Advancement in synthetic strategies of bisdimedones: Two decades study

Bisdimedones have emerged as an important and versatile moiety in the field of synthetic and medicinal chemistry. It is screened as a precursor for the synthesis of several heterocycles such as acridinediones, xanthenediones, thioxanthenes, and benzopyrans that exhibited immense pharmacological as well as industrial applications. Its extensive characteristics have attracted the scientists to develop various protocols for the synthesis of bisdimedones and their derivatives from the reaction of dimedone with several aldehydes under different environmental conditions using various types of catalysts. This review encapsulates the recent progress in the synthesis of bisdimedone derivatives under several reaction protocols such as the use of nanoparticles, ionic liquids, metal salts, simple organic compounds, and catalyst-free conditions, and so forth in the last 20 years.     

Potentiometric sensor for the nanoscale monitoring of Ni2+ ion in environmental samples by the fabrication of coated pyrolytic graphite electrode based on a novel C–C-coupled compound

Novel ligand 5,5?-((3-nitrophenyl)methylene)bis(2,6-diaminopyrimidin-4(3H)-one) (L) was synthesised and characterised. Preliminary studies on L have showed that it has more affinity towards the Ni²⁺ ion. Thus, the L was used as the electroactive material in the fabrication of poly(vinyl chloride) (PVC)-based membrane sensors such as coated graphite electrode (CGE) and coated pyrolytic graphite electrode (CPGE). Several polymeric membranes were fabricated by incorporating L as ionophore, NaTPB as anion excluders and BA, 1-CN, DBP, DOP and o-NPOE as solvent mediators and their effect on potentiometric response studied. Comparative electroanalytical studies performed on the CGE and CPGE depict that the CPGE with optimised membrane composition of L:PVC:o-NPOE:NaTPB in the ratio of 7:33:58:2 (w/w, mg) exhibited the best response in terms of wide working concentration range from 2.0 × 10^?8 to 1.0 × 10^?1 mol L^?1, (3.64 µg L^?1 –18.2 g L^?1) lower detection limit of 8.1 × 10^–9 mol L^?1 (1.47 µg L^?1) with Nernstian compliance of 29.4 ± 0.2 mV decade^?1 of activity of Ni²⁺ ion in the pH range of 3.5–9.0. The sensor can work satisfactorily in water–acetonitrile and water–methanol mixtures. It can tolerate 30% acetonitrile and 20% methanol content in the mixtures. The sensor showed fast response time of 8 s and could be used successfully for a period of 4 months. The sensor reflects its utility in the quantification of Ni²⁺ ion in real samples and has been successfully employed as an indicator electrode in the potentiometric titration of Ni²⁺ ion with EDTA.     

Anti-Inflammatory Activity of an In Vitro Digested Anthocyanin-Rich Extract on Intestinal Epithelial Cells Exposed to TNF-α

Background: The consumption of foods rich in anthocyanins (ACN) have been associated with beneficial properties in chronic inflammatory disorders such as intestinal bowel diseases (IBD). These effects were attributed not only to a direct antioxidant mechanism but also to the modulation of cell redox-dependent signaling. However, ACN bioavailability is low for their poor stability in the digestive tract, so ACN gastrointestinal digestion should be considered. Methods: To have a more realistic knowledge of the effects of ACN, we performed an in vitro simulated gastrointestinal digestion of an ACN-rich purified and standardized bilberry and blackcurrant extract (BBE), followed by an evaluation of ACN composition modification (HPLC-DAD and pH differential method) and antioxidant activity (FRAP assay). Then, we studied the effects of BBE gastrointestinal extract on Caco-2 exposed to TNF-α. Results: The results confirmed the high instability of ACN in the mild alkaline environment of the small intestine (17% recovery index). However, the digested BBE maintained part of its bioactivity. Additionally, BBE gastrointestinal extract inhibited the TNF-α-induced NF-κB pathway in Caco-2 and activated the Nrf2 pathway. Conclusions: Although ACN stability is affected by gastrointestinal digestion, the anti-inflammatory and antioxidant activity of digested extracts were confirmed; thus, the loss of ACN can probably be counterweighed by their metabolites. Then, ACN introduced by diet or food supplements could represent an approach for IBD prevention.     

Exquisite 1D Assemblies Arising from Rationally Designed Asymmetric Donor–Acceptor Architectures Exhibiting Aggregation‐Induced Emission as a Function of Auxiliary Acceptor Strength

One‐dimensional nanostructures with aggregation‐induced emission (AIE) properties have been fabricated to keep the pace with growing demand from optoelectronics applications. The compounds 2‐[4‐(4‐methylpiperazin‐1‐yl)benzylidene]malononitrile ( PM1 ), 2‐{4‐[4‐(pyridin‐2‐yl)piperazin‐1‐yl]‐benzylidene}malononitrile ( PM2 ), and 2‐{4‐[4‐(pyrimidin‐2‐yl)piperazin‐1‐yl]benzylidene}malononitrile ( PM3 ) have been designed and synthesized by melding piperazine and dicyanovinylene to investigate AIE in an asymmetric donor–acceptor (D–A) construct of A′–D–π–A‐ topology. The synthetic route has been simplified by using phenylpiperazine as a weak donor (D), dicyanovinylene as an acceptor (A), and pyridyl/pyrimidyl groups ( PM2/PM3 ) as auxiliary acceptors (A′). It has been established that A′ plays a vital role in triggering AIE in these compounds because the same D–A construct led to aggregation‐caused quenching upon replacing A′ with an electron‐donating ethyl group ( PM1 ). Moreover, the effect of restricted intramolecular rotation and twisted intramolecular charge transfer on the mechanism of AIE has also been investigated. Furthermore, it has been clearly shown that the optical disparities of these A′–D–π–A architectures are a direct consequence of comparative A′ strength. Single‐crystal X‐ray analyses provided justification for role of intermolecular interactions in aggregate morphology. Electrochemical and theoretical studies affirmed the effect of the A′ strength on the overall properties of the A′–D–π–A system.     

Electrochemical performance of multi-walled carbon nanotube composite electrodes is enhanced with larger diameters and reduced specific surface area

Multi-walled carbon nanotubes (MWCNT) have been widely used to fabricate composite electrodes due to their electrochemical properties. MWCNTs can be fabricated by various approaches and a range of MWCNT types and sizes has been developed. This study focuses on understanding the influence MWCNT diameter and specific surface area has on the electrochemical properties of a composite electrode. MWCNTs with fixed length range and diameters ranging from 10–20 to 50–80 nm were examined in this study. The amount of MWCNT utilised to fabricate the electrodes was identical and above the percolation threshold. MWCNT electrodes fabricated with larger diameters showed enhanced thermodynamic and kinetic properties towards common redox species which covered surface-insensitive, surface-sensitive and adsorption-based processes. Overall, these findings indicate that the number of strands of MWCNT alone is not essential for enhanced conductivity in composite materials but other geometric parameters play important roles.     

Designs of all-optical buffer and OR gate using SOA-MZI

In the paper a novel scheme for an all-optical buffer and OR logic gates based on Mach–Zehnder interferometer structure is discussed. The operations of the scheme with 10 Gb/s return to zero pseudorandom bit streams simulated correctly with extinction ratio 19.21 and 17.61 dB where Q-factor 25.94 and 11.22 for buffer and OR gate respectively. With the help of numerical analyses, it can be seen that the extinction ratio of the OR operation is degraded and the output pattern effect is decreased by 0.9 dB compared to optical buffer schemes under the same condition. Furthermore, the carrier recovery time of a semiconductor optical amplifier is no longer a crucial parameter to restrict the operation speed of this scheme. The scheme is also potentially capable of multi input OR operation at higher speed.     

Production of reactive oxygen species on photolysis of dilute aqueous quinone solutions

We have examined the generation of the reactive oxygen species (ROS) superoxide and hydrogen peroxide (H2O2) by irradiation of dilute aqueous solutions of disodium anthraquinone-2-6-disulfonate (AQDS) with simulated sunlight. Irradiating a solution of AQDS in 2 mM NaHCO3 and 0.01 M NaCl produced superoxide and H2O2 at nanomolar concentrations. Experiments in which initial concentrations of dioxygen, H2O2, the superoxide radical trap nitroblue tetrazolium and the electron donor dimethyl sulfoxide were varied suggested that the interaction of solvent water with photo-excited quinone moieties produces dioxygen-reducing radicals, and that these are the primary source of ROS in the system. A kinetic model for ROS production is proposed based on our experimental data.     

Analysis of a ginger extract by high-performance liquid chromatography coupled to nuclear magnetic resonance spectroscopy using superheated deuterium oxide as the mobile phase

A methanolic extract of powdered ginger was separated on a Xterra RP 18 column using deuterium oxide as the eluent and a temperature gradient from 50 to 130 degrees C at 4 degrees C/min. On-line and off-line HPLC-NMR analysis yielded spectra for vanillin, dihydroferulic acid, zingerone and ferulic acid. The identification of dihydroferulic acid and zingerone were confirmed by mass spectroscopy.