Comparison of different sample preparation treatments for the analysis of wine phenolic compounds in human plasma by reversed phase high-performance liquid chromatography

Effect of ultrasonic treatment on the polyphenol content and antioxidant capacity of extract from defatted hemp, flax and canola seed cakes

The effectiveness of ultrasonic extraction of phenolics and flavonoids from defatted hemp, flax and canola seed cakes was compared to the conventional extraction method. Ultrasonic treatment at room temperature showed increased polyphenol extraction yield and antioxidant capacity by two-fold over the conventional extraction method. Different combinations of ultrasonic treatment parameters consisting of solvent volume (25, 50, 75 and 100 mL), extraction time (20, 30 and 40 min) and temperature (40, 50, 60 and 70 °C) were selected for polyphenol extractions from the seed cakes. The chosen parameters had a significant effect (p<0.05) on the polyphenol extraction yield and subsequent antioxidant capacity from the seed cakes. Application of heat during ultrasonic extraction yielded higher polyphenol content in extracts compared to the non-heated extraction. From an orthogonal design test, the best combination of parameters was 50 mL of solvent volume, 20 min of extraction time and 70 °C of ultrasonic temperature.

Biological analysis of herbal medicines used for the treatment of liver diseases

Herbal medicines have been used to treat liver disorders for thousands of years in the East and have now become a promising therapy internationally for pathological liver conditions. Biological analysis of hepatoprotective herbs is an important issue from the pharmacokinetic perspective in developing new therapeutic managements for liver disease. The biological analysis focuses on the pretreatment methods, separation and quantification of herbal medicines in biological samples. We have compiled and discuss the biological analytical method of six herbal medicines for liver protection containing Silybum marianum(silymarin), Glycyrrhiza glabra, Scutellaria baicalensis, Schisandra chinensis, Salvia miltiorrhiza and Astragalus membranaceus. This review provides a convenient reference for researchers to reduce time-consuming method optimization.

Ultrasound-assisted hydrolysis and gas chromatography-mass spectrometric determination of phenolic compounds in cranberry products

An ultrasound-assisted hydrolysis and gas chromatography-mass spectrometric (GC-MS) method has been developed for determination of phenolics in cranberry products. Prior to GC-MS separation and characterisation, the phenolics in samples were hydrolysed by hydrochloric acid with ultrasound-assistance, extracted with ethyl acetate, and derivatised with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA)+1% trimethylchlorosilane (TMCS) reagents. The application of ultrasonication significantly accelerated the acidic hydrolysation of the conjugated phenolics. A baseline separation of the 20 phenolics and internal standard was achieved in 25min. Standard calibration curves were linear over the concentration range of 0.0-50μg/mL and detection limits were 0.06-0.70μg/mL. Twenty phenolics were identified in cranberry samples and all of them occurred mainly in conjugated forms. Of those, the benzoic acid, quercetin, and myricetin were most abundant phenolics. The total phenolics were 12.4mg/g in cranberry fruits, 9.1mg/mL in 100% cranberry juice, and 11.1mg/g in cranberry sauces, respectively.

Critical topics in ensuring data quality in bioanalytical LC–MS method development

The use of LC–MS for bioanalysis of pharmaceuticals is entering its third decade and may be considered to be a mature technology. In many respects this is true, considering the advances made in such areas as instrument performance, electronics, software and automation of use. However, there remain instrumental and noninstrumental areas that require significant attention to ensure data quality. Increasing regulatory focus on analytical method performance and unaddressed method issues require the bioanalyst to understand those areas that most greatly impact data quality. This review will focus on instrumental and noninstrumental areas that can influence data quality, including reference standard and internal standard quality and physicochemical properties, matrix effects, stability in matrix, sample preparation, LC and MS.

Phenolic acids and flavonoids: occurrence and analytical methods

Phenolics are structurally assorted and are generally part of a complex mixture isolated from plant and biological origin matrices. A wide gamut of natural products have been the focus of main study for phenolic compounds while urine and blood are the two main biological fluids that have been analyzed for metabolism studies. Traditional and more advanced techniques have come to prominence for sample preparation, detection, and identification. This review is devoted to a short discussion of the occurrence of phenolic acids and flavonoids, their role in human health, and focuses on a detailed presentation of the analytical methods, concluding with the advantages of analytical methods employed so far and prospects. Strategies and practical aspects for the determination of phenolic acids and flavonoids in biological fluids, beverages, plants, and food are reported. Novel and past applications are provided with significant treatment and detection-related developments on the basis of the employment of separation and non-separation analytical techniques.

Extraction, separation, and detection methods for phenolic acids and flavonoids

The impetus for developing analytical methods for phenolic compounds in natural products has proved to be multifaceted. Hundreds of publications on the analysis of this category of compounds have appeared over the past two decades. Traditional and more advanced techniques have come to prominence for sample preparation, separation, detection, and identification. This review provides an updated and extensive overview of methods and their applications in natural product matrices and samples of biological origin. In addition, it critically appraises recent developments and trends, and provides selected representative bibliographic examples.

An effective sample preparation approach for screening the anticancer compound piceatannol using HPLC coupled with UV and fluorescence detection

Piceatannol, compared with the renowned resveratrol, is a better anticancer agent and a superior agent with other biological activities. However, as there are only few plants reported to contain minute quantity of piceatannol, the scarcity of sources greatly impedes the piceatannol-related researches. To explore new sources of piceatannol, we established a sample preparation approach for screening the piceatannol in plants using HPLC-UV-fluorescence detection. When the HPLC is coupled with UV and fluorescence detectors, the decrease of signals in interferences and increase of signal in piceatannol in the fluorescence chromatogram mark clearly the position of the piceatannol peak; ultimately, it allows identification without standards. In this study, we systematically evaluated the factors affecting the extraction efficiency of piceatannol in sample preparation. Of the sample preparation strategies studied, direct solvent extraction and liquid nitrogen treatment followed by solvent extraction gave satisfactory recoveries for both piceatannol and resveratrol. These approaches avoided time-consuming lyophilization procedure. In addition, all procedures must be done in the dark to avoid negative impact of irradiation from fluorescence light on the recoveries of piceatannol and resveratrol. With the present method, we re-examined the plants previously claimed to contain only resveratrol for their piceatannol contents. The species examined included Polygonum cuspidatum, Arachis hypogaea, Vitis thunbergii, and Ampelopsis brevipedunculaata. The results showed, for the first time, all these plants contain piceatannol. The finding implies that the resveratrol-containing plants may also contain piceatannol. The results demonstrate the feasibility of these sample preparation approaches and may further the understanding for the distribution of piceatannol in plants.

Liquid chromatography with tandem mass spectrometry for the simultaneous determination of baicalein, baicalin, oroxylin A and wogonin in rat plasma

A rapid, sensitive and selective liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for the determination of baicalein, baicalin, oroxylin A and wogonin, Scutellaria baicalensis active components in rat plasma was developed. After liquid-liquid extraction with 2-(3,4-dimethoxy-phenyl)-5,7-dihydroxy-chromen-4-one as internal standard, baicalein, baicalin, oroxylin A and wogonin were eluted from an Atlantis C(18) column within 7 min with isocratic mobile phase consisting of methanol and 0.1% formic acid (60:40, v/v). The analytes were detected using an electrospray ionization tandem mass spectrometry in the multiple reaction monitoring (MRM) mode. The standard curves were linear (r=1.000) over the concentration ranges of 5-500 ng/ml for baicalein, wogonin and oroxylin A and 5-5000 ng/ml for baicalin. The coefficients of variation and relative errors of baicalein, wogonin, oroxylin A and baicalin for intra- and inter-assay at three or four quality control (QC) levels were 0.8-6.1% and -4.0 to 5.8%, respectively. The lower limits of quantification for baicalein, wogonin, oroxylin A and baicalin were 5ng/ml using 50 microl of plasma sample. This method was successfully applied to the pharmacokinetic study of baicalein, baicalin, wogonin and oroxylin A after an intravenous administration of Scutellariae radix extract to male Sprague-Dawley rats.

Analysis of phenolic acids as chloroformate derivatives using solid phase microextraction–gas chromatography

In the presented study, a simple and original procedure of phenolic acids derivatization treated by ethyl and methyl chloroformate performed in an aqueous media consisting of acetonitrile, water, methanol/ethanol and pyridine has been modified and optimized. Seven phenolic acid standards-caffeic, ferulic, gallic, p-coumaric, protocatechuic, syringic and vanillic were derivatized into corresponding methyl/ethyl esters and subsequently determined by the means of gas chromatography connected to the flame-ionisation detector (FID). Some selected validation parameters as linearity, detection and quantitation limits and peak area repeatability were valued. The total time of gas chromatography (GC) analysis was 24 min for methyl chloroformate and 30 min for ethyl chloroformate derivatization. The more suitable methyl chloroformate derivatization was used for further experiments on the possibility of multiple pre-concentration by the direct solid phase microextraction technique (SPME). For this purpose, polyacrylate (PA), polydimethylsiloxane (PDMS), carboxen/polydimethylsiloxane (CAR/PDMS) and polydimethylsiloxane/divinylbenzene (PDMS/DVB) fibres were tested and the extraction conditions concerning time of extraction, temperature and time of desorption were optimized. The most polar PA fibre gave the best results under optimal extraction conditions (50 min extraction time, 25 degrees C extraction temperature and 10 min desorption time). As a result, the total time of SPME-GC analysis was 74 min and an increase in method sensitivity was reached. The limits of quantitation (LOQ) of p-coumaric, ferulic, syringic and vanillic acid esters after SPME pre-concentration were 0.02, 0.17, 0.2 and 0.2 microg mL(-1), respectively, showing approximately 10 times higher sensitivity in comparison with the original GC method.

Chromatographic, capillary electrophoretic and capillary electrochromatographic techniques in the analysis of flavonoids

An overview is presented of chromatographic methods currently in use to determine flavonoids, including free aglycones, their corresponding glycosides, one by one, and, in the presence of each other. As a basis of selection, the following approaches can be distinguished: critical evaluation of the preliminary steps (extraction/isolation and hydrolysis) as well as the separation, identification and quantitation of constituents both on the basic research level and/or subsequently to various work up procedures. Chromatographic techniques were discussed after extraction/isolation of various flavonoids from several natural matrices. Papers were classified and compared from analytical point of view, primarily on the chromatographic, secondly on the detection techniques applied.

High-performance liquid chromatographic method for simultaneous determination of baicalein and baicalein 7-glucuronide in rat plasma

A simple HPLC method with ultraviolet detection was developed for the simultaneous determination of baicalein and its major metabolite, baicalein 7-glucuronide (baicalin) in rat plasma. Following solid phase extraction with HLB cartridge, the analytes were separated using a gradient mobile phase consisting of methanol-acetonitrile-phosphate buffer. The flow-rate was set at 1ml/min and the eluent was detected at 320nm. The method is linear over the studied range of 1-10 and 0.05-1microg/ml for baicalein and baicalin, respectively. The intra-day and inter-day variations of the analysis were less than 6.38%, with relative error ranging from -3.6 to 6%. The limit of quantification in plasma was 0.05microg/ml for both baicalein and baicalin. The developed method proves to be an improved and more reliable method because of its capability for determining baicalein and baicalin simultaneously in a single chromatographic run.