Nour-Eddine Es-Safi

Study of the acetaldehyde induced polymerisation of flavan-3-ols by liquid chromatography-ion spray mass spectrometry

In some fruits, the loss of astringency has been attributed to the insolubilization of recombinated tannins, formed by reaction with acetaldehyde. This route has been investigated by on-line coupling of liquid chromatography with ion spray mass spectrometry (LC-ISP-MS). The results reported herein indicate that LC-ISP-MS can be successfully applied to tannin polymers and is very helpful in their identification. It also allows direct monitoring of the progress of polymerisation reactions. The mechanism of the acetaldehyde-induced polymerisation of flavan-3-ols has thus been demonstrated.

Structure of a new xanthylium salt derivative

A new polyphenolic compound with a xanthylium skeleton has been synthesised from (+)-catechin and glyoxylic acid. Its structural elucidation was achieved by UV, MS and NMR spectroscopies. Its formation involved glyoxylic acid-mediated dimerisation of (+)-catechin1 giving thus compound2, followed by cyclisation to a xanthene derivative3 which by oxidation afforded the xanthylium compound4. The detection and structural determination of the xanthene compound confirmed the postulated mechanism.

New phenolic compounds obtained by evolution of (+)-catechin and glyoxylic acid in hydroalcoholic medium

Abstract The reaction between (+)-catechin 1 and glyoxylic acid in model solution system was investigated by LC/DAD and LC/ESI-MS analysis and the formation of new phenolic compounds 2 , 3 , 4 exhibiting absorption maxima near 300 nm were observed. The structures of these compounds were elucidated by ESI-MS and 1D and 2D NMR spectroscopy.

In vitro antioxidant properties of Salvia verbenaca L. hydromethanolic extract

Objective: To investigate the in vitro antioxidant activity of the hydromethanolic extract of the aerial parts (leaves and stems) of Salvia verbenaca L. towards fatty acids (linoleic and linolenic acids) and human, low density lipoproteins (LDL) peroxidation. Materials and Methods: Lipid peroxidation was carried out in the presence of the S. verbenaca L. hydromethanolic extract (10 and 100 µg of extract/ml). CuSO4 (10 µM) was used as the oxidation initiator. Conjugated dienes (CD) formation, oxygen consumption and thiobarbituric acid reactive substances (TBARS) formation were assessed to monitor the antioxidant properties of the plant extract. Butylated hydroxytoluene (BHT) at 50 µg/ml was used as a standard antioxidant. The quantification of total polyphenolic compounds was carried out, according to the Folin-Ciocalteu method. Results: The hydromethanolic extract of S. verbenaca showed a significant antioxidant effect at 100 µg/mL. A strong inhibition of oxygen consumption (92%, P <0.001) and CD formation of LDL peroxidation (92%, P <0.001) as well as TBARS formation of linolenic acid oxidation (93%, P <0.001) were observed. The quantitative analysis revealed that the extract used contained a high amount of phenolic compounds, suggesting a possible role of these products in the observed antioxidant properties. Conclusion: S. verbenaca could be considered as a potential source of natural antioxidants.

In vitro antioxidant effect of Globularia alypum L. hydromethanolic extract

Objective : To investigate the in vitro antioxidant activity of the hydromethanolic extract of aerial parts (leaves and stems) of Globularia alypum L. toward linoleic acid emulsion and human low-density lipoproteins (LDL) peroxidation. Materials and Methods : Lipid peroxidation was carried out in the presence of G. alypum hydromethanolic extract (10 and 100 µg of extract/ml). CuSO4 (10 µM) was used as the oxidation initiator. Conjugated dienes (CD) formation and oxygen consumption were assessed for monitoring the antioxidant properties of the plant extract. Butylated hydroxytoluene at 50 µg/ml was used as standard antioxidant. Quantification of total polyphenolic compounds was carried out according to the Folin-Ciocalteu method. Results : The hydromethanolic extract of G. alypum exhibited significant antioxidant effect. There was a significant inhibition of CD formation in copper ions-mediated linoleic acid emulsion as well as human LDL peroxidation. Analysis of the plant extract revealed a high amount of polyphenols, suggesting a possible role of these compounds in the antioxidant properties. Conclusion : The obtained results suggested that G. alypum could be a potential source of antioxidants. Further investigations are in progress to determine the active constituent(s).

Synthesis and Spectroscopic Structural Elucidation of New Quinoxaline Derivatives

Abstract A quinoxaline‐2,3‐dione derivative was synthesized, and its chemical structure was determined through spectral analysis. Alkylation of this compound under phase transfer catalysis (PTC) conditions yielded monoalkylated and diakylated adducts. The monolalkylation process was shown to be regioselective occurring on the quinoxalic nitrogen atom rather than on its pyrazolic analogue. The full characterization of the synthesized compounds was studied by concerted use of NMR and MS techniques. Assignments of proton and carbon atoms were achieved through analysis of the 1D 1H and 13C NMR spectra combined with homo‐ and hetero-nuclear 2D NMR experiments. Determination of the alkylation site was achieved through long‐range proton–carbon coupling correlations spectroscopy.

Fragmentation Study of Globularin Through Positive and Negative ESI/MS, CID/MS, and Tandem MS/MS

Abstract The structure of globularin was studied by a mass spectrometric methodology based on the combined use of positive and negative electrospray ionization, collision‐induced dissociation (CID), and tandem mass spectrometry. The mass spectrometry investigation was achieved through in‐source fragmentation of the deprotonated [M−H]−, protonated [M+H]+, lithiated [M+Li]+, sodiated [M+Na]+, and potassium‐cationized [M+K]+ ions. This allowed collision‐induced dissociation spectra of the ionized molecular ions to be obtained to give valuable structural information regarding the nature of both the glycoside and the aglycone moieties and the effect of metal cationization on the CID spectra. Glycosidic fission and ring cleavages of both aglycone and sugar moieties were the major fragmentation pathways observed during collision‐induced dissociation, where the losses of small molecules, the cinnamoyl and the cinnamate parts were also observed. Alkali metal cationization offers additional fragmentation pathways involving cross rings cleavage under CID conditions. Unlike the dissociation of protonated molecular ions, that of metal‐cationized molecules also provides sugar fragments where the C0 + fragment corresponding with the glucose ion was obtained as a major daughter peak for all the studied compounds. Even with low abundance, fragment ions coordinated to K+ were also observed from [M+K]+.

Mass Spectrometry as a Powerful Analytical Technique for the Structural Characterization of Synthesized and Natural Products

Mass spectrometry is an important tool for the identification and structural elucidation of natural and synthesized compounds. Its high sensitivity and the possibility of coupling liquid chromatography with mass spectrometry detection make it a technique of choice for the investigation of complex mixtures like raw natural extracts. The mass spectrometer is a universal detector that can achieve very high sensitivity and provide information on the molecular mass. More detailed information can be subsequently obtained by resorting to collision-induced dissociation tandem mass spectrometry (CID-MS/MS). In this review, the application of mass spectrometric techniques for the identification of natural and synthetic compounds is presented. The gas-phase fragmentation patterns of a series of four natural flavonoid glycosides, three synthesized benzodiazepines and two synthesized quinoxalinone derivatives were investigated using electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry techniques. Exact accurate masses were measured using a modorate resolution quadrupole orthogonal time-of-flight QqTOF-MS/MS hybrid mass spectrometer instrument. Confirmation of the molecular masses and the chemical structures of the studied compounds were achieved by exploring the gas-phase breakdown routes of the ionized molecules. This was rationalized by conducting low-energy collision CID-MS/MS analyses (product ion- and precursor ion scans) using a conventional quadrupole hexapole-quadrupole (QhQ) tandem mass spectrometer.

A Convenient Method for the Synthesis of 1,5-benzodiazepin-2-one

New 3-hydroxy-1,5-benzodiazepin-2-ones were synthesized through condensation between o- phenylenediamines with glycidic ester. Alkylation and oxidation of some of the obtained compounds were also explored in different conditions yielding various oxidized and alkylated benzodiazepines. The structural elucidation of the synthe- sized compounds was achieved by MS, NMR spectroscopy and also through X-ray diffraction analysis. The glycidic ester was thus shown to be an interesting synthon in the synthesis of new 1,5-benzodiazepines used in alkylation and oxidation reactions. Synthesis of 3-hydroxy -4-phenyl tetrahydro-1,5- benzodiazepin-2-one (4) and (5) A mixture of o-phenylenediamine 1 or its dimethylated derivative 2 (0.03 mole) and ethyl glycidate (0.03 mole) was refluxed in 80 mL of xylene during 48 hours. The obtained crude mixture was left at room temperature during one night. The trans diastereoisomers 4a or 5a which precipitate were filtered under reduced pressure.

Gas‐phase fragmentation study of novel synthetic 1,5‐benzodiazepine derivatives using electrospray ionization tandem mass spectrometry

The fragmentation patterns of a series of three novel synthesized 3-hydroxy-4-phenyl-tetrahydro-1,5-benzodiazepin-2-ones (1-3), possessing the same backbone structure, were investigated using electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (MS/MS) techniques. A simple methodology, based on the use of ESI (positive ion mode) and by increasing the declustering potential in the atmospheric pressure/vacuum interface, collision-induced dissociation (CID), was used to enhance the formation of the fragment ions. In general, the novel synthetic 1,5-benzodiazepine derivatives afforded, in the gas phase, both protonated and sodiated molecules. This led to the confirmation of the molecular masses and chemical structures of the studied compounds. Exact accurate masses were measured using a high-resolution ESI-quadrupole orthogonal time-of-flight (QqToF)-MS/MS hybrid mass spectrometer instrument. The breakdown routes of the protonated molecules were rationalized by conducting low-energy collision CID-MS/MS analyses (product ion- and precursor ion scans) using a conventional quadrupole-hexapole-quadrupole (QhQ) tandem mass spectrometer. All the observed major fragmentations for the 1,5-benzodiazepines occurred in the saturated seven-membered ring containing the nitrogen atoms. These formed a multitude of product ions by different breakdown routes. All the major fragmentations involved cleavages of the N-1-C-2 and C-3-C-4 bonds. These occurred with concomitant eliminations of glyoxal, benzene and ethyl formate, forming the product ion at m/z 119, which was observed in all the studied compounds. In addition, an unique simultaneous CID-MS/MS fragmentation was noticed for the 1,5-benzodiazepines 1 and 3, which occurred by a pathway dictated by the substituent located on the N-1-position. It was evident that the aromatic ring portion of the 1,5-benzodiazepines was resistant to CID-MS/MS fragmentation. Re-confirmation of the various geneses of the product ions was achieved by conducting a series of precursor ion scans. ESI-MS and CID-MS/MS analyses have thus proven to be a specific and very sensitive method for the structural identification of these novel 1,5-benzodiazepine derivatives.