Evaluation of antioxidant activities of the edible and medicinal Acacia albida organs related to phenolic compounds

This study compared phenolic contents and antioxidant activity in different organs of Acacia albida (leaves and bark) and focuses on identification of phenolic compounds of leaves by HPLC-DAD. The analysed organs exhibited differences in total polyphenol contents (100 and 59.5 mg GAE g^? 1 DW). Phenolic contents of leaves were two times higher than those in bark. Ethanolic extracts exhibited good antioxidant activities with IC₅₀ = 26 μg mL^? 1 for DPPH and EC₅₀ = 50 μg mL^? 1 for FRAP. Identification by HPLC-DAD revealed the presence of nine phenolic compounds known for their high antioxidant activity. The results suggested that this species can be used as source of natural antioxidants.     

Crystal structure,Hirshfeld surface analysis,vibrational properties,and electrical and dielectric studies of the bis (4-benzylpyridinium) tetrachlorocuprate (II)

The present paper undertakes the study of (C₁₂H₁₂N)₂CuCl₄, which is a new hybrid compound. It is synthesized and characterized by single-crystal X-ray diffraction, Hirshfeld surface analysis, and FT-IR, FT-Raman, and impedance spectroscopies. It is crystallized in the monoclinic system with C2/c space group. Its crystal structure was determined and refined down to an R value of 0.05 and a wR value of 0.14. The structure can be described by the alternation of two different, cationic–anionic layers parallel to (110) plan. This complex is assembled into 3D supramolecular architecture by hydrogen bonds (N–H…Cl, C–H…Cl) and π–π interactions. Hirshfeld surface analyses and fingerprint plots are used for decoding intermolecular interactions in the crystal network and contribution of component units for the construction of the 3D architecture. The presence of different functional groups and the nature of their vibrations were identified by FT-IR and FT-Raman spectroscopies. The material is characterized by impedance spectroscopy technique measured in 209–500 MHz frequency and 296–390 K temperature ranges. In addition, the Cole–Cole (Z? versus Z?) plots were well fitted to an equivalent circuit built up by a parallel combination of resistance (R) and constant phase elements (CPEs). The close values of activation energies obtained from the analysis of equivalent circuit data confirm that the transport is through ion hopping mechanism in the bis (4-benzylpyridinium) tetrachlorocuprate.     

Circularly Polarized Fluorescent Helicene-Boranils: Synthesis,Photophysical and Chiroptical Properties

Mono- and di-boranil-substituted helicenes were prepared by BF₂-borylation of the corresponding anils, readily synthesized by condensation of 2-amino- and 2,15-diamino-helicenes with 4-(diethylamino)salicylaldehyde. After enantiomeric resolution using HPLC, their chiroptical properties including circularly polarized fluorescence in solution and in PMMA films were investigated and rationalized with the help of NMR, X-ray and quantum-chemical calculations.     

Highly Sensitive Impedimetric Biosensor Based on Thermolysin Immobilized on a GCE Modified with AuNP-decorated Graphene for the Detection of Ochratoxin A

The fabrication of a thermolysin-based biosensor capable of detecting ochratoxin A (OTA) from food samples is described. The electrochemical deposition of calcium cross-linked cellulose film (CCLC) and gold nanoparticles (AuNPs) on graphene (GR) for modification of a glassy carbon electrode (GCE) is the first step. Then the thermolysin (TLN) enzyme in a polyvinyl alcohol (PVA)/polyethylenimine (PEI) matrix is immobilized. The impedimetric biosensor response is linear from 0.2 nM to 100 nM with a detection limit of 0.2 nM. The obtained stable and reproducible biosensor is then applied for the detection of OTA in spiked extracts from coffee beans.     

Direct Synthesis of 4-Acetyl-1-alkyl-1H-pyrrol-2(5H)-ones from Difunctionalized Allyl Bromide

We describe a simple and efficient protocol for accessing some unsaturated heterocyclic compounds in a direct evaluation of allyl bromide as Z-ethyl 3-bromomethyl-4-oxopent-2-enoate. The latter reacts with primary amines via two successive nucleophilic substitutions followed by a 5-exo-trig cyclization to produce selectively 4-acetyl-1-alkyl-1H-pyrrol-2(5H)-ones in good yields.     

Phenyl Silicates with Substituted Catecholate Ligands: Synthesis,Structural Studies and Reactivity

While the generation of aryl radicals by photoredox catalysis under reductive conditions is well documented, it has remained challenging under an oxidative pathway. Because of the easy photo-oxidation of alkyl bis-catecholato silicates, a general study of phenyl silicates bearing substituted catecholate ligands has been achieved. The newly synthesized phenyl silicates have been fully characterized, and their reactivity has been explored. It was found that, thanks to the substitution of the catecholate moiety, notably with the 4-cyanocatecholato ligand, the phenyl radical could be generated and trapped. Computational studies provided a rationale for these findings.