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Biomedical subjects

Giuliano Delle Monache

Publications and source records attributed to Giuliano Delle Monache.

16 recordsLinked to original sources
PubMed2006

Gas-phase enantioselectivity of chiral amido[4]resorcinarene receptors.

Diastereomeric proton-bound [1(L)HA]+ complexes between selected amino acids (A=phenylglycine (Phg), tryptophan (Trp), tyrosine methyl ester (TyrOMe), threonine (Thr), and allothreonine (AThr)) and a chiral amido[4]resorcinarene receptor (1(L)) display a significant enantioselectivity when undergoing loss of the amino acid guest A by way of the enantiomers of 2-aminobutanes (B) in the gas phase. The enantioselectivity of the B-to-A displacement is ascribed to a combination of thermodynamic and kinetic factors related to the structure and the stability of the diastereomeric [1(L)HA]+ complexes and of the reaction transition states. The results of the present and previous studies allow classification of the [1(L)HA]+ complexes in three main categories wherein: i) guest A does not present any additional functionalities besides the amino acid one (alanine (Ala), Phg, and phenylalanine (Phe)); ii) guest A presents an additional alcohol function (serine (Ser), Thr, and AThr); and iii) guest A contains several additional functionalities on its aromatic ring (tyrosine (Tyr), TyrOMe, Trp, and 3,4-dihydroxyphenylalanine (DOPA)). Each category exhibits a specific enantioselectivity depending upon the predominant [1(L)HA]+ structures and the orientation of the 2-aminobutane reactant in the relevant adducts observed. The results may contribute to the understanding of the exceptional selectivity and catalytic properties of enzyme mimics towards unsolvated biomolecules.

Amino Acids↗
PubMed2006

Cilistepoxide and cilistadiol, two new withanolides from Solanum sisymbiifolium.

In addition to the known cilistol A, two new withanolides have been isolated from leaves and stem of Solanum sisymbiifolium, and assigned the structures 1-oxo-5,6; 22,26; 24,25-triepoxy-17,26-dihydroxyergost-2-ene and 1-oxo-22,26; 24,25-diepoxy-5,6,17,26-tetrahydroxy ergost-2-ene, namely cilistepoxide and cilistadiol.

Brazil↗
PubMed2005

Novel prenyltransferase enzymes as a tool for flavonoid prenylation.

The recent identification of genes encoding a novel family of soluble aromatic prenyltransferases from Streptomyces species and the structural characterization of one of these proteins are challenging discoveries in the biochemistry of natural compounds. In addition to their notable physiological role in the biosynthesis of aminocoumarin antibiotics, these enzymes represent an advanced tool for exploring novel isoprenoid substitutions in aromatic compounds and are expected to foster the emerging pharmacological applications of prenylated flavonoids.

Dimethylallyltranstransferase↗
PubMed2005

Prenylated flavonoids: pharmacology and biotechnology.

Within the flavonoid class of natural products the prenylated sub-class is quite rich in structural variety and pharmacological activity. In the last twenty years a huge number of new structures has been reported, mostly from Leguminosae and Moraceae, with few coming from other genera. The presence, in different forms, of the isoprenoid chain can lead to impressive changes in biological activity, mostly attributed to an increased affinity for biological membranes and to an improved interaction with proteins. Molecules, such as xanthohumol and sophoraflavanone G, while being very structurally simple, show numerous pharmacological applications and are ideal candidates for SAR aimed to the discovery of new drugs. Only recently the biogenesis of these compounds has been more extensively studied and much attention has been focused on the enzymes involved in the modification and transfer of the prenyl unit.

Animals↗
PubMed2004

Chiral recognition by resorcin[4]arene receptors: intrinsic kinetics and dynamics.

Molecular recognition of representative amino acids (A) by a chiral amido[4]resorcinarene receptor (1(L)) was investigated in the gas phase by ESI-FT-ICR mass spectrometry. The ligand displacement reaction between noncovalent diastereomeric [1(L).H.A](+) complexes and the 2-aminobutane enantiomers (B) exhibits a distinct enantioselectivity with regard to both the leaving amino acid A and the amine reactant B. The emerging selectivity picture, discussed in the light of molecular mechanics and molecular dynamics calculations, points to chiral recognition by 1(L), as determined by the effects of the host asymmetric frame on the structure, stability, and rearrangement dynamics of the diastereomeric [1(L).H.A](+) complexes and the orientation of the amine reactant B in encounters with [1(L).H.A](+). The results contribute to the development of a dynamic model of chiral recognition of biomolecules by enzyme mimics in the unsolvated state.

Amino Acids↗
PubMed2004

Chalcone dimethylallyltransferase from Morus nigra cell cultures. Substrate specificity studies.

A new prenyltransferase (PT) enzyme derived from the microsomal fractions of cell cultures of Morus nigra was shown to be able to prenylate exclusively chalcones with a 2',4'-dihydroxy substitution and the isoflavone genistein. Computational studies were performed to shed some light on the relationship between the structure of the substrate and the enzymatic activity. PT requires divalent cations, particularly Mg(2+), to be effective. The apparent K(m) values for gamma,gamma-dimethylallyldiphosphate and 2',4'-dihydroxychalcone were 63 and 142 microM, respectively. The maximum activity of the enzyme was expressed during the first 10 days of cell growth.

Cells, Cultured↗
PubMed2003

Synthesis and molecular modelling studies of resorcin[4]arene-capped porphyrins.

Three new resorcin[4]arene-capped porphyrins (3, 5 and 7) different in the porphyrin skeleton, in the linking arms and in the cavity dimensions, have been synthesised. Molecular modelling calculations explored the conformations and the cavity size of the three compounds and showed that their hydrophobic pockets can accommodate one molecule of water or methane (3 and 5), or benzene (7) without any distortion. Notably, the capped porphyrin 5 was able to inhibit the oxidation of Co(II) to Co(III), whereas compound 7 did it only partially.

Journal Article↗
PubMed2003

Novel hypotensive agents from Verbesina caracasana: structure, synthesis and pharmacology.

The number and the pharmacological activities of drugs featuring a guanidine group is actually amazing. Many synthetic guanidine derivatives have attracted pharmacologists in search of new antihypertensive drugs for their ability to block adrenergic nerve activity through central and/or peripheral mechanisms. As a result, compounds such as guanethidine, guanabenz, guanfacine, and pinacidil have been introduced in antihypertensive drug therapy. A crude methanol extract of the Venezuelan plant Verbesina caracasana Fries (Compositae), intravenously administered to mice, was found to induce biological effects such as erection of hair, initial stimulation and subsequent blockade of breathing. Biologically controlled purification yielded a series of active guanidine derivatives, namely G1-G7, which were extensively studied with the focus on the following items: (1) The structure determination of the active compounds by spectral data and a set of reactions; (2) The confirmation of the structures by a biogenetically oriented synthesis; (3) The study of the pharmacological profiles of the isolated drugs; (4) The synthesis of analogous and homologous products in the effort to shed some light on the structure-activity relationship. The metabolites of V. caracasana were characterized, in anesthetized rats, as hypotensive drugs of high (G2), mild (G1, G7) and low (G3,G5,G6) potency, devoid of consistent actions in heart rate, and provided with moderate stimulatory effects on cardiac inotropism and breathing (at selected non-toxic intravenous doses). Autonomic neurogenic components and/or peripheral adrenergic and cholinergic receptor-related pathways were involved in the cardiovascular effects. Synthetic analogs and homologs of G1 and G5 were all shown to be hypotensive drugs of low-mild potency, not affecting appreciably cardiac inotropism and/or breathing. The pharmacodynamic differences among the studied compounds were likely to depend on their ability to cross the blood-brain barrier, lipophilicity and pharmacokinetics. Since most of the compounds did not induce reflex tachycardia and depression of myocardial contractility as the majority of the antihypertensive drugs, they might be useful in the treatment of arterial hypertension of various genesis.

Animals↗
PubMed2002

Enantioselective guest exchange in a chiral resorcin[4]arene cavity.

Gas-phase proton-bound complexes between a chiral resorcin[4]arene and some representative amino acids, that is, L- and D-alanine or L- and D-serine, were generated in the source of a Fourier transform ion cyclotron resonance mass spectrometer. Gas-phase exchange of the amino acid from the diastereomeric complexes with the enantiomers of 2-butylamine exhibits a significant enantioselectivity, which depends not only upon the configuration of the leaving guest but also on that of the incoming amine. These findings, coupled with molecular dynamic calculations, point to the observed gas-phase enantioselectivity as determined by the effects of the resorcin[4]arene chiral cavity upon the diastereomeric exchange transition structures.

Alanine↗
PubMed2002

Synthesis and interaction with copper(II) cations of cyano- and aminoresorcin[4]arenes.

Following our studies on resorcin[4]arenes, we synthesized new macrocycles containing cyanomethyl and aminomethyl side chains. Three stereoisomers (2a-c) of the former were obtained by BF3*Et2O tetramerization of the corresponding trans-cinnamic acid derivative and were shown to be in the 1,2-alternate, cone, and 1,3-alternate conformations. Conversely, the tetraamino derivative 6a in the cone conformation was prepared from the corresponding tetrabromide 3a. The interactions with Cu(II) cations of the new compounds were analyzed by measurements of 1H NMR and EPR spectra in parallel with molecular modeling calculations.

Journal Article↗
PubMed2002

Abietane diterpenoids from callus cultures of Taxus baccata.

A new compound was isolated from calli of Taxus baccata L. and assigned the structure 3beta,11-dihydroxy-12-methoxyabieta-8,11,13-triene-7-one. Two other metabolites were identified as 3-oxocryptojaponol and taxamairein C, both previously isolated from Taxus mairei.

Cell Culture Techniques↗
PubMed2002

Labdane diterpenes from Haplopappus illinitus.

A chemical study of aerial parts of Haplopappus illinitus afforded five labdane diterpenoids whose structures were elucidated by high field NMR spectroscopy and 2D techniques. Four of them are dicarboxylic acids previously reported as the corresponding dimethyl ester derivatives and the fifth is a new compound.

Chile↗
PubMedDate not supplied

Derivatization does not influence antimicrobial and antifungal activities of applanoxidic acids and sterols from Ganoderma spp.

Applanoxidic acids and sterols, isolated from Ganoderma spp., were acetylated and/or methylated. The antibacterial activity against Escherichia coli and Staphylococcus aureus and the antifungal activity against Candida albicans and Trichophyton mentagrophytes of the derivatives were investigated by a microdilution method, and compared with those of the natural products. Both natural and modified compounds exhibited comparable antibacterial and antifungal activities in a range of 1.0 to > 2.0 mg/ml minimal inhibitory concentration.

Anti-Bacterial Agents↗