Synthesis and antioxidant evaluation of lipophilic oleuropein aglycone derivatives.

Oleuropein is the most important phenolic compound present in olive cultivars, but it is scarcely present in extra virgin olive oil (EVOO) due to its high hydrophilicity and degradability. Thus, a set of oleuropein aglycone derivatives were synthesized by transacetylation under mild conditions with the aim of circumventing these drawbacks and making the active moiety in oleuropein suitable to be added to food fats. The oleuropein aglycone (closed ring form) is obtained by hydrolyzing oleuropein using Lewis acid catalysis. Then, the permeation profiles as well as the antioxidant capacity of the oleuropein aglycone derivatives were evaluated by ORAC, DPPH assays and by ROS formation using the SH-SY5Y cell line. The biological activities of the obtained compounds exhibited a dependence on their level of lipophilicity.

Tandem mass spectrometry: a convenient approach in the dosage of steviol glycosides in Stevia sweetened commercial food beverages.

The use of sweeteners extracted from leaves of the plant species Stevia rebaudiana is increasing worldwide. They are recognized as generally recognized as safe by the US-FDA and approved by EU-European Food Safety Authority, with some recommendation on the daily dosage that should not interfere with glucose metabolism. The results presented here introduce an easy analytical approach for the identification and assay of Stevia sweeteners in commercially available soft drink, based on liquid chromatography coupled to tandem mass spectrometry, using a natural statin-like molecule, Brutieridin, as internal standard. Copyright © 2017 John Wiley & Sons, Ltd.

Identification and assay of carbohydrates in olive drupes by cesium attachment electrospray tandem mass spectrometry (ESI-MS/MS).

Identification and assay of sugars in olive drupes during their ripening phase is evaluated by tandem mass spectrometry. Recent achievements have shown that the quality of an extra virgin olive oil can be directly correlated to the ripening degree of the drupes that is likely linked to their saccharides content. An innovation in this peculiar food chain is now proposed that considers a high throughput assessment of the carbohydrate content by a recently introduced protocol based on the gas-phase chemistry of sugar-cesium adducts by ESI-MS/MS.

Anti-inflammatory effect of 3,4-DHPEA-EDA [2-(3,4 -hydroxyphenyl) ethyl (3S, 4E)-4-formyl-3-(2-oxoethyl)hex-4-enoate] on primary human vascular endothelial cells.

Diets in which fat is significantly provided by olive oil and are relatively rich in vegetables, have been associated with a low incidence of cardiovascular diseases, mostly due to the presence of several phenolic compounds which have anti-oxidant and antiinflammatory properties. [1]. In this work, we describe the anti-inflammatory effect of 3,4-DHPEA-EDA in a cell model that we developed to mimic inflammatory injury of endothelium. This was based on the production of the proinflammatory chemokine CCL2, following in vitro stimulation of primary human endothelial cells. Pre-treatment of cells with 3,4-DHPEA-EDA resulted in a dose-dependent inhibition of CCL2 secretion. The effect of 3,4-DHPEA-EDA on CCL2 expression was observed at the transcriptional level. Functional data have shown that 3,4-DHPEA-EDA diminished monocyte adhesion to HUVECs. These results point on the use of 3,4- DHPEA-EDA as a novel drug aimed to prevent or reduce inflammation of endothelium.

An efficient and highly selective deprotection of N-Fmoc-alpha-amino acid and lipophilic N-Fmoc-dipeptide methyl esters with aluminium trichloride and N,N-dimethylaniline.

A novel procedure for the deprotection of the carboxyl group of amino acid methyl esters is presented. The process is carried out by the reagent system aluminium trichloride/N,N-dimethylaniline that can successfully be applied to unblock the carboxyl moiety either of N-Fmoc-protected amino acid methyl esters and N-Fmoc-protected short dipeptide methyl esters. The chiralities of the optically pure amino acid or peptide precursors are maintained totally unchanged.

Reactivity models of 1-N-vinyluracil and synthesis of a new class of potential antiviral agents by the use of 1,3-dipolar cycloaddition reactions.

By the use of a convergent approach based on 1,3-dipolar cycloaddition reactions between N-protected formylnitrones generated in situ and 1-N-vinyluracil, a new class of 4'-aza-analogues of 2',3'-dideoxynucleosides is synthesized. Competitive reaction for the endocyclic bond of uracil also brings to a new isoxazolidine derivative fused with the pyrimidine nucleus.

Structural characterization of isoxazolidinyl nucleosides by fast atom bombardment tandem mass spectrometry.

4'-Aza-2',3'-dideoxyerythrofuranosyl derivatives of thymine (AdT, 1) and uracil (AdU, 2) are analogues of 2',3'-dideoxyribofuranosyl thymine (ddT, 3) and uracyl (ddU, 4). Compounds 1 and 2 are representative of a new class of antiviral agents where the sugar moiety is replaced by an isoxazolidine ring. The increasing importance of isoxazolidinyl nucleosides has encouraged the exploitation of simple mass spectrometric rules for unambiguously assigning their structure. The species 1, 2, 5 and 6 were therefore synthesized in order to evaluate the role of the basic centre of the modified sugar moiety in their gas-phase chemistry. The tandem mass spectra of these compounds are similar to those of the wild-type nucleosides and display fragment ions corresponding to [B + 2H](+),[M - BH](+) and [B + 27](+) species, where B is the nucleobase. The last species derives from a retrocycloaddition process which is less evident in 2'-deoxyribosides. This behaviour is consistent with protonation of the analytes at the pyrimidine rings. Model isoxazolidines, in which the nucleobase was replaced by a phenyl or a naphthyl moiety, displayed the expected behaviour of species with a localized charge on the N-O moiety of the isoxazolidine ring.

Facile approach to enantiomerically pure alpha-amino ketones by Friedel-Crafts aminoacylation and their conversion into peptidyl ketones.

In this article we describe a versatile and straightforward preparative approach to chiral aryl alpha-amino ketones via a Friedel-Crafts-type reaction of stable and enantiomerically pure N-Fmoc protected L-amino acid chlorides with toluene in the presence of aluminum trichloride. The developed methodology provided aryl alpha-amino-p-methylphenyl ketones, which can be obtained and isolated as free bases or recovered as their N-acetyl derivatives, after treatment with acetic anhydride in chloroform at room temperature, subsequent to the Lewis acid induced removal of the 9-fluorenylmethoxycarbonyl protecting group. The Friedel-Crafts-like process and the cleavage of the amino function masking group can selectively be performed since, as verified in all cases, the alpha-aminoacylation step occurred with kinetics that were faster than those required to remove the N-protection. The presented approach was also explored as a facile and useful synthetic tool for the preparation of optically pure ketone di- and tripeptides. These compounds can be obtained in exceptionally overall yields without need of chromatographic purification. Moreover, either aryl alpha-amino ketones or modified di- and tripeptides, in all cases, can be isolated in very high chemical and optical purity without recourse to resolution of diastereomeric mixtures, since the chiralities of the asymmetric amino acid educts were completely conserved throughout the entire process.

Site selectivity in the synthesis of O-methylated hydroxamic acids with diazomethane.

In this paper we report the results obtained by treating some selected hydroxamic acids with diazomethane in ethereal media. The multitask reagent diazomethane was used either as a base to induce deprotonation of the chosen hydroxamic acids or as conjugated acid which undergoes one-pot methylation processes of the generated anions. Product distributions clearly showed that a high site selectivity is expressed by the different deprotonated species in the alkylation processes. Under the adopted conditions, the prevalent site of methylation is in all the cases the oxygen of the hydroxamic acid. While in aliphatic hydroxamic acids only O-alkylation is observed, in the aromatic substrates, the NH group competes with the OH function as the nucleophilic site, although the OH reactivity still dominates.

Electron transfer vs. proton transfer within radical-cation clusters of guanosine and deoxyguanosine with substituted naphthalenes and sinapinic acid.

Guanosine (G) and deoxyguanosine (dG) radical cations can be generated in the gas phase by single electron transfer (SET) within nucleoside-dimethoxynaphthalenes (1-2) electron-bound heterodimers produced by fast atom bombardment in a four sector mass spectrometer. The nucleobase guanine is much more easily oxidized when it is linked to a ribose moiety. The radical cation dimers formed by G and dG with sinapinic acid behave as proton-bound heterodimers. The experiments mimic to some extent the migration of radical sites within stacking bases which causes DNA damaging through depurination processes.

Virtual freezing of the hemiacetal-aldehyde equilibrium of the aglycones of oleuropein and ligstroside present in olive oils from Carolea and Coratina cultivars by ionspray ionization tandem mass spectrometry

The composition of the equilibrium between aldehydes and hemiacetals was evaluated by ionspray ionization tandem mass spectrometry. The methanolic extracts of virgin olive oil from Carolea and Coratina cultivars contain a complex mixture of hydroxytyrosol (3) and tyrosol (4) derivatives (5, 6) characterized by the presence of aldehyde moieties in equilibrium with their hydrated form (8) or with the corresponding methanol hemiacetals 9 and 10. The equilibrium was frozen by droplet evaporation, thus allowing the structure determination of each component. The formation of the decarboxylated species 11-14, reported previously, was not observed.

Survey of the proton affinities of adenine, cytosine, thymine and uracil dideoxyribonucleosides, deoxyribonucleosides and ribonucleosides.

The kinetic method was applied to the determination of the proton affinities (PAs) of modified deoxy- and dideoxyribonucleosides. A correlation between the measured PAs and the replacement of one of the three hydroxyl groups of the ribose unit is presented. A PA scale was obtained which shows that the replacement of the primary or of one or both secondary hydroxyl groups of a ribonucleoside with a hydrogen atom induces the lowering or the enhancement of the nucleoside PA, respectively. The scale extends over a very narrow range of approximately 2 kcal mol(-1), thus demonstrating the sensitivity of the kinetic method in the evaluation of small differences in thermodynamic parameters.

Quantitation of oleuropein in virgin olive oil by ionspray mass spectrometry-selected reaction monitoring.

This work describes the unambiguous evaluation of the presence of oleuropein in virgin olive oils by ionspray tandem mass spectrometry (ISI-MS/MS). The oil samples obtained from different cultivars, such as Carolea, Cassanese, Coratina, Dolce di Rossano, Roggianella, and Tonda di Strongoli, grown in different geographical areas of Calabria, Italy, have shown an average content of oleuropein ranging from 1 ppb to 11 ppm. Commercial virgin oil samples, blended in some cases, contain significant amounts of this pharmacologically important antioxidant. The MS/MS methodology was applied in a triple-quadrupole instrument, through continuous scanning of the third analyzer to detect oleuropein in methanol extracts and in selected ion monitoring (SRM) for its quantitative assay.

Synthesis of isoxazolidino analogues of 2',3'-dideoxynucleosides.

The complete set of the 4'-aza analogues of 2',3'-dideoxynucleosides was synthesized by cycloaddition of N-tetrahydropiranyl or N-trityl methylene nitrones on suitably protected vinyl nucleobases. The convertible nucleoside approach was used in the preparation of cytosine and 5-methyl cytosine analogues.

Nonionic surfactants regioselective synthesis of fatty acid esters of alpha- and beta-glucopyranose.

Lipophilic esters of saccharides belong to the family of nonionic surfactants widely employed in pharmaceutical and cosmetics formulations. A very simple method is presented whereby 6-O-esters of alpha- and beta-glucose can be prepared and isolated. Good results have been obtained in the synthesis of 6-O-oleyl derivatives by simple acylation with appropriate oleyl chloride. The condensing agent bis(2-oxo-3-oxazolidinyl) phosphinic chloride (BOP-Cl) allows the preparations of the same esters with better regioselectivity but with yields strongly dependent on the aliphatic chain length of the carboxylic acids employed.

Fusapyrone and deoxyfusapyrone, two antifungal alpha-pyrones from Fusarium semitectum.

A strain of Fusarium semitectum Berk. & Rav. from maize stalk rot in southern Italy produced bioactive metabolites when cultured on autoclaved rice kernels at room temperature for 4 weeks. The organic extracts of fungal culture showed a strong antibiotic activity towards Geotrichum candidum in disk diffusion assays, but they were not toxic to Artemia salina larvae. Two antifungal metabolites were isolated and characterized by chemical and spectroscopic methods as two 3-substituted-4-hydroxy-6-alkyl-2-pyrones, in particular, the 3-(4-deoxy-beta-xylo-hexopyranosyl)-4-hydroxy-6-[2-hydroxy-7-hydroxymeth yl- 1,1,5,9,11-pentamethyl-3,5,8-heptadecatrienyl]-2H-pyran-2-one and its 6-[2-hydroxy-1,1,5,7,9,11-hexamethyl] analog, which were named fusapyrone and deoxyfusapyrone, respectively.

Determination of substituent effects on the proton affinities of natural nucleosides by the kinetic method.

The kinetics of the unimolecular dissociations of proton-bound dimers produced by fast-atom bombardment from nucleosides and reference amines enables the evaluation of the proton affinities (PA) of ribonucleosides. The PAs of cytosine, guanosine, adenosine, uridine and deoxyuridine have been thus determined. These values and those already available for the corresponding DNA homologues allow the evaluation of the effect of the hydroxyl group in position 2' of the sugar moiety, which lowers the PAs of RNA nucleosides by 0.6-1 kcal/mol, and of the methyl group in position 5 of the thymine ring which enhances the basicity of deoxythymidine over deoxyuridine by 0.6 kcal/mol.

Redox processes of ruthenium (II) polypyridine complexes induced by fast-atom bombardment mass spectrometry.

Fast-atom bombardment (FAB) mass spectrometry in the negative ionization mode enables the sputtering into the gas phase of the ruthenium complexes [Ru(2,2'-bipyridine[bpy])2(2,5-bis) (pyrydil)pyrazine[dpp])](PF6)2; [Ru(bpy)2,(2,3dpp)](PF6)2;[Ru(bpy)2,(2,3-dpp-Me)]( PF6)3; and [Ru(bpy)2(ώ-2,3-dpp)]2 RuCl2(PF6)4 as intact radical anions. These data, combined with those avaiiable from the positive FAB spectra allow a full characterization of the analytes.

Sequence effect on the slow degradations of dinucleotides by fast atom bombardment tandem mass spectrometry.

The mass-analysed ion kinetic energy spectrum of isomeric dinucleotides having dTpdU and dUpdT structure is characterized by the preferred elimination of the pyrimidine base linked to the 5' end deoxyribose unit. Similar results have been obtained with differently substituted dimers such as dCpdT and DMTdTp(S)dU. The observed selectivity in the glycosidic bond dissociation provides a straightforward criterion for the sequencing of the sampled species.