Seasonal Changes in Essential Oil Constituents of Cystoseira compressa: First Report

Marine macroalgae are well known to release a wide spectrum of volatile organic components, the release of which is affected by environmental factors. This paper aimed to identify the essential oil (EO) compounds of the brown algae Cystoseira compressa collected in the Adriatic Sea monthly, from May until August. EOs were isolated by hydrodistillation using a Clavenger-type apparatus and analyzed by gas chromatography coupled with mass spectrometry (GC–MS). One hundred four compounds were identified in the volatile fraction of C. compressa, accounting for 84.37–89.43% of the total oil. Samples from May, June, and July were characterized by a high share of fatty acids (56, 69, and 34% respectively) with palmitic acid being the dominant one, while in the August sample, a high content of alcohols (mainly phytol and oleyl alcohol) was found. Changes in the other minor components, which could be important for the overall aroma and biological activities of the algal samples, have also been noted during the vegetation periods. The results of this paper contribute to studies of algal EOs and present the first report on C. compressa EOs.     

Palladium-catalyzed reaction of aryl iodides with acetic anhydride. A carbon monoxide-free synthesis of acetophenones

[reaction: see text] The palladium-catalyzed reaction of aryl iodides with acetic anhydride provides a straightforward and experimentally simple carbon monoxide-free route to acetophenones. The reaction tolerates a wide range of functionalized aryl iodides. Acetophenones are isolated in excellent yield with a variety of neutral, slightly electron-rich, and slightly electron-poor aryl iodides, whereas moderate yields are obtained with aryl iodides containing strongly electron-withdrawing substituents.     

Access to Enantiopure Advanced Intermediates en Route to Madangamines

The synthesis of enantiopure ABCE and ABCD tetracyclic advanced intermediates en route to madangamine alkaloids and studies for the construction of the triunsaturated 15-membered D ring of madangamine B and the saturated 13-membered D ring of madangamine E are reported.     

Study on the racemization of synephrine by off-column chiral high-performance liquid chromatography

In this study, the racemization kinetic parameters of R-(−)-synephrine, the active phenethylamine alkaloid of Citrus aurantium L., were determined by means of an off-column HPLC method. Enantioseparation was carried out in different buffer solutions and solvents on a chiral stationary phase (CSP) with cellobiohydrolase as the chiral selector (Chiral-CBH, 100 mm × 4.0 mm i.d., 5 μm). The mobile phase was 10 mM sodium phosphate buffer (pH 6.0)-2-propanol (95:5, w/w), with 50 μM disodium EDTA, at 0.8 mL/min. The column was thermostatted at 20 °C and detection was set at 225 nm. The influence of pH value, ionic strength, temperature and addition of organic modifier on the rate constant, the half-life of racemization and the free energy barrier of racemization of R-(−)-synephrine were determined. Among the different chemical and physical parameters evaluated as affecting the racemization of naturally occurring R-(−)-synephrine, pH, temperature and addition of an organic co-solvent appear to have the strongest effect, while ionic strength does not exert a significant influence on the racemization rate. The results of the present study indicated that synephrine racemization is possible at high temperature at both acidic and basic pH values; therefore, the extraction procedure of R-(−)-synephrine from the plant material should be carried out under specific conditions to preserve the stereochemical integrity and the biological activity of this secondary metabolite.     

Characterization of dendrimer properties by capillary electrophoresis and their use as pseudostationary phases

The general properties of dendrimers and in particular their electrolytic characteristics that are relevant in electrokinetic separations, are described. In order to confirm theoretical considerations on commercial dendrimer charge and hydrodynamic radius, several capillary zone electrophoresis (CZE) experiments were performed. Electrophoretic mobilities measured at different pH values indicated a sensible increase of dendrimer hydrodynamic radius at pH values lower than 2.5. This was probably due to the Coulombic repulsion of charged amine groups of the inner dendrimer shells. The principal reasons that should address the use of dendrimers as pseudostationary phases in micellar electrokinetic chromatography (MEKC) are discussed. Moreover, a survey of different separations performed utilizing dendrimers in MEKC as well as of several future plausible uses of various classes of dendrimers is presented.     

Environmentally degradable bio-based polymeric blends and composites

Blends and composites based on environmentally degradable-ecocompatible synthetic and natural polymeric materials and fillers of natural origin have been prepared and processed under different conditions. Poly(vinyl alcohol) (PVA) was used as the synthetic polymer of choice by virtue of its capability to be processed from water solution or suspension as well as from the melt by blow extrusion and injection molding. Starch and gelatin were taken as the polymeric materials from renewable resources. The fillers were all of natural origin, as waste from food and agro-industry consisted of sugar cane bagasse (SCB), wheat flour (WF), orange peels (OR), apple peels (AP), corn fibres (CF), saw dust (SD) and wheat straw (WS). All the natural or hybrid formulations were intended to be utilized for the production of: a) Environmentally degradable mulching films (hydro-biomulching) displaying, in some cases, self-fertilizing characteristics by in situ spraying of water solutions or suspensions; b) Laminates and containers to be used in agriculture and food packaging by compression and injection molding followed by baking. Some typical prototype items have been prepared and characterized in relation to their morphological and mechanical properties and tested with different methodology for their propensity to environmental degradation and biodegradation as ultimate stage of their service life. A relationship between chemical composition and mechanical properties and propensity to biodegradation has been discussed in a few representative cases.     

New N6‐substituted 8‐alkyl‐2‐phenylmethylsulfanyl‐adenines. II

Title compounds bearing substituents on C(2), C(6) and C(8) were prepared from a newly synthesized pyrimidine derivative 11. The new pyrimidine 11 was generated from compound 2 through two different synthetic schemes. In one pathway, compound 2 was nitrosated, reduced and alkylated to produce com pounds 9 , 10 and 11 respectively (Scheme). In an alternate route using compound 2 as the starting material, a coupling reaction using the diazonium salt derived from p‐methylaniline afforded the azo derivative 7 , which was subsequently alkylated and reductively cleaved to form compounds 8 and 11 respectively (See Scheme). Compound 11 was annulated to the corresponding hypoxanthine derivatives 12–14 ; compounds 12 and 13 were chlorinated with phosphorus oxychloride, then reacted with amines to yield compound 17 and 20 respectively. Compounds 21 , 22 and 23 were obtained by oxidation of the corresponding sulfide as depicted in Scheme. Alkylation of the thiol function of 1 gave a mixture of 3 and 4. Compound 3 was chlo rinated to 5. Nitration of 5 resulted in electrophilic aromatic substitution of the aryl ring and concomitant oxidation of the sulfide to the sulfoxide, producing 6.     

Accelerated Koenigs-Knorr glucuronidation of a deactivated nitrophenol: unveiling the role of polyamine additive 1,1,4,7,10,10-hexamethyltriethylenetetramine through design of experiments

1,1,4,7,10,10-Hexamethyltriethylenetetramine (HMTTA) emerged from a limited parallel screening of selected polyamines as the most appropriate additive for an especially problematic Koenigs-Knorr glucuronidation. This initial finding rapidly evolved into a reliable and high-yielding procedure through the use of two sets of experimental designs. The detailed effect of the stoichiometry of reagents and the amount of amine additive on reaction yield was elucidated. The complexity of the response surface for product yield, described by a third-order polynomial equation, together with ancillary kinetic experiments evidenced the multiple role of HMTTA in the present glucuronidation process.     

HPLC-ESI-MS and MS/MS structural characterization of multifucosylated N-glycoforms of the basic proline-rich protein IB-8a CON1+ in human saliva

This study describes the characterization of the glycan moieties and the peptide backbone of six glycoforms of IB-8a CON1(+), a basic proline-rich protein present in human saliva. MS analyses on the intact glycoproteins before and after N-deglycosylation with PNGase F and high-resolution MS/MS sequencing by LTQ Orbitrap XL of peptides and glycopeptides from tryptic digests allowed the structural characterization of the glycan moieties and the polypeptide backbone, as well as to establish the glycosylation site at the asparagine residue at 98th position. Five of the glycoforms carry a biantennary N-linked glycan fucosylated in the innermost N-acetylglucosamine of the core and showing from zero to four additional fucoses in the antennal region. The sixth glycoform carries a monoantennary monofucosylated oligosaccharide. The glycoform cluster was detected on 28 of 71 adult saliva specimens. Level of fucosylation showed interindividual variability with the major relative abundance for the trifucosylated glycoform. Nonglycosylated IB-8a CON1(+) and the variant IB-8a CON1(-), lacking of the glycosylation site, have been also detected in human saliva.     

Rational Design and Development of Anisotropic and Mechanically Strong Gelatin‐Based Stress Relaxing Hydrogels for Osteogenic/Chondrogenic Differentiation

Rational design and development of tailorable simple synthesis process remains a centerpiece of investigational efforts toward engineering advanced hydrogels. In this study, a green and scalable synthesis approach is developed to formulate a set of gelatin‐based macroporous hybrid hydrogels. This approach consists of four sequential steps starting from liquid‐phase pre‐crosslinking/grafting, unidirectional freezing, freeze‐drying, and finally post‐curing process. The chemical crosslinking mainly involves between epoxy groups of functionalized polyethylene glycol and functional groups of gelatin both in liquid and solid state. Importantly, this approach allows to accommodate different polymers, chitosan or hydroxyethyl cellulose, under identical benign condition. Structural and mechanical anisotropy can be tuned by the selection of polymer constituents. Overall, all hydrogels show suitable structural stability, good swellability, high porosity and pore interconnectivity, and maintenance of mechanical integrity during 3‐week‐long hydrolytic degradation. Under compression, hydrogels exhibit robust mechanical properties with nonlinear elasticity and stress‐relaxation behavior and show no sign of mechanical failure under repeated compression at 50% deformation. Biological experiment with human bone marrow mesenchymal stromal cells (hMSCs) reveals that hydrogels are biocompatible, and their physicomechanical properties are suitable to support cells growth, and osteogenic/chondrogenic differentiation, demonstrating their potential application for bone and cartilage regenerative medicine toward clinically relevant endpoints.