没食子酸在电活化玻碳电极上的电化学行为及测定

采用循环伏安法和线性扫描伏安法对没食子酸在电活化玻碳电极上的电化学行为进行了研究。玻碳电极在pH7.0的磷酸盐缓冲溶液中,用恒电位法在1.7 V电位阳极氧化400 s。然后在pH3.0的柠檬酸盐缓冲溶液中,没食子酸在0.479 V和0.442 V处有一良好的氧化还原峰,在0.02～0.40 V s-1范围内,其氧化峰电流与扫描速率呈良好线性关系,表明电极过程为受吸附控制的准可逆过程。线性循环伏安法的氧化峰电流与没食子酸浓度1×10-6～1×10-4mol L-1范围内呈良好的线性关系(r=0.980 6),检出限为7.6×10-7mol L-1(S/N=3)。该方法操作简便,重现性较好,并应用此法分析了健民咽喉片剂中的没食子酸的含量。     

Radiolytic degradation mechanism of gallic acid and its end-products

Gallic acid is one of the most representative biorecalcitrant phenolic compounds present in cork processing wastewater. In this communication, chemical oxidation of gallic acid was studied by gamma irradiation as an advanced oxidation process. This technology turns out to be an advantageous tool for the degradation of gallic acid. The results obtained by UV-Vis and electrospray ionization mass spectrometry (ESI-MS) techniques are in agreement concerning the suitability of this technique to degrade gallic acid. ESI-MS and ESI-MS(2) monitoring of the non-irradiated and irradiated gallic acid solutions leads to the identification of the main intermediate products. Based on the overall results obtained a consistent mechanism of radiolytic degradation of gallic acid is proposed. The application of radiation as a tool to increase the biodegradability of wastewaters is an important issue from the perspective of Green Chemistry.     

Studies on the interaction of gallic acid with human serum albumin in membrane mimetic environments

In this study the interaction between gallic acid and human serum albumin (HSA) in AOT/isooctane/water microemulsions was characterized for the first time using fluorescence quenching technique in combination with UV absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD) spectroscopy and dynamic light scattering (DLS) technique. In water-surfactant molar ratio (omega(o))=20 microemulsions fluorescence data revealed the presence of one binding site of gallic acid on HSA and its binding constants (K) were (1.18+/-0.02)x10(4), (1.13+/-0.02)x10(4), (1.03+/-0.02)x10(4), (0.95+/-0.02)x10(4), (0.87+/-0.02)x10(4) and (0.82+/-0.03)x10(4)M(-1) at 282, 289, 296, 303, 310 and 317 K, respectively. The affinities in microemulsions were much higher than that in buffer solution. FT-IR and CD data suggested that the protein conformations were altered with the reductions of alpha-helices from 54-56% for free HSA in buffer to 40-41% for free HSA in microemulsion. After binding with gallic acid, the alpha-helices of HSA in microemulsion increased 2-7% for different drug-protein molar ratio. The thermodynamic functions standard enthalpy (Delta H(0)) and standard entropy (DeltaS(0)) for the reaction were calculated to be -8.10 kJ mol(-1) and 49.42 J mol(-1)K(-1). These results indicated that gallic acid bound to HSA mainly by hydrophobic interaction and electrostatic interaction in microemulsions. In addition, the displacement experiments confirmed that gallic acid could bind to the site I of HSA, which was approved by the molecular modeling study. Furthermore, the DLS data suggested that HSA may locate at the interface of the microemulsion and gallic acid could interact with them.     

TLC Densitometric Method for the Quantification of Eugenol and Gallic Acid in Clove

Eugenol and gallic acid are reported from the flower buds of Syzygium aromaticum (L.) Merr. & Perry (clove). Both the compounds have been shown to give interesting biological activities and hence serve as biomarkers. We report a simple TLC densitometric method for the quantification of eugenol and gallic acid in clove. The method was validated for precision, repeatability and accuracy. The method was found to be precise with RSD of 0.61 and 1.3 (intraday) and 0.96 and 0.24 (interday) for different concentrations of eugenol and gallic acid respectively. Instrumental precision was 0.24 and 0.21 (% CV) for eugenol and gallic acid respectively. Accuracy of the method was checked by conducting recovery study at two different levels for eugenol and gallic acid and the average percentage recoveries were found to be 99.79% and 97.90% respectively. The contents of eugenol and gallic acid in different samples of clove, as estimated by the proposed method, were found to be in the range of 12.9–14.6% and 0.31–0.61% respectively. The proposed HPTLC method for the estimation gallic acid and eugenol was found to be simple, precise, specific, sensitive and accurate and can be used for routine quality control of clove.     

Optimization of microwave‐assisted extraction for anthocyanins,polyphenols, and antioxidants from raspberry (Rubus Coreanus Miq.) using response surface methodology

Anthocyanins (Acys), polyphenols, and antioxidants were extracted from raspberry (Rubus Coreanus Miq.) using a highly efficient microwave‐assisted extraction technique. Different solvents, including methanol, ethanol, and acetone, were tested. The colors of the extracts varied from light yellow to purple red or dark red. SEM and other nutrient analyses verified that ethanol was the most favorable medium for the microwave‐assisted extraction of raspberry due to its high output and low toxicity. Effects of process parameters, including microwave power, irradiation time, and solvent concentration, were investigated through response surface methodology. Canonical analysis estimated that the highest total Acys content, total polyphenols content, and antioxidant activity of raspberry were 17.93 mg cyanidin‐3‐O‐glucoside equivalents per gram dry weight, 38.57 mg gallic acid equivalents per gram dry weight, and 81.24%, respectively. The polyphenol compositions of raspberry extract were identified by HPLC with diode array detection, and nine kinds of polyphenols were identified and quantified, revealing that chlorogenic acid, syringic acid, and rutin are the major polyphenols contained in raspberry fruits. Compared with other fruits and vegetables, raspberry contains higher Acy and polyphenol contents with stronger antioxidant activity, suggesting that raspberry fruits are a good source of natural food colorants and antioxidants.     

Validated HPTLC method for quantitative determination of gallic acid in stem bark of Myrica esculenta Buch.-Ham. ex D. Don, myricaceae

A simple, rapid, and precise HPTLC method was developed for quantitative estimation of gallic acid in stem bark of Myrica esculenta, family Myricaceae. Separation was performed on silica gel 60F254 HPTLC plates using toluene-ethyl acetate-formic acid-methanol (3 + 3 + 0.6 + 0.4, v/v/v/v) mobile phase for separation of the extracted components. The determination was carried out in the UV densitometric absorbance-reflection mode at 280 nm. The amount of gallic acid in free and combined form in the stem bark powder was found to be 0.276 and 0.541%, respectively, on a dry weight basis. The method was validated in terms of linearity, accuracy, precision, and specificity according to International Conference on Harmonization guidelines. Gallic acid response was found to be linear over a broad concentration range of 0.4-2.0 microg/band. LOD and LOQ were 0.103 and 0.312 microg/spot, respectively. The developed method is capable of quantifying amounts of gallic acid in stem bark powder of M. esculenta.     

High-performance thin-layer chromatography densitometric method for the simultaneous determination of three phenolic acids in Syzygium aromaticum (L.) Merr. & Perry

A simple, precise, and rapid high-performance thin-layer chromatographic (HPTLC) method has been developed for the simultaneous determination of 3 phenolic acids, i.e., gallic acid, caffeic acid, and syringic acid, in the dried buds of Syzygium aromaticum, commonly known as clove. HPTLC was performed on silica gel 60F254 plates with toluene-ethyl acetate-formic acid (8 + 2 + 1) mobile phase and densitometric scanning at 280 nm. The method was validated for selectivity, linearity, precision, and repeatability. Instrumental precision coefficient of variation (CV) was 0.88, 0.93, and 0.98% and repeatability of the method (CV) was 0.76, 0.64, and 0.69% for gallic acid, caffeic acid, and syringic acid, respectively. The linear concentration ranges were 400-3200 ng/spot with a correlation coefficient of 0.993 for gallic acid, 440-3520 ng/spot with a correlation coefficient of 0.994 for caffeic acid, and 400-4000 ng/spot with a correlation coefficient of 0.993 for syringic acid. The average recoveries of gallic acid, caffeic acid, and syringic acid were 96.3, 95.7, and 92.4%, respectively. Gallic acid, caffeic acid, and syringic acid were present at levels of 1.58, 0.06, and 0.05% (w/w), respectively, in S. aromaticum. This method is simple, accurate, precise, and economical and can be used for routine quality control.     

Highly selective and efficient imprinted polymers based on carboxyl‐functionalized magnetic nanoparticles for the extraction of gallic acid from pomegranate rind

With the combined surface imprinting technique and immobilized template strategy, molecularly imprinted magnetic nanoparticles were successfully prepared and coupled with high‐performance liquid chromatography to selectively separate and determine gallic acid from the pomegranate rind. On the surface of carboxyl‐functionalized magnetic nanospheres, thin imprinting shells were formed using dopamine as monomer and crosslinker. The characteristics, polymerization conditions, and adsorption performances of the resultant nanomaterials were investigated in detail. In addition of good crystallinity, satisfactory magnetism, and uniform morphology of the obtained polymers, they had rapid binding kinetics, high adsorption capacity, and favorable reusability. In the mixed solution of four hydroxybenzoic acids, the prepared nanomaterials have an excellent selectivity to gallic acid with an imprinting factor of as high as 17.5. Therefore, the polymers have great potentials in specific extraction and enrichment of gallic acid from the complex natural resources.     

微波辅助-旋转回流提取叶下珠中的没食子酸

A new kind of microwave-assisted circumrotation reflux extraction device was constructed and used to study the extraction technology of gallic acid from phyllanthus urmaria L.The extraction principle of the device was same as that of microwave-assisted solvent extraction but using circumrotation techniques as auxiliary stirrer to accelerate the process.Capillary electrophoresis was used to determinate gallic acid in phyllanthus urmaria L extracts in order to evaluate the extraction efficiency of the method.It was found that the most important factors influencing extraction gallic acid were solvent kind and microwave power.The optimum extraction conditions were as follows:water using as irradiate time 4 minute.Under the optimum extraction conditions,five experiments were carried out and the average extraction rate of gallic acid in phyllanthus urmaria L was 4.32 mg/g,relative standard deviations (R.S.D.) was 2.2%.Compared with other extraction methods e.g.reflux extraction and microwave-assisted extraction,better extraction efficiency was observed for the microwave-assisted circumrotation reflux extraction.     

Mathematical modeling and simulation of inulinase adsorption in expanded bed column

A mathematical model for an expanded bed column was developed to predict breakthrough curves for inulinase adsorption on Streamline SP ion-exchange adsorbent, using a crude fermentative broth with cells as the feedstock. The kinetics and mass transfer parameters were estimated using the PSO (particle swarm optimization) heuristic algorithm. The parameters were estimated for each expansion degree (ED) using three breakthrough curves at initial inulinase concentrations of 65.6 U mL⁻¹. In sequence, the model parameters for an ED of 2.5 were validated using the breakthrough curve at an initial concentration of 114.4 U mL⁻¹. The applicability of the validated model in process optimization was investigated, using the model as a process simulator and experimental design methodology to optimize the column and process efficiencies. The results demonstrated the usefulness of this methodology for expanded bed adsorption processes.     

Ultrafiltration of oil-in-water emulsion by using ceramic membrane: Taguchi experimental design approach

In this study, a Taguchi experimental design methodology was used to determine the importance of process parameters influencing the ultrafiltration (UF) of oil-in-water emulsions. Four parameters including pH (5–11), oil concentration (φ) (0.5–3% (v/v)), temperature (T) (25–45°C) and trans-membrane pressure (TMP) (1–5 bar) were studied at three levels. The highest flux was used as optimization criterion. In order to reduce the number of experiments, a Taguchi method was applied. Analysis of variance (ANOVA) was used to determine the most significant parameters affecting the optimization criterion. Filtration experiments were performed in a cross-flow operation at a total recycle condition in a laboratory-scale plant. The ceramic UF membrane with a pore size of 50 nm was employed in a tubular module with an active area of 0,418 m². We used water-soluble cutting oil mixed with water as a model oil-in-water emulsion. During the experiment, the drop size and zeta potential distributions were evaluated. The optimum conditions for UF providing the highest flux were found at TMP = 5 bar, pH = 7, and φ = 0.5 v/v%. The pH of emulsion had the highest impact on COD retention. The results of this study could be used as a guideline for operating UF systems with ceramic membranes at optimal conditions.     

Determination of tannic acid and its phenolic metabolites in biological fluids by high-performance liquid chromatography.

A method for the identification and determination of tannic acid and its phenolic metabolites in biological fluids by high-performance liquid chromatography was developed. Tannic acid and four phenolic compounds, namely gallic acid, pyrogallol, 4-O-methylgallic acid and ellagic acid, were successfully extracted from the biological fluids by using ethyl acetate at acidic conditions. Gallic acid, pyrogallol and 4-O-methylgallic acid were found in the sheep urine, gallic acid, 4-O-methylgallic acid and ellagic acid in plasma, and gallic acid and ellagic acid in abomasal fluid after abomasal dosing of tannic acid. Tannic acid was found in the plasma apart from the abomasal fluid into which it was administered. The concentrations of tannic acid, gallic acid, pyrogallol, 4-O-methylgallic acid and ellagic acid in plasma, abomasal fluid and urine were measured. This method could be applied to measurement of other hydrolysable tannins and their phenolic metabolites in biological materials.     

Radiolysis of polycationic systems exhibiting antimutagenic activity

The radiolysis of synthetic (based on diallyldimethylammonium) and natural (based on the biopolymer chitosan) polycations as antimutagens was studied by means of the ESR technique. It was shown that the introduction of gallic acid units into a polymer structure leads to stabilization of the macromolecule toward radiation and a reduction in radical formation during γ-irradiation, a change that correlates with a considerable increase in the antimutagenic activity of the modified polycations. Approaches to the targeted synthesis of effective animutagens and optimization of their composition were developed.     

Development and Validation of a Green Capillary Electrophoretic Method for Determination of Polyphenolic Compounds in Red Wine Samples

A sensitive, simple, rapid, experimentally convenient, cost-effective, environmentally friendly and high-throughput green chemistry by capillary electrophoresis (CE) approach for the determination of eight polyphenolics frequently found in red wines from USA was carried without using toxic organic modifier. Several parameters which affect the separation were investigated to determine the optimum conditions. At room temperature, the eight polyphenolics could be well separated within 15 min in a 55-cm length capillary at a separation voltage of 26 kV with 40-mM borate buffer (pH 8.9). The method was fully validated showing satisfactory data for all method validation parameters tested. The limits of detection varied from 0.15 to 0.32 µM. The relative standard deviations of migration varied from 0.208 to 0.630 %. The Californian red wine samples analyzed were bought in the local markets, and the polyphenolic compound recoveries were in the range of 98–99.7 %. The method was successfully applied to the determination of the studied polyphenolics in red wine samples with satisfactory recoveries. Catechin, syringic acid, apigenin, myricetin, luteolin, quercetin, caffeic acid, and gallic acid were detected in all samples, with gallic acid and myricetin occurring in the highest concentration.

     

Analysis of phenolic constituents of biological interest in red wines by high-performance liquid chromatography

We describe a reversed-phase HPLC method that uses gradient elution and diode array detection to determine four biologically active phenolic constituents of red wines: gallic acid, trans-resveratrol, quercetin and rutin. The method permits direct injection without sample pre-treatment. ODS Hypersil served as the stationary phase; the gradient was formed by acetic acid, methanol, and water. Each analysis required an equilibration period of 10 min and a run time of 50 min for completion. Previously, total phenols were analysed according to the Folin-Ciocalteu method, using gallic acid as the standard, and the results are given as gallic acid equivalent.     

A rapid densitometric method for simultaneous quantification of gallic acid and ellagic acid in herbal raw materials using HPTLC

Gallic acid and ellagic acid are two widely occurring phenolic compounds of plant origin, to which many biological activities including anticancer and antiviral activity have been attributed. A simple HPTLC method has been developed for the simultaneous quantification of gallic acid and ellagic acid. The method was validated for precision, repeatability, and accuracy. Instrumental precision was found to be 0.083 and 0.78, and the repeatability of the method was found to be 1.07 and 1.50 (% CV) for gallic acid and ellagic acid, respectively. The accuracy of the method was checked by a recovery study conducted at two different levels and the average percentage recovery was found to be 101.02% for gallic acid and 102.42% for ellagic acid. The above method was used for the quantification of gallic acid and ellagic acid content in seeds of Abrus precatorius Linn., whole plant of Phyllanthus maderaspatensis Linn., and flowers of Nymphaea alba Linn. The proposed HPTLC method for the simultaneous quantification of gallic acid and ellagic acid was found to be simple, precise, specific, sensitive, and accurate and can be used for routine quality control of herbal raw materials and for the quantification of these compounds in plant materials.     

Determination of Gallic Acid by Flow Injection with Electrochemiluminescent Detection

ABSTRACT

Potential dependent inhibition and enhancement effects of gallic acid on the electrochemiluminescence (ECL) of luminol in alkaline solutions were found. On the basis of the enhancement effect, a flow injection method was developed for the determination of gallic acid. The method was simple, convenient and sensitive. A detection limit of 1.8×10^?8 mol/L, linear range of 3.0×10^?8 - 1.0×10^?4 mol/L, relative standard deviation of 1.0% for eleven measurements of 5.0×10^?6 mol/L of gallic acid was found. This method was successfully applied to determine the content of gallic acid in Chinese gall (moshizi).     

A carbon quantum dots‐enhanced chemiluminescence method for the determination of gallic acid in food samples

In this work, we show that gallic acid can significantly inhibit the chemiluminescence (CL) intensity of carbon quantum dots (CQDs)‐enhanced K₃Fe(CN)₆–luminol system. Under optimum conditions, the decrease in the CL intensity is proportional to the concentration of gallic acid over the range 0.01–1.0 μM, and the detection limit is 1.0 nM. The relative standard deviation of repeated intraday and interday determinations of gallic acid was 1.2–4.2%. This method was successfully applied to the determination of gallic acid in food samples, with recoveries in the range 94.0–103.0%. A possible mechanism of CL is discussed.     

LC–MS/MS method for the simultaneous determination of ethyl gallate and its major metabolite in rat plasma

A simple, rapid and sensitive liquid chromatography–tandem mass spectroscopy (LC–MS/MS) method was developed and validated for the determination of ethyl gallate, a pharmacologically active constituent isolated from Lagerstroemia speciosa (Linn.) Pers. This method was used to examine the pharmacokinetics of ethyl gallate and its major metabolite gallic acid in rat plasma using propyl gallate as an internal standard. After precipitation of the plasma proteins with acetonitrile, the analytes were separated on a Zorbax SB‐C₁₈ column (3.5 μm, 2.1 × 50 mm) with an isocratic mobile phase consisted of methanol–acetonitrile–10 mM ammonium acetate (10 : 25 : 65, v/v/v) containing 0.1% formic acid at a flow rate of 0.25 mL/min. The Agilent G6410A triple quadrupole LC/MS system was operated under the multiple‐reaction monitoring mode using the electrospray ionization technique in negative mode. The lower limits of quantification of gallic acid and ethyl gallate of the method were 0.5 and 1.0 ng/mL. The intra‐day and inter‐day accuracy and precision of the assay were less than 8.0%. This method has been applied successfully to a pharmacokinetic study involving the intragastric administration of ethyl gallate to rats. Copyright © 2009 John Wiley & Sons, Ltd.     

The recovery of gallic acid with triphenylphosphine oxide in different kind of solvents

In this study, gallic acid was separated by triphenylphosphine oxide in the presence of conventional solvents. Triphenylphosphine oxide is an organophosphorus extractant and highly selective towards carboxylic acids. Reactive extraction results were compared with physical extraction results. The extraction efficiencies reached up to 61, 76, 86, 67, and 84% in the presence of triphenylphosphine oxide with oleyl alcohol, dimethyl adipate, isobutanol, methyl isopropyl ketone, and methyl ethyl ketone, respectively. Further, the number of theoretical units and the solvent to feed ratio were calculated for the practical design of a liquid-liquid extraction column. Roughly 2 to 4 theoretical units were calculated to meet the targeted extraction efficiencies. This study is the first to investigate the reactive extraction of gallic acid by triphenylphosphine oxide, and include fundamental information for the recovery of gallic acid.