Free energy and states of fractional-order hereditariness

Complex materials, often encountered in recent engineering and material sciences applications, show no complete separations between solid and fluid phases. This aspect is reflected in the continuous relaxation time spectra recorded in cyclic load tests. As a consequence the material free energy cannot be defined in a unique manner yielding a significative lack of knowledge of the maximum recoverable work that can extracted from the material. The non-uniqueness of the free energy function is removed in the paper for power-laws relaxation/creep function by using a recently proposed mechanical analogue to fractional-order hereditariness.     

Selective MAO-B inhibitors: a lesson from natural products

Monoamine oxidases (MAOs) are mitochondrial bound enzymes, which catalyze the oxidative deamination of monoamine neurotransmitters. Inside the brain, MAOs are present in two isoforms: MAO-A and MAO-B. The activity of MAO-B is generally higher in patients affected by neurodegenerative diseases like Alzheimer’s and Parkinson’s. Therefore, the search for potent and selective MAO-B inhibitors is still a challenge for medicinal chemists. Nature has always been a source of inspiration for the discovery of new lead compounds. Moreover, natural medicine is a major component in all traditional medicine systems. In this review, we present the latest discoveries in the search for selective MAO-B inhibitors from natural sources. For clarity, compounds have been classified on the basis of structural analogy or source: flavonoids, xanthones, tannins, proanthocyanidins, iridoid glucosides, curcumin, alkaloids, cannabinoids, and natural sources extracts. MAO inhibition values reported in the text are not always consistent due to the high variability of MAO sources (bovine, pig, rat brain or liver, and human) and to the heterogeneity of the experimental protocols used.     

CHIRAL VARIANTS OF ARYLALKYL SULFUR REAGENTS. (R)-CAMPHOR KETIMINES OF OGIOVANNA AMINOTHIOETHERS AND OXIDES

Abstract

Ketimines la-d derived from ortho-aminosubstituted phenylthioethers were prepared in order to determine the degree of chirality transfer from the chiral auxiliary to the sulfur atom in the formation of the sulfoxide or to the α-carbon atom in the reaction of the anion with alkyl halides or benzaldehyde. Oxidation to the sulfoxide occurred with little or no asymmetric induction. The crystalline benzyl sulfone 4c was deprotonated by alkyllithium or Grignard reagents and reacted with alkyl halides and benzaldehyde, in all cases with little to fair transfer of chirality. The major diastereoisomer from methylation of the anion of 4c with methyl iodide, was isolated, and afforded the enantiomerically pure amine 5 after removal of the chiral auxiliary. An X-ray structure determination of 4d allowed the assignment of the absolute configuration of the asymmetric carbon and revealed that the conformation of the ketimine in the crystal state is not homogeneous.     

Interaction of Naproxen with Crystalline and Amorphous Methylated β-Cyclodextrin in the Liquid and Solid State

Abstract

Interactions of naproxen (NAP) with amorphous, randomly methylated β-cyclodextrin at a degree of substitution per anhydroglucose unit of 1.8 (RAMEB) and with crystalline heptakis-(2,6-di-O-methyl)-β-cyclodextrin (DIMEB) were studied in aqueous solution and in the solid state using, respectively, phase-solubility analysis (at 25 °C, 37 °C and 47 °C) and differential scanning calorimetry (DSC) supported by X-ray powder diffractometry. RAMEB and DIMEB displayed similar solubilizing and complexing abilities towards NAP, suggesting analogous inclusion modes of the drug in the host cavity in aqueous solution. Differences were instead observed in interactions in the solid state, where the amorphizing capacity of RAMEB toward NAP (evaluated by DSC) was about twice that of DIMEB at each drug-to-carrier ratio. Assuming that inclusion complexation is also involved in solid-state interactions, molecular modelling accounted for the experimental results in terms of structural features of DIMEB, i.e. the particular inwards orientation of O-6-C-8 groups of three alternate glucoses on the primary hydroxyl side which hampers a deep penetration of NAP in the DIMEB cavity in the solid state. On the contrary, no obstruction of the cavity apparently occurs with RAMEB due its noncrystalline state. The aqueous dissolution rate of NAP from NAP-RAMEB and NAP-DIMEB blends containing 0.59, 0.73, 0.85, and 0.92 mass fraction of carrier linearly increased at decreasing drug-to-carrier ratios. The improvement was 5 to 20 times (from powders) and 50 to 200 times (from discs) the dissolution rate of NAP alone for both carrier. Therefore the choice of the amorphous RAMEB in pharmaceutical formulations can be recommended mainly for economic reasons, though the anhydrous and non-hygroscopic nature of crystalline DIMEB might be of particular advantage in case of moisture sensitive formulations.     

Conformational investigation of some macrobicyclic compounds and of their monoprotonated cations through a comparison between X-ray crystal structures and molecular dynamics simulations

Abstract

In preceding works, which have dealt with the synthesis and characterisation of a series of macrobicyclic compounds with five donor atoms, the unusually high basicity constants of these polyaminic cage-like molecules have been ascribed to the inclusion of the proton inside the macrobicyclic cavity which results in a very efficient hydrogen-bond network. The present paper, based on previously reported X-ray crystal structures regarding five-atoms bridging units and on molecular modelling studies shows that the disposition of the five donor atoms in the monoprotonated species is related to the protonation site. Precisely, if the protonation occurs on a bridge-head nitrogen the resulting geometry of the donors is a trigonal bipyramid, whereas it is square pyramidal when the proton is bound to a nitrogen belonging to a macrobicyclic chain. For what concerns the geometrical array of the donor atoms in the free amines, the favoured array seems to be the trigonal bipyramidal.     

Ultra high performance liquid chromatography with ion‐trap TOF‐MS for the fast characterization of flavonoids in Citrus bergamia juice

We have developed a fast ultra HPLC with ion‐trap TOF‐MS method for the analysis of flavonoids in Citrus bergamia juice. With respect to the typical methods for the analysis of these matrices based on conventional HPLC techniques, a tenfold faster separation was attained. The use of a core–shell particle column ensured high resolution within the fast analysis time of only 5 min. Unambiguous determination of flavonoid identity was obtained by the employment of a hybrid ion‐trap TOF mass spectrometer with high mass accuracy (average error 1.69 ppm). The system showed good retention time and peak area repeatability, with maximum RSD% values of 0.36 and 3.86, respectively, as well as good linearity (R² ≥ 0.99). Our results show that ultra HPLC can be a useful tool for ultra fast qualitative/quantitative analysis of flavonoid compounds in citrus fruit juices.     

Qualitative and quantitative analysis of the unsaponifiable fraction of vegetable oils by using comprehensive 2D GC with dual MS/FID detection

The present investigation is focused on the development of a comprehensive two-dimensional GC (GC?×?GC) method, with dual MS/FID detection, for the qualitative and quantitative analysis of the entire unsaponifiable fraction of vegetable oils. The unsaponifiable fraction forms a minor, highly specific part of a vegetable oil, and can be used as an indicator of genuineness. The column set used consisted of a low-polarity first dimension, and a medium-polarity secondary one, both characterized by a high thermal stability. The use of dual detection enabled the attainment of both mass spectral information and relative % FID data. The complexity of the fingerprint, generated by the unsaponifiable fraction, fully justified the employment of the two-dimensional GC technology. Furthermore, two other GC?×?GC benefits contributed greatly to the attainment of promising results, namely sensitivity enhancement and the formation of group-type patterns. The method herein proposed could potentially open a new opportunity for the more in-depth knowledge of the unsaponifiable fraction of vegetable oils.     

Optimisation of analytical procedures for the quantification of ionic and carbonaceous fractions in the atmospheric aerosol and applications to ambient samples

In the last decade, our research group set up and optimised analytical techniques for the characterisation of the major components of atmospheric aerosol (i.e. secondary inorganic ions and carbonaceous material) and source markers (e.g. levoglucosan, carbonates). In this study, we present a complete overview on the most problematic aspects that can be encountered during the quantification of the two main components of aerosol, i.e. the ionic and carbonaceous fractions. More in detail, different liquid chromatographic approaches were set up for main ions and anhydrosugars determination. Quality assurance procedures (i.e. tests on data reliability) were applied during the set-up phase and they are presented in this work. As regards the carbonaceous component characterisation, two evolved gas analysis techniques were set up and applied: the thermogravimetric technique coupled to the Fourier transformed infrared spectroscopy (TGA/FTIR) and the thermal–optical transmittance method (TOT). A suitable protocol for organic and elemental carbon separation was set up for the TGA/FTIR system and a comparison with the results obtained by the TOT method was carried out. Studies on the impact of filter load, field blanks, and sample composition on OC/EC quantification by the TOT method were performed. Moreover, approaches for carbonate carbon quantification on different kinds of filters were developed. It was demonstrated that this approach allows to reach the ionic balance in samples impacted by carbonate compounds. The optimised methods have been applied for the analysis of thousands of PM filters allowing the obtainment of reliable results.     

Simple One-Pot Synthesis of New Derivatives of the Macrocyclic Aminal 1,3,7,9,13,15,19,21-Octaazapentacyclo-[19.3.1.13,7.19,13.115,19]octacosane (OAPO)

A series of 2,2′-(dihydropyrimidine-1,3(2H,4H)-diyldimethanediyl)bis(substituted-phenols) was synthesized using a Mannich-type reaction between the macrocyclic aminal 1,3,7,9,13,15,19,21-octaazapentacyclo[19.3.1.1^3,7.1^9,13.1^15,19]octacosane (OAPO) (1) and substituted phenols in basic media. These previously unreported compounds were separated from the reaction mixture by column chromatography in highly pure form with 25–75% yields. The most stable conformer was predicted using AM1-type semiempirical quantum chemical calculations.     

Identification of Ros Produced by Photodynamic Activity of Chlorophyll/Cyclodextrin Inclusion Complexes

Photodynamic therapy (PDT) is a way of treating malignant tumors and hyperproliferative diseases. It is based on the use of photosensitizer, herein the chlorophyll a (chl a), and a light of an appropriate wavelength. The interaction of the photosensitizer (PS) with the light produces reactive oxygen species (ROS), powerful oxidizing agents, which cause critical damage to the tissue. To solubilize chl a in aqueous solution and to obtain it as monomer, we have used cyclodextrins, carriers which are able to interact with the pigment and form the inclusion complex. The aim of this study is to examine which types of ROS are formed by Chl a/cyclodextrin complexes in phosphate buffered solution and cell culture medium, using specific molecules, called primary acceptors, which react selectively with the reactive species. In fact the changes of the absorption and the emission spectra of these molecules after the illumination of the PS provide information on the specific ROS formation. The ¹O₂ formation has been tested using chemical methods based on the use of Uric Acid (UA), 9,10‐diphenilanthracene (DPA) and Singlet oxygen sensor green (SOSG) and by direct detection of Singlet Oxygen (¹O₂) luminescence decay at 1270 nm. Moreover, 2,7‐dichlorofluorescin and ferricytochrome c (Cyt Fe³⁺) have been used to detect the formation of hydrogen peroxide and superoxide radical anion, which reduces Fe³⁺ of the ferricytochrome to Fe²⁺, respectively.