Sample preparation and determination of ginkgo terpene trilactones in selected beverage, snack, and dietary supplement products by liquid chromatography with evaporative light-scattering detection

Ginkgo biloba leaf extract has been widely used in dietary supplements and more recently in some foods and beverages. Sample preparation procedures for determination of ginkgo terpene trilactones (including bilobalide and ginkgolides A, B, C, and J) in various sample matrixes were developed in this study. Ginkgo leaves and capsules were extracted with 5% KH2PO4 aqueous solution under sonication. Tea bags were extracted with boiling water, whereas drink samples were taken directly from the bottles. After filtration and the addition of NaCl to approximately 30% (w/v), the terpene trilactones in aqueous solutions were quantitatively extracted with ethyl acetate-tetrahydrofuran (4 + 1, v/v). Puff samples (a cereal-based fried snack item) were first defatted by using hexane or by using supercritical fluid extraction and then extracting under sonication with methanol-acetic acid (99 + 1, v/v). After evaporation of the organic phase, the terpene trilactones were redissolved in methanol and determined on a C18 reversed-phase column by liquid chromatography (LC) with evaporative light-scattering detection. The method of standard additions and gas chromatography with flame ionization detection were used for method validation. For most samples, the relative standard deviation was <10%. The identities of target compounds in ginkgo leaves and drink samples were confirmed by LC/electrospray ionization-tandem mass spectrometry.     

Chemistry and biology of terpene trilactones from Ginkgo biloba

Ginkgo biloba, the ginkgo tree, is the oldest living tree, with a long history of use in traditional Chinese medicine. In recent years, the leaf extracts have been widely sold as phytomedicine in Europe and as a dietary supplement worldwide. Effects of Ginkgo biloba extracts have been postulated to include improvement of memory, increased blood circulation, as well as beneficial effects to sufferers of Alzheimer's disease. The most unique components of the extracts are the terpene trilactones, that is, ginkgolides and bilobalide. These structurally complex molecules have been attractive targets for total synthesis. Terpene trilactones are believed to be partly responsible for the neuromodulatory properties of Ginkgo biloba extracts, and several biological effects of the terpene trilactones have been discovered in recent years, making them attractive pharmacological tools that could provide insight into the effects of Ginkgo biloba extracts.     

Application of reverse-flow micellar electrokinetic chromatography for the simultaneous determination of flavonols and terpene trilactones in Ginkgo biloba dosage forms

A reverse-flow micellar electrokinetic chromatographic (RF-MEKC) method was developed for the simultaneous qualitative determination of 10 components consisting of the flavonol glycosides, rutin and quercitrin, the flavonol aglycones, isorhamnetin, kaempferol and quercetin, the terpene trilactones, ginkgolides A, B, C and J and the sesquiterpene, bilobalide. This method was used to fingerprint Ginkgo biloba solid oral dosage forms and validated for the quantitation of the marker compounds, rutin and quercetin in some commercial products. In addition to the usual variables, the influence of some essential background electrolyte (BGE) components such as sodium dodecyl sulphate (SDS) and -cyclodextrin concentrations were investigated. A polyimide fused-silica square capillary column (75 microm I.D. x 360 microm O.D.) with a total length of 60.0 cm and effective length of 45.0 cm was used for the separation. The final BGE consisted of 20 mM phosphoric acid, 40 mM SDS and 12 mM -cyclodextrin (pH 2.2) using reverse polarity with a voltage of -17.5 kV. Samples were injected electrokinetically at -5 kV for 3 s for the qualitative analysis and hydrodynamically at 20 mbar for 0.6 s for the quantitative assay. The total run time was 22 min and the limits of detection were 3.13 microg/ml and 1.88 microg/ml for rutin and quercetin, respectively. Fingerprint profiles of the solid oral dosage forms and the results of the quantitative analysis indicated that there were major discrepancies in the marker content between products and illustrates the value of this method for use as a procedure to assess product quality of commercially available Ginkgo biloba products.     

Selective separation and determination of uranium in calcite and gypsum after EDTA-mediated sample dissolution and cation-exchange

Journal of Radioanalytical and Nuclear Chemistry - The present paper describes a relatively simple, effective, very selective and economic method for the determination of uranium in calcite and...     

Selective mono N-alkylations of cyclen in one step syntheses

In this Letter, we describe selective one step mono N-alkylations of cyclen (1,4,7,10-tetraazacyclododecane) using a range of functionalized alkyl halides. This ‘easy to use’ synthesis gives rise to mono-derivatives of cyclen from various alkyl halides or, when using alkyl dihalides, bis-cyclen derivatives, where the alkyl group links two cyclen macrocycles together. While the reaction conditions require the use of 1:4 stoichiometry (alkyl halide:cyclen), any unreacted cyclen can be recovered with an aqueous extraction and successfully reused. This procedure was found to be quite versatile, being particularly well-suited for cyclen targets bearing protected thiol groups, as well as α-chloroamide-derived chromophores; such cyclen pendant chromophores are employed as antennae for lanthanide luminescence probes and sensors.     

Rapid microwave-assisted hydrolysis for determination of ginkgo flavonol glycosides in extracts of Ginkgo biloba leaves

A rapid microwave-assisted hydrolysis (MAH) method is presented for the sample pretreatment of the determination of ginkgo flavonol glycosides in extracts of Ginkgo biloba L. (EGb). By this method, flavonol glycosides can be completely hydrolyzed within 2 min. After investigating the effects of solvents, acidity, microwave power, and microwave radiation time on hydrolysis, the optimal hydrolysis conditions are as follows: 300 W of microwave power, 2 min of hydrolysis time, 5.7% of hydrochloric acid in the hydrolysis solution, and n-propanol as the hydrolysis solvent. After MAH of the samples, three flavonol aglycones, such as quercetin, kaempferol, and isorhamnetin are analyzed by high-performance liquid chromatography. Compared with conventional reflux hydrolysis, this method owns offers several advantages: it saves time, costs less, and is environmentally friendly.     

Deep eutectic solvents as green media for efficient extraction of terpene trilactones from Ginkgo biloba leaves

Deep eutectic solvents (DESs)-based ultrasonic extraction of terpene trilactones (TTLs) from Ginkgo biloba leaves was efficiently developed. Sixteen DESs were prepared, and DESs composed of choline chloride-urea (ChCl-U) and betaine-ethylene glycol (BE-EG) gave higher TTL extraction yields than the present, most efficient solvent 70% ethanol. The extraction conditions were further optimized, and the optimum conditions were as follows: taking BE-EG containing 40% (w/w) water as the extraction solvent, 1:10 of G. biloba leaves powder-to-solvent ratio, and ultrasonic treatment at 45°C and 100?W for 20?min. A total extraction yield of 1.94?±?0.03?mg/g was obtained under the optimum conditions, which indicated that 99.37% of TTLs could be extracted from the G. biloba leaves powder by a single extraction. Moreover, the polyamide resin was used to recover the TTLs in DES extracting solution, and recovery yield of 95.1% was attained. Therefore, BE-EG containing 40% (w/w) water was a potential alternative solvent for TTLs extraction from G. biloba leaves.     

Selective potentiometric determination of phenol and alkylphenols in nonaqueous extracts

Some systems of extraction of phenols from aqueous solutions (R=97–99%) are recommended. Methods of separate extraction-potentiometric determination of phenol and alkylphenols in nonaqueous extracts are developed.     

Selective conversion of furfural to cyclopentanol over cobalt catalysts in one step

A series of cobalt catalysts with different supports were prepared for the selective conversion of biomassderived furfural to cyclopentanol(CPL) in one step.The best CPLyield was 82 mol%at 160 ℃,2 MPa H_2,4 h when cobalt was supported on ZrO_2-La_2O_3.The supports were characterized by X-ray diffraction(XRD)and temperature-programmed desorption of ammonia(NH_3-TPD).The XRD results indicated that the more stable t-ZrO_2 formed by doping La_2O_3.The amount of acid sites of the catalyst increased,too.The influences of parameters such as reaction temperature,hydrogen pressure,and reaction time on the catalytic activity were also investigated.The polymer formed during the reaction may cause the deactivation of the Co/ZrO_2-La_2O_3 catalyst.This work provides a possibility to prepare the stable t-ZrO_2and apply with cobalt metal for biomass valorization.     

Single step LC method for determination of folypolyglutamate synthetase activity and separation of polyglutamates

Summary An HPLC assay has been developed for measuring folylpolyglutamate synthetase (FPGS) activity. It is based on the incorporation of U(¹⁴C)-glutamic acid into a folate derivative. The method has the advantage over previous procedures of offering in a single step full separation of the unreacted U(¹⁴C)-glutamic acid from that incorporated in folylpolyglutamates, as well as the possibility of identifying the chain length of the polyglutamates formed. It has been applied to determine FPGS activity in murine leukaemic lymphoblasts L5178Y. Activity was proportional over a wide range both to the incubation time and the amount of protein. Maximum activity was observed with folinic acid and the antifolate aminopterin (AMT) as substrates.     

Spectroscopic investigation of Ginkgo biloba terpene trilactones and their interaction with amyloid peptide Abeta(25-35)

The beneficial effects of Ginkgo biloba extract in the "treatment" of dementia are attributed to its terpene trilactone (TTL) constituents. The interactions between TTLs and amyloid peptide are believed to be responsible in preventing the aggregation of peptide. These interactions have been investigated using infrared vibrational absorption (VA) and circular dichroism (VCD) spectra. Four TTLs, namely ginkgolide A (GA), ginkgolide B (GB), ginkgolide C (GC) and bilobalide (BB) and amyloid Abeta(25-35) peptide, as a model for the full length peptide, are used in this study. GA-monoether and GA-diether have also been synthesized and investigated to help understand the role of individual carbonyl groups in these interactions. The precipitation and solubility issues encountered with the mixture of ginkgolide+Abeta peptide for VA and VCD studies were overcome using binary ethanol-D(2)O solvent mixture. The experimental VA and VCD spectra of GA, GB, GC and BB, GA-monoether and GA-diether have been analyzed using the corresponding spectra predicted with density functional theory. The time-dependent experimental VA and VCD spectra of Abeta(25-35) peptide and the corresponding experimental spectra in the presence of TTLs indicated that the effect of the TTLs in modulating the aggregation of Abeta(25-35) peptide is relatively small. Such small effects might indicate the absence of a specific interaction between the TTLs and Abeta(25-35) peptide as a major force leading to the reduced aggregation of amyloid peptides. It is possible that the therapeutic effect of G. biloba extract does not originate from direct interactions between TTLs and the Abeta(25-35) peptide and is more complex.     

Selective molecular sequestration with concurrent natural product functionalization and derivatization: from crude natural product extracts to a single natural product derivative in one step

A resin-bound nitroso compound sequestered a single unexpected component from crude plant seed extracts. Several plants, including Piper nigrum, Eugenia caryophyllata, and Pimenta dioica, were extracted with organic solvent in the presence of a nitroso-containing resin. The nitroso resin selectively sequestered a single compound, β-caryophyllene, via a chemo- and regioselective ene reaction. The ene product was released from the resin, and proper selection of the solid-phase linker and cleavage cocktail allowed concomitant further transformation of the primary ene product to a novel functionalized polycycle. Preliminary studies indicate that the new hydroxylamine-containing natural product derivatives have antibiotic activity.     

电堆积-非水毛细管电泳法同时分离测定虎杖中的有效成分

建立了电堆积富集-非水毛细管电泳同时分离测定中药虎杖中的大黄素、白藜芦醇和虎杖苷的新方法.对各种影响因素做了系统的研究,确立了中药虎杖中3种有效成分的最佳电堆积和分离条件,以甲醇为非水介质,30mmol/L NaAc-4 mmol/L NaOH-2 mmol/L CTAB溶液为背景电解质,运行电压为-25 kV,在220 nm波长下紫外检测.该法已应用于中药虎杖中大黄素、白藜芦醇和虎杖苷同时分离测定.     

Selective separation and determination of isoproterenol on thin layers of bismuth silicate ion-exchanger

A simple and sensitive method for the separation and determination of isoproterenol from other doping drugs has been developed on thin layers of bismuth silicate, a synthetic inorganic ion exchanger as adsorbent in thin layer chromatography (TLC). A mixture of methanol and 0.1 mol/L formic acid (3:7, v/v) was employed as the mobile phase. The development time was 32 min. The quantitative measurement were performed with a Camag TLC Scanner-3 at wavelength (λ) of 410 nm. The isoproterenol recovery in this procedure was 98.9%. The linear correlation coefficient was greater than 0.9871 and the relative standard deviation (RSD) was less than 0.94. The limit of detection (LOD) and limit of quantification (LOQ) were 7.7×10^-7mol/L and 3.85 ×10^-6mol/L, respectively. This method has been applied in the determination of isoproterenol in dosage forms and in biological fluids.     

Selective sequential dissolution for the determination of inorganic indium compounds in the particulate matter of emissions and workplace air.

A speciation method was developed for the determination of inorganic indium compounds in the particulate matter of emissions and from the workplace, based on selective sequential extractions. The main inorganic indium compounds that are expected to be present in the atmospheric particulate matter involving the industrial production of indium and in the manufacture of indium compounds were separated and determined. The procedure has been tested on standard reference materials. The indium recovery was in the range 93 - 105%.     

Determination of SCFAs in water using GC-FID. Selection of the separation system

In the present study, an analytical procedure was developed for the determination of short-chain fatty acids (SCFAs) in landfill leachate and municipal wastewater employing injection of aqueous samples to gas chromatograph with flame ionization detector (GC-FID). Chromatographic conditions such as a separation system, injection volume, oven temperature program were investigated and selected. With two columns, one with a polar (polyethylene glycol) and one with a non-polar (dimethylpolisiloxane) stationary phase, good separation of SCFAs, containing from 2 to 8 carbon atoms, was achieved. The sample volume was 2 μL and the temperature program 80 °C (30 s) then 7 °C min⁻¹ to 220 °C (2 min). LOQs values were below 0.25 mg L⁻¹. The concentrations of the acids in the landfill leachate studied ranged from 0.45 ± 0,059 (average ± extended uncertainty) mg L⁻¹ for pentanoic acid to 15.2 ± 0.73 mg L⁻¹ for ethanoic acid. Concentrations of SCFAs in the municipal wastewater were lower than LOQs.     

Selective separation and determination of dissolved chromium species in natural waters by atomic absorption spectrometry

A procedure for determining the concentrations of dissolved chromium species in natural waters is described. Chromium(III) and chromium(VI), separated by co-precipitation with hydrated iron(III) oxide, and total dissolved chromium are determined separately by conversion to chromium(VI), extraction with APDC into MIBK and determination by a.a.s. The detection limit is 40 ng l^?1 Cr. The dissolved chromium not amenable to separation and direct extraction is calculated by difference. In the waters investigated, total concentrations were relatively high (1–5 μg l^?1) with Cr(VI) the predominant species in all areas sampled with one exception, where organically bound chromium was the major species.     

Microchip-based one step DNA extraction and real-time PCR in one chamber for rapid pathogen identification

Optimal detection of a pathogen present in biological samples depends on the ability to extract DNA molecules rapidly and efficiently. In this paper, we report a novel method for efficient DNA extraction and subsequent real-time detection in a single microchip by combining laser irradiation and magnetic beads. By using a 808 nm laser and carboxyl-terminated magnetic beads, we demonstrate that a single pulse of 40 seconds lysed pathogens including E. coli and Gram-positive bacterial cells as well as the hepatitis B virus mixed with human serum. We further demonstrate that the real-time pathogen detection was performed with pre-mixed PCR reagents in a real-time PCR machine using the same microchip, after laser irradiation in a hand-held device equipped with a small laser diode. These results suggest that the new sample preparation method is well suited to be integrated into lab-on-a-chip application of the pathogen detection system.     

Development of a rapid resolution HPLC method for the separation and determination of 17 phenolic compounds in crude plant extracts

Rapid Resolution HPLC/DAD method, on a 1.8 μm, 4.6×50 mm column, was developed to enable a rapid separation of a mixture of 17 compounds, which consisted of hydroxybenzoic acids, hydroxycinnamic acids, flavones, flavonols, flavanone, flavonol-glycoside and antraquinone, in a single run, within 22 minutes. The developed method is precise, accurate and sensitive enough for simultaneous quantitative evaluation of major compounds in crude and hydrolyzed extracts of parsley, buckthorn, mint, caraway and birch. In order to overcome the inability to quantify all the phenolic compounds present in the samples caused by lack of external standards, HPLC approaches for the total phenolic content estimation based on sum of all integrated peak areas were made. These results were compared with the total phenolic content determined by Folin-Cioacalteu method. Although the correlation between the series of data was not significant (p<0.05), the difference between the results of total phenolic content obtained spectrophotometrically and by HPLC was not high in the case of parsley, buckthorn and mint extract. Regarding the obtained results, the HPLC approach could serve as an excellent tool for total phenolic content estimation, without the need for complete identification of the individual compounds.