Comment on Tremmel et al. In Vitro Metabolism of Six C-Glycosidic Flavonoids from Passiflora incarnata L. Int. J. Mol. Sci. 2021, 22, 6566.

In recent years, growing attention has been paid to the chemical composition of aerial parts extracts and the bioavailability of active compounds from different species of Passiflora genus [...].

Extraction with Acidified Methanol-An Easy and Effective Method of Methyl Chlorogenate Formation, as Studied by ESI-MS.

Among the different Hawthorn species, Crataegus monogyna seems to be one of the most often used in herbal medicine, and is commercially available. The methanolic extract and the acidified methanol extract of an herbal medicinal product based on Crataegus monogyna inflorescences were analyzed by using high-pressure liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS). On the basis of m/z of [M-H]- ions and characteristic fragmentation patterns, a number of polyphenolic compounds, namely flavonoids and chlorogenic acids, were identified. It was found that the contents of the acid extract were enriched with methyl chlorogenates showing attractive biochemical properties. Analogous results were obtained for other plant materials, e.g., nectarine kernels. Apart from that, acid extraction had a minor influence on the polyphenolic compounds present in the plants, and thus it did not affect the natural antioxidant values of the plant extracts.

Elucidation of glycosylation sites of kaempferol di-O-glycosides from methanolic extract of the leaves of Prunus domestica subsp. syriaca.

RATIONALE: Flavonol glycosides containing the glycosylation patterns 3,4'-di-O and 4',7-di-O are rare in nature and they have not yet been studied in detail by electrospray ionization mass spectrometry (ESI-MS(+/-), in contrast to the flavonol glycosides containing the glycosylation pattern 3,7-di-O. METHOD: The leaves from Prunus domestica L. subsp. syriaca were extracted with pure methanol or, in order to perform hydrolysis and extraction simultaneously, with a 5% methanolic solution of hydrochloric acid. The high-performance liquid chromatography (HPLC)/ESI-MS(+/-) analyses were performed using a Waters model 2690 HPLC pump and a Waters/Micromass ZQ2000 mass spectrometer. RESULTS: Three kinds of kaempferol di-O-glycosides have been identified, namely kaempferol-3-O-hexoside-7-O-rhamnosides, kaempferol-3-O-pentoside-4'-O-rhamnosides and kaempferol 4',7-di-O-rhamnoside. The identification was performed on the basis of the abundances of the respective Y-type product ions. CONCLUSIONS: The abundances of [Yn 0 - H]-· , Yn 0 - and Yn 0 + product ions were of crucial importance for the determination of glycosylation patterns. The obtained results can be useful for HPLC/ESI-MS identification of rare flavonol-di-O-glycosides.

Differentiation of bisphenol F diglycidyl ether isomers and their derivatives by HPLC-MS and GC-MS-comment on the published data.

Positional isomers of bisphenol F diglycidyl ether (BFDGE) have been analyzed by high-pressure liquid chromatography-mass spectrometry and by gas chromatography-mass spectrometry (HPLC-MS, GC-MS). Positional isomers of BFDGE derivatives (BFDGEx2H2O, BFDGExH2OxHCl) have been analyzed by HPLC-MS. On the basis of the obtained fragmentation patterns, the elution order of the isomers has been unequivocally determined, in standard solutions and in the sample of liquid obtained after rinsing an empty mackerel fish can with acetonitrile. Under HPLC condition, para,para isomers are eluted first, then ortho,para isomers' elution follows, and ortho,ortho isomers are eluted last. Under GC condition, the reverse elution order has been obtained. For the first time, two ortho,para isomers of BFDGExH2OxHCl have been detected and their elution order has been determined. The obtained results are of key importance for determination of the isomer distribution of BFDGE and its derivatives in food samples.

Electrospray ionisation mass spectrometric behaviour of flavonoid 5-O-glucosides and their positional isomers detected in the extracts from the bark of Prunus cerasus L. and Prunus avium L.

INTRODUCTION: Literature data concerning the electrospray ionisation mass spectrometry (ESI-MS) behaviour of flavonoid 5-O-glycosides are poor and sometimes disputable. Therefore, we decided to analyse the compounds of this kind present in the bark of Prunus cerasus and Prunus avium by using high-performance liquid chromatography HPLC/ESI-MS. OBJECTIVE: The aim of this study is to obtain the comprehensive information about the ESI-MS(+/-) behaviour of flavonoid 5-O-glucosides, to compare their behaviour with that of their positional isomers, to confirm that the known susceptibility of flavonoid 5-O-glucosides to hydrolysis may be successfully used for their identification. METHOD: The bark from Prunus trees was extracted with pure methanol or, in order to perform hydrolysis and extraction simultaneously, with 5% methanolic solution of hydrochloric acid. The HPLC-ESI-MS analyses were performed using a Waters model 2690 HPLC pump and Waters/Micromass ZQ2000 mass spectrometer. RESULTS: Flavonoid 5-O-glycosides were completely hydrolysed under the acid conditions used, in contrast to their positional isomers. In positive ion mode, at low cone voltage, flavonoid 5-O-glycosides yield abundant Y0 + aglycone ions, in contrast to their positional isomers. In the negative ion mode, flavonoid 5-O-glycosides do not yield [Y0 - H]-· fragment ions, in contrast to their positional isomers. When aglycone contains only two hydroxyl groups, the flavonoid 5-O-glycosides can be detected in negative ion mode, whereas their positional isomers do not yield [M - H]- ions. CONCLUSION: It has been demonstrated that the susceptibility to hydrolysis of the analysed compounds, the abundances of respective fragment ions formed, and their ESI(-) response allow unambiguous identification of flavonoid 5-O-glycosides and their differentiation from their positional isomers.

Hydration of serine-metal cation complexes: implication for the role of water in the origin of homochirality on the Earth.

It may be taken for granted that the processes that occurred in water were of crucial importance for the origin of life. Therefore, it is quite likely that water was also important with respect to the origin of homochirality. Here, it is shown, using electrospray ionization mass spectrometry, that the efficiency of hydration of homochiral serine-metal cation complexes is different from that of heterochiral serine-metal cation complexes. The differences in the efficiency of hydration of homo and heterochiral metal cation-amino acid complexes could lead to the amplification of formation of homochiral peptides in water solution from which life emerged.

Differentiation of isomeric heptylamines by in-source collision-induced dissociation of [M + H]+ ions.

RATIONALE: 1,3-Dimethylamylamine (1,3-DMAA), 1,4-dimethylamylamine (1,4-DMAA) and 2-aminoheptane are isomeric heptylamines commonly used as stimulants. The fragmentations of their [M + H]+ ions (m/z 116) are almost identical and consist of the formation of a fragment ion C4 H9 + at m/z 57. It is interesting to check if analysis of electrospray ionization (ESI) mass spectra of these three amines enables their differentiation. In order to better understand the fragmentation of isomeric heptylamines, 1-, 3- and 4-aminoheptane were also included in the study. METHODS: ESI in-source collision-induced dissociation (CID) mass spectra were obtained with a Waters/Micromass ZQ2000 mass spectrometer (single quadrupole-type instrument) at a cone voltage of 12-34 V. The influence of three commonly used solvents on the fragmentation of [M + H]+ ions was tested, namely methanol, methanol/water (1/1) and acetonitrile/water (1/1). RESULTS: Only one quantitative difference was observed in the mass spectra of 1,3-DMAA, 1,4-DMAA and 2-aminoheptane, namely formation of a product ion at m/z 57 from the [M + H]+ ion of 1,3-DMAA is more efficient than the formation of this ion from [M + H]+ ions of 2-aminoheptane and 1,4-DMAA. In-source CID of 3- and 4-aminoheptane consists of (besides the formation of ion C4 H9 + ) the formation of a low-abundance, but clearly seen, fragment ion at m/z 114 (loss of H2 ). CONCLUSIONS: Differentiation of 1,3-DMAA from 1,4-DMAA and 2-aminoheptane seems to be possible by in-source CID of their [M + H]+ ions. However, comparison of the mass spectrum obtained for the analysed sample with that of a standard seems to be necessary. Only 3- and 4-aminoheptane may be easily differentiated from the other heptylamines by the presence of fragment ions at m/z 114.

Signals of diagnostic ions in the product ion spectra of [M - H]- ions of methoxylated flavonoids.

RATIONALE: The main feature of the fragmentation of [M - H]- ions of methoxylated flavonoids is the loss of methyl radical (formation of the [M - H - CH3 ]-• product ion). Subsequent decomposition of [M - H - CH3 ]-• product ions may be useful for identification of a given compound by HPLC/MS. This paper describes how the selected diagnostic fragment ions can be useful during HPLC/MS(-) analysis of methoxylated flavonoids. METHODS: Product ion spectra (ESI-CID-MS/MS spectra) of [M - H]- ions of 17 methoxylated flavonoids (flavones, isoflavones and flavonols) were obtained with a Q-TOF mass spectrometer. Full scan mass spectra (ESI-MS) were obtained with a single quadrupole type of instrument. RESULTS: A number of product ions were recognized as useful from the point of view of structural elucidation. In most cases they were diagnostic product ions, formed as a result of C ring breaking. CONCLUSIONS: The most important conclusions drawn from this study are: the product ion at m/z 132 indicates that the analysed compound is an isoflavone; the product ion at m/z 117 indicates the presence of one hydroxy group at ring B or at the 3-position; biochanin A and prunetin can be differentiated by their 'in-source' fragmentation, by the relative abundances of product ions at m/z 195, 183 and 167; loss of mass 102 from the [M - H - CH3 ]-• ion indicates that ring B is not substituted and there is no hydroxy group at the 3-position; and rhamnetin can be detected using three diagnostic product ions, namely at m/z 121, 165 and 193.

Gas-phase stability of sandwich complexes of crown ethers with metal cations - as studied by collision induced dissociation tandem mass spectrometry.

RATIONALE: The gas-phase stabilities of the sandwich complexes formed by 12-crown-4 or 15-crown-5 with metal cations (Na+ , K+ , Rb+ , Tl+ , Ag+ , Ca2+ , Sr2+ , Ba2+ , Pb2+ , Hg2+ , Cd2+ ) are compared with the stability of the sandwich complex formed by benzo-12-crown-4 or benzo-15-crown-5 with the cations. It is interesting to check if the possible cation-π interactions increase the gas-phase stabilities of the sandwich complexes of benzo-crown ethers with metal cations. METHODS: The sandwich complexes were generated in the gas phase by electrospray ionization (ESI) and then they were subjected to the collision induced dissociation tandem mass spectrometry experiments (CID-MS/MS). On the basis of the obtained product ion spectra, the respective breakdown plots of the ion abundances ratios against collision energy expressed in the terms of center-of-mass were made. RESULTS: The gas-phase stabilities of [(B12C4)2 +Tl]+ , [(B15C5)2 +SrNO3 ]+ , [(B15C5)2 +PbNO3 ]+ and [(B15C5)2 +SrCl]+ were higher than those of [(12C4)2 +Tl]+ , [(15C5)2 +SrNO3 ]+ , [(15C5)2 +PbNO3 ]+ and [(15C5)2 +SrCl]+ , respectively. For the other sandwich complexes the stabilities of the complexes with benzo-crown ethers were not higher than those of the complexes of simple crown ethers. CONCLUSIONS: It is reasonable to assume that the cation-π interaction increases the stability of the sandwich complex of B12C4 with Tl+ and the stabilities of sandwich complexes of B15C5 with Sr2+ and Pb2+ .

Detection of the iron complexes with hydrolysis products of cephalexin and cefradine upon high-performance liquid chromatography/electrospray ionization mass spectrometry analysis.

RATIONALE: Cephalosporins (e.g. cephalexin, cefradine) are a major group of widely used ß-lactam antibiotics. Hydrolysis of the ß-lactam ring is an important reaction (often undesired) which leads to deactivation of ß-lactams. To the best of our knowledge there is no electrospray ionization mass spectrometry (ESI-MS) data reported concerning the products of hydrolysis of cephalosporins. METHODS: The hydrolysis of cephalexin and cefradine was performed in aqueous NaOH solutions. After the process the solutions were analyzed by high-performance liquid chromatography (HPLC)/ESI-MS. The elemental compositions of the ions discussed were confirmed by the accurate mass measurements on a quadrupole time-of-flight (QTOF) mass spectrometer. RESULTS: Unexpectedly, complexes between the hydrolysis products of cephalexin and cefradine (CFLh and CFRh ) and iron cation were detected upon HPLC/ESI-MS analysis, namely the ions [(CFLh -H)2 +Fe]+ and [(CFRh -H)2 +Fe]+ , although iron was not added to the analyzed solutions or to the mobile phase. These ions were found to be very stable in the gas phase. CONCLUSIONS: The detection of the complexes between the hydrolysis products of cephalosporins and iron may have a positive impact on the sensitivity and specificity of HPLC/ESI-MS analyses of the hydrolysis products of some cephalosporins.

Scorpionate complexes of aza-18-crown-6 containing fluoronitrophenyl substituents as studied by electrospray ionization mass spectrometry.

RATIONALE: Coordination of a metal cation by a nitro group is rare and the interaction between them is usually weak. Examples of complexes in which such an interaction takes place are metal complexes of cyclams containing nitrophenyl or nitrobenzyl substituents. It seemed to be interesting to check if in the complexes of the respective crown ether conjugates the interaction can also take place. METHODS: We synthesized the respective conjugates of aza-18-crown-6, namely fluoro-substituted N-nitrophenylaza-18C6 conjugates. Their complexes with alkali and alkali earth metal cations were generated in the gas phase by electrospray ionization mass spectrometry (ESI-MS). Both collision-induced dissociation 'in-source' and collision-induced dissociation tandem mass spectrometry (ESI-CID-'in-source' and ESI-CID-MS/MS) were used to study the gas-phase stabilities of the generated complexes. RESULTS: The gas-phase decomposition of the studied complexes indicated that the complexes formed by the conjugates containing a nitro group at the ortho position are more stable than those formed by the conjugates with a nitro group at the para position. CONCLUSIONS: This indicates that a metal cation complexed by crown ether ring is additionally coordinated by a nitro group in the scorpionate mode. To the best of our knowledge, our finding provide the first example of a complex in which a metal cation complexed by a crown ether ring is additionally coordinated by a nitro group.

Determination of conditional stability constants for phytic acid complexes with Mg2+, Ca2+ and Zn2+ ions using electrospray ionization mass spectrometry.

The electrospray ionization mass spectrometry competitive method has been used for the determination of the conditional stability constants of phytic acid complexes with Mg2+, Ca2+ and Zn2+ ions. The competing complexation between ethylenediaminetetraacetic acid (EDTA) and phytic acid was studied. For EDTA complexes with Mg2+, Ca2+ and Zn2+ ions, the values of the conditional stability constants are known and were used for the calculation of this constant for the phytic acid complexes. The values obtained are in agreement with the literature data. The method applied permitted a fast and simple determination of conditional stability constants by measuring the response of the ionized coordination complexes.

UNUSUALLY STABLE ADDUCT BETWEEN METHANOLYZED AMOXICILLIN OR AMPICILLIN AND THEIR DIKETOPIPERAZINE DERIVATIVES.

Amoxicillin and ampicillin were subjected to methanolysis. As expected, the methanolysis products were observed by HPLC-ESI-MS. Besides these products, diketopiperazine derivatives were also detected. Additionally, unusually stable adduct formed between the products of methanolysis and diketopiperazine derivatives was also identified. Analogical adducts were detected when ethanolysis was performed instead of methanolysis. HPLC-ESI-MS analysis of the separated adducts confirmed that the adducts were composed of methanolysis products and diketopiperazine derivatives.

Complexation of phosphates by 1,3-bis(3-(2-pyridylureido)propyl)-1,1,3,3-tetramethyldisiloxane.

RATIONALE: Compounds containing a urea or thiourea moiety form complexes with anions thanks to the ability to form quite strong hydrogen bonds. We have synthesized 1,3-bis(3-(2-pyridylureido)propyl)-1,1,3,3-tetramethyldisiloxane (1). Compound 1 contains two urea moieties connected by a long flexible linker; thus, it should be able to adopt a structure suitable for formation of quite stable complexes with anions. METHODS: The ability to form complexes of compound 1 with phosphates was tested by electrospray ionization mass spectrometry (ESI-MS). Full scan ESI mass spectra and collision-induced dissociation tandem mass (CID-MS/MS) spectra of the ions of interest were obtained on a quadrupole time-of-flight (QTOF) mass spectrometer. RESULTS: It has been found that compound 1 is not only much more prone to form complexes with the phosphate anion than with other inorganic anions, but it is also able to form complexes with organic phosphates, namely nucleotides and phospholipids. However, compound 1 is not able to form complexes with organic compounds not containing a phosphate group (e.g. nucleosides, sugars, glycerolipids). CONCLUSIONS: Compound 1 can be regarded as selective towards phosphate-containing organic compounds. Formation of such complexes may have some interesting applications for identification of organic phosphates in crude extracts from biological materials.

Electrospray ionization collision-induced dissociation tandem mass spectrometry of amoxicillin and ampicillin and their degradation products.

RATIONALE: Detailed analysis of the literature results on the electrospray ionization mass spectrometry (ESI-MS) fragmentation of amoxicillin and ampicillin, and their comparison with our results, have revealed some incorrect suggestions or incomplete interpretations of mass spectra of these compounds. Therefore, this paper contains a comprehensive discussion devoted to the ESI-MS/MS of ampicillin and amoxicillin as well as their degradation products, namely products of hydrolysis and methanolysis. METHODS: Electrospray ionization collision-induced dissociation tandem mass (ESI-CID-MS/MS) spectra and accurate mass measurements were made on a quadrupole time-of-flight (Q-tof) mass spectrometer. Hydrolysis of the antibiotics was performed by heating, for a few hours, their aqueous solutions adjusted to pH 10. Methanolysis of the antibiotics was performed by heating their methanol solutions for a few minutes. Additionally, mass spectra of isotope-labeled compounds were also obtained. RESULTS: A number of fragment ions, previously wrongly interpreted or not interpreted, have been rationalized. For example, formation of an abundant fragment at m/z 208 originating from the protonated amoxicillin molecule (ion [Amox + H](+)) was previously rationalized as a result of breaking of two bonds of the ß-lactam ring. We found that this fragment ion had to be formed by the loss of ammonia and breaking of three bonds of the bicyclic system. CONCLUSIONS: The discussion presented enables a better understanding of the MS decompositions of amoxicillin and ampicillin as well as their degradation products. MS decomposition is used for the determinations of these compounds, when the so-called multiple-reaction monitoring is applied during liquid chromatography (LC)/ESI-MS analysis. Thus, better understanding of MS decompositions of the above compounds seems to be important.

Teaching mass spectrometry: A compilation of approaches to teaching theory and practice of mass spectrometry.

The areas of mass spectrometry applications seem to be much larger than those of any other analytical techniques. They extend from the determination of molecular mass in organic chemistry, through the analytical applications in forensic, environmental and omics sciences, the application in extra-terrestrial exploration and many others. Mass spectrometry, usually coupled with chromatographic techniques, has also found wide application in the pharmaceutical industry, forensic laboratories, laboratories of sanitary inspection or environmental inspection, etc. The growing areas of applications give rise to the demand for the comprehensive mass spectrometry education of undergraduates. This overview covers the body of literature describing various interesting ideas that can be successfully used for teaching mass spectrometry. Since mass spectrometry is a multidisciplinary field, old but dynamically developing, teaching mass spectrometry may be more problematic in comparison to teaching other analytical techniques, for example, there is the problem of position of mass spectrometry in the chemistry curriculum. On the other hand, it is obvious that the mass spectrometry community, besides difficult scientific work, does great and admirable teaching work, in order to perfectly educate undergraduates in the field of mass spectrometry and to make learning mass spectrometry as attractive as possible.

Oligoester Identification in the Inner Coatings of Metallic Cans by High-Pressure Liquid Chromatography-Mass Spectrometry with Cone Voltage-Induced Fragmentation.

The application of polyesters as food contact materials is an alternative to epoxy resin coatings, which can be a source of endocrine migrants. By using high-pressure liquid chromatography/electrospray ionization-mass spectrometry (HPLC/ESI-MS) with cone voltage-induced fragmentation in-source, a number of polyester-derived migrants were detected in the extracts of inner coatings of metallic cans. The polyester-derived migrants were detected in each inner coating of fish product-containing cans (5/5) and in one inner coating of meat product-containing can (1/5). They were not detected in the inner coatings of vegetable/fruit product-containing cans (10 samples). The respective detected parent and product ions enabled differentiation between cyclic and linear compounds, as well as unambiguous identification of diol and diacid units. Most of the detected compounds, cyclic and linear, were composed of neopentyl glycol as diol and two diacid comonomers, namely isophthalic acid and hexahydrophthalic acid. The other detected oligoesters were composed of neopentyl glycol or propylene glycol and adipic acid/isophthalic acid as comonomers. The compounds containing propylene glycol as diol were found to be exclusively linear cooligoesters. On the basis of abundances of [M+Na]+ ions, the relative contents of cyclic and linear oligoesters were evaluated.

Comment on Hu et al. Determination of 2-Pentanol Enantiomers via Chiral GC-MS and Its Sensory Evaluation in Baijiu. Foods 2022, 11, 2584.

Recently, Hu et al. have published a very interesting paper concerning the GC-MS analysis of 2-pentanol enantiomers in four types of Baijiu, a strong alcoholic beverage, which is of importance to Chinese social culture [...].

Comment on Villalva et al. Antioxidant, Anti-Inflammatory, and Antibacterial Properties of an Achillea millefolium L. Extract and Its Fractions Obtained by Supercritical Anti-Solvent Fractionation against Helicobacter pylori. Antioxidants 2022, 11, 1849.

Villalva et al. evaluated the potential utility of an Achillea millefolium (yarrow) extract in the control of H. pylori infection. The agar-well diffusions bioassay was applied to determine the antimicrobial activity of yarrow extracts. The supercritical anti-solvent fractionation process of yarrow extract was made to give two different fractions with polar phenolic compounds and monoterpenes and sesquiterpenes, respectively. Phenolic compounds were identified by HPLC-ESIMS by using the accurate masses of [M-H]- ions and the characteristic product ions. However, some of the reported product ions seem to be disputable, as described below.