Antonio Selva

Non-covalent associations of cyclomaltooligosaccharides (cyclodextrins) with trans-β-carotene in water: evidence for the formation of large aggregates by light scattering and NMR spectroscopy

Abstract Light scattering and NMR experiments provide evidence for the formation of large aggregates, like micelles, from β -carotene complexes with β - and γ -cyclodextrin in water. High-resolution NMR spectra of the system γ -cyclodextrin/ β -carotene in D 2 O point out guest-induced chemical shift variation of the sugar protons, thus suggesting host–guest interaction in solution.

The structure of trisporic-C acid

Abstract Trisporic-C acid is the major component of a biologically active acidic fraction isolated from submerged cultures of Choanephora trispora . On the basis of the chemical and spectrochemical data and synthesis, structure I′—a monocyclic trienic hydroxyketo acid—has been assigned to the product. Trisporic-B acid differs from the C acid by the absence of an alcoholic hydroxyl group.

Non-covalent associations of cyclomaltooligosaccharides (cyclodextrins) with carotenoids in water. A study on the α- and β-cyclodextrin/ψ, ψ-carotene(lycopene) systems by light scattering, ionspray ionization and tandem mass spectrometry

Water-soluble complexes of the dietary carotenoid ψ,ψ-carotene (lycopene 1) with cyclomaltohexaose (α-cyclodextrin, αCD) and cyclomaltoheptaose (β-cyclodextrin, βCD) have been prepared and characterized via multiangle light scattering (MALS), ionspray/electrospray ionization (IS/ESI) mass spectrometry (MS) and tandem MS. MALS experiments point out that large aggregates of particles, on the nanometer-size scale, are present in water, with meaningful differences in the shape of the αCD/1 aggregates with respect to βCD/1 analogues. The true 1:1 αCD/1 inclusion complex has been observed by IS/ESIMS and confirmed by tandem MS. The structure of CD/1 aggregations in water is proposed which are consistent with the combined MALS and MS experimental results.

Study of β-cyclodextrin-ketoconazole-tartaric acid multicomponent non-covalent association by positive and negative ionspray mass spectrometry

In continuation of studies of multicomponent non-covalent associations (MCAs) of cyclodextrin (CD) inclusion or host–guest (H–G) complexes of hydrophobic or barely water-soluble drugs with suitable counter ions, which can dramatically increase the hydrosolubility of the guest drug, was the β-CD–KC–tartaric acid (TA) MCA, where KC=ketoconazole, an antifungal drug, investigated by ionspray (IS) mass spectrometry (MS) and MS/MS in both the positive and negative ion modes. In the positive IS mode a protonated 1:1:1 β-CD–KC–TA gaseous species is obtained, which dissociates by the loss of TA upon collisional activation (CA), thus reproducing the same behaviour as observed previously for a β-CD–terfenadine–TA MCA. Unprecedented results were obtained in the negative ion mode. In particular, deprotonated 1:1:1 β-CD–KC–TA MCA was detected, which upon CA yielded mainly deprotonated 1:1 β-CD–TA and tartrate anion. Hence, while a relatively strong interaction binding β-CD to TA within the MCA parent anion emerges, the fair abundance of tartrate anion could suggest the formation of its neutral complementary fragment, 1:1 β-CD–KC, a possibly H–G complex not observed as a negatively charged MS/MS fragmentation product. The role of the KC–TA ionic bonding of the neutral MCA appears very pertinent to the study by positive and negative ISMS of the non-covalent interactions within the gaseous protonated or deprotonated ternary complex thereof.

Structural and physicochemical characterization of the inclusion complexes of cyclomaltooligosaccharides (cyclodextrins) with melatonin

The stoichiometry, geometry, stability, and solubility of the inclusion complexes of melatonin (MLT) with native cyclomaltooligosaccharides (alpha-, beta- or gamma-cyclodextrins, CDs) are determined experimentally by high-resolution NMR spectroscopy, calorimetric and solubility measurements, and mass spectrometry. The observed differences are discussed in terms of molecular recognition expression of the host-guest (h-g) interactions within the hydrophobic CDs cavities of different size. The 1:1 h-g stoichiometry in water solution prevails at low CD concentrations; the trend to form higher order associations is observed at increasing CD concentrations. The stability order beta-CD>gamma-CD>alpha-CD for the complexes in water solution and beta-CD>alpha-CD>gamma-CD for the protonated or alkali-cationated complexes in the gas phase are rationalized on the grounds of the structural data from NMR spectroscopy and of the thermodynamic parameters from calorimetric measurements.

Cardopatine and isocardopatine, two novel cyclobutane substances from Cardopatium corymbosum

Abstract Two new natural substances containing a cyclobutane unit, cardopatine and isocardopatine, the trans and cis isomers respectively of 5,5″ (cyclobut-1,2-ylene-diethynylene) bis 2,2′-bithiophene), together with the known α-terthienyl and 5-(but-3-en-1-ynyl)-2,2′-bithienyl, have been isolated from the roots of Cardopatium corymbosum. Evidence is given that the novel cyclobutane substances are not the products of a spontaneous dimerization of a bithienyl monomeric unit. Structure determination and conformational analysis are reported.

Fast-atom bombardment mass spectrometric and tandem mass spectrometric study of (—)-menthol-β-( D )-glucopyranoside, neohesperidin dihydrochalcone and their non-covalent association with β-cyclodextrin. Two examples of interaction of a carbohydrate host with glycoconjugate guests

(−)-Menthol-β-(D)-glucopyranoside 1 and neohesperidin dihydrochalcone 2 are glycoconjugates of practical interest. Compound 1 releases (−)-menthol in foods by slow hydrolysis and 2 is a sweetener used as an alternative to sucrose for diet food and beverages. Their molecular encapsulation in β-cyclodextrin (βCD) is currently under investigation with the purpose of obtaining long lasting properties in the final product. From a mass spectrometric point of view, the study of the protonated gaseous 1:1 host–guest complexes of 1 and 2 with βCD is of particular interest, since the guest molecules possess an apolar aglycon, likely to interact with the lipophilic cavity of βCD, and a saccharidic part, whose capability of interaction with the polar external surface of βCD has not been investigated so far. We carried out a fast-atom bombardment (FAB) mass spectrometric and tandem mass spectrometric (MS/MS) study in thioglycerol on 1 and 2 and their gaseous protonated 1:1 association complexes with βCD. The FAB and tandem mass spectrometry results are later presented and discussed. Collisionally-activated decomposition data from native 1 and 2 are compared with those of the complexes of 1 and 2 with βCD. The experimental data indicate that the presence of βCD may dramatically alter the fragmentation pattern of the two glycoconjugates. The observed fragmentation patterns are consistent with an attractive interaction between the polar external surface of βCD and the sugar residues of the guest molecules 1 and 2. The mass spectrometric data not only provide information on the nature of non-covalent interaction in controlling binding phenomena, but also point out a role for carbohydrate–carbohydrate interactions, possibly mediated via hydrogen bonding.

Hydroboration—V : A new synthesis of androsterone and 19-norandrosterone☆☆☆

Abstract A new approach to androsterone and 19-norandrosterone from androst-5-ene-3β-ol-17-one and 19-nortestosterone is described. The synthesis is accomplished by a stereospecific hydroboration of Δ 3 - 5α-steroids.

Fast Atom Bombardment Mass Spectrometric and Tandem Mass Spectrometric Investigation in Thioglycerol on Protonated Non‐covalentAssociations of β‐Cyclodextrin with 2‐Acetyl,2‐Propionyl‐1‐pyrroline and 5‐Acetyl‐2,3‐dihydro‐1,4‐thiazine, Roast Smelling Odorants in Food. Role of the Matrix

2-Acetyl-1-pyrroline (1), 2-propionyl-1-pyrroline (2) and 5-acetyl-2,3-dihydro-1,4-thiazine (3), roast smelling odorants in food, form stable inclusion compounds with β-cyclodextrin. Fast atom bombardment (FAB) mass spectra of such complexes in thioglycerol showed abundant [G+Hs+Mx+H] + ions, where G = guest (1, 2 or 3), Hs = host (β-cyclodextrin) and Mx = one molecule of matrix, consistent with protonated noncovalent three-component adducts, and nearly negligible 1:1 associations of the type [G + Hs + H] + . Collision-activated decomposition (CAD) experiments indicated that [G + Hs + Mx + H] + are made of neutral β-cyclodextrin and protonated 1:1 guest-matrix adducts. The nature of these latter adducts was investigated by FAB mass spectrometric experiments on 1, 2 and 3 in thioglycerol without β-cyclodextrin. In all cases the most intense signals are due to [G + Mx + H] + and [G + H] + , with a small contribution of [G + Mx - H 2 O + H] + to the total ion current. CAD experiments on [G + Mx + H] + afforded protonated guest molecules as the base peak, consistent with the decomposition of protonated noncovalent 1:1 guest-matrix associations, possibly mediated by an intermolecular hydrogen bond. According to these data, there is a significant contribution of non-covalent three-component associations to [G + Hs + Mx + H] + complexes, although the possibility of the formation of covalent guest-matrix adducts is not ruled out definitely, as discussed in the text

Letter: Fast atom bombardment, electrospray, ionspray and tandem mass spectrometry of 1 : 1 β-cyclodextrin/5-methoxytryptamine hydrochloride host-guest complex: host protonation and fragmentation due to guest deamination a

The 1:1 inclusion complex of β-cyclodextrin (βCD) with 5-methoxytryptamine (5MTA) hydrochloride was studied by mass spectrometry (MS) and tandem-MS with fast atom bombardment (FAB), electrospray (ES) and ionspray (IS) ionisation and triple quadrupole or ion trap analysers. A protonated 1:1 βCD/MTA gaseous association was always observed; the protonated species of deaminated 5MTA and of some typical βCD fragments were obtained, in addition to the expected protonated 5MTA, as tandem-MS dissociation products. A reaction pattern starting from the deamination of protonated 5MTA, as a recently described high pressure chemical ionisation or ES process of primary amines, was suggested, which accounts for the formation of excited protonated βCD and its fragmentation by tandem-MS, even under unimolecular conditions.