Product Ion Scan Experiments Research Articles

Molecular networking-based dereplication of strictosidine-derived monoterpene indole alkaloids from the curare ingredient Strychnos peckii.

Monoterpene indole alkaloids (MIAs) are a large group of biologically active compounds produced by hundreds of plant species in numerous plant families, such as Apocynaceae, Loganiaceae and Rubiaceae. Although this diversity is biosynthetically intermediated by strictosidine, there are no works focused on the fragmentation patterns under collision-induced dissociation of strictosidine-derived alkaloids. Initially, the alkaloid fingerprint of Strychnos peckii was established using leaf spray with tandem mass spectrometry (LS-MS/MS). Then, high-performance liquid chromatography coupled to tandem mass spectrometry (HPLC/MS/MS) analyses were carried out to focus on the patterns of neutral losses in product ion scan experiments with the leaf aqueous extract. Finally, the product ion spectra from a set of presumable strictosidine-type derivatives were analyzed and organized via molecular networking (MN), and dereplicated by manual interpretation of MS/MS spectra. LS-MS/MS allowed the tentative identification of strictosidine-derived alkaloids in the leaves of S. peckii, showing useful neutral losses for the dereplication of strictosidine analogues by HPLC/MS/MS experiments. The use of MN combined with manual interpretation of the fragmentation patterns highlighted characteristic fragmentation pathways, and allowed the tentative identification of strictosidine, desoxycordifoline, strictosidinic acid, 10-hydroxystrictosidine, 5-carboxystrictosidine, lyaloside, 3,4-dehydrostrictosidine and strictosidine lactam. The use of MN combined with the analysis of the fragmentation patterns proved to be a useful strategy for the dereplication of strictosidine-derived MIAs from S. peckii, highlighting known and unprecedented structures, as well as useful diagnostic product ions. Therefore, this workflow is an effective approach for the characterization of strictosidine-type alkaloids in future dereplication works.

HPLC–MS/MS profiling of wild-growing scentless chamomile

Scentless chamomile (Tripleurospermum inodorum = M. inodora) is a plant belonging to Anthemideae tribe of Asteraceae family, with phenotype similar to the common chamomile, a plant used in human consumption in the form of herbal tea infusion. In order to be able to understand possible health-promoting properties and adverse effects of the scentless chamomile's consumption, it is of essence to examine its chemical composition. The aim of the study was to perform phenolic profiling using high-performance liquid chromatography–tandem mass spectroscopy (HPLC–MS/MS), in comparison to the common chamomile. In the investigated extracts, qualitative and quantitative analyses enabled the identification of 66 compounds based on their retention times, mass (MS/MS) spectra, and analysis of their characteristic fragmentation patterns in MS/MS Product Ion Scan experiments. A new HPLC–MS/MS method for quantitation of common plant metabolites was hereby developed, enabling quantitation of 47 compounds. All examined M. inodora samples have relatively high combined phenolic and flavonoid contents (25.2–51.9 mg/g). Apigenin, apigenin-7-O-glucoside, luteolin, luteolin-7-O-glucoside, quinic acid, and 5-O-caffeoyl quinic acid were the compounds with highest concentration in both inodorous and common chamomile. The results obtained hereby represent the first and most detailed chemical profile of scentless chamomile so far.

Qualitative Confirmation of 9 Synthetic Cannabinoids and 20 Metabolites in Human Urine Using LC–MS/MS and Library Search

Synthetic cannabinoids are an emerging illicit drug class. The variety of available substances is large and ever-changing, making it difficult for laboratories to remain current. We present a qualitative LC-MS/MS method identifying urinary metabolites of JWH-018, JWH-073, JWH-081, JWH-122, JWH-200, JWH-210, JWH-250, RCS-4, and AM2201 and the parent compounds JWH-018, JWH-073, JWH-081, JWH-122, JWH-210, JWH-250, RCS-4, AM2201, and MAM2201. After enzymatic hydrolysis, urinary proteins were precipitated with acetonitrile. Chromatography utilized a 10 min gradient on a Kinetex XB-C18 column with 0.1% formic acid in water and acetonitrile. Scheduled multiple reaction monitoring "survey scans" were followed by information-dependent acquisition-enhanced product ion scan experiments on an ABSciex 5500 QTRAP mass spectrometer. Analytes were identified by software-assisted library searching against reference spectra. The method was fully validated, including proof of selectivity (no exogenous or endogenous interferences were observed), assessment of matrix effects (95-122%) and recovery (53-95%), determination of limits of detection (0.5-10 ng/mL), carry-over studies (thresholds between 100 and 1000 ng/mL), and determination of autosampler stability (samples were stable for at least 3 days). Hydrolysis efficiency was thoroughly investigated for a wide range of glucuronides and for the reference standard, JWH-018 5-hydroxypentyl glucuronide.

Multistep Mass Spectrometry Methodology for Direct Characterization of Polar Lipids in Green Microalgae using Paper Spray Ionization

Paper spray ionization, an ambient ionization method, has been applied for the identification of polar lipids in green microalgae with no sample preparation. A multistep experimental protocol was employed to characterize the lipid species of two microalgae strains, Kyo-Chlorella in tablet form and Nannochloropsis in paste form by mass spectrometry (MS). Tandem mass spectrometry (MS/MS) experiments using collision induced dissociation (CID) were employed for initial characterization of the detected lipid species, which were dominated by polar glycolipids and phospholipids. Product ion scan experiments were performed to determine the lipid head groups and fatty acid composition. Precursor ion scan experiments using fragment ions such as m/z 184, which is characteristic of the phosphocholine headgroup, were then used to confirm the lipid classification. Lipid elemental compositions were determined by exact mass measurements using high resolution mass spectrometry. Finally, the position of unsaturation was determined using reactive paper spray ionization experiments with ozone used as a reagent to cleave double bonds. Ozone was produced in situ using dielectric barrier discharge from a low temperature plasma, and it reacted in ambient air with the spray of ions produced by paper spray ionization. Using the precursor ion scan experiment, the resulting ozone cleavage product ions were used to determine the position of unsaturation for some of these species. By applying this experimental protocol, the molecular formulas and key aspects of the structures of glycerophosphocholines (PCs) such as 9Z-16:1/9Z,12Z-16:2 PC and 6Z,9Z-18:2/6Z,9Z,12Z-18:3PC and monogalactosyldiacylglycerols (MGDGs) such as 18:3/16:3MGDG were identified in the positive ion mode, while glycerophosphoglycerols (PGs) such as 18:3/16:0 PG and sulfoquinovosyldiacylglycerols (SQDGs) such as 18:3/16:0 SQDG were identified in the negative ion mode.

Metabolism of Growth Hormone Releasing Peptides

New, potentially performance enhancing compounds have frequently been introduced to licit and illicit markets and rapidly distributed via worldwide operating Internet platforms. Developing fast analytical strategies to follow these new trends is one the most challenging issues for modern doping control analysis. Even if reference compounds for the active drugs are readily obtained, their unknown metabolism complicates effective testing strategies. Recently, a new class of small C-terminally amidated peptides comprising four to seven amino acid residues received considerable attention of sports drug testing authorities due to their ability to stimulate growth hormone release from the pituitary. The most promising candidates are the growth hormone releasing peptide (GHRP)-1, -2, -4, -5, -6, hexarelin, alexamorelin, and ipamorelin. With the exemption of GHRP-2, the entity of these peptides represents nonapproved pharmaceuticals; however, via Internet providers, all compounds are readily available. To date, only limited information on the metabolism of these substances is available and merely one metabolite for GHRP-2 is established. Therefore, a comprehensive in vivo (po and iv administration in rats) and in vitro (with human serum and recombinant amidase) study was performed in order to generate information on urinary metabolites potentially useful for routine doping controls. The urine samples from the in vivo experiments were purified by mixed-mode cation-exchange solid-phase extraction and analyzed by ultrahigh-performance liquid chromatography (UHPLC) separation followed by high-resolution/high-accuracy mass spectrometry. Combining the high resolution power of a benchtop Orbitrap mass analyzer for the first metabolite screening and the speed of a quadrupole/time-of-flight (Q-TOF) instrument for identification, urinary metabolites were screened by means of a sensitive full scan analysis and subsequently confirmed by high-accuracy product ion scan experiments. Two deuterium-labeled internal standards (triply deuterated GHRP-4 and GHRP-2 metabolite) were used to optimize the extraction and analysis procedure. Overall, 28 metabolites (at least three for each GHRP) were identified from the in vivo samples and main metabolites were confirmed by the human in vitro model. All identified metabolites were formed due to exopeptidase- (amino- or carboxy-), amidase-, or endopeptidase activity.

Determination of IGF-I in horse plasma by LC electrospray ionisation mass spectrometry

The insulin-like-growth factor (IGF-I) peptide is considered to be the main indirect marker for growth hormone administration (GH) in a horse. Further to a previous investigation on measurement of IGF-I in plasma samples by mass spectrometry, this study focuses on quantitative and qualitative analysis of intact IGF-I in horse plasma. First, protein-transposing software has been developed for IGF-I to facilitate its quantification by HPLC-electrospray-ion-trap mass spectrometry. Second, product-ion scan experiments on IGF-I have been conducted on standard samples, non-fortified equine plasma samples, fortified plasma samples, and equine GH post-administration samples. This "top-down" approach method enables characterisation of fragment ions corresponding to the carboxy terminal end, which can be useful for the confirmation of the presence of IGF-I in plasma samples.

A fragmentation study of two compounds related to 4′‐demethylepipodophyllotoxin in negative ion electrospray ionization by MSn ion‐trap time‐of‐flight mass spectrometry

High-resolution electrospray ionization multistage tandem mass spectrometry (MS 1-7) in negative ion mode was used to determine the accurate masses and fragmentation pathways of two compounds, 4'-demethylepipodophyllotoxin and 4'-demethyl-4-azido-4-deoxyepipodophyllotoxin, which are key intermediate compounds for the preparation of podophyllotoxin-type anti-cancer drugs. The deprotonated molecules [M-H]* of both compounds were readily observed in the conventional single-stage mass spectra due to the presence of the phenolic hydroxyl group in the molecules. Abundant information on the product ions was obtained from tandem mass spectra (MS 2-7) in negative ion mode. Based on the exact masses acquired from 14 different tandem mass spectra, a similar MSn fragmentation pathway was proposed for both compounds. A characteristic product ion produced in the MS 2-4 product ion scan experiments is the cyclohexylenetrione anion [M-H-2Me-RH]* or [M-H-RH-2Me]* at m/z 351 (C19H11O7) formed by the consecutive losses of two CH3 radicals at the 3'- and 5'-positions and the neutral loss of RH, where R = a 4-substituted group (-OH or -N3), from the [M-H]* ion. This anion may be considered as diagnostic for the presence of this type of compound. The other common cleavages are the neutral losses of CO at least two times in the MS 6,7 product ion spectra. The results of this work could serve as an effective tool for the detection or determination of other derivatives of 4'-demethyl-4beta-substituted podophyllotoxin, which are widely used as intermediates for the preparation of anti-tumor drugs.

Insulins in equine urine: qualitative analysis by immunoaffinity purification and liquid chromatography/tandem mass spectrometry for doping control purposes in horse‐racing

Insulin is a peptide hormone consisting of two peptide chains (A- and B-chain) that are cross-linked by two disulfide bonds. To obtain improved pharmacokinetic onset of action profiles of insulin treatment in diabetic patients, recombinant long-, intermediate-, and rapid-acting insulin analogs are produced, in which the C-terminal end of the B-chain plays an especially important role.A review of the veterinary literature reveals the low prevalence of equine type I diabetes mellitus, which indicates that the therapeutic use of insulin in racing horses is unlikely. Although there is no unequivocal evidence of an overall performance-enhancing effect of insulin, in human sports the misuse of insulin preparations is reported among elite athletes. The desired effects of insulin include the increase of muscular glycogen prior to sports event or during the recovery phase, in addition to a chalonic action, which increases the muscle size by inhibiting protein breakdown. In the present study urinary insulin was detected in equine samples and differences between equine insulin, human insulin, as well as rapidly acting recombinant insulin variants were examined. The method was based on sample purification by solid-phase extraction (SPE) and immunoaffinity chromatography (IAC), and subsequent analysis by microbore liquid chromatography (LC) and tandem mass spectrometry (MS/MS) using top-down sequencing for the determination of various insulins. Product ion scan experiments of intact proteins and B-chains enabled the differentiation between endogenously produced equine insulin, its DesB30 metabolite, human insulin and recombinant insulin analogs, and the assay allowed the assignment of individual product ions, especially those originating from modified C-termini of B-chains.

Screening for unknown synthetic steroids in human urine by liquid chromatography‐tandem mass spectrometry

Chemically modified steroids (designer steroids), including tetrahydrogestrinone and norbolethone, pose a threat to the integrity of the sport community. These compounds have recently been detected in urine specimens from athletes, resulting in temporary or permanent suspension from amateur and/or professional competition. Triple quadrupole mass spectrometers enable doping control laboratories to screen for unknown, anabolic, androgenic steroids utilizing precursor ion scans. On the basis of common dissociation patterns of steroids with common structural features, characteristic product ions were selected to serve as diagnostic markers for previously unidentified drugs or drug metabolites in human urine samples. An assay was established to complement standard screening procedures. Urine specimens were enzymically hydrolyzed, partitioned into ether, concentrated, and analyzed by precursor ion scanning. Spectra from samples fortified with eight standard compounds (methyltestosterone, ethyltestosterone, 1-testosterone, gestrinone, dihydrogestrinone, tetrahydrogestrinone, norbolethone, and propyltrenbolone) and one deuterium-labeled analog (d(4)-tetrahydrogestrinone) at 50 ng/ml of urine, had precursor ion peaks other than those from common endogenous steroids. Subsequent product ion scan experiments on precursor ions of peaks of unknown origin provided structural identification of the unknown compounds.

Qualitative Determination of Synthetic Analogues of Insulin in Human Plasma by Immunoaffinity Purification and Liquid Chromatography−Tandem Mass Spectrometry for Doping Control Purposes

Synthetic insulins such as Humalog Lispro, Novolog Aspart, or Lantus Glargine, are commonly employed for the treatment of insulin-dependent diabetes mellitus owing to convenient handling and fast or prolonged bioavailability. However, the misuse of insulin in sports has been reported often, and the international doping control system requires a reliable and robust assay to determine the presence or absence of related drugs prohibited by the World Anti-Doping Agency. Qualitative evidence of administered substances, which is preferably obtained by mass spectrometry, is of utmost importance. Plasma specimens of 2 mL were fortified with three synthetic insulin analogues and purified by immunoaffinity chromatography, and extracts were analyzed by microbore liquid chromatography and tandem mass spectrometry. Product ion scan experiments of intact proteins enabled the differentiation between endogenously produced insulin and its synthetic analogues by collisionally activated dissociation of multiply charged precursor ions. This top-down sequencing-based assay allows the assignment of individual fragment ions, in particular, of those comprising modifications that are originating from C-termini of B-chains. Recoveries of synthetic insulins from plasma aliquots ranged from 91 to 98%, and detection limits were accomplished at 0.5 ng/mL for all target analytes.

Study of protein modification by 4-hydroxy-2-nonenal and other short chain aldehydes analyzed by electrospray ionization tandem mass spectrometry

A convenient way to study lipid oxidation products-modified proteins by means of suitable model systems has been investigated. As a model peptide, the oxidized B chain of insulin has been chemically modified by either 4-hydroxy-2-nonenal (HNE) or hexanal and the extent, sites, and structure of modifications were assessed by electrospray mass spectrometry. A reduction step, using either NaCNBH 3 or NaBH 4, was also studied to stabilize the alkylated compounds. From the data gathered, it appeared that NaCNBH 3, when added at the beginning of incubation, dramatically influenced the HNE-induced modifications in terms of the addition mechanism (Schiff base formation instead of Michael addition) but also of the amino acid residues modified (N-terminal amino acid instead of histidine residues). However, by reducing the HNE-adducted species at the end of the reaction with NaBH 4, the fragment ions obtained in the product ion scan experiments become more stable and thus, easier to interpret in terms of origin and mechanism involved. With regard to hexanal induced modifications, we have observed that hexanal addition under reductive conditions led to an extensive modification of the peptide backbone. Moreover, as confirmed by “in-source” collision followed by collision induced dissociation (CID) experiments on selected precursor ions (pseudo-MS 3 experiments), N,N-di-alkylations were first observed on the N-terminal residue and further on Lys 29 residue. On the other hand, compared to the native peptide, no significant changes in MS/MS fragmentation patterns (b and y ions series) were observed whatever the basic site modified by the aldehyde-addition.