Rapid screening and characterization of drug metabolites using a multiple ion monitoring-dependent MS/MS acquisition method on a hybrid triple quadrupole-linear ion trap mass spectrometer

Chemical-tag-based semi-annotated metabolomics facilitates gene identification and specialized metabolic pathway elucidation in wheat

The importance of metabolite modification and species-specific metabolic pathways has long been recognized. However, linking the chemical structure of metabolites to gene function in order to explore the genetic and biochemical basis of metabolism has not yet been reported in wheat (Triticum aestivum). Here, we profiled metabolic fragment enrichment in wheat leaves and consequently applied chemical-tag-based semi-annotated metabolomics in a genome-wide association study in accessions of wheat. The studies revealed that all 1,483 quantified metabolites have at least one known functional group whose modification is tailored in an enzyme-catalyzed manner and eventually allows efficient candidate gene mining. A Triticeae crop-specific flavonoid pathway and its underlying metabolic gene cluster were elucidated in further functional studies. Additionally, upon overexpressing the major effect gene of the cluster TraesCS2B01G460000 (TaOMT24), the pathway was reconstructed in rice (Oryza sativa), which lacks this pathway. The reported workflow represents an efficient and unbiased approach for gene mining using forward genetics in hexaploid wheat. The resultant candidate gene list contains vast molecular resources for decoding the genetic architecture of complex traits and identifying valuable breeding targets and will ultimately aid in achieving wheat crop improvement.

High-Throughput Metabolic Soft-Spot Identification in Liver Microsomes by LC/UV/MS: Application of a Single Variable Incubation Time Approach

CYP-mediated fast metabolism may lead to poor bioavailability, fast drug clearance and significant drug interaction. Thus, metabolic stability screening in human liver microsomes (HLM) followed by metabolic soft-spot identification (MSSID) is routinely conducted in drug discovery. Liver microsomal incubations of testing compounds with fixed single or multiple incubation time(s) and quantitative and qualitative analysis of metabolites using high-resolution mass spectrometry are routinely employed in MSSID assays. The major objective of this study was to develop and validate a simple, effective, and high-throughput assay for determining metabolic soft-spots of testing compounds in liver microsomes using a single variable incubation time and LC/UV/MS. Model compounds (verapamil, dextromethorphan, buspirone, mirtazapine, saquinavir, midazolam, amodiaquine) were incubated at 3 or 5 µM with HLM for a single variable incubation time between 1 and 60 min based on predetermined metabolic stability data. As a result, disappearances of the parents were around 20-40%, and only one or a few primary metabolites were generated as major metabolite(s) without notable formation of secondary metabolites. The unique metabolite profiles generated from the optimal incubation conditions enabled LC/UV to perform direct quantitative estimation for identifying major metabolites. Consequently, structural characterization by LC/MS focused on one or a few major primary metabolite(s) rather than many metabolites including secondary metabolites. Furthermore, generic data-dependent acquisition methods were utilized to enable Q-TOF and Qtrap to continuously record full MS and MS/MS spectral data of major metabolites for post-acquisition data-mining and interpretation. Results from analyzing metabolic soft-spots of the seven model compounds demonstrated that the novel MSSID assay can substantially simplify metabolic soft-spot identification and is well suited for high-throughput analysis in lead optimization.

Long Noncoding RNAs Hepatocyte Nuclear Factor 4A Antisense RNA 1 and Hepatocyte Nuclear Factor 1A Antisense RNA 1 are Involved in Ritonavir-induced Cytotoxicity in Hepatoma Cells

Ritonavir (RTV), a pharmacoenhancer used in anti-HIV regimens, can induce liver damage. RTV is primarily metabolized by cytochrome P450 3A4 (CYP3A4) in the liver. HNF4A antisense RNA 1 (HNF4A-AS1) and HNF1A antisense RNA 1 (HNF1A-AS1) are long noncoding RNAs (lncRNAs) that regulate the expression of pregnane X receptor (PXR) and CYP3A4. This study investigated the role and underlying mechanisms of HNF4A-AS1 and HNF1A-AS1 in RTV-induced hepatotoxicity. HNF4A-AS1 and HNF1A-AS1 were knocked down by small hairpin RNAs in Huh7 and HepG2 cells. Lactate dehydrogenase and reactive oxygen species assays were performed to assess RTV-induced hepatotoxicity. Chromatin immunoprecipitation qPCR was used to detect PXR enrichment and histone modifications in the CYP3A4 promoter. HNF4A-AS1 knockdown increased PXR and CYP3A4 expression and exacerbated RTV-induced cytotoxicity, whereas HNF1A-AS1 knockdown generated the opposite phenotype. Mechanistically, enrichment of PXR and trimethylation of histone 3 lysine 4 (H3K4me3) in the CYP3A4 promoter was increased, and trimethylation of histone 3 lysine 27 (H3K27me3) was decreased after HNF4A-AS1 knockdown. However, PXR and H3K4me3 enrichment decreased after HNF1A-AS1 knockdown. Alterations in RTV-induced hepatotoxicity caused by decreasing HNF4A-AS1 or HNF1A-AS1 were reversed by knockdown or overexpression of PXR. Increased susceptibility to RTV-induced liver injury caused by the PXR activator rifampicin was attenuated by HNF4A-AS1 overexpression or HNF1A-AS1 knockdown. Taken together, these results revealed that HNF4A-AS1 and HNF1A-AS1 modulated RTV-induced hepatotoxicity by regulating CYP3A4 expression, primarily by affecting the binding of PXR and histone modification status in the CYP3A4 promoter. Significance Statement HNF4A-AS1 and HNF1A-AS1, transcribed separately from neighboring antisense genes of the human transcription factor genes HNF4A and HNF1A, were identified as lncRNAs that can affect RTV-induced hepatotoxicity and susceptibility to RTV-induced hepatotoxicity caused by rifampicin exposure, mainly by affecting the expression of CY3A4 via alterations in PXR enrichment and histone modification status in the CYP3A4 promoter. This discovery provides directions for further research on the mechanisms of RTV-induced liver injury.

Insight into chemical basis of traditional Chinese medicine based on the state-of-the-art techniques of liquid chromatography-mass spectrometry

Traditional Chinese medicine (TCM) has been an indispensable source of drugs for curing various human diseases. However, the inherent chemical diversity and complexity of TCM restricted the safety and efficacy of its usage. Over the past few decades, the combination of liquid chromatography with mass spectrometry has contributed greatly to the TCM qualitative analysis. And novel approaches have been continuously introduced to improve the analytical performance, including both the data acquisition methods to generate a large and informative dataset, and the data post-processing tools to extract the structure-related MS information. Furthermore, the fast-developing computer techniques and big data analytics have markedly enriched the data processing tools, bringing benefits of high efficiency and accuracy. To provide an up-to-date review of the latest techniques on the TCM qualitative analysis, multiple data-independent acquisition methods and data-dependent acquisition methods (precursor ion list, dynamic exclusion, mass tag, precursor ion scan, neutral loss scan, and multiple reaction monitoring) and post-processing techniques (mass defect filtering, diagnostic ion filtering, neutral loss filtering, mass spectral trees similarity filter, molecular networking, statistical analysis, database matching, etc.) were summarized and categorized. Applications of each technique and integrated analytical strategies were highlighted, discussion and future perspectives were proposed as well.

SWATH Based Quantitative Proteomics Reveals Significant Lipid Metabolism in Early Myopic Guinea Pig Retina

Most of the previous myopic animal studies employed a single-candidate approach and lower resolution proteomics approaches that were difficult to detect minor changes, and generated limited systems-wide biological information. Hence, a complete picture of molecular events in the retina involving myopic development is lacking. Here, to investigate comprehensive retinal protein alternations and underlying molecular events in the early myopic stage, we performed a data-independent Sequential Window Acquisition of all Theoretical Mass Spectra (SWATH) based proteomic analysis coupled with different bioinformatics tools in pigmented guinea pigs after 4-day lens-induced myopia (LIM). Myopic eyes compared to untreated contralateral control eyes caused significant changes in refractive error and choroid thickness (p < 0.05, n = 5). Relative elongation of axial length and the vitreous chamber depth were also observed. Using pooled samples from all individuals (n = 10) to build a species-specific retinal ion library for SWATH analysis, 3202 non-redundant proteins (with 24,616 peptides) were identified at 1% global FDR. For quantitative analysis, the 10 individual retinal samples (5 pairs) were analyzed using a high resolution Triple-TOF 6600 mass spectrometry (MS) with technical replicates. In total, 37 up-regulated and 21 down-regulated proteins were found significantly changed after LIM treatment (log2 ratio (T/C) > 0.26 or < -0.26; p ≤ 0.05). Data are accepted via ProteomeXchange with identifier PXD025003. Through Ingenuity Pathways Analysis (IPA), "lipid metabolism" was found as the top function associated with the differentially expressed proteins. Based on the protein abundance and peptide sequences, expression patterns of two regulated proteins (SLC6A6 and PTGES2) identified in this pathway were further successfully validated with high confidence (p < 0.05) using a novel Multiple Reaction Monitoring (MRM) assay on a QTRAP 6500+ MS. In summary, through an integrated discovery and targeted proteomic approach, this study serves as the first report to detect and confirm novel retinal protein changes and significant biological functions in the early LIM mammalian guinea pigs. The study provides new workflow and insights for further research to myopia control.

Metabolite Profiling and Characterization of LW6, a Novel HIF-1α Inhibitor, as an Antitumor Drug Candidate in Mice

A novel HIF (hypoxia-inducible factor)-1α inhibitor, the (aryloxyacetylamino)benzoic acid derivative LW6, is an anticancer agent that inhibits the accumulation of HIF-1α. The aim of this study was to characterize and determine the structures of the metabolites of LW6 in ICR mice. Metabolite identification was performed using a predictive multiple reaction monitoring-information dependent acquisition-enhanced product ion (pMRM-IDA-EPI) method in negative ion mode on a hybrid triple quadrupole-linear ion trap mass spectrometer (QTRAP). A total of 12 metabolites were characterized based on their MS/MS spectra, and the retention times were compared with those of the parent compound. The metabolites were divided into five structural classes based on biotransformation reactions: amide hydrolysis, ester hydrolysis, mono-oxidation, glucuronidation, and a combination of these reactions. From this study, 2-(4-((3r,5r,7r)-adamantan-1-yl)phenoxy)acetic acid (APA, M7), the metabolite produced via amide hydrolysis, was found to be a major circulating metabolite of LW6 in mice. The results of this study can be used to improve the pharmacokinetic profile by lowering the clearance and increasing the exposure relative to LW6.

Enzymatic-fingerprinting workflow of polysaccharides in Hericium erinaceus fruiting bodies: From HILIC-ESI--MS screening to targeted MIM profiling

In this study, an uncommon enzymatic-fingerprinting workflow, was proposed for characterization and discrimination of mushroom polysaccharides (MPs) by hydrophilic interaction liquid chromatography-negative electrospray mass spectrometry (HILIC-ESI^--MS). Firstly, the HILIC-ESI^--MS was used to screen and identify the enzymatic digestion products of MPs using HILIC-Orbitrap based on full scan and MS/MS modes. Secondly, a targeted structural-fingerprinting of polysaccharides (SFP) was built in a multiple-ion monitoring (MIM) mode using the same HILIC separation with a triple quadrupole MS. Thirdly, a case study of polysaccharides in Hericium erinaceus fruiting bodies (HEP) was performed to obtain the expected SFP based on dextranase digestion that allows for visual discrimination of polysaccharides from other five edible mushrooms attributed to Agrocybe cylindracea, Arimillaria mellea, Flammulina velutipes, Pleurotus eryngii, and Lentinula edodes. Furthermore, a major structural backbone of HEP was unveiled by occurrence of → ⁶(Hex)¹ → along with multiple possible substitutions including of terminal GalA, Fuc, acetyl, → ⁴Hex¹ →, and → ³Hex¹ →. Finally, the similarity analysis, hierarchical cluster analysis (HCA), and partial least squares discriminant analysis (PLS-DA) were performed to visualize various MPs. As a result, the enzymatic-fingerprinting workflow presents an effective example for quality evaluation of fungi polysaccharides using a SFP strategy.

The Establishment of Tandem Mass Spectrometric Fingerprints of Phytosterols and Tocopherols and the Development of Targeted Profiling Strategies in Vegetable Oils

Phytosterols and tocopherols are essential for plant biochemistry, and they possess beneficial health effects for humans. Evaluating the tandem mass spectrometric (MS/MS) behavior of phytosterols and tocopherols is needed for the development of a qualitative and quantitative method for these biologically active plant metabolites. Herein, the MS/MS dissociation behavior of phytosterols and tocopherols is elucidated to establish generalized MS/MS fingerprints. MS/MS and multistage (MS³) analysis revealed common fragmentation behavior among the four tested phytosterols, namely β-sitosterol, stigmasterol, campesterol, and brassicasterol. Similar analysis was conducted for the tocopherols (i.e., alpha (α), beta (β), gamma (γ), and delta (δ)). As such, a universal MS/MS fragmentation pathway for each group was successfully established for the first time. Based on the generalized MS/MS fragmentation behavior of phytosterols, diagnostic product ions were chosen for the development of profiling methods for over 20 naturally occurring phytosterols. A precursor ion scan-triggered-enhanced product ion scan (PIS-EPI) method was established. Due to enhanced chromatographic peaks, multiple ion monitoring-triggered-enhanced product ion scan (MIM-EPI) was employed for confirmation. The screening approach was applied successfully to identify blinded samples obtained from standard mixtures as well as sesame and olive oils. The oil samples contain other phytosterols, and their successful identification indicates that, the generalized MS/MS fragmentation behavior is applicable to various structures of phytosterols. A similar approach was attempted for tocopherols and was only hindered by the low concentration of these bioactive metabolites present in the oil samples.

Determination of the in vitro metabolic stability and metabolites of the anticancer derivative riccardin D-N in human and mouse hepatic S9 fractions using HPLC-Q-LIT-MS

Riccardin D-N (RD-N) is an aminomethylated derivative of the macrocyclic bisbibenzyl compound riccardin D (RD), which has shown stronger activity against cancer cells than RD. However, there has been no research on the metabolism of RD-N. The present study aimed to characterize the in vitro metabolism and metabolic stability of RD-N after incubation with mouse and human hepatic S9 fractions using high performance liquid chromatography-hybrid triple quadrupole/linear ion trap mass spectrometry (HPLC-Q-LIT-MS). Multiple ion monitoring (MIM) and multiple reaction monitoring (MRM)-information dependent acquisition-enhanced product ion (MIM/MRM-IDA-EPI) scans were used to identify the metabolites formed. MRM scans were also used to quantify the changes in the amount of RD-N and to semi-quantify the main metabolites. Twenty-eight metabolic products were detected and 25 structures were predicted. Hydroxylation, dehydrogenation, glucuronidation, and methylation were proposed to be the principle metabolic pathways in the in vitro incubation with human and mouse hepatic S9 fractions. There were differences in the number and abundance of RD-N metabolites between the human and mouse hepatic S9 fractions. RD-N was shown to have good metabolic stability. After 2 h of incubation, 44% of the original RD-N remained in the human hepatic S9 fraction compared with 22% in the mouse. The major metabolites of RD-N, M4, M8, M20 and M21, were monitored semi-quantitatively using the typical transitions. Finally, HPLC-Q-LIT-MS was used for the identification and quantitation of the metabolites of R D-N, which is a simple and efficient method to rapidly screen potential drug candidates.

Pregnane X receptor activation potentiates ritonavir hepatotoxicity

Ritonavir (RTV) is on the World Health Organization's List of Essential Medicines for antiretroviral therapy, but can cause hepatotoxicity by unknown mechanisms. Multiple clinical studies found that hepatotoxicity occurred in 100% of participants who were pretreated with rifampicin or efavirenz followed by RTV-containing regimens. Both rifampicin and efavirenz are activators of the pregnane X receptor (PXR), a transcription factor with significant inter-species differences in ligand-dependent activation. Using PXR-humanized mouse models, we recapitulated the RTV hepatotoxicity observed in the clinic. PXR was found to modulate RTV hepatotoxicity through CYP3A4-dependent pathways involved in RTV bioactivation, oxidative stress, and endoplasmic reticulum stress. In summary, the current work demonstrated the essential roles of human PXR and CYP3A4 in RTV hepatotoxicity, which can be applied to guide the safe use of RTV-containing regimens in the clinic.

Exploring Chemical Basis of Toxicity Reduction for Processed Roots of Stellera chamaejasme L. Using Ultraperformance Liquid Chromatography-Triple Quadrupole Tandem Mass Spectrometry

Some herbal medicines are treated with various processing methods to ensure their safe and effective use. However, chemical basis of toxicity reducing for most herbal medicines remains unclear. Stellera chamaejasme L., particularly the root (ruixianglangdu), is toxic. Thus, ruixianglangdu is commonly processed with vinegar or milk to reduce toxicity. Here, with help of multiple-ion monitoring (MIM)-based metabolomics, we comprehensively capture chemical information of ruixianglangdu. Then, 33 differential components between crude drugs and processed products were identified or tentatively characterized by multiple-ion monitoring–information dependent acquiring–enhanced product ion (MIM-IDA-EPI), whose level changed after being processed by vinegar or milk. It was found that flavonoids especially biflavonones could be the important chemical basis of toxicity reduction for processed ruixianglangdu. In addition, some coumarins and lignanoids could also play a role in reducing toxicity. It is believed that MIM-based metabolomics method was valuable for exploring chemical basis of toxicity reduction for processing. The data is critical to further study the mechanism of toxicity reducing for processed ruixianglangdu.

Exploring the Diversity of Plant Metabolism

Plants produce a huge array of metabolites, far more than those produced by most other organisms. Unraveling this diversity and its underlying genetic variation has attracted increasing research attention. Post-genomic profiling platforms have enabled the marriage and mining of the enormous amount of phenotypic and genetic diversity. We review here achievements to date and challenges remaining that are associated with plant metabolic research using multi-omic strategies. We focus mainly on strategies adopted in investigating the diversity of plant metabolism and its underlying features. Recent advances in linking metabotypes with phenotypic and genotypic traits are also discussed. Taken together, we conclude that exploring the diversity of metabolism could provide new insights into plant evolution and domestication.

Screening and identification of steroidal saponins from Anemarrhena asphodeloides employing UPLC tandem triple quadrupole linear ion trap mass spectrometry

This study presents a practical and valid strategy for the screening and structural characterization of Anemarrhena asphodeloides Bge steroidal saponins (SSs) using ultra-high performance liquid chromatography coupled with triple quadrupole linear ion trap mass spectrometry. The whole analytical protocols integrate four-step procedures in the positive mode: (1) rational deduction of mass fragmentation pathways of A. asphodeloides SSs; (2) untargeted screening of potential A. asphodeloides SSs by multiple-ion monitoring-information-dependent-acquiring-enhanced product ion (MIM-IDA-EPI) scan through reverse phase liquid chromatography; (3) comprehensive construction of an ammoniated precursor ion database by combining untargeted MIM-IDA-EPI scans and data literature; and (4) structural interpretation of targeted A. asphodeloides SSs using MIM-IDA-EPI and multiple reaction monitoring (MRM)-IDA-EPI with an energy-resolved technique. The protocols were used to analyze SSs in A. asphodeloides; of the 87 detected SSs that were unambiguously characterized or tentatively identified, 19 compounds were the first to be reported from A. asphodeloides and 13 ones were characterized as potential new compounds. Accuracy of the analytical procedure was demonstrated by structural identification of three SSs by NMR spectroscopy. The proposed schemes hold an excellent promise in the structural prediction and interpretation of complex SSs from plant medicines by mass spectrometry.

Metabolite identification of bentysrepinine (Y101), a novel anti-HBV agent in rats using a five-step strategy based on a combined workflow with two different platforms of liquid chromatography-tandem mass spectrometry

Bentysrepinine (Y101), a derivative of repensine (a compound isolated from Dichondrarepens Forst), is a novel phenyalanine dipeptide inhibiting DNA-HBV and cccDNA activities and is currently under development for the treatment of hepatitis B virus (HBV)-infected hepatitis. Our previous study implied that there might be an existence of extensive metabolism of Y101 in rats. Therefore, it is necessary to perform metabolic profiling study to further evaluate its safety and drug-like properties. In this study, the metabolism of Y101 in rats was investigated by a convincible five-step strategy to characterize metabolites in plasma and that excreted into urine, bile and feces. The five-step strategy was realized by using an combined workflow on two different MS platforms, including various scan modes of liquid chromatography with hybrid quadruple-linear ion trap mass spectrometry (LC-QTRAP-MS/MS) and various post-acquiring data mining tools of liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (LC-QTOF-MS/MS). QTOF MS/MS was employed as a powerful complementary tool to enable high confidence of metabolites identification using its functions of accurate MS and MS/MS fragmentation. As a result, a total of 30 metabolites were detected, including 25 phase I and 5 phase II metabolites. Among them, four primary metabolites (M6-M9) were further identified by comparing with the authentic standards chemically synthesized. The possible metabolic pathways of Y101 in rats were proposed to be amide hydrolysis, monohydroxylation, dihydroxylation, N-oxidation, demethylation, methylation, glucosidation and glucuronidation. This is the first study of the metabolism of Y101 in rats. The five-step strategy was successfully used to systematically characterize metabolites of Y101 in rats, and it would be generally applied for metabolite identification of new drug candidate.

An Integrated Strategy for Global Qualitative and Quantitative Profiling of Traditional Chinese Medicine Formulas: Baoyuan Decoction as a Case

Clarification of the chemical composition of traditional Chinese medicine formulas (TCMFs) is a challenge due to the variety of structures and the complexity of plant matrices. Herein, an integrated strategy was developed by hyphenating ultra-performance liquid chromatography (UPLC), quadrupole time-of-flight (Q-TOF), hybrid triple quadrupole-linear ion trap mass spectrometry (Qtrap-MS), and the novel post-acquisition data processing software UNIFI to achieve automatic, rapid, accurate, and comprehensive qualitative and quantitative analysis of the chemical components in TCMFs. As a proof-of-concept, the chemical profiling of Baoyuan decoction (BYD), which is an ancient TCMF that is clinically used for the treatment of coronary heart disease that consists of Ginseng Radix et Rhizoma, Astragali Radix, Glycyrrhizae Radix et Rhizoma Praeparata Cum Melle, and Cinnamomi Cortex, was performed. As many as 236 compounds were plausibly or unambiguously identified, and 175 compounds were quantified or relatively quantified by the scheduled multiple reaction monitoring (sMRM) method. The findings demonstrate that the strategy integrating the rapidity of UNIFI software, the efficiency of UPLC, the accuracy of Q-TOF-MS, and the sensitivity and quantitation ability of Qtrap-MS provides a method for the efficient and comprehensive chemome characterization and quality control of complex TCMFs.

Metabolism and bioactivation of the tricyclic antidepressant amitriptyline in human liver microsomes and human urine

Aim: Amitriptyline is a widely used tricyclic antidepressant, but the metabolic studies were conducted almost 20 years ago using high-performance liquid chromatography coupled with ultraviolet detector or radiolabeled methods. Results: First, multiple ion monitoring (MIM)- enhanced product ion (EPI) scan was used to obtain the diagnostic ions or neutral losses in human liver microsome incubations with amitriptyline. Subsequently, predicted multiple reaction monitoring (MRM)-EPI scan was used to identify the metabolites in human urine with the diagnostic ions or neutral losses. Finally, product ion filtering and neutral loss filtering were used as the data mining tools to screen metabolites. Consequently, a total of 28 metabolites were identified in human urine after an oral administration using LC–MS/MS. Conclusion: An integrated workflow using LC–MS/MS was developed to comprehensively profile the metabolites of amitriptyline in human urine, in which five N-acetyl-l-cysteine conjugates were characterized as tentative biomarkers for idiosyncratic toxicity.

Multiple stage MS in analysis of plasma, serum, urine and in vitro samples relevant to clinical and forensic toxicology

This paper reviews MS approaches applied to metabolism studies, structure elucidation and qualitative or quantitative screening of drugs (of abuse) and/or their metabolites. Applications in clinical and forensic toxicology were included using blood plasma or serum, urine, in vitro samples, liquids, solids or plant material. Techniques covered are liquid chromatography coupled to low-resolution and high-resolution multiple stage mass analyzers. Only PubMed listed studies published in English between January 2008 and January 2015 were considered. Approaches are discussed focusing on sample preparation and mass spectral settings. Comments on advantages and limitations of these techniques complete the review.

Identification and Characterization of Kukoamine Metabolites by Multiple Ion Monitoring Triggered Enhanced Product Ion Scan Method with a Triple-Quadruple Linear Ion Trap Mass Spectrometer

Kukoamines are a series of bioactive phytochemicals conjugated by a polyamine backbone and phenolic moieties. Understanding the structural diversity of kukoamine metabolites in plants is meaningful for drug discovery. In this study, an LC-MS/MS method was established for kukoamine profiling and characterization from lycii cortex (LyC) via a triple-quadrupole linear ion trap mass spectrometry (Q-TRAP). On the basis of the typical fragmentation of kukoamine, a diagnostic ion, which represents the features of the backbone and phenolic substitute, was chosen as the product ion for precursor ion scan, and then the screened precursor ions were applied to a successive multiple ion monitoring triggered enhanced product ion scan (MIM-EPI) to simultaneously present the profile survey and MS/MS acquisition. Because the MIM narrowed the ion scan range in Q1 and the ion trap enhanced the ion fragments passing through Q2, the qualitative capability of quadrupole MS can be greatly improved, especially for capture of the uncommon metabolites. There are 12 kukoamine metabolites identified from LyC, with either spermine or spermidine backbone and with conjugation of one to three dihydrocaffeoyls or other kinds of phenolic moieties. Except for kukoamines A and B, other metabolites were identified in LyC for the first time. This approach can be utilized for metabolite identification in other substrates.

Characterization of fimasartan metabolites in human liver microsomes and human plasma

1. The metabolites of fimasartan (FMS), a new angiotensin II receptor antagonist, were characterized in human liver microsomes (HLM) and human subjects. 2. We developed a method for a simultaneous quantitative and qualitative analysis using predictive multiple reaction monitoring information-dependent acquisition-enhanced product ion scanning. To characterize metabolic reactions, FMS metabolites were analyzed using quadrupole-time of flight mass spectrometer in full-scan mode. 3. The structures of metabolites were confirmed by comparison of chromatographic retention times and mass spectra with those of authentic metabolite standards. 4. In the cofactor-dependent microsomal metabolism study, the half-lives of FMS were 56.7, 247.9 and 53.3 min in the presence of NADPH, UDPGA and NADPH + UDPGA, respectively. 5. The main metabolic routes in HLM were S-oxidation, oxidative desulfuration, n-butyl hydroxylation and N-glucuronidation. 6. In humans orally administered with 120 mg FMS daily for 7 days, the prominent metabolites were FMS S-oxide and FMS N-glucuronide in the 0-8-h pooled plasma sample of each subject. 7. This study characterizes, for the first time, the metabolites of FMS in humans to provide information for its safe use in clinical medicine.

Determination of species-difference in microsomal metabolism of amitriptyline using a predictive MRM-IDA-EPI method

We investigated to compare species differences in amitriptyline (AMI) metabolism among mouse, rat, dog, and human liver microsomes. We developed a method for simultaneous determination of metabolic stability and metabolite profiling using predictive multiple reaction monitoring information-dependent acquisition-enhanced product ion (MRM-IDA-EPI) scanning. In the cofactor-dependent microsomal metabolism study, AMI was metabolized more rapidly in rat and human liver microsomes incubated with NADPH than UDPGA. AMI incubated with NADPH+UDPGA in rat, dog, or mouse liver microsomes disappeared rapidly with a half-life of 3.5, 8.4, or 9.2 min, respectively, but slowly in human liver microsomes with a half-life of 96 min. In total, 9, 10, 11, and 6 putative metabolites of AMI were detected in mouse, rat, dog, and human liver microsomes, respectively, based on mass spectrometric analyses. Kinetic analysis of metabolites in liver microsomes from each species over 120 min showed common metabolic routes of AMI, such as N-demethylation, hydroxylation, and glucuronidation, and subtle interspecies differences in AMI metabolism. The main metabolic routes in mouse, rat, dog, and human liver microsomes were hydroxylation followed by glucuronide conjugation, methyl hydroxylation, and N-demethylation, respectively. The MRM-IDA-EPI method can provide quantitative and qualitative information about metabolic stability and metabolite profiling simultaneously. Moreover, time course analysis of metabolites can not only eliminate false identification of metabolites, but also provide a rationale for proposed metabolic pathways. The MRM-IDA-EPI method combined with time course analysis of metabolites is useful for investigating drug metabolism at the early drug discovery stage.

Improving natural products identification through targeted LC-MS/MS in an untargeted secondary metabolomics workflow

Tandem mass spectrometry is a widely applied and highly sensitive technique for the discovery and characterization of microbial natural products such as secondary metabolites from myxobacteria. Here, a data mining workflow based on MS/MS precursor lists targeting only signals related to bacterial metabolism is established using LC-MS data of crude extracts from shaking flask fermentations. The devised method is not biased toward specific compound classes or structural features and is capable of increasing the information content of LC-MS/MS analyses by directing fragmentation events to signals of interest. The approach is thus contrary to typical auto-MS(2) setups where precursor ions are usually selected according to signal intensity, which is regarded as a drawback for metabolite discovery applications when samples contain many overlapping signals and the most intense signals do not necessarily represent compounds of interest. In line with this, the method described here achieves improved MS/MS scan coverage for low-abundance precursor ions not captured by auto-MS(2) experiments and thereby facilitates the search for new secondary metabolites in complex biological samples. To underpin the effectiveness of the approach, the identification and structure elucidation of two new myxobacterial secondary metabolite classes is reported.

A generic multiple reaction monitoring based approach for plant flavonoids profiling using a triple quadrupole linear ion trap mass spectrometry

Flavonoids are one of the largest classes of plant secondary metabolites serving a variety of functions in plants and associating with a number of health benefits for humans. Typically, they are co-identified with many other secondary metabolites using untargeted metabolomics. The limited data quality of untargeted workflow calls for a shift from the breadth-first to the depth-first screening strategy when a specific biosynthetic pathway is focused on. Here we introduce a generic multiple reaction monitoring (MRM)-based approach for flavonoids profiling in plants using a hybrid triple quadrupole linear ion trap (QTrap) mass spectrometer. The approach includes four steps: (1) preliminary profiling of major aglycones by multiple ion monitoring triggered enhanced product ion scan (MIM-EPI); (2) glycones profiling by precursor ion triggered EPI scan (PI-EPI) of major aglycones; (3) comprehensive aglycones profiling by combining MIM-EPI and neutral loss triggered EPI scan (NL-EPI) of major glycone; (4) in-depth flavonoids profiling by MRM-EPI with elaborated MRM transitions. Particularly, incorporation of the NH3 loss and sugar elimination proved to be very informative and confirmative for flavonoids screening. This approach was applied for profiling flavonoids in Astragali radix (Huangqi), a famous herb widely used for medicinal and nutritional purposes in China. In total, 421 flavonoids were tentatively characterized, among which less than 40 have been previously reported in this medicinal plant. This MRM-based approach provides versatility and sensitivity that required for flavonoids profiling in plants and serves as a useful tool for plant metabolomics.

A novel integrated method for large-scale detection, identification, and quantification of widely targeted metabolites: application in the study of rice metabolomics

Liquid chromatography-mass spectrometry (LC-MS)-based metabolomics has been facilitated by the construction of MS(2) spectral tag (MS2T) library from the total scan ESI MS/MS data, and the development of widely targeted metabolomics method using MS/MS data gathered from authentic standards. In this report, a novel strategy called stepwise multiple ion monitoring-enhanced product ions (stepwise MIM-EPI) was developed to construct the MS2T library, in which stepwise MIM was used as survey scans to trigger the acquisition of EPI. A total number of 698 (almost) non-redundant metabolites with MS(2) spectra were obtained, of which 135 metabolites were identified/annotated. Integrating the data gathered from our MS2T library and other available multiple reaction monitoring (MRM) information, a widely targeted metabolomics method was developed to quantify 277 metabolites, including some phytohormones. Evaluation of the dehydration responses and natural variations of these metabolites in rice leaf not only suggested the coordinated regulation of abscisic acid (ABA) with metabolites such as serotonin derivative(s), polyamine conjugates under drought stress, but also revealed some C-glycosylated flavones as the potential markers for the discrimination of indica and japonica rice subspecies. The new MS2T library construction and widely targeted metabolomics strategy could be used as a tool for rice functional genomics.

Single laboratory method validation comparing MS3 with FI/MS fingerprinting, and quantitation strategies for the accurate determination of ochratoxins in beer

The current mycotoxin safety concerns demand the availability of reliable and selective control systems to measure the content of mycotoxins present in daily food. To address this, we report a prospective analytical tool involving the application of a flow injection mass spectrometry (FI/MS) tandem artificial neural network (ANN) strategy to predict the amount of ochratoxin A and B (OTA and OTB) in beer. Triple stage mass spectrometry (MS3) aided by chromatographic separation was applied as a reference method for comparison. 0.1% formic acid and methanol were used to convert ochratoxins into their respective ions under negative MS polarity. For experiments involving MS3, ochratoxins were separated by reversed-phase liquid chromatography in a 6 min run, ionised using electrospray ionisation, and detected by tandem mass spectrometry. Analyte-specific mass-to-charge ratios were used to perform quantitation in MS3 mode. For experiments involving FI/MS, no chromatographic separation was performed. Approximately 2% of the mass spectra was used for model construction. ANN models representing each ochratoxin were individually trained and validated using three sets of matrix-matched and matrix-free calibration curves at nine concentration levels of 2.5, 10, 25, 50, 100, 200, 300, 400 and 500 μg/l. Quintuplicate analyses were made in FI/ MS mode providing a total of 270 spectra for both OTA and OTB. Single measurement was made for each sample in MS3 mode. A root-mean-square error value of <1% was reported for both ochratoxin models in beer. Limits of quantitation were determined to be 0.2 μg/kg for both MS3 and FI/MS mode. Recovery assessment was performed over two days using beer blanks (n=6) spiked at three concentration levels of 5, 100 and 200 μg/kg. Extraction using acetonitrile provided excellent recovery ranges of 88 to 102% for both MS techniques. Relative standard deviations of 10% or better were achieved for interday spike recovery experiments. The successful utilisation of FI/MS without performing chromatographic separation implies the availability of a new analytical tool relevant to the field of mycotoxin analysis, possibly offering analyte specificity exceeding the capability of MS3 through chemometry.

Software automation tools for increased throughput metabolic soft-spot identification in early drug discovery

Background: The ability to supplement high-throughput metabolic clearance data with structural information defining the site of metabolism should allow design teams to streamline their synthetic decisions. However, broad application of metabolite identification in early drug discovery has been limited, largely due to the time required for data review and structural assignment. The advent of mass defect filtering and its application toward metabolite scouting paved the way for the development of software automation tools capable of rapidly identifying drug-related material in complex biological matrices. Two semi-automated commercial software applications, MetabolitePilot™ and Mass-MetaSite™, were evaluated to assess the relative speed and accuracy of structural assignments using data generated on a high-resolution MS platform. Results/Conclusion: Review of these applications has demonstrated their utility in providing accurate results in a time-efficient manner, leading to acceleration of metabolite identification initiatives while highlighting the continued need for biotransformation expertise in the interpretation of more complex metabolic reactions.

The application of quantification techniques in proteomics for biomedical research

The systematic analysis of biological processes requires an understanding of the quantitative expression patterns of proteins, their interacting partners and their subcellular localization. This information was formerly difficult to accrue as the relative quantification of proteins relied on antibody-based methods and other approaches with low throughput. The advent of soft ionization techniques in mass spectrometry plus advances in separation technologies has aligned protein systems biology with messenger RNA, DNA, and microarray technologies to provide data on systems as opposed to singular protein entities. Another aspect of quantitative proteomics that increases its importance for the coming few years is the significant technical developments underway both for high pressure liquid chromatography and mass spectrum devices. Hence, robustness, reproducibility and mass accuracy are still improving with every new generation of instruments. Nonetheless, the methods employed require validation and comparison to design fit for purpose experiments in advanced protein analyses. This review considers the newly developed systematic protein investigation methods and their value from the standpoint that relative or absolute protein quantification is required de rigueur in biomedical research.

Simultaneous screening of glutathione and cyanide adducts using precursor ion and neutral loss scans-dependent product ion spectral acquisition and data mining tools

Drugs can be metabolically activated to soft and hard electrophiles, which are readily trapped by glutathione (GSH) and cyanide (CN), respectively. These adducts are often detected and structurally characterized using separate tandem mass spectrometry methods. We describe a new method for simultaneous screening of GSH and CN adducts using precursor ion (PI) and neutral loss (NL) scans-dependent product ion spectral acquisition and data mining tools on an triple quadrupole linear ion trap mass spectrometry. GSH, potassium cyanide, and their stable isotope labeled analogues were incubated with liver microsomes and a test compound. Negative PI scan of m/z 272 for detection of GSH adducts and positive NL scans of 27 and 29 Da for detection of CN adducts were conducted as survey scans to trigger acquisition of enhanced resolution (ER) spectrum and subsequent enhanced product ion (EPI) spectrum. Post-acquisition data mining of EPI data set using NL filters of 129 and 27 Da was then performed to reveal the GSH adducts and CN adducts, respectively. Isotope patterns and EPI spectra of the detected adducts were utilized for identification of their molecular weights and structures. The effectiveness of this method was evaluated by analyzing reactive metabolites of nefazodone formed from rat liver microsomes. In addition to known GSH- and CN-trapped reactive metabolites, several new CN adducts of nefazodone were identified. The results suggested that current approach is highly effective in the analysis of both soft and hard reactive metabolites and can be used as a high-throughput method in drug discovery.

Role of CYP2A5 in the bioactivation of the lung carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in mice

The tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a potent lung carcinogen. Previously, we have demonstrated that NNK-induced lung tumorigenesis in mice depends on target-tissue bioactivation by pulmonary cytochrome P450 (P450) enzymes. The present study was designed to test the hypothesis that mouse CYP2A5 plays an essential role in NNK bioactivation in mouse lung. The role of CYP2A5 in NNK bioactivation was studied both in vitro and in vivo, by comparing the kinetic parameters of microsomal NNK metabolism and tissue levels of O(6)-methylguanine (O(6)-mG) (the DNA adduct highly correlated with lung tumorigenesis) between wild-type (WT) and Cyp2a5-null mice. In both liver and lung microsomes, the loss of CYP2A5 resulted in significant increases in the apparent K(m) values for the formation of 4-oxo-4-(3-pyridyl)butanone, which represents the reactive intermediate that produces O(6)-mG in vivo. The loss of CYP2A5 did not change circulating levels of NNK or 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol in mice treated intraperitoneally with NNK at either 20 or 100 mg/kg. However, the levels of lung O(6)-mG were significantly lower in Cyp2a5-null than in WT mice; the extent of the reduction was greater at the 20 mg/kg dose (∼40%) than at the 100 mg/kg dose (∼20%). These results indicate that CYP2A5 is the low-K(m) enzyme for NNK bioactivation in mouse lung. It is noteworthy that the remaining NNK bioactivation activities in the Cyp2a5-null mice could be inhibited by 8-methoxypsoralen, a P450 inhibitor used previously to demonstrate the role of CYP2A5 in NNK-induced lung tumorigenesis. Thus, P450 enzymes other than CYP2A5 probably also contribute to NNK-induced lung tumorigenesis in mice.

Respective roles of CYP2A5 and CYP2F2 in the bioactivation of 3-methylindole in mouse olfactory mucosa and lung: studies using Cyp2a5-null and Cyp2f2-null mouse models

The aim of this study was to determine whether mouse CYP2A5 and CYP2F2 play critical roles in the bioactivation of 3-methylindole (3MI), a tissue-selective toxicant, in the target tissues, the nasal olfactory mucosa (OM) and lung. Five metabolites of 3MI were identified in NADPH- and GSH-fortified microsomal reactions, including 3-glutathionyl-S-methylindole (GS-A1), 3-methyl-2-glutathionyl-S-indole (GS-A2), 3-hydroxy-3-methyleneindolenine (HMI), indole-3-carbinol (I-3-C), and 3-methyloxindole (MOI). The metabolite profiles and enzyme kinetics of the reactions were compared between OM and lung, and among wild-type, Cyp2a5-null, and Cyp2f2-null mice. In lung reactions, GS-A1, GS-A2, and HMI were detected as major products, and I-3-C and MOI, as minor metabolites. In OM reactions, all five metabolites were detected in ample amounts. The loss of CYP2F2 affected formation of all 3MI metabolites in the lung and formation of HMI, GS-A1, and GS-A2 in the OM. In contrast, loss of CYP2A5 did not affect formation of 3MI metabolites in the lung but caused substantial decreases in I-3-C and MOI formation in the OM. Thus, whereas CYP2F2 plays a critical role in the 3MI metabolism in the lung, both CYP2A5 and CYP2F2 play important roles in 3MI metabolism in the OM. Furthermore, the fate of the reactive metabolites produced by the two enzymes through common dehydrogenation and epoxidation pathways seemed to differ with CYP2A5 supporting direct conversion to stable metabolites and CYP2F2 supporting further formation of reactive iminium ions. These results provide the basis for understanding the respective roles of CYP2A5 and CYP2F2 in 3MI's toxicity in the respiratory tract.

Metabolomic screening and identification of the bioactivation pathways of ritonavir

Ritonavir-boosted protease inhibitor regimens are widely used for HIV chemotherapy. However, ritonavir causes multiple side effects, and the mechanisms are not fully understood. The current study was designed to explore the metabolic pathways of ritonavir that may be related to its toxicity. Metabolomic analysis screened out 26 ritonavir metabolites in mice, and half of them are novel. These novel ritonavir metabolites include two glycine conjugated, two N-acetylcysteine conjugated, and three ring-open products. Accompanied with the generation of ritonavir ring-open metabolites, the formation of methanethioamide and 2-methylpropanethioamide were expected. Upon the basis of the structures of these novel metabolites, five bioactivation pathways are proposed, which may be associated with sulfation and epoxidation. By using Cyp3a-null mice, we confirmed that CYP3A is involved in four pathways of RTV bioactivation. In addition, all these five bioactivation pathways were recapitulated in the incubation of ritonavir in human liver microsomes. Further studies are suggested to determine the role of CYP3A and these bioactivation pathways in ritonavir toxicity.

In vitro metabolic stability and metabolite profiling of TJ0711 hydrochloride, a newly developed vasodilatory β-blocker, using a liquid chromatography-tandem mass spectrometry method

In this paper, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous analysis of metabolic stability and metabolite profiling of 1-[4-(2-methoxyethyl) phenoxy]-3-[[2-(2-methoxyphenoxy) ethyl]amino]-2-propanol hydrochloride (TJ0711 HCl), a new vasodilatory β-blocker. Multiple reaction monitoring (MRM) was used as a survey scan to quantify the parent compound and to trigger the acquisition of enhanced product ions (EPI) for the identification of formed metabolites. In addition, comparison between MRM-only and MRM-information dependent acquisition-EPI (MRM-IDA-EPI) methods was conducted to determine analytical variables, including linearity, limit of detection (LOD), lower limit of quantification (LLOQ), as well as intra-day and inter-day accuracy and precision. Results demonstrated that MRM-IDA-EPI quantitative analysis was not affected by the addition of EPI scans to obtain qualitative information during the same chromatographic run, compared to MRM-only method. Thereafter, metabolic stability and metabolite identification of TJ0711 HCl were investigated using human liver microsomes (HLM) by the MRM-IDA-EPI method. The in vitro metabolic stability parameters were calculated and t(1/2), microsomal intrinsic clearance (CL(int)), as well as hepatic CL, were 13.0 min, 106.5 μL/min/mg microsomal protein, and 1082.2 mL/min, respectively. The major formed metabolites were also simultaneously monitored and the metabolite profiling data demonstrated that this MRM-IDA-EPI method was capable of targeting a large number of metabolites, in which demethylation and hydroxylation were the principle metabolism pathways during the in vitro incubation with HLM.

Quantitative and confirmative performance of liquid chromatography coupled to high-resolution mass spectrometry compared to tandem mass spectrometry

The quantitative and confirmative performance of two different mass spectrometry (MS) techniques (high-resolution MS and tandem MS) was critically compared. Evaluated was a new extraction and clean-up protocol which was developed to cover more than 100 different veterinary drugs at trace levels in a number of animal tissues and honey matrices. Both detection techniques, high-resolution mass spectrometry (HRMS) (single-stage Orbitrap instrument operated at 50 000 full width at half maximum) and tandem mass spectrometry (MS/MS) (quadrupole technology) were used to validate the method according to the EU Commission Decision 2002/657/EEC. Equal or even a slightly better quantitative performance was observed for the HRMS-based approach. Sensitivity is higher for unit mass resolution MS/MS if only a subset of the 100 compounds has to be monitored. Confirmation of suspected positive findings can be done by evaluating the intensity ratio between different MS/MS transitions, or by accurate mass based product ion traces (no precursor selection applied). MS/MS relies on compound-specific optimized transitions; hence the second, confirmatory transition generally shows relatively high ion abundance (fragmentation efficacy). This is often not the case in single-stage HRMS, since a generic (not compound-optimized) collision energy is applied. Hence, confirmation of analytes present at low levels is superior when performed by MS/MS. Slightly better precision, but poorer accuracy (fortified matrix extracts versus pure standard solution) of ion ratios were observed when comparing data obtained by HRMS versus MS/MS.

Advances in structure elucidation of small molecules using mass spectrometry

The structural elucidation of small molecules using mass spectrometry plays an important role in modern life sciences and bioanalytical approaches. This review covers different soft and hard ionization techniques and figures of merit for modern mass spectrometers, such as mass resolving power, mass accuracy, isotopic abundance accuracy, accurate mass multiple-stage MS(n) capability, as well as hybrid mass spectrometric and orthogonal chromatographic approaches. The latter part discusses mass spectral data handling strategies, which includes background and noise subtraction, adduct formation and detection, charge state determination, accurate mass measurements, elemental composition determinations, and complex data-dependent setups with ion maps and ion trees. The importance of mass spectral library search algorithms for tandem mass spectra and multiple-stage MS(n) mass spectra as well as mass spectral tree libraries that combine multiple-stage mass spectra are outlined. The successive chapter discusses mass spectral fragmentation pathways, biotransformation reactions and drug metabolism studies, the mass spectral simulation and generation of in silico mass spectra, expert systems for mass spectral interpretation, and the use of computational chemistry to explain gas-phase phenomena. A single chapter discusses data handling for hyphenated approaches including mass spectral deconvolution for clean mass spectra, cheminformatics approaches and structure retention relationships, and retention index predictions for gas and liquid chromatography. The last section reviews the current state of electronic data sharing of mass spectra and discusses the importance of software development for the advancement of structure elucidation of small molecules. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s12566-010-0015-9) contains supplementary material, which is available to authorized users.

Targeted proteomics by selected reaction monitoring mass spectrometry: applications to systems biology and biomarker discovery

Mass Spectrometry-based proteomics is now considered a relatively established strategy for protein analysis, ranging from global expression profiling to the identification of protein complexes and specific post-translational modifications. Recently, Selected Reaction Monitoring Mass Spectrometry (SRM-MS) has become increasingly popular in proteome research for the targeted quantification of proteins and post-translational modifications. Using triple quadrupole instrumentation (QqQ), specific analyte molecules are targeted in a data-directed mode. Used routinely for the quantitative analysis of small molecular compounds for at least three decades, the technology is now experiencing broadened application in the proteomics community. In the current review, we will provide a detailed summary of current developments in targeted proteomics, including some of the recent applications to biological research and biomarker discovery.

Identification of chemicals and their metabolites from PHY906, a Chinese medicine formulation, in the plasma of a patient treated with irinotecan and PHY906 using liquid chromatography/tandem mass spectrometry (LC/MS/MS)

Traditional Chinese Medicine (TCM) is increasingly being used in combination with Western medicine. In general, TCM is comprised of multiple components in sharp contrast to Western medicine, where a single active chemical is used. Presently, there are no well-established standards for most of the chemical compounds of TCM and their respective metabolites. Moreover, there are no formal analytical methods for the identification of these chemicals, especially in trace amounts. The ability to measure the pharmacokinetic behaviors of chemicals and their metabolites from these herbal formulations are critical in understanding of the action of TCM. This paper describes the use of LC/MS/MS along with enzyme treatments and n-octanol/water partition coefficient, to investigate the chemical components of PHY906 and their metabolites in the plasma of a patient with metastatic colorectal cancer (mCRC) treated with irinotecan and PHY906. The chemicals from an aqueous extract of PHY906 and the plasma from a patient was prepared and separated on an Agilent ZORBAX-SB C(18) column, and eluted with acetonitrile/0.05% (v/v) formic acid. From the PHY906 aqueous extract, a total of 57 compounds and 27 metabolites were identified and tentatively assigned structures based on their identified mass spectrometry, enzyme digestion and n-octanol/water partition coefficient. In contrast, analysis of patient plasma identified only 33 chemicals and new metabolites. These findings demonstrated that LC/MS/MS was and effective and reliable method for studying the parent chemicals of the Chinese herbal medicine PHY906 and their metabolites in a patient with metastatic colorectal cancer.

Determination of bicyclol in dog plasma using liquid chromatography-tandem mass spectrometry

A sensitive and accurate method for determination of bicyclol in dog plasma was developed. Thermo Scientific TSQ Quantum triple quadrupole system with multiple ion monitoring (MIM) positive scanning mode was applied. Bicyclol and DDB (IS) sodium adduct molecular ions were monitored at m/z 413 and m/z 441 in both Q1 and Q3, respectively. The collision energy in Q2 was set to 15 eV. Precipitation method was employed in the extraction of bicyclol and DDB from the biological matrix. The method was validated over 1-500 ng/mL for bicyclol. The recovery was 96.5-109.5%, and the limit of quantitation (LOQ) detection was 1 ng/mL for bicyclol. The intra- and inter-day precision of the method at three concentrations was 3.3-14.3% with accuracy of 99.9-109.0%. The method was successfully applied to bioequivalence studies of bicyclol controlled-release formulation to obtain the pharmacokinetic parameters.

Comparison of triple quadrupole, hybrid linear ion trap triple quadrupole, time-of-flight and LTQ-Orbitrap mass spectrometers in drug discovery phase metabolite screening and identification in vitro--amitriptyline and verapamil as model compounds

Liquid chromatography in combination with mass spectrometry (LC/MS) is a superior analytical technique for metabolite profiling and identification studies performed in drug discovery and development laboratories. In the early phase of drug discovery the analytical approach should be both time- and cost-effective, thus providing as much data as possible with only one visit to the laboratory, without the need for further experiments. Recent developments in mass spectrometers have created a situation where many different mass spectrometers are available for the task, each with their specific strengths and drawbacks. We compared the metabolite screening properties of four main types of mass spectrometers used in analytical laboratories, considering both the ability to detect the metabolites and provide structural information, as well as the issues related to time consumption in laboratory and thereafter in data processing. Human liver microsomal incubations with amitriptyline and verapamil were used as test samples, and early-phase 'one lab visit only' approaches were used with all instruments. In total, 28 amitriptyline and 69 verapamil metabolites were found and tentatively identified. Time-of-flight mass spectrometry (TOFMS) was the only approach detecting all of them, shown to be the most suitable instrument for elucidating as comprehensive metabolite profile as possible leading also to lowest overall time consumption together with the LTQ-Orbitrap approach. The latter however suffered from lower detection sensitivity and false negatives, and due to slow data acquisition rate required slower chromatography. Approaches with triple quadrupole mass spectrometry (QqQ) and hybrid linear ion trap triple quadrupole mass spectrometry (Q-Trap) provided the highest amount of fragment ion data for structural elucidation, but, in addition to being unable to produce very high-important accurate mass data, they suffered from many false negatives, and especially with the QqQ, from very high overall time consumption.