Tb)

The phosphors NaGdFPO₄:Ln³⁺ and GdPO₄:Ln³⁺ (for Ln³⁺=Ce³⁺ and Tb³⁺) were prepared by solid-state reaction technique, the VUV-vis spectroscopic properties of the phosphors were investigated, and we vividly compare the luminescence of Ce³⁺ and Tb³⁺ in the hosts. For phosphors GdPO₄:Ln³⁺, the band near 155 nm in VUV excitation spectrum is assumed to be the host-related absorption, and for NaGdFPO₄:Ln³⁺ the absorption is moved to longer wavelength, near 170 nm, showing the P-O bond covalency increased after fluoridation. The f-d transitions of Ce³⁺ and Tb³⁺ in the host lattices are assigned and corroborated, and it was found that the 5d states are with lower energy in NaGdFPO₄:Ln³⁺ than those in GdPO₄:Ln³⁺. For fluoridation of GdPO₄:Ln³⁺ to NaGdFPO₄:Ln³⁺, the energy change of Ln³⁺ (Ln=Ce, Tb) 5d states is consistent with that of host-related absorption.     

Thyonosides A and B, two new saponins isolated from the holothurian Thyone aurea

The structures of two saponins, thyonosides A and B, isolated from the holothurian Thyone aurea collected in Namibia, were elucidated by 1D and 2D NMR (¹H, ¹³C, ¹H-¹H COSY, ¹H-¹H J-resolved, TOCSY, HMQC, HMBC and NOESY). The two compounds have the same aglycon but different oligosaccharidic chains. Thyonoside A has a 3-O-methyl-β-d-xylopyranosyl-(1→3)-6-O-sodium sulphate-β-d-glucopyranosyl-(1→4)-β-d-quinovopyranosyl-(1→2)-4-O-sodium sulphate-β-d-xylopyranosyl chain, and thyonoside B a 3-O-methyl-β-d-xylopyranosyl-(1→4)-β-d-xylopyranosyl-(1→4)-β-d-quinovopyranosyl-(1→2)-4-O-sodium sulphate-β-d-xylopyranosyl chain. The holostane-type aglycon features an endocyclic double bond at position 7-8, a double bond at position 25-26 and a β-acetoxy group at C16.     

Synthesis and properties of the Co7Se8−xSx and Ni7Se8−xSx solid solutions

We report the synthesis and elementary properties of the Co₇Se_8−xS_x (x=0-8) and Ni₇Se_8−xS_x (x=0-7) solid solutions. Both systems form a NiAs-type structure with metal vacancies. In general, the lattice parameters decrease with increasing x, but in the Ni₇Se_8−xS_x system c increases on going from x=5 to 7. Magnetic susceptibility measurements show that all samples exhibit temperature-independent paramagnetism from 25-250 K. Samples within the Co₇Se_8−xS_x system, as well as Ni₇Se₈ and Ni₇SeS₇, were found to be poor metals with resistivities of ∼0.20 and ∼0.06 mΩ cm at 300 K, respectively. The Sommerfeld constant (γ) was determined from specific heat measurements to be ∼13 mJ/mol_CoK² and ∼7 mJ/mol_NiK² for Co₇Se_8−xS_x and Ni₇Se_8−xS_x, respectively.     

Synthesis and structure of a 1,6-hexyldiamine heptaborate, [H3N(CH2)6NH3][B7O10(OH)3]

A new 1,6-hexyldiamine heptaborate, [H₃N(CH₂)₆NH₃][B₇O₁₀(OH)₃] (1), has been solvothermally synthesized and characterized by single-crystal X-ray diffraction, FTIR, elemental analysis, and thermogravimetric analysis. Compound 1 crystallizes in monoclinic system, space group P2₁/n with a=8.042(2) Å, b=20.004(4) Å, c=10.103(2) Å, and β=90.42(3)°. The anionic [B₇O₁₀(OH)₃]_n²ⁿ⁻ layers are interlinked via hydrogen bonding to form a 3D supramolecular network containing large channels, in which the templated [H₃N(CH₂)₆NH₃]²⁺ cations are located.     

Superoxide sensor based on cytochrome c immobilized on mixed-thiol SAM with a new calibration method

Cytochrome c was immobilized on a mixed-thiol (mercaptoundecanoic acid/mercaptoundecanol) modified gold electrode (MUA:MU/cyt c electrode). Characterization of the cyt c electrode showed a quasi-reversible, electrochemical redox behavior with a formal potential of −13±5 mV (versus Ag/AgCl) for the surface adsorbed protein and 3±5 mV for covalently immobilized cyt c. The heterogeneous electron transfer rate constants were determined to be about 70 and 40 s⁻¹ for both states of the protein, respectively. They were found to be significantly higher than those of pure MUA-modified cyt c electrodes (MUA/cyt c electrodes). The interaction of superoxide radicals (O₂⁻) with the (MUA:MU)/cyt c electrode was characterized and used for an amperometric O₂⁻ detection. The influence of H₂O₂ and uric acid on the sensor signal was investigated. The sensitivity of the (MUA:MU)/cyt c electrode to O₂⁻ was significantly improved compared with that of the MUA/cyt c electrode. Based on a kinetic model for the superoxide detection system, a new calibration method was established. This simple and fast method used the spontaneous dismutation of KO₂ and was compared with the enzymatic superoxide generation system using xanthine oxidase.     

Synthesis, properties, and oxidizing function of 6-substituted 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]pyrrole-8(7H),10(9H)-dionylium tetrafluoroborates

Uracil-annulated heteroazulenes, 6-substituted 7,9-dimethylcyclohepta[b]pyrimido[5,4-d]pyrrole-8(7H),10(9H)-dionylium tetrafluoroborates 7a,b·BF₄⁻, which are the isoelectronic compounds of 5-dezazaflavin, were synthesized. X-Ray crystal analysis and MO calculations were carried out to clarify the structural characteristics of 7a,b·BF₄⁻. The stability of cations 7a,b is expressed by the pK_R+ values which were determined spectrophotometrically to be 10.9 and 11.2, respectively. The electrochemical reduction of 7a,b exhibited high reduction potentials at −0.84 and −0.87 (V vs Ag/AgNO₃) upon cyclic voltammetry (CV). A good linear correlation between the pK_R+ values and reduction potentials (E1_red) of 7a,b·BF₄⁻ and reference compounds 4·BF₄⁻ and 5·BF₄⁻ was obtained. In a search of the reactivity, reactions of 7a,b·BF₄⁻ with some nucleophiles, hydride and diethylamine, were carried out to clarify that the introduction of nucleophiles to give regio-isomers is dependent on the nucleophile. The photo-induced oxidation reactions of 7a,b·BF₄⁻ toward some alcohols under aerobic conditions were carried out to give the corresponding carbonyl compounds in more than 100% yield [based on compounds 7a,b·BF₄⁻], suggesting the oxidizing function of 7a,b·BF₄⁻ toward alcohols in the autorecycling process.