Biomimetic oxidation of curcumin with hydrogen peroxide catalyzed by 5,10,15,20-tetraarylporphyrinatoiron(III) chlorides in dichloromethane

The biomimetic oxidation of curcumin, a main turmeric pigment with hydrogen peroxide catalyzed by different 5,10,15,20-tetraarylporphyrinatoiron(III) chlorides [TAPFe(III)Cl] in dichloromethane has been studied to give a C-C coupled curcumin dimer in 40-70% yield. The structure of the dimer has been elucidated by (1)H-, (13)C-NMR, IR and FAB-Mass spectroscopic data.     

Minimal logarithmic signatures for classical groups

The minimal logarithmic signature conjecture states that in any finite simple group there are subsets A _i , 1 ≤ i ≤ k such that the size |A _i | of each A _i is a prime or 4 and each element of the group has a unique expression as a product \({\prod_{i=1}^k x_i}\) of elements \({x_i \in A_i}\). The conjecture is known to be true for several families of simple groups. In this paper the conjecture is shown to be true for the groups \({\Omega^-_{2m}(q), \Omega^+_{2m}(q)}\), when q is even, by studying the action on suitable spreads in the corresponding projective spaces. It is also shown that the method can be used for the finite symplectic groups. The construction in fact gives cyclic minimal logarithmic signatures in which each A _i is of the form \({\{y_i^j \ |\ 0 \leq j < |A_i|\}}\) for some element y _i of order ≥ |A _i |.     

Fabrication of hollow SiO2 and Au (core)–SiO2 (shell) nanostructures of different shapes by CdS template dissolution

Core–shell silica (SiO₂) coated CdS nanorods (NR) and nanospheres (NS) were prepared (SiO₂@CdS) by deposition of a Si–O–Si amorphous layer over the CdS surface through the hydrolysis of 3-mercaptopropyltrimethoxysilane and tetraethylorthosilicate. Nanoporous SiO₂ matrix (NPSM), hollow SiO₂ nanotubes (HSNT) and nanospheres (HSNS) useful for efficient adsorption and catalytic processes were prepared by chemical dissolution of CdS–NS (size: 9–10 nm) and CdS–NR (length: 116–128 nm and width: 6–11 nm) template from SiO₂@CdS with 2 M HNO₃. These SiO₂ nanostructures were characterized by optical absorption, TEM, EDX, SAED and BET surface area analysis. TEM images revealed the fabrication of slightly distorted HSNS (size: 9–12 nm) and closed HSNT (length: 30–45 nm and diameter: 9–14 nm) of shorter dimensions than the CdS–NR template used. The BET surface area (112–134 m² g^?1) of NPSM and HSNS is found to be larger than the surface area (29–51 m² g^?1) of SiO₂@CdS composites indicating hollow SiO₂ morphology. Silica coated Au (SiO₂@Au) composites formed by CdS dissolution from Au (2 wt%) deposited CdS–NR core-encapsulated into SiO₂ shell (SiO₂@Au–CdS–NR) exhibited a surface plasmon band at 550 nm and displayed high catalytic activity for 4-nitrophenol reduction by Au nanoparticle.     

Conducting polymers: Efficient thermoelectric materials

This review highlights the recent progress made in the area of thermoelectric (TE) applications of conducting polymers and related composites. Several examples of such materials and their TE properties are discussed. TE properties of new poly(2,7‐carbazole) derivatives are highlighted. References are also made to carbon nanotube/polymer composites and their improved electrical and TE performance. Studies on polymer/inorganic materials composites have also taken a step forward and have shown very promising TE properties. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

A study on interaction of Be, Mg and Ca with phenylalanine: Binding energies, metal ion affinities and IR signature of complex stability

The interaction between divalent metal cations and amino acids plays an important role in many biological processes. In present report, we have examined the effect of metal cations (Be⁺⁺, Mg⁺⁺ and Ca⁺⁺) interaction on structures, binding energies (BE), metal ion affinities (MIA) and infrared (IR) spectra of phenylalanine (Phe) molecule by density functional theory (DFT) calculations at B3LYP/6-311++G(d,p) level. Nine different ground state isomers of Phe molecule have been optimized at B3LYP/6-311++G (d,p) level of theory. The relative ground state energies of these nine isomers are lying between 0.0-1.9 kcal/mol with respect to the ground state energy of most stable Phe isomer. Seven most stable complexes of Phe molecule with Be⁺⁺, Mg⁺⁺ and Ca⁺⁺ [Phe+M]⁺⁺ (M = Be⁺⁺, Mg⁺⁺ and Ca⁺⁺) were studied. The calculated values of metal ion affinity (MIA), BE and the Gibbs free energies of each [Phe+M] ⁺⁺ complexes were found to be in the order of Be⁺⁺ > Mg⁺⁺ > Ca⁺⁺. Among the seven [Phe+M]⁺⁺ complexes, the most stable conformer has charge solvation structure where the metal cations coordinated through tridentate bonds with -N, -O atoms and benzene ring (N/O/Ring). The [Phe+Be]⁺⁺ complex has maximum MIA value, 353.3 kcal/mol than that of [Phe+Mg]⁺⁺ and [Phe + Ca]⁺⁺ complexes. Thus, the complex [Phe+Be]⁺⁺ is energetically more stable than that of [Phe+Mg]⁺⁺ and [Phe + Ca]⁺⁺. The IR spectra of each seven conformers of [Phe+M]⁺⁺ complexes have been also calculated. The wavnumber position of (-CO) stretching mode was used to determine the charge/salt bridge structures of the [Phe+M]⁺⁺ complex. The most stable [Phe+M]⁺⁺ complex has been also verified through the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) analysis.     

Dielectric behaviour of emeraldine base polymer–ZnO nanocomposite film in the low to medium frequency

Emeraldine base (EB) polymer–ZnO nanoparticles composite films has been synthesized by solution casting technique on ITO-coated glass substrate and characterized by XRD, FTIR and TEM for their structure and morphology. Dielectric behaviour of these composite films has been investigated in the very low frequency region to medium frequency region (1 kHz–1 MHz). The dielectric constant of the composite with 30% nanoparticles is almost one-tenth of the pure EB. The dielectric value becomes constant in the frequency region greater than 400 kHz. The change in dielectric behaviour of the composite is explained on the basis of multilayered interface formed between the ZnO nanoparticles and emeraldine chains. Nanoparticles have high energy surface which is responsible for the decrease of free volume for the orientation of polymer chains consequently decrease in dielectric constant of the composite. TEM images shows about 10 nm ZnO particles embedded in the emeraldine matrix. From the XRD data it has been observed that the lattice parameters of ZnO have been modified due to the alignment of polymer chains along the basal planes of the nanoparticles. The shift of N=Q=N and N–B–N vibration bands to higher wave number in IR indicates that interaction between emeraldine chain and nanoparticles which provides stability to emeraldine matrix.     

In Silico Evaluation of Natural Flavonoids as a Potential Inhibitor of Coronavirus Disease

The recent coronavirus disease (COVID-19) outbreak in Wuhan, China, has led to millions of infections and the death of approximately one million people. No targeted therapeutics are currently available, and only a few efficient treatment options are accessible. Many researchers are investigating active compounds from natural plant sources that may inhibit COVID-19 proliferation. Flavonoids are generally present in our diet, as well as traditional medicines and are effective against various diseases. Thus, here, we reviewed the potential of flavonoids against crucial proteins involved in the coronavirus infectious cycle. The fundamentals of coronaviruses, the structures of SARS-CoV-2, and the mechanism of its entry into the host’s body have also been discussed. In silico studies have been successfully employed to study the interaction of flavonoids against COVID-19 M^pro, spike protein PL^pro, and other interactive sites for its possible inhibition. Recent studies showed that many flavonoids such as hesperidin, amentoflavone, rutin, diosmin, apiin, and many other flavonoids have a higher affinity with M^pro and lower binding energy than currently used drugs such as hydroxylchloroquine, nelfinavir, ritonavir, and lopinavir. Thus, these compounds can be developed as specific therapeutic agents against COVID-19, but need further in vitro and in vivo studies to validate these compounds and pave the way for drug discovery.     

Valorization of Wild-Type Cannabis indica by Supercritical CO2 Extraction and Insights into the Utilization of Raffinate Biomass

Supercritical CO₂ extraction (SCCO₂) extraction of cannabis oil from Indian cannabis (Cannabis indica) leaves was optimized through a central composite design using CO₂ pressure (150–250 bar), temperature (30–50 °C) and time (1–2 h). From the regression model, the optimal CO₂ pressure, extraction temperature and time were 250 bar, 43 °C and 1.7 h, respectively resulting in the experimental yield of 4.9 wt% of cannabis oil via SCCO₂ extraction. The extract contained cannabidiol, tetrahydrocannabivarin, Δ⁹-tetrahydrocannabinol and Δ⁸-tetrahydrocannabinol as well as two terpenoids such as cis-caryophyllene and α-humulene. Besides SCCO₂ extraction of cannabis oil, the raffinate biomass was utilized to extract polyphenols using water as the extraction medium. Cannabis oil and water extractive were investigated for their half-maximal inhibitory concentration (IC₅₀) values, which were found to be 1.3 and 0.6 mg/mL, respectively. This is comparable to the commercially available antioxidant such as butylated hydroxytoluene with an IC₅₀ value of 0.5 mg/mL. This work on SCCO₂ extraction of cannabinoids and other valuable bioactive compounds provides an environmentally sustainable technique to valorize cannabis leaves.     

Transfer Hydrogenation(TH) of Carbonyl Compounds Catalytically Promoted by Pd17Se15 Nanoparticles and PdP2 Nanoflowers

Nanosized Pd₁₇Se₁₅ and PdP₂ were synthesized at moderate temperature (using less toxic TOPO in case of PdP₂) and explored for the first time to catalyze transfer hydrogenation (TH) of aldehydes / ketones using 2-propanol as a source of hydrogen. The optimum catalyst loading was equivalent to 1.0 mol % of Pd. The round shaped Pd₁₇Se₁₅ NPs (15 to 30 nm), resulted on reacting (3-(phenylseleno)propylamine) with Na₂PdCl₄ in a mixture (1 : 1) of olylamine and 1-octadecene at 250 °C for 50 min. Nanoflowers of PdP₂ (25 to 55 nm) were obtained by reacting Na₂PdCl₄ with trioctylphosphine oxide (TOPO) in a similar solvent mixture at 350 °C for 60 min. Both the NPs were found air insensitive and authenticated with powder X-ray diffraction, HR-TEM, SEM, SEM-EDX and XPS. The conversion was found more efficient for aldehydes in comparison to that of ketones. In comparison to most of the other Pd based nano-phases, reported earlier, the present NPs are somewhat better activators for TH.