Herbal medicine analysis by liquid chromatography/time-of-flight mass spectrometry

The fact that the effects of herbal medicines (HMs) are brought about by their chemical constituents has created a critical demand for powerful analytical tools performing the chemical analysis to assure their efficacy, safety and quality. Liquid chromatography coupled to mass spectrometry (LC–MS) is an excellent technique to analyze multi-components in complex herbal matrices. Due to its inherent characteristics of accurate mass measurements and high resolution, time-of-flight (TOF) MS is well-suited to this field, especially for qualitative applications. The purpose of this article is to provide an overview on the potential of TOF, including the hybrid quadrupole- and ion trap-TOF (QTOF and IT-TOF), hyphenated to LC for chemical analysis in HMs or HM-treated biological samples. The peculiarities of LC–(Q/IT)TOF-MS for the analysis of HMs are discussed first, including applied stationary phase, mobile-phase selection, accurate mass measurements, fragmentation and selectivity. The final section is devoted to describing the applicability of LC–(Q/IT)TOF-MS to routine analysis of multi-components, including target and non-target (unknown) compounds, in herbal samples, emphasizing both the advantages and limitations of this approach for qualitative and quantitative purposes. The potential and future trends of fast high-performance liquid chromatography (HPLC) (e.g. rapid resolution LC and ultra-performance LC) coupled to (Q)TOF-MS for chemical analysis of HMs are highlighted.     

A purge and trap technique to capture volatile compounds combined with comprehensive two‐dimensional gas chromatography/time‐of‐flight mass spectrometry to investigate the effect of sulfur‐fumigation on Radix Angelicae Dahuricae

Sulfur‐fumigation is known to reduce volatile compounds that are the main active components in herbs used in herbal medicine. We investigated changes in chemical composition between sun‐dried and sulfur‐fumigated Radix Angelicae Dahuricae using a purge and trap technique to capture volatile compounds, and two‐dimensional gas chromatography/time‐of‐flight mass spectrometry for identification. Using sun‐dried Radix Angelicae Dahuricae samples as a reference, the results showed that 73 volatile compounds, including 12 sulfide compounds, were found to be present only in sulfur‐fumigated samples. Furthermore, 32 volatile compounds that were found in sun‐dried Radix Angelicae Dahuricae samples disappeared after sulfur‐fumigation. The proposed method can be applied to accurately discriminate sulfur‐fumigated Radix Angelicae Dahuricae from different commercial sources. Copyright © 2014 John Wiley & Sons, Ltd.     

Static headspace‐multicapillary column with gas chromatography coupled to ion mobility spectrometry as a simple approach for the discrimination of crude and processed traditional Chinese medicines

The processing procedure can alter the nature and chemical transformation of traditional Chinese medicine to accommodate different clinical dispensing and preparation requirements. In this study, static headspace‐multicapillary column with gas chromatography coupled to ion mobility spectrometry was developed for the rapid and sensitive discrimination of crude and processed traditional Chinese medicine. Using Radix Paeoniae Alba as a traditional Chinese medicine model, the combined power of this approach was illustrated by classifying the crude and processed Radix Paeoniae Alba samples into two main categories. The contents of the main components in Radix Paeoniae Alba varied significantly. The established method could promote the use of ion mobility spectrometry in intrinsic quality control and differentiation of herbal medicines from other processed products or preparations.     

Comparative analysis of volatile constituents between recipe jingfangsan and its single herbs by GC‐MS combined with alternative moving window factor analysis method

Comparative analysis of volatile constituents between recipe jingfangsan and its single herbs was performed by GC‐MS combined with alternative moving window factor analysis (AMWFA), a new chemometric resolution method. Identification of the compounds was also assisted by comparison of temperature‐programmed retention indices (PTRIs) on the OV‐1 column with authentic samples. In total, 36, 29, and 42 volatile components in essential oil of Herba schizonepetae (HS), Radix saposhnikoviae (RS), and the recipe were respectively determined qualitatively and quantitatively, accounting for 81.80, 82.62 and 85.98% total contents of volatile oil of HS, RS, and the recipe respectively. Analysis by the method of AMWFA indicates that there are 22 common volatile constituents between the recipe and single herbal medicine HS, and 14 common volatile constituents between the recipe and single herb medicine RS. The experimental results also show that the volatile components of the recipe in number are almost addition of that of two single herbal medicines HS and RS, and are mainly from the single herbal medicine HS.     

Chemical fingerprinting of Gardenia jasminoides fruit using direct sample introduction and gas chromatography with mass spectrometry detection

A rapid, rugged, and inexpensive approach is described to develop chemical fingerprints of volatile and semivolatile fractions in herbal medicine. The method is based on the combination of direct sample introduction and gas chromatography (GC) analysis with mass spectrometry detection. In comparison with routine methods, the proposed approach provides the most informative fingerprint and does not demand time-consuming extraction, pretreatment, and cleanup procedures. The approach was applied to establish the GC fingerprint of gardenia fruit (Gardenia jasminoides Ellis), in which 39 components were identified. With the help of principal components analysis, the obtained fingerprint could reveal the variation in and within different herb samples as affected by season and developmental state (wild or cultivated). The results indicated that the proposed approach could serve as a rapid, simple, and effective technique for the quality control of herbal medicines.     

Quantitative fingerprinting based on the limited‐ratio quantified fingerprint method for an overall quality consistency assessment and antioxidant activity determination of Lianqiao Baidu pills using HPLC with a diode array detector combined with chemometric methods

Lianqiao Baidu pills are widely used herbal medicinal preparation that were analyzed to develop a quality consistency technique. The characteristic fingerprints of 28 batches of Lianqiao Baidu pill samples were established at five wavelengths and simultaneously assessed by using a limited‐ratio quantified fingerprint method using 15 marker compounds. The principal component analysis and fingerprinting results were compared, and the qualitative classification of the samples by principal component analysis agreed with their quantitative evaluation by the limited‐ratio quantified fingerprint method. Furthermore, the antioxidant activities of the samples were surveyed and determined using a 2,2‐diphenyl‐1‐picrylhydrazyl radical‐scavenging approach. A relationship between the common peaks in the fingerprints and the antioxidant activities was established using a partial least squares model. The relationship can be used both to determine the antioxidant activities of the Lianqiao Baidu pill preparations in vitro and as a reference for the selection of active constituents for sample quality classification. The classification results for the samples based on principal component analysis agreed with the quantitative evaluation by the limited‐ratio quantified fingerprint method, which demonstrated that the method can be applied to the holistic quality control of traditional Chinese medicine and herbal preparations.     

Identification of the chemical constituents of Chinese medicine Yi‐Xin‐Shu capsule by molecular feature orientated precursor ion selection and tandem mass spectrometry structure elucidation

The incomplete identification of the chemical components of traditional Chinese medicinal formula has been one of the bottlenecks in the modernization of traditional Chinese medicine. Tandem mass spectrometry has been widely used for the identification of chemical substances. Current automatic tandem mass spectrometry acquisition, where precursor ions were selected according to their signal intensity, encounters a drawback in chemical substances identification when samples contain many overlapping signals. Compounds in minor or trace amounts could not be identified because most tandem mass spectrometry information was lost. Herein, a molecular feature orientated precursor ion selection and tandem mass spectrometry structure elucidation method for complex Chinese medicine chemical constituent analysis was developed. The precursor ions were selected according to their two‐dimensional characteristics of retention times and mass‐to‐charge ratio ranges from herbal compounds, so that all precursor ions from herbal compounds were included and more minor chemical constituents in Chinese medicine were identified. Compared to the conventional automatic tandem mass spectrometry setups, the approach is novel and can overcome the drawback for chemical substances identification. As an example, 276 compounds from the Chinese Medicine of Yi‐Xin‐Shu capsule were identified.     

Quality assessment of Fructus xanthii based on fingerprinting using high-performance liquid chromatography

Because almost every traditional Chinese medicine (TCM) is a multicomponent system, QC of TCMs always involves various difficulties. As a current popular quality assessment approach, focusing on qualitative and quantitative analysis of certain compounds contained in herbal medicine has been widely used for the sake of expediency rather than being a practical and realistic way. However, this method does not take the existence of other constituents into account. Comparatively, the chromatographic fingerprint of the components is a more suitable approach to holistically assess the quality of herbal drugs. Fructus xanthii is a well-known herbal drug listed in all editions of the Chinese Pharmacopoeia. However, there is no quality evaluation method given in its monograph, even for the above-mentioned expediency. This paper reports an HPLC fingerprinting method for quality evaluation of F. xanthii. The HPLC profiles of 27 batches of commercial samples were further analyzed using chemometric methods, including similarity evaluation and principal component analysis. As a result, the established HPLC fingerprint contained 23 characteristic peaks; therein, 13 peaks were unambiguously assigned by comparing their retention times and UV spectra with those of reference compounds, and five peaks were tentatively identified on the basis of their MS/MS fragmentation patterns and UV spectra. Moreover, it could be clearly observed that caffeoylquinic acid and its analogs predominate in F. xanthii. Except for three samples identified as outliers, 24 other commercial samples displayed similar HPLC profiles, indicating that the quality of the herbs from different markets is stable and consistent.     

气相色谱/质谱-化学计量学法分析测定药对桃仁-红花挥发油

药对是中药配伍中最基本、最常用的形式,具有中药配伍的基本特点。药对化学是复方化学的核心内容。联用色谱和化学计量学方法是分析中药复方复杂体系的有效工具。采用GC/MS法分离测定了药对桃仁-红花、单味药桃仁和红花的挥发油成分,并对其重叠色谱峰采用化学计量学解析法进行了分辨,得到药对和各单味药的纯色谱曲线和质谱。药对桃仁-红花、单味药桃仁和红花分辨出的色谱峰,通过质谱库对其进行定性,分别得到84、27和52个定性结果,占总含量的92.06%、89.43%和94%。实验结果表明:桃仁-红花挥发油成分与单味药桃仁和红花的存在较大差别,也不是两者挥发油成分之加和。     

Gas chromatography-mass spectrometry following pressurized hot water extraction and solid-phase microextraction for quantification of eucalyptol, camphor, and borneol in Chrysanthemum flowers

Chrysanthemum flower is a common traditional Chinese medicine (TCM). In this work, pressurized hot water extraction (PHWE) followed by headspace solid-phase microextraction (HS-SPME) and GC-MS was developed for the determination of three main active volatile compounds of eucalyptol, camphor, and borneol in Chrysanthemum flowers from four different growing areas in China by internal standard method. The parameters of PHWE and HS-SPME were optimized. The method was also validated. The results showed that PHWE-SPME-GC-MS is a simple, rapid, efficient, and solvent-free technique for the quantitative determination of eucalyptol, camphor, and borneol in TCMs and is potentially useful for the TCM quality assessment.     

Quality fluctuation detection of an herbal injection based on biological fingerprint combined with chemical fingerprint

Herbal injection is one of the most important preparations of traditional Chinese medicine. More than 130 types of herbal injections are used clinically for 400 million patients annually with total sales of over four billion US dollars per year. However, the current quality control (QC) methods relying mainly on chemical fingerprints (CF) can hardly ensure quality and safety of the herbal injections with complex chemical composition and have resulted in an increase in serious adverse drug reactions. In this study, a comprehensive approach for the QC of a controversial herbal injection Shuang-Huang-Lian lyophilized powder (SHL) was established based on the quality fluctuation detection by a combination of CF and biological fingerprint (BF). High-performance liquid chromatography and the impedance-based xCELLigence system were applied to establish the CF and BF, respectively. In addition, multivariate analysis was performed to evaluate the discriminant ability of the two methods. The results showed that being subjected to environmental influence like oxygen/air, high temperature, and extreme illumination could lead to quality fluctuation of SHL. The combination of chemical and biological fingerprint method is a more powerful tool for the QC of SHL because it can clearly discriminate different groups of abnormal samples. This method can be used for the detection of quality fluctuation of SHL and can provide reference for the quality control of other herbal injections.     

杭白菊和杭黄菊挥发油的GC-MS分析

通过气相色谱-质谱联用仪检测杭白菊和杭黄菊的挥发油化学成分,分别从杭白菊和杭黄菊挥发油中分离鉴定出59种和65种化合物,其主要成分为单萜、倍半萜及其含氧衍生物.     

Ultra-performance liquid chromatography coupled with high-resolution quadrupole time-of-flight mass spectrometry analysis of the impact of bran-processing on the chemical profile of Radix Paeoniae Alba (Baishao)

In this study, a rapid and versatile ultra-performance liquid chromatography coupled with high-resolution quadrupole time-of-flight mass spectrometry-based chemical profiling approach was applied to evaluate chemical constitution of crude and processed Radix Paeoniae Alba (RPA) samples. A total of 44 compounds were identified, among which the contents of 9 compounds in processed samples were obviously decreased and 8 compounds were increased. Furthermore, compound 28 was not found in RPA sample after stir-frying with wheat bran. The proposed method provided a chemical basis for exploring the processed mechanism of herbal medicine.     

Herbal medicine in healthcare--an overview

It is generally accepted by all concerned that modern pharmaceuticals will remain out of reach of many people and 'health for all' may only be realized by the use of adequately assessed herbal products. Mankind has been using herbal medicine for healing right from the beginning of human civilization. With the advent of 'modern medicine' herbal products have been looked down upon, especially by western societies. Yet, in recent times, use of herbal medicine for heathcare has increased steadily all over the world. However, serious concerns are being realized regarding the safety, claimed efficacy and quality of herbal products used as herbal medicine, nutraceuticals, health food and cosmetics. Although herbal products are generally considered safe due to their age-old usage, significant side effects have been reported for many herbal products, including herbal medicine. Accidental contamination and intentional adulteration are considered as primary reasons for the side effects. The historical perspective and the philosophy of herbal medical practice along with its present status in the light of present day science have been reviewed and included in the present article. Assurance of safety by identification of contaminants and assessment of toxicity has been outlined. Assessment of claimed efficacy of herbal medicine is difficult due to its holistic approach. Practical ways of assessing efficacy of herbal medicine by adapting the methodologies used for modern pharmaceutical are described. The maintenance of standard of herbal medicine has been stressed and pragmatic approaches of assuring quality of herbal medicine by using modern tools of fingerprinting the chemical profile of herbal medicine are discussed. As much of the traditional herbal medical knowledge is scattered around the world at the family and community levels, and more so in the indigeneous people, the knowledge base is continuously being lost and so needs immediate documentation. Difficulties in documentation due to concerns of Intellectual Property Rights (IPR) have been highlighted.     

A target and nontarget strategy for identification or characterization of the chemical ingredients in Chinese herb preparation Shuang‐Huang‐Lian oral liquid by ultra‐performance liquid chromatography–quadrupole time‐of‐flight mass spectrometry

A target and nontarget strategy based on in‐house chemical components library was developed for rapid and comprehensive analysis of complicated components from traditional Chinese medicine preparation Shuang‐Huang‐Lian oral liquid. The sample was analyzed by ultra‐performance liquid chromatography–quadrupole time‐of‐flight mass spectrometry using generic acquisition parameters. Automated detection and data filtering were performed on the UNIFI™ software and the detected peaks were evaluated against an in‐house library. As a result, a total of 170 chemical components (110 target compounds and 60 nontarget ones) were identified or tentatively characterized, including 54 flavonoids, 30 phenylethanoid glycosides, 16 iridoid glycosides, 14 lignans, 32 organic acids, 19 triterpenoid saponins and five other types of compounds. Among them, 44 compounds were further confirmed by comparison with reference standards. It was demonstrated that this systematical approach could be successfully applied for rapid identification of multiple compounds in traditional Chinese medicine and its preparations. Furthermore, this work established the foundation for the further investigation on the metabolic fates of multiple ingredients in Shuang‐Huang‐Lian oral liquid.     

Detection of sulfur-fumigated paeoniae alba radix in complex preparations by high performance liquid chromatography tandem mass spectrometry

Detection of sulfur-fumigated Paeoniae Alba Radix (PAR) in different complex preparations is challenging due to the relatively lower content of PAR and interference from more complicated components in complex preparations with different multiple constituent herbs. In this study, a high performance liquid chromatography- triple-quadrupole tandem mass spectrometry method was developed for detecting sulfur-fumigated PAR in different complex preparations. Paeoniflorin, the major component of PAR, and paeoniflorin sulfonate, the characteristic artifact transformed from paeoniflorin during sulfur-fumigation of PAR, were used as chemical markers. Multiple reaction monitoring (MRM) scan was employed to maximize sensitivity and selectivity. Through optimizing full mass scan and daughter ion scan conditions, two mass transitions were selected and employed respectively for unequivocal identification of paeoniflorin and paeoniflorin sulfonate. The detection limits for paeoniflorin and paeoniflorin sulfonate using MRM were much lower than those detected with UV 270 nm. Paeoniflorin and paeoniflorin sulfonate could be simultaneously detected in different commercial PAR-containing complex preparations without interference of other components using the established method, indicating that the newly established method was selective and sensitive enough for screening sulfur-fumigated PAR in commercial complex preparations.     

The discriminant pixel approach: A new tool for the rational interpretation of GCxGC-MS chromatograms

GCxGC is now recognized as the most suited analytical technique for the characterization of complex mixtures of volatile compounds; it is implemented worldwide in academic and industrial laboratories. However, in the frame of comprehensive analysis of non-target analytes, going beyond the visual examination of the color plots remains challenging for most users. We propose a strategy that aims at classifying chromatograms according to the chemical composition of the samples while determining the origin of the discrimination between different classes of samples: the discriminant pixel approach.After data pre-processing and time-alignment, the discriminatory power of each chromatogram pixel for a given class was defined as its correlation with the membership to this class. Using a peak finding algorithm, the most discriminant pixels were then linked to chromatographic peaks. Finally, crosschecking with mass spectrometry data enabled to establish relationships with compounds that could consequently be considered as candidate class markers.This strategy was applied to a large experimental data set of 145 GCxGC-MS chromatograms of tobacco extracts corresponding to three distinct classes of tobacco.     

Plasma pharmacochemistry combined with microdialysis to screen potential bioactive components and their metabolites in Anemarrhena asphodeloides saponin extract using ultrahigh‐performance liquid chromatography/quadrupole‐time‐of‐flight mass spectrometry

Although various techniques have been employed to analyze drug metabolites, the metabolism of multicomponent herbal medicine has seldom been fully addressed. In contrast to chemical drugs, a number of compounds in herbal medicine could get into circulation and then be metabolized. Metabolism study on active constituents in herbal medicine is a good way for us to explain and predict a variety of events related to the efficacy and toxicity of herbal medicine. The present work aims to elucidate the multicomponent metabolic characteristics of a herbal medicine by the combination of plasma pharmacochemistry and microdialysis sampling. Anemarrhena asphodeloides, a well‐known traditional Chinese medicine, was chosen as a model. After oral administration of A. asphodeloides saponin extract to rats, microdialysis samples were collected continuously in the jugular vein and analyzed by ultrahigh‐performance LC/quadrupole‐TOF MS. The identification of compounds in biosamples was achieved by accurate mass measurement and detailed fragmentation pathway analysis. The results showed that unbound constituents in blood circulation of the rat included seven parent saponins and six metabolites, which might be the potential active components in vivo. Among which, three metabolites have not been previously reported and were identified in this study. It is the first report on systemic metabolism of total saponins of A. asphodeloides in mammalian plasma.     

色谱数据可视化及天然植物药指纹特征发现方法

提出一类色谱分析数据可视化方法,并用于发现天然植物药的化学指纹特征。选取中药材川芎作为典型研究对象,采用核主成分分析和空间投影变换法对色谱分析数据进行预处理,提取特征信息,再利用二维灰度映像对变换后的数据进行可视化表达,发现其化学指纹特征,从而直接反映出药材质量类别间的化学模式差异。将该方法用于辨识34个不同产地及等级的川芎样品,结果令人满意,证明其具有视觉模式分辨优点,是表达隐含特征指纹和辨识复杂化学物质体系的有力工具。     

Analysis of organic compounds in environmental samples by headspace solid phase microextraction

The analysis of samples contaminated by organic compounds is an important aspect of environmental monitoring. Because of the complex nature of these samples, isolating target organic compounds from their matrices is a major challenge. A new isolation technique, solid phase microextraction, or SPME, has recently been developed in our laboratory. This technique combines the extraction and concentration processes into one step; a fused silica fiber coated with a polymer is used to extract analytes and transfer them into a GC injector for thermal desorption and analysis. It is simple, rapid, inexpensive, completely solvent-free, and easily automated. To minimize matrix interferences in environmental samples, SPME can be used to extract analytes from the headspace above the sample. The combination of headspace sampling with SPME separates volatile and semi-volatile analytes from non-volatile compounds, thus greatly reducing the interferences from non-target compounds. This paper reports the use of headspace SPME to isolate volatile organic compounds from various matrices such as water, sand, clay, and sludge. By use of the technique, benzene, toluene, ethyl-benzene, and xylene isomers (commonly known as BTEX), and volatile chlorinated compounds can be efficiently isolated from various matrices with good precision and low limits of detection. This study has found that the sensitivity of the method can be greatly improved by the addition of salt to water samples, water to soil samples, or by heating. Headspace SPME can also be used to sample semi-volatile compounds, such as PAHs, from complex matrices.