Nuclear magnetic resonance approaches to the rationalization of chromatographic enantiorecognition processes

NMR spectroscopy represents a valuable tool for obtaining information about structure and dynamics at a molecular level on the diastereoisomeric complexes formed by enantiomeric substrates and chromatographic chiral selectors or modifiers. Some examples collected from the literature show the potentialities of solution NMR spectroscopy in the rationalization of chromatographic enantiorecognition processes and the different NMR approaches needed according to the chiral selector features.     

Scattering of surface state electrons at large organic molecules

The scattering of surface state electrons at Lander-type molecules on Cu(111) is investigated by means of scanning tunneling microscope (STM) experiments at low temperature and model calculations. Specific information concerning the electronic interaction of the different internal groups of the molecule with the surface is obtained. Remarkably, the central molecular wire of the molecule, although decoupled from the surface by spacer groups and therefore not visible in STM images, is the main one responsible for scattering of surface state electrons.     

Simultaneous quantitation of free and conjugated phytoestrogens in Leguminosae by liquid chromatography-tandem mass spectrometry

Phytoestrogens are diphenolic compounds that are present in several edible plants and are particularly abundant in soybeans. Because of their estrogenical, antriestrogenical, anticarcinogenic and antioxidant activities in animal and humans, they became of great interest. Dietary factors are considered important in determination of risks, in fact, studies have revealed beneficial or protective effects of the consumption of vegetables, in particular soy and soybean products. So that in the present paper the simultaneous determination of eight isoflavones and coumestrol in vegetables is reported.The quantitative analysis has been made by means of LC separation combined with tandem mass spectrometry. In particular, a new simple and fast extraction methodology and a clean-up, based on cold aided de-fatting, is proposed. Method performance was evaluated by comparison with a reference procedure.The developed procedure was then used for a survey of phytoestrogens concentration in some selected vegetables.     

Efficient 3D database screening for novel HIV-1 IN inhibitors

We describe the use of pharmacophore modeling as an efficient tool in the discovery of novel HIV-1 integrase (IN) inhibitors. A three-dimensional hypothetical model for the binding of diketo acid analogues to the enzyme was built by means of the Catalyst program. Using these models as a query for virtual screening, we found several compounds that contain the specified 3D patterns of chemical functions. Biological testing shows that our strategy was successful in searching for new structural leads as HIV-1 IN inhibitors.     

Efficient preparation of 2-indolyl-1-nitroalkane derivatives employing nitroalkenes as versatile Michael acceptors: new practical linear approach to alkyl 9h-beta-carboline-4-carboxylate

The combination of cerium(III) chloride heptahydrate and sodium iodide supported on silica gel is known to promote Michael-type additions. Continuing our work on solvent-free conditions, the CeCl3.7H2O-NaI-SiO2 system catalyzes the addition of a variety of indoles and nitroalkenes, giving 2-indolyl-1-nitroalkane derivatives in good yields. Development of this method has resulted in a new protocol for the synthesis of 4-substituted beta-carbolines.     

Gel-like lyomesophases formed in organic solvents by self-assembled guanine ribbons

Lipophilic guanosine derivatives are self-assembled into ribbonlike aggregates, both in the crystal state and in solution. The structure of the ribbons has been characterised by single-crystal X-ray diffraction and, in solution, by NMR spectroscopy and ESI-MS. Two different ribbons with different patterns of hydrogen bonds are present in the solid state and in chloroform solutions. The gel-like phases obtained in hexadecane, toluene and chloroform have been investigated by optical microscopy and small-angle X-ray diffraction: the type of phase observed is related to the molecular structure of the compounds and depends dramatically on the solvent. The structures of the phases are discussed, with the presence of the two different ribbons being taken into account.     

Ocimum campechianum Mill. from Amazonian Ecuador: Chemical Composition and Biological Activities of Extracts and Their Main Constituents (Eugenol and Rosmarinic Acid)

The essential oil (EO), the methanolic (MeOH), and the 70% ethanolic (70% EtOH) extracts obtained from the aerial parts of Ocimum campechianum Mill. (Ecuador) were chemically characterized through gas-chromatography coupled to mass spectrometry detector (GC-MS), high-performance liquid chromatography coupled to diode array-mass spectrometry detectors (HPLC-DAD-MS) and studied for their in vitro biological activity. The radical scavenger activity, performed by spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays, highlighted significant IC₅₀ values for the EO, extracts and their main constituents (eugenol and rosmarinic acid). EO (and eugenol) showed noteworthy activity against Pseudomonas syringae pv. syringae and a moderate effect against clinical Candida strains, with possible synergism in association to fluconazole against the latter microorganisms. The extracts and pure molecules exhibited weak cytotoxic activity against the HaCat cell line and no mutagenicity against Salmonella typhimurium TA98 and TA100 strains, giving indication of safety. Instead, EO showed a weak activity against adenocarcinomic human alveolar basal epithelial cells (A549). The above-mentioned evidence leads us to suggest a potential use of the crude drug, extracts, and EO in cosmetic formulation and food supplements as antioxidant agents. In addition, EO may also have a possible application in plant protection and anti-Candida formulations.