Chemical constituents of Genista numidica Spach aerial parts and their antimicrobial,antioxidant and antityrosinase activities

A previously undescribed triterpenoid saponin, 3-O-[α-l-rhamnopyranosyl-(1→2)-{β-d-glucopyranosyl-(1→6)-}β-d-galactopyranosyl-(1→2)-β-d-glucuronopyranosyl]-sophoradiol (1), in addition to twenty-nine known constituents (2–30) were isolated from the aerial parts of Genista numidica Spach. Structures elucidation was performed by comprehensive 1D- and 2D-NMR analyses and HRESIMS. The extracts, fractions and isolated compounds were evaluated for their antibacterial, antioxidant and tyrosinase inhibitory activities. The experimental findings indicated that genistin (16), isosalipurpol (27), and koaburaside (29) have moderate to low antibacterial activity against E. faecalis, S. aureus, S. epidermidis and P. aeruginosa bacteria with MICs ranging from 31.2 to 125 μg/mL. Compounds 19 and 27 exhibited a good antiradical activity potential (IC₅₀ 11.8 and 11.1 μg/mL, respectively). Only compounds 23, 27 and 28 exhibited low inhibitory effect against mushroom tyrosinase (IC₅₀ from 90.2 to 225.6 μg/mL).     

Unrepaired cyclobutane pyrimidine dimers do not prevent proliferation of UV-B-irradiated cultured human fibroblasts

Mutagenic and carcinogenic UV-B radiation is known to damage DNA mostly through the formation of bipyrimidine photoproducts, including cyclobutane dimers (CPD) and (6-4) photoproducts ((6-4) PP). Using high-performance liquid chromatography coupled to tandem mass spectrometry, we investigated the formation and repair of thymine-thymine (TT) and thymine-cytosine (TC) CPD and (6-4) PP in the DNA of cultured human dermal fibroblasts. A major observation was that the rate of repair of the photoproducts did not depend on the identity of the modified pyrimidines. In addition, removal of CPD was found to significantly decrease with increasing applied UV-B dose, whereas (6-4) PP were efficiently repaired within less than 24 h, irrespective of the dose. As a result, a relatively large amount of CPD remained in the genome 48 h after the irradiation. Because the overall applied doses (<500 J m(-2)) were chosen to induce moderate cytotoxicity, fibroblasts could recover their proliferation capacities after transitory cell cycle arrest, as shown by 5-bromo-2'-deoxyuridine (BrdUrd) incorporation and flow cytometry analysis. It could thus be concluded that UV-B-irradiated cultured primary human fibroblasts normally proliferate 48 h after irradiation despite the presence of high levels of CPD in their genome. These observations emphasize the role of CPD in the mutagenic effects of UV-B.     

Polymer inclusion membranes: The concept of fixed sites membrane revised

The mechanism of facilitated transport of metal ions across polymer inclusion membranes (PIMs) is revised on the basis of transport flux measurements and of new data brought by techniques sensitive to local inter-molecular interactions and molecular diffusion. Cellulose triacetate (CTA) membranes built with two types of inclusion carriers: a liquid one Aliquat 336 and a crystalline one Lasalocid A, both able to carry metal ions across PIMs and supported liquid membranes (SLMs) made of the same components, have been compared. Both PIM systems show similar effects for what concern the need of a carrier threshold concentration for the occurrence of a transport flux across PIM as revealed by flux and fluorescence correlation spectroscopy (FCS) measurements, and the dependence of the chemical nature of plasticizers on the metal ion flux. These systems also present similar Raman and far IR signatures of structural evolution of PIMs with the increase of the carrier concentration within the CTA matrix.

All the presented data are interpreted as concern PIMs, according to an evolution of chemical interactions between components of the polymeric membrane able to lead to a phase transition. This phase transition type of the carrier-plasticized polymer system is induced by the increase of carrier concentration in the polymer chains. The PIM progressively organizes itself like a liquid SLM because of the enhancement of preferential solvent interactions between the carrier and the plasticizer.

The main conclusion of this study is that the classically adopted “hopping” transport mechanism between fixed carrier sites in a PIM does not apply to such carrier chemically unbound to polymer membrane systems.     

Total synthesis of amiclenomycin, an inhibitor of biotin biosynthesis

We describe the first synthesis of amiclenomycin, a natural product that has been found to inhibit biotin biosynthesis and, as a consequence, to exhibit antibiotic properties. Structure 1, with a trans relationship between the ring substituents. had previously been proposed for amiclenomycin on the basis of its 1H NMR spectrum. We have prepared the trans and cis isomers 1 and 2 by unequivocal routes and we conclude that the natural product is in fact the cis isomer 2. The properly substituted cyclohexadienyl rings were constructed first. A cycloaddition reaction between 1,2-di(phenylsulfonyl)ethylene and the N-allyloxycarbonyl diene 13, followed by reductive elimination of the phenylsulfinyl groups, gave the cis isomer 15. To obtain the trans isomer, the O-trimethylsilyl diene was used to give the cis hydroxylated Diels-Alder adduct 33, which was transformed into the corresponding trans amino derivative by means of a Mitsunobu reaction. The L-alpha-amino acid functionality was introduced by means of a Strecker reaction on the aldehydes 16 and 42, followed by enzymatic hydrolysis with immobilised pronase.     

PEDOT/Superoxide Dismutase Electrode Surface Modification for Superoxide Bioelectrochemical Sensing

An amperometric biosensor for the sensitive detection of superoxide was designed utilizing a drop‐coating approach for immobilizing the superoxide dismutase enzyme on Pt electrode modified with a thin layer of poly (3,4‐ethylenedioxythiophene) (PEDOT). The layer electrodeposited on Pt was characterized by cyclic voltammetry and atomic force microscopy (AFM). Then, drop‐coating procedure was chosen for the immobilization of superoxide dismutase (SOD), which was incorporated at the electrode surface using a solution containing SOD, glutaraldehyde and bovine serum albumin (optimized composition: SOD 0.1 % – BSA 2 % – GA 2.5 %.) This simple procedure allows forming a reproducible enzymatic biocomposite layer that allows optimal sensitivity and limit of detection for superoxide sensing. The synergistic effect integrates an effective conductivity and permselectivity attributed to the PEDOT layer, as well as the specificity and selectivity of SOD for the detection of superoxide. A high sensitivity (0.82±0.01 μA/μM) and a low detection limit of 11 nM were obtained, as well as good selectivity against main interfering biological compounds such as uric acid and ascorbic acid. Our results suggest that the biosensor could be used for the detection and quantification of in vitro and in vivo.     

Structure and Dynamics of Lanthanide Complexes of Triethylenetetramine‐N,N,N′,N″,N′′′,N′′′‐hexaacetic Acid (H6ttha) and of Diamides H4ttha(NHR) Derived from H6ttha as Studied by NMR,NMRD, and EPR

A multinuclear NMR study on [Ln(ttha)]^3? and [Ln{ttha(NHR)₂}]^? complexes (R=Et, CH₂(CHOH)₄CH₂OH) shows that coordinating groups of the organic ligands in these complexes are occupying all coordination sites of the metal ions, leaving no space for coordination of H₂O molecules (H₆ttha=triethylenetetramine‐N,N,N′,N″,N′′′,N′′′‐hexaacetic acid). The lanthanides of the first half of the series bind the ttha‐type ligands in a decadentate fashion, while the complexes formed with the smaller ions of the second half of the lanthanide series are nonadentate. One carboxylate group of the ligand remains unbound in the latter complexes. In principle, the ttha complexes can exist in six enantiomeric forms. Only one of the pair of diastereoisomers can interconvert without decoordination of the ligand. This pair of isomers seems to be predominant in solution. For the [Ln{ttha(NHR)₂}]^? complexes, the number of chiral centers is larger, resulting in 32 possible enantiomeric forms of the complexes. The NMR spectra of [Nd{ttha(NHEt)₂}]^? indicate that two dynamic processes occur between the isomers in solution. The NMRD curves of [Gd(ttha)]^3?, [Gd{ttha(NHEt)₂}]^?, and [Gd{ttha(NHgluca)₂}]^? (NHgluca=D ‐glucamine) show significant differences with the previously determined outer‐sphere contributions to the NMRD profiles of the corresponding [Gd{dtpa(NHR)₂}]^? complexes, which can be ascribed to differences in the parameters determining the electronic relaxation.     

A Simply Synthesized,Tough Polyarylene with Transient Mechanochromic Response

A simple and high‐yielding route to tough polyarylenes of the type poly(meta,meta,para‐phenylene) (PmmpP) is developed. PmmpP is tough even in its as‐synthesized state which has an intermediate molar mass of M_w≈60 kg mol^?1 and exhibits outstanding mechanical properties at further optimized molecular weight of M_w=96 kg mol^?1, E=0.9 GPa, ?=300 %. Statistical copolymers with para,para‐spiropyran (SP) are mechanochromic, and the toughness allows mechanochromism to be investigated. Strained samples instantaneously lose color upon force release. DFT calculations show this phenomenon to be caused by the PmmpP matrix that allows build‐up of sufficiently large forces to be transduced to SP, and the relatively unstable corresponding merocyanine (MC) form arising from the aromatic co‐monomer. MC units covalently incorporated into PmmpP show a drastically reduced half life time of 3.1 s compared to 4.5 h obtained for SP derivatives with common 6‐nitro substitution.     

Convenient synthesis of 10H-indolo[3,2-b]quinolines and 6H-indolo[2,3-b]quinolines by sequential chemoselective Suzuki reaction followed by double C-N coupling

A convenient and regioselective synthesis of two series of indolo[2,3-b]quinolines, namely 10H-indolo[3,2-b]quinolines and 6H-indolo[2,3-b]quinolines, has been developed. The synthesis, proceeds in moderate to high yields, involving chemoselective palladium catalyzed Suzuki reaction of 2,3-dihaloquinolines with 2-bromophenylboronic acid, followed by a double Buchwald-Hartwig C-N coupling.     

Extraction and refinement of agricultural plant fibers for composites manufacturing

Because of their excellent tensile properties, low density, and natural abundance, cellulose-based plant fibers are a sustainable and biodegradable alternative for synthetic fibers in fiber-reinforced composite materials. However, the extraction of plant fibers can be costly and difficult to control because the fibers are enmeshed in a complex network of biopolymers (principally lignin, pectin, and hemicellulose), which serve both to strengthen the fibers and to bind them to their parent organism. It is necessary to extract or degrade these biopolymers to produce fine plant fibers without adversely altering the fibers themselves in the process. In particular, it is important that both the molecular weight and the degree of crystallinity of the cellulose in the fibers be kept as high as possible. This article reviews chemical treatments, which have been used to extract and refine fibers both from purpose-grown fiber crops, such as hemp and flax, and agricultural waste such as coconut husks and pineapple leaves. The treatments are discussed in terms of changes in the mechanical properties and surface chemistry of the fibers.     

Torsion-induced phase transitions in fluids confined between chemically decorated substrates

In this paper we investigate the phase behavior of a "simple" fluid confined to a chemically heterogeneous slit pore of nanoscopic width s(z) by means of Monte Carlo simulations in the grand canonical ensemble. The fluid-substrate interaction is purely repulsive except for elliptic regions of semiaxes A and B attracting fluid molecules. On account of the interplay between confinement (i.e., s(z)) and chemical decoration, three fluid phases are thermodynamically permissible, namely, gaslike and liquidlike phases and a "bridge phase" where the molecules are preferentially adsorbed by the attractive elliptic patterns and span the gap between the opposite substrate surfaces. Because of their lack of cylindrical symmetry, bridge phases can be exposed to a torsional strain 0相似文献