A fragmentation study on four C19-diterpenoid alkaloids by electrospray ionization ion-trap time-of-flight tandem mass spectrometry

High-resolution electrospray ionization ion-trap time-of-flight tandem mass spectrometry (HR-ESI-IT-TOF-MSⁿ) in positive-ion mode was used to determine the accurate masses and fragmentation pathways of four C₁₉-diterpenoid alkaloids, aconitine (1), yunnaconitine (2), crassicauline A (3), and benzoylmesaconine (4). The [M+H]⁺ ions of compounds 1–4 were readily observed in conventional single-stage mass spectrometry. Based on the MS^1–6 analyses, detailed fragmentation rules of the four compounds were proposed. The neutral losses of AcOH, MeOH, H₂O, CO, C₂H₄, PhCOOH and p-OMePhCOOH segments were the characteristic eliminations from the precursor ions due to the presence of acetyl, methoxyl, hydroxyl, N-ethyl, benzoyl and p-methoxyl-benzoyl units in the structures. Benefited from the high resolution of the mass analyzer, the loss of 28 Da corresponding to CO or CH₄ segment in product ions was unambiguously distinguished. The losing sequence of the main substituent groups was summarized as: C(8)-acetyl>C(16)-methotyl>C(15)-hydroxyl>C(6)-methoxyl>C(1)-methoxyl/C(3)-hydroxyl>C(18)-methoxyl>>C(13)-hydroxyl. The sequential loss of (16)-methoxyl moiety and CO (generating from enol–ketone tautomerism) groups could be recognized as the characteristic eliminations for the compounds with C(16)-methoxyl and C(15)-hydroxyl groups simultaneously. The application of HR-ESI-IT-TOF-MSⁿ technique to investigate the fragmentation of C₁₉-diterpenoid alkaloids provided useful information to understand their fragmentation behaviors.     

Identification of the designer steroid Androsta‐3,5‐diene‐7,17‐dione in a dietary supplement

A liquid chromatography‐mass spectrometry (LC–MS) screen for known anabolic‐androgenic steroids in a dietary supplement product marketed for “performance enhancement” detected an unknown compound having steroid‐like spectral characteristics. The compound was isolated using high performance liquid chromatography with ultraviolet detection (HPLC–UV) coupled with an analytical scale fraction collector. After the compound was isolated, it was then characterized using gas chromatography with simultaneous Fourier Transform infrared detection and mass spectrometry (GC–FT–IR–MS), liquid chromatography–high resolution accurate mass–mass spectrometry (LC–HRAM–MS) and nuclear magnetic resonance (NMR). The steroid had an accurate mass of m/z 285.1847 (error?0.57 ppm) for the protonated species [M + H]⁺, corresponding to a molecular formula of C₁₉H₂₄O₂. Based on the GC–FT–IR–MS data, NMR data, and accurate mass, the compound was identified as androsta‐3,5‐diene‐7,17‐dione. Although this is not the first reported identification of this designer steroid in a dietary supplement, the data provided adds information for identification of this compound not previously reported. This compound was subsequently detected in another dietary supplement product, which contained three additional active ingredients.     

长鞭红景天化学成分的研究

长鞭红景天化学成分的研究彭江南，葛永潮，李晓晖（军事医学科学院放射医学研究所，北京１００８５０）红景天是滋补强壮药物，目前正引起人们极大的兴趣，现已有一些产品上市。我们曾对数种红景天的化学成分进行过研究［１～４］。长鞭红景天（Ｒｈｏｄｉｏｌａｆａｓｔ...     

Characterization and determination of the major constituents in Belamcandae Rhizoma by HPLC-DAD-ESI-MS(n)

Belamcandae Rhizoma, derived from the rhizome of Belamcanda chinensis (L.) DC., has been used as traditional Chinese medicine for the treatment of coughing and pharyngitis. However, there have been few studies dealing with the systematic analysis of the bioactive constituents in Belamcandae Rhizoma. In this work, high performance liquid chromatography-diode array detection-electrospray ionization multiple-stage mass spectrometry (HPLC-DAD-ESI-MSⁿ) combined with liquid chromatography-time of flight-mass spectrometry (HPLC-TOF/MS) was established for profiling and characterization of multi-constituent in Belamcandae Rhizoma. The ESI-MSⁿ fragmentation behaviors of the authentic references were proposed for aiding the structural identification of components in the extract. Thirty-five flavonoids, including 30 isoflavones and five xanthones, were identified or tentatively identified by comparing their retention times, UV and MS spectra with those of authentic compounds or literature data. Twelve of the identified compounds (neomangiferin, mangiferin, tectoridin, iristectorin B, iristectorin A, iridin, tectorigenin, iristectorigenin A, irigenin, irisflorentin, irilone and dichtomitin) were determined by HPLC-DAD using a C₁₈ column. The results indicated that the developed analysis method could be employed as a rapid, effective technique for structural characterization of chemical constituents in herbal medicine. This work is expected to provide comprehensive information for the quality evaluation of Belamcandae Rhizoma, which would be a valuable reference for the further study and development of this herb and related medicinal products.     

赤芝子实体中三萜化学成分的研究

自赤芝[Ganoderma lucidum (Fr.)Karst]的二氯甲烷溶解部分分离得到一个新的三萜内酯化合物,命名为灵芝内酯(ganolactone)。根据光谱(UV,IR,¹HNMR,¹³CNMR,MS和2DNMR)解析,确定其结构为I式。同时还从赤芝子实体中分到三个已知化合物,即灵芝醇A(ganoderiolA,II),灵芝醇B(ganoderiolB,II)和灵芝三醇(ganodermatriolIV)。     

Identification of five pyrrolidinyl substituted cathinones and the collision‐induced dissociation of electrospray‐generated pyrrolidinyl substituted cathinones

This article reports on the analytical properties of five pyrrolidinyl substituted cathinones: α ‐pyrrolidinononaphenone (α ‐PNP, 1 ), 4‐chloro‐α ‐pyrrolidinopropiophenone (4‐Cl‐α ‐PPP, 2 ), 4‐chloro‐α ‐pyrrolidinovalerophenone (4‐Cl‐α ‐PVP, 3 ), 5‐dihydrobenzofuranpyrovalerone (5‐DBFPV, 4 ), and 2‐(pyrrolidin‐1‐yl)‐1‐(5,6,7,8‐tetrahydronaphthalen‐2‐yl)hexan‐1‐one (β ‐THNPH, 5 ). These identifications were based on liquid chromatography–quadrupole time‐of‐flight‐mass spectrometry (LC–QTOF–MS), gas chromatography–mass spectrometry (GC–MS) and nuclear magnetic resonance spectroscopy (NMR). To our knowledge, no analytical data about α ‐PNP, 4‐Cl‐α ‐PPP, 4‐Cl‐α ‐PVP, and β ‐THNPH have appeared until now, making this the first report on these compounds. Moreover, in order to study the collision‐induced dissociation (CID) characteristic fragmentation routes of pyrrolidinyl substituted cathinones, a total number of 13 pyrrolidinyl substituted cathinones were selected and discussed. The major fragmentation pathways under CID mode are produced, leading to the formation of characteristic ions. Product ions of [M‐C₄H₉N]⁺ and C_nH_2nN⁺ indicate the presence of pyrrolidinyl substitution. Characteristic fragments are also produced via the cleavages of the CH–N(CH₂)₄ bond and the CO‐CHN bond. Copyright © 2016 John Wiley & Sons, Ltd.     

LC and LC–MS/TOF studies on stress degradation behaviour of candesartan cilexetil

Stress degradation studies were conducted on candesartan cilexetil under the ICH prescribed conditions of hydrolysis (acidic, basic and neutral), photolysis, oxidation and thermal stress. Maximum degradation was observed on hydrolysis, especially in the neutral condition. The drug was also degraded significantly under photolytic conditions. However, it was stable to oxidative and thermal stress. A total of eight degradation products were formed, the separation of which was successfully achieved on a C-18 column employing a gradient method. In order to characterize each degradation product, a complete mass fragmentation pathway of the drug was initially established with the help of MSⁿ and MS/TOF accurate mass studies. Subsequently, degradation products were also subjected to LC–MS/TOF investigations, which resulted in their fragmentation pattern and also accurate masses. The latter helped in the elucidation of the structure of all the degradation products, which was achieved through comparison of their fragmentation pattern with that of the drug. The major product was isolated and its structure was confirmed through NMR studies. On the whole, a more comprehensive fragmentation behaviour and degradation profile of the drug was established than reported in the literature.     

Synthesis of 13C‐labelled cutin and suberin monomeric dicarboxylic acids of the general formula HO213C‐(CH2)n‐13CO2H (n = 10, 12, 14, 16, 18, 20, 22, 24, 26, 28)

¹³C‐labeled dicarboxylic acids HO₂¹³C‐(CH₂)_n‐¹³CO₂H (n = 10, 12, 14, 16, 18, 20, 22, 24, 26, 28) have been synthesized as internal standards for LC‐MS and GC‐MS analysis of cutin and suberin monomer degradation by soil‐based microorganisms. Different synthetic strategies had to be applied depending on the chain length of the respective synthetic target and because of economic considerations. ¹³C‐labels were introduced by nucleophilic substitution of a suitable leaving group with labelled potassium cyanide and subsequent hydrolysis of the nitriles to produce the corresponding dicarboxylic acids. All new compounds are characterized by GC/MS, IR, and NMR methods as well as by elemental analysis.     

线性变温法预测硫酸链霉素化学稳定性

本文用线型变温法,同时用经典恒温法,对同一批号硫酸链霉素水溶液进行稳定性预测,得到硫酸链霉素在pH=6.50水溶液中的分解活化能分别为E=33 kcal·mol^-1及E=34 kcal·mol^-1;室温速度常数分别为k_20℃=5.7×10^-6h^-1及k_20℃=5.0×10^-6h^-1。     

Study on the aconitine‐type alkaloids of Radix Aconiti Lateralis and its processed products using HPLC‐ESI‐MSn

The type and content change of alkaloids of Radix Aconiti Lateralis (Lateral root of Aconitum carmichaeli Debx, an important and popular medicinal herb in Traditional Chinese Medicine) in processing were studied using high performance liquid chromatography‐electrospray ionization‐multi‐stage mass spectrometry (HPLC‐ESI‐MSⁿ). Extract containing alkaloids, which were known to be the main bioactive components of the herb, was prepared by 1% (v/v) hydrochloric acid solution. An HPLC method which can simultaneously separate these alkaloids was established with gradient elution mode. Forty‐eight compounds were structurally identified by employing LC‐MSⁿ techniques; the MSⁿ spectra of most alkaloids displayed a characteristic behaviour of loss of CH₃COOH (60 u), CH₃OH (32 u), C₆H₅COOH (122 u), CO (28 u) and H₂O (18 u). Among them, the fragmentation ion C6H5COOH (122 u) was reported for the first time. By comparison, 22 compounds were found both in the crude materials and the processed products; 17 alkaloids were only found in the processed products and 9 alkaloids,which existed in crude material, could not be detected after processing. In the process of identification, we found new kinds of alkaloids, with protonated molecules at m/z 452, 468, and 482. We called these compounds dehydra‐hypaconine, dehydra‐mesaconine, and dehydra‐aconine, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

Chemical investigation on Sijunzi decoction and its two major herbs Panax ginseng and Glycyrrhiza uralensis by LC/MS/MS

Sijunzi decoction consists of Panax ginseng, Poria cocos, Atractylodes macrocephala and Glycyrrhiza uralensis. High performance liquid chromatography coupled with tandem mass spectrometry (LC/MSⁿ) was applied to identify and characterize three types of active components, ginsenoside (from P. ginseng), flavonoid and triterpenoid (from G. uralensis) in Sijunzi decoction. Spectra of MS and MS/MS from [M + Na]⁺ ions of ginsenosides were acquired and interpreted for their identification. Fragmentations with losing masses of 194 or 176 Da were the characteristic ions of triterpenoids in the MS/MS analysis. A characteristic fragment ion of the aglycon moiety at m/z 257 from source collision-induced dissociation was observed for flavonoid. LC/MS was also applied for the comparison of relative peak area of major active components between Sijunzi decoction and the single herb extracts. The concentration ratios of major active components detected in the individual herbs of P. ginseng and G. uralensis were found different from those in Sijunzi decoction. The experimental data indicated that the decocting process could result in the difference in the amount of active components.     

Study of forced decomposition behavior of lamivudine using LC,LC–MS/TOF and MS

Lamivudine was subjected to forced decomposition conditions of hydrolysis (neutral, acidic and alkaline), oxidation, photolysis and thermal stress, as suggested in the ICH guideline Q1A(R2). The drug showed instability in acid and alkali, while it remained stable in neutral conditions. It also degraded extensively under oxidative environment. It remained stable to light and thermal stress. In total, five degradation products were formed, which could be separated by LC on a C18 column using a gradient method. To characterize the products, first a complete fragmentation pathway of the drug was established by carrying out multi-stage (MSⁿ) and MS/TOF accurate mass studies. The same was compared to fragment pattern of the degradation products resulting from LC–MS/TOF studies. The accurate mass values obtained from LC–MS/TOF were used to obtain elemental compositions, and the total information helped in identification of the degradation products. Subsequently, degradation pathway of the drug was laid down, along with mechanisms of formation of the degradation products. There is no previous information on these aspects on the drug in the literature.     

Characterization of a novel impurity in bulk drug eprosartan by ESI/MS and NMR

A simple and sensitive liquid chromatography tandem multi-stage mass spectrometry (HPLC/MSⁿ) method suitable for eprosartan analysis was developed, by which an unknown impurity in bulk drug eprosartan was detected. The fragmentation behavior of eprosartan and the impurity in negative mode was investigated. Two molecules of CO₂ lost from eprosartan precursor ion were observed, while four molecules of CO₂ were extruded from the deprotonated molecular ion to the MS³ product ions of the impurity. Furthermore, a characteristic fragmentation ion at m/z 335 was observed in both eprosartan and the impurity indicated that the impurity might have two eprosartan units. The unknown impurity was initially proposed to be eprosartan dimer connected via methylene unit at the thiophene moiety on the basis of the multi-stage mass spectrometric and exact mass evidences, and it was finally elucidated as 4,4′-(5,5′-(1E,1′E)-3,3′-(4,4′-methylenebis(thiophene-4,2-diyl))bis(2-carboxyprop-1-ene-3,1-diyl)bis(2-butyl-1H-imidazole-5,1-diyl))bis(methylene) dibenzoic acid by NMR experiments including 1D (¹H NMR, ¹³C NMR, DEPT135⁰) and 2D (¹H-¹HCOSY, HMQC and HMBC) data.     

Preparation and properties of novel gramicidin S analogs possessing a tri-, tetra- or pentamethylene bridge between ornithine side chains

Abstract: Gramicidin S (GS) analogs in which the N^δ atoms of the two Orn side chains are linked by an oligomethylene bridge [-(CH₂)_n-; n=3–5] were prepared via the bis(p-nitrobenzenesulfonyl) derivative [Orn(NBS)^2,2′]GS. For comparison the nonbridged secondary amino group-containing analog [Orn(Me)^2,2′]GS was also prepared. ¹H NMR and CD spectral analysis indicated that these analogs adopt the same β-sheet conformation as GS. The antimicrobial activities of these analogs were very similar, but were slightly dependent on the bridge chain length, the trimethylene-bridged analog being the most potent.     

Study on the Fragmentation Pathway of the Aconitine-Type Alkaloids under Electrospray Ionization Tandem Mass Spectrometry Utilizing Quantum Chemistry

Objective

With the aim of developing a rapid and sensitive method for the relative molecular mass and the fragmentation pathway of target compounds without complicated experiments, we combined mass spectrometry (MS) with quantum chemistry to analyze protonated molecules and fragmentation pathway of target compounds.

Methods

In this study, aconitine, mesaconitine, hypaconitine, benzoylaconine, benzoylmesaconine, and benzoylhypaconine were investigated by electrospray ionization multi-stage mass spectrometry, and the lost sequence of four CH₃OH molecules was studied using quantum chemistry.

Results

The results showed that the typical neutral losses correspond to the molecules CO, CH₃OH, H₂O, –C₆H₅CO, and –CH₃, and so the lost sequence of four methoxyl groups and the structures of more fragmentation ions were identified for the first time.

Conclusions

The study demonstrated that the method of MS coupled with quantum chemistry can be used to estimate the fragmentation pathway of compounds quickly and conveniently.     

The preparation of genistein and LC‐MS/MS on‐line analysis

Genistein, a promising agent for cancer chemoprevention or treatment, can be obtained from soybean seeds, via a complex isolation procedure. The objective of this study was to investigate whether natural and high purity genistein could be acquired from Sophora japonica L. via a simple approach. High‐performance liquid chromatography electrospray ionization combined with tandem mass spectrometry (LC‐ESI‐MS/MS) was used to monitor the whole process of genistein preparation. The results showed there were at least 13 types of flavonoid in the crude extracts from sophora fruits with sophoricoside being the predominant component. The products obtained from our preparation were unambiguously identified as genistein based on molecular ion [M+H]⁺, UV spectra, retention time, IR spectra, ¹HNMR, ¹⁴CNMR spectra, and tandem mass spectrometric analysis. It demonstrated that 99.6% (w/w) genistein could be obtained via our preparation protocol. Drug Dev. Res. 61: 6–12, 2004. © 2004 Wiley‐Liss, Inc.     

马桶花抑菌新活性成分马桶花酮的分离及化学结构

马桶花(Incarvillea arguta Royle)为紫葳科角蒿属植物。四川民间用于治疗肝炎及感染性疾病。我们将该植物的提取物用于治疗传染性肝炎,有较好疗效。从马桶花植物的叶子中分离到四个结晶性单体,分别为甲、乙、丙和丁素。前三个化合物已经报道,丁素经药理试验,具有较强的抑菌作用和镇静作用。该新化合物命名为马桶花     

Metabolic studies of four soy isoflavones in rats by HPLC–HR-MS

In this paper, the metabolites of four soy isoflavones, daidzein, daidzin, genistein, and genistin, on perfused rat intestine–liver model were investigated by high-performance liquid chromatography coupled with high-resolution mass spectrometer/tandem mass spectrometer. Totally 16 metabolites were detected and identified based on accurate mass, fragmentation patterns, and multiple-stage mass data (MSⁿ). The metabolic site of dadzein-7-methyl ether (D-7-M) was further confirmed by nuclear magnetic resonance. Methylation, glucuronide conjugation, and sulfate conjugation were the primary metabolic processes. Among them, six metabolites, daidzin-4′,7-diglucoside, genistein-4′-glucoside, D-7-M, dadzein-4′,7-dimethyl ether, genistein-4′-methyl ether, and genistein-7-methyl ether were detected in rats for the first time and not reported in humans. The metabolic pathways of daidzein, daidzin genistein, and genistin in rats were postulated. The biological effects of these metabolites are worthy of further investigation.