夏佛塔苷的电喷雾电离裂解规律解析

目的研究夏佛塔苷的质谱多级裂解过程,探讨质谱技术在黄酮碳酐中的应用规律。方法应用电喷雾电离(ESI)结合串联质谱(MS~n)技术,对黄酮碳酐化合物夏佛塔苷在ESI-MS/MS质谱中的裂解规律进行研究。结果夏佛塔苷在负离子模式下,其准分子离子m/z563多级质谱图中主要出现[M-H-120]~-、[M-H-90]~-、[M-H-120-90]~-、[M-H-120-60]~-和[M-H-120-90-CO]~-等离子碎片-。结论夏佛塔苷在ESI-MS/MS质谱中的裂解行为符合黄酮碳酐的裂解规律,有利于利用质谱技术对各种黄酮碳苷类化合物所含糖基种类进行分析和研究。     

电喷雾离子化多级质谱解析环孢菌素结构

应用电喷雾离子化多级质谱法分析四种环孢菌素同系物，并对它们的裂解规律进行分析归纳。在电喷雾离子化多级质谱条件下，环孢菌素先形成N端加质子的[M＋H]^＋分子离子，然后沿肽链的酰胺键发生断裂，产生相应的碎片离子，开环裂解主要发生在2和3位、1和11位以及5位和6位氨基酸残基之间。这一裂解规律可应用于环孢菌素类化合物的快速结构鉴定。     

蟛蜞菊内酯的电喷雾离子阱质谱分析

目的：应用电喷雾离子阱质谱（ESI-MSn）技术对蟛蜞菊内酯进行质谱裂解分析,通过主要特征碎片离子研究其裂解规律。方法：样品溶液进样后,采用ESI-MS1～3碰撞裂解方式,解析蟛蜞菊内酯的特征碎片离子。结果：蟛蜞菊内酯在正离子模式下,采用ESI-MS1获得准分子离子峰[M＋H]＋m/z 315;采用ESI-MS2获得了离子碎片m/z 297、m/z 287;采用ESI-MS3获得m/z259、m/z231等离子碎片。负离子模式下采用ESI-MS1获得[M-H]-m/z313,采用ESI-MS2获得了离子碎片m/z298;采用ESI-MS3获得m/z270、m/z254等离子碎片。结论：蟛蜞菊内酯在软电离模式下,正负离子模式对质谱裂解方式产生差异,其中主要产生的正负离子碎片分别为m/z287和m/z298。本研究为进一步研究蟛蜞菊内酯化合物的体内代谢过程与结构修饰提供实验依据。     

运用量子化学方法解析大黄酚ESI-ITMSn中质谱行为

目的:研究大黄酚及其主要碎片离子在电喷雾-离子阱多级质谱(ESI-ITMSn)中的质谱行为。方法:获取大黄酚分子的一级质谱和多级质谱碰撞诱导解离下的碎片离子,运用量子化学方法计算质谱碎片离子的几何参数、键断裂能、电荷变化以及自旋密度,探讨碎片离子的断裂位点。结果:获得m/z:252.9、237.9、224.9、209.9、196.9、181.9、180.9、168.9、153.1离子的稳定构型,推断出大黄酚质谱裂解途径。结论:计算结果与CIDMS所推断的裂解规律相吻合,成功地解释了大黄酚分子在ESI-ITMSn中裂解现象。     

6种罕见核苷糖电喷雾质谱裂解规律的初步研究

本文在负离子模式下, 应用电喷雾电离多级串联质谱技术对6种罕见胸苷二磷酸单糖的裂解规律进行了初步研究。结果表明: 二级串联质谱中观察到6种罕见胸苷二磷酸单糖的高丰度碎片离子源于磷酸二酯键部分的裂解, 出现一系列特征的m/z 321、383和401碎片离子, 对应 [TDP−H]⁻ 及该碎片离子分别失去水分子和磷酸基得到的碎片离子; 罕见糖环上4位取代基的改变显著影响两个重要特征碎片离子 [glycosyl-1'-PO₃]⁻ 和[glycosyl-1'-P₂O₆]⁻ 的稳定性。     

盐酸苯达莫司汀的电喷雾串联质谱分析

目的:应用电喷雾串联质谱(ESI-MSn)技术对盐酸苯达莫司汀进行质谱裂解分析,通过主要特征碎片离子研究其裂解规律。方法:样品溶液进样后,采用ESI-MS1～4碰撞裂解方式,解析盐酸苯达莫司汀的特征碎片离子。结果:盐酸苯达莫司汀在正离子模式下,采用ESI-MS1获得了分子离子峰[M+H]+m/z 358;采用ESI-MS2获得了离子碎片m/z340;采用ESI-MS3获得m/z304、m/z276等离子碎片;采用ESI-MS4得到的主要离子碎片分别为m/z240、m/z268、m/z276等。负离子模式下采用ESI-MS1获得了[M-H]-m/z356,而采用ESI-MS2～4碰撞裂解,基本无响应。结论:盐酸苯达莫司汀在正离子模式下,主要通过脱去羧基中的H2O、CO碎片和5位N上的HCl、CH3Cl以及CH2=CHCl碎片的方式进行裂解。负离子模式下,只有一级电离产生的分子离子峰[M-H]-m/z356有一定响应。说明盐酸苯达莫司汀在负离子模式下比较稳定,而在正离子模式下容易裂解产生一系列碎片。本研究为盐酸苯达莫司汀的结构修饰及其代谢产物结构判断提供参考依据。     

巴龙霉素电喷雾电离负离子模式多级质谱裂解方式

目的研究巴龙霉素电喷雾电离负离子模式下的多级质谱裂解方式。方法采用电喷雾电离(Election Spray Ionization Source,ESI)多级质谱,极性检出模式为负模式。结果通过分析碎片离子信息,获得巴龙霉素电喷雾电离负离子模式下多级质谱的裂解方式。结论巴龙霉素的多级质谱裂解方式可用于巴龙霉素及其类似物的快速结构解析和定量分析,并为药代动力学研究提供可靠的理论依据。     

他克莫司和子囊霉素电喷雾多级质谱负离子模式下的裂解分析

目的应用电喷雾多级质谱法分析他克莫司(FK506)和子囊霉素(FK520)在负离子模式下的特征碎片离子和裂解规律。方法采用电喷雾电离离子阱多级质谱,极性检出模式为负离子模式。结果获得他克莫司和子囊霉素在负离子模式下的质谱裂解规律。结论该质谱裂解规律可应用于他克莫司及其类似物的快速结构解析、定量分析和药动学研究。     

新霉素和硫酸新霉素电喷雾电离负离子模式多级质谱裂解方式

目的研究新霉素和硫酸新霉素电喷雾电离负离子模式下的多级质谱裂解方式。方法采用电喷雾电离(Election Spray IonizationSource,ESI)多级质谱,极性检出模式为负模式。结果通过分析碎片离子信息,获得新霉素和硫酸新霉素电喷雾电离负离子模式下多级质谱的裂解方式。结论新霉素和硫酸新霉素的质谱裂解方式可用于新霉素和新霉素盐及其类似物的快速结构解析、定量分析、药代动力学研究,并对新霉素的生产具有指导意义。     

知母皂苷类化合物的质谱裂解规律研究进展

目的总结归纳知母皂苷类化合物的质谱裂解规律。方法通过查阅分析近年来国内外文献,结合本实验室研究工作,整理出46种知母皂苷类成分化学结构信息,并比较它们在正负离子模式下的质谱裂解途径及碎片离子。结果螺甾烷醇类皂苷首先丢失C-3位糖链上的各单糖,然后E环断裂脱去侧链(如144u和114u),最后生成苷元的特征碎片离子m/z255或253或251、m/z285或283或281;而呋甾烷醇类皂苷首先脱去C-22位的—OH/—OMe后出现[M+H-H2O]+/[M+H-MeOH]+的分子离子峰,然后丢失C-26位糖链,其进一步的裂解规律与螺甾烷醇类皂苷类似。结论正负离子模式下的质谱裂解规律及其它们的特征碎片离子将有助于知母皂苷类化合物的结构解析。     

Rapid biomonitoring of heterocyclic aromatic amines in human urine by tandem solvent solid phase extraction liquid chromatography electrospray ionization mass spectrometry

A rapid and facile tandem solvent solid phase extraction method was established to isolate the heterocyclic aromatic amines (HAAs) 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (8-MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, and 2-amino-9H-pyrido[2,3-b]indole from urine. The HAAs were separated by reversed phase liquid chromatography and quantified by electrospray ionization tandem mass spectrometry (ESI/MS/MS) using selected reaction monitoring. The limits of detection and quantitation of these HAAs approached 1-3 and 2-8 pg/mL, respectively, using only 0.3 mL of urine for analysis. Full product ion spectra were acquired to corroborate analyte identities. The pretreatment of urine from human volunteers that had consumed a grilled beef meal with acid or base at 70 degrees C increased the concentration of HAAs by as much as 6-fold, indicating the presence of phase II conjugates of the parent compounds. HAAs containing an N-methylimidazole moiety undergo facile cleavage of the N-methyl group under collision-induced dissociation conditions, and MS/MS analysis in the constant neutral loss scan mode monitoring the transition [M + H](+) --> [M + H - CH(3)(*)](+) revealed the presence of two other HAAs. 2-Amino-3-methylimidazo[4,5-f]quinoxaline (IQx) was identified by coelution of the analyte with synthetic IQx and by acquisition of the product ion spectrum. The second HAA was present in a relatively high abundance in urine. The molecule had the same nominal mass as 8-MeIQx (MH(+) at m/z 214), and the product ion spectrum was similar to that of 8-MeIQx. This novel HAA was also found in the grilled meat consumed by the volunteers at a concentration of 8 parts per billion. The accurate mass measurement and product ion spectrum of this molecule by ESI quadrupole time-of-flight mass spectrometry revealed that it was an isomer of 8-MeIQx. This tandem solvent solid phase extraction LC/ESI/MS/MS procedure may be used to rapidly assess the daily exposure to a variety of HAAs in urine.     

Oxaliplatin Degradation in the Presence of Chloride: Identification and Cytotoxicity of the Monochloro Monooxalato Complex

PURPOSE: To study the degradation of oxaliplatin in chloride media and evaluate the cytotoxicity of oxaliplatin in normal and chloride-deficient medium. METHODS: The products of the reaction of oxaliplatin with chloride were separated on a Hypercarb S column with a mobile phase containing 40% methanol in 0.05 M ammonia and subjected to electrospray ionization mass spectrometry. The cytotoxicity of oxaliplatin in normal and chloride-deficient medium was evaluated by 30-min incubations on human colon adenocarcinoma cells (HT-29). RESULTS: We identified a new intermediate degradation product, the monochloro monooxalato complex ([Pt(dach)oxCl]-) and the final product. the dichloro complex (Pt(dach)Cl2), by liquid chromatography-mass spectrometry. [Pt(dach)oxCl]- was found as the negative ion, M-, at m/z 431, and the positive ion, [M+2H]+, m/z 433. Pt(dach)Cl2 was found as the negative ion, [M-H]-, m/z 377, and the positive ion, [M+NH4]+, m/z 396. The fast initial degradation of oxaliplatin can be coupled to the fast formation of [Pt(dach)oxCl]-. In the cytotoxic assay, the cell survival was not affected by the chloride levels. CONCLUSIONS: [Pt(dach)oxCl]-, a new transformation product of oxaliplatin, has been identified. Its in vitro cytotoxic effect does not appear to exceed that of oxaliplatin.     

Characterization of human urinary metabolites of the antimalarial piperaquine.

Five metabolites of the antimalarial piperaquine (PQ) (1,3-bis-[4-(7-chloroquinolyl-4)-piperazinyl-1]-propane) have been identified and their molecular structures characterized. After a p.o. dose of dihydroartemisinin-piperaquine, urine collected over 16 h from two healthy subjects was analyzed using liquid chromatography (LC)/UV, LC/tandem mass spectrometry (MS/MS), Fourier transform ion cyclotron resonance (FTICR)/MS, and H NMR. Five different peaks were recognized as possible metabolites [M1, 320 m/z; M2, M3, and M4, 551 m/z (PQ + 16 m/z); and M5, 567 m/z (PQ + 32 m/z)] using LC/MS/MS with gradient elution. The proposed carboxylic M1 has a theoretical monoisotopic molecular mass of 320.1166 m/z, which is in accordance with the FTICR/MS (320.1168 m/z) findings. The LC/MS/MS results also showed a 551 m/z metabolite (M2) with a distinct difference both in polarity and fragmentation pattern compared with PQ, 7-hydroxypiperaquine, and the other 551 m/z metabolites. We suggest that this is caused by N-oxidation of PQ. The results showed two metabolites (M3 and M4) with a molecular ion at 551 m/z and similar fragmentation pattern as both PQ and 7-hydroxypiperaquine; therefore, they are likely to be hydroxylated PQ metabolites. The molecular structures of M1 and M2 were also confirmed using H NMR. Urinary excretion rate in one subject suggested a terminal elimination half-life of about 53 days for M1. Assuming formation rate-limiting kinetics, this would support recent findings that the terminal elimination half-life of PQ has been underestimated previously.     

Characterization of benzoquinone-peptide adducts by electrospray mass spectrometry

Benzoquinone adducts were prepared with model peptides to identify characteristic features of adduct fragmentation in tandem mass spectrometry (MS) experiments. Model peptides contained cysteine and had a molecular mass of less than 2 kDa to facilitate peptide fragmentation in tandem MS analyses. Peptides were adducted with an excess of benzoquinone, and the adducts were analyzed by LC/MS. Adducts were identified by addition of 108 Da to the monoisotopic mass of the peptide, except in the case of oxytocin, which formed a bis adduct with addition of 216 Da. Tandem MS experiments were performed on the [M + 2H](2+) ions and/or the [M + H](+) ions. Sequence information obtained from modified peptides was comparable to that of their unmodified counterparts. A unique ion pair separated by 141 or 142 Da corresponding to beta-elimination of benzoquinol-S or benzoquinol-SH from a b(n) or y(n) series ion indicated attachment at the sulfur of the cysteine residue. An alternate ion pair of 211 Da corresponded to fragmentation at the peptide bond on either side of the adducted cysteine. Enzymatic digestion of BSA and a 2560 Da frog peptide with trypsin yielded tryptic peptides, which were treated with benzoquinone. In addition to ion pairs of 142 and 211 Da, singly and doubly charged tryptic peptide adducts showed a neutral loss of 142 Da from the precursor. Either one or both ion pairs were present in more than half of all the peptides that were examined. The neutral loss of 142 Da was present in all singly charged tryptic peptide adducts and in 11 out of 14 doubly charged tryptic peptide adducts. The data indicate that reliable detection of benzoquinone-cysteinyl peptide adducts requires monitoring of multiple spectral characteristics.     

碳青霉烯类抗生素的电喷雾质谱裂解规律分析

目的:研究碳青霉烯类抗生素的质谱(MS)裂解特征,探讨该类化合物的MS裂解规律。方法:正离子检测模式下,利用电喷雾三重四极杆MS对4种碳青霉烯类抗生素(亚胺培南、美罗培南、帕尼培南、比阿培南)的[M+H]+离子,以及由其产生的特征碎片离子进行MS/MS及准MS/MS/MS分析。结果:正离子检测模式下,碳青霉烯类抗生素主要以[M+H]+准分子离子形式存在;其裂解行为是离子[M+H]+主要发生四元环裂解反应、脱羧基反应及碳-硫键的裂解反应,产生相应的特征子离子C、D、G、H。结论:该方法可获得碳青霉烯类抗生素的多级MS信息;依靠MS裂解规律,可以对其类似物、衍生物及代谢物进行快速定性鉴别,并为其定量分析提供有力的理论依据。     

Determination of travoprost and travoprost free acid in human plasma by electrospray HPLC/MS/MS

A quantitative method for the analysis of AL-5848, the (+)-enantiomer of fluprostenol (FP), in human plasma is described. Plasma was spiked with a tetradeuterated analog of travoprost free acid (AL-5848X) as internal standard (IS) and acidified with 0.1 M formic acid. Sample clean up was performed using reversed phase solid-phase extraction. Following elution of the compounds of interest and evaporation to dryness, the residue was reconstituted in methanol:water (1:1) and chromatographed on an octadecylsilica (C18) column with negative ion electrospray ionization tandem mass spectrometry. The [M[bond]H](-) ions at m/z 457 and 461 for the analyte and IS, respectively, were subjected to collisional fragmentation with argon to yield the same intense 3-trifluoromethylphenolate (m/z 161) product ion. The validated concentration range was 0.010-3.00 ng/ml based on a 1.0 ml plasma aliquot. Fully adequate accuracy, precision, specificity, recovery and stability for routine use in clinical pharmacokinetic studies were demonstrated. Analysis of a second plasma aliquot following incubation with rabbit esterase allows the isopropyl ester pro-drug, travoprost (AL-6221), to be determined by difference.     

Characterization of two cyclic metabolites of sitagliptin.

Two novel metabolites of the dipeptidyl peptidase inhibitor sitagliptin (MK-0431, (2R)-4-oxo-4-[3-(trifluoromethyl)-5,6-dihydro[1,2,4]triazolo[4,3-a]pyrazin-7(8H)-yl]-1-(2,4,5-trifluorophenyl)-butan-2-amine), were identified after purification from dog urine. The metabolites (referred to as M2 and M5) were characterized by hydrogen/deuterium exchange tandem mass spectrometry and NMR spectroscopy nuclear Overhauser effect experiments as the cis and trans stereoisomers formed by cyclization of the primary amino group with the alpha carbon of the piperazine ring, following oxidative desaturation.     

Rapid profiling and identification of triterpenoid saponins in crude extracts from Albizia julibrissin Durazz. by ultra high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry

Ultra high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC/ESI-Q-TOF-MS/MS) was applied to separate and identify triterpenoid saponins in crude extract from the stem bark of Albizia julibrissin Durazz. The molecular weights were determined by comparing quasi-molecular ions [M+NH(4)](+) in positive mode and [M-H](-) and [M-2H](2-) ions in negative mode. The MS/MS spectra of the [M-H](-) ions for saponins provided a wealth of structural information related to aglycone skeletons, sugar types and linked sequence. On the basis of the fragmentation behavior of known saponins isolated before, saponins from this plant were identified, even though references were not available. As a result, a total of twenty-eight saponins in the crude extract were identified, which all had a common basic skeleton of the triterpene oleanolic acid and eight of them were new compounds.     

Sensitive and selective liquid chromatography-electrospray ionisation-mass spectrometry analysis of astragaloside-IV in rat plasma

Astragaloside-IV (3-O-beta-d-xylopyranosyl-6-O-beta-d-glucopyranosyl-cycloastragenol) is the major active constituent contained in Radix Astragali. This paper describes a rapid, sensitive and specific assay for quantitative determination of astragaloside-IV in rat plasma. After a liquid/liquid extraction (LLE) with n-butanol and high-performance liquid chromatography (HPLC) gradient separation with acetonitrile-NH4Cl solution (0.5 micromol/L) as the mobile phase, the anions adduct [M + Cl]- at m/z 819.4 of astragaloside-IV, and [M + Cl]- at m/z 815.35 of internal standard (IS) digoxin were analyzed by electrospray ionisation-mass spectrometry (LC-ESI-MS) in selected ion monitoring (SIM) mode. Chromatographic separation was achieved in less than 9 min and calibration curve was linear over a concentration range of 2-200 ng/ml. The described assay method was successfully applied to the preclinical pharmacokinetic study of astragaloside-IV. After intragastric administration of astragaloside-IV to rats, Cmax and Tmax of astragaloside-IV were 134.73 +/- 39.86 ng/ml and 1.5 h, respectively, and the elimination half-life (t1/2) was 5.45 +/- 0.39 h.     

Structural analysis of photo-degradation in thiazole-containing compounds by LC-MS/MS and NMR

The photo-degradation behavior of a pharmaceutical compound previously under development for treatment of overactive bladder was studied. Samples of {4-(4-chloro-3-fluorophenyl)-2-[4-(methyloxy)phenyl]-1,3-thiazol-5-yl} acetic acid were stressed with visible light and were observed to degrade into a single primary photo-degradation product. This unknown product was analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS) with accurate mass measurement and hydrogen/deuterium exchange to determine its molecular weight and formula, isotope distribution patterns and exchangeable protons, and product ion structures. By comparison of the fragmentation pathways of the protonated and sodiated species, the charge was found to locate in the electron-rich part of the molecule after fragmentation. MS-derived structural information combined with stopped-flow 1H LC-nuclear magnetic resonance (NMR) analysis suggested that the degradation product was 4-chloro-N-(4-methoxybenzoyl)-3-fluorobenzamide. This unique photo-degradation product was subsequently isolated using preparative-scale chromatography, and its structure was confirmed using 1D and 2D NMR techniques involving the 1H, 13C, 15N and 19F nuclei. The structure of this product suggests that {4-(4-chloro-3-fluorophenyl)-2-[4-(methyloxy)phenyl]-1,3-thiazol-5-yl} acetic acid has reacted with singlet oxygen (1Deltag) via a [4+2] Diels-Alder cycloaddition upon photo-irradiation to cause photo-oxygenation in the solid-state (as is common in solution phase), resulting in an unstable endoperoxide that rearranges to the final degradation product structure. Photo-degradation of a structurally related thiazole, 4-(4-Chlorophenyl)thiazol-2-amine, proceeded via a similar process but in a less reactive manner. However, when exposed to the same conditions, sulfathiazole did not degrade, indicating that this photo-degradation process may only occur for thiazole-containing compounds with specific substituents, such as aryl rings.