Polyphenolics profile and antioxidant properties of Raphanus sativus L

Raphanus sativus, a common cruciferous vegetable has been attributed to possess a number of pharmacological properties. Antioxidant and radical scavenging activity of R. sativus root extracted with solvents of varying polarity were evaluated using different model systems. Polyphenolic content was estimated to be in the range 13.18-63.54?mg?g?1 dry weight, with a considerable amount being obtained with polar solvents. High-performance liquid chromatography analysis indicated the presence of an array of polyphenolics. Catechin was found to be the most abundant phenolic compound in water extract and sinapic acid, the predominant phenolic compound in methanolic, ethyl acetate and hexane extracts. The methanolic extract showed significant ferric reducing ability, moderate metal chelating activity and strong radical scavenging activity. The methanolic extract could be successfully utilised as an ingredient in functional foods. However, water extract could be more pertinent to human nutrition as it contained a significant amount of catechin, which was comparable to traditional sources like green and black tea.     

An efficient synthesis of tert-butyl ethers/esters of alcohols/amino acids using methyl tert-butyl ether

A facile synthesis of a wide variety of tert-butyl ethers and tert-butyl ester derivatives under mild conditions is described. Alcohols etherified with tert-butyl methyl ether as tert-butyl source and solvent, in the presence of sulfuric acid. Many amino acid tert-butyl esters have been synthesized by this procedure. The reaction is simple, inexpensive, easily scaled up, and proceeds without observable racemization. A green method was developed for the deprotection of this group using Amberlite resin IR 120-H as catalyst.     

(E)‐N‐Benzyl­idene‐3‐chloro‐4‐fluoro­aniline

The title mol­ecule, C₁₃H₉ClFN, is substantially planar. The phenyl and 3‐chloro‐4‐fluoro­phenyl rings are on opposite sides of the C=N bond. There is an intermolecular C—H?F short contact with a C?F distance of 3.348 (2) Å and a C—H?F angle of 137.4 (1)°. The mol­ecules are held in layers parallel to the bc plane.     

Kinetics and mechanism of chloramine-T oxidation of cinnamaldehyde in two acid media

Kinetics of oxidation of cinnamaldehyde (Cinn) by chloramine-T (CAT) has been studied in solutions containing HCl and H₂SO₄ at 313 K. The respective experimental rate laws obtained in HCl and H₂SO₄ media are as follows: and Here the value of x varies from 0.9 to zero while the values of y and z are 0.83 and 0.72, respectively. Effects, on the reaction rate, of ionic strength, reaction product (p-toluenesulfonamide), dielectric constant of the solvent medium, and the anions, Cl⁻ and SO₄²⁻, have been investigated. Activation parameters have been computed, based on the rate constants determined at different temperatures. Mechanisms proposed and the rate laws derived are consistent with the observed kinetic data represented by the experimental rate laws.     

Novel photosensitizer for dye-sensitized solar cell based on ionic liquid–doped blend polymer electrolyte

The existing energy situation demands not only the huge energy in a short time but also clean energy. In this regard, an integrated photo-supercapacitor device has been fabricated in which photoelectric conversion and energy storage are achieved simultaneously. A novel carbazole-based dye is synthesized and characterized for photosensitizer. The silver-doped titanium dioxide (Ag-TiO₂) is synthesized, and it is used as photoanode material. Different concentrations of tetrabutylammonium iodide (TBAI)-doped polyvinyl alcohol–polyvinylpyrrolidone (PVA-PVP) blend polymer electrolytes are prepared, and their conductivity and dielectric properties were studied. Reduced graphene oxide (r-GO) is synthesized by a one-pot synthesis method and confirmed using Raman spectroscopy for counter electrode material in dye-sensitized solar cell (DSSC) and supercapacitor electrodes. The DSSC having 4% Ag-TiO₂–based photoanode showed the highest efficiency of 1.06% (among r-GO counter electrodes) and 2.37% (among platinum counter electrodes). The supercapacitor before integration and after integration exhibits specific capacitance of 1.72 Fg⁻¹ and 1.327 Fg⁻¹, respectively.

Graphical Abstract

     

Kinetics and mechanism of oxidation of thiocarbohydrazide in the free state and in its metal complex and thiocarbohydrazone by chloramine-T and dichloramine-T

Kinetics of oxidation of thiocarbohydrazide (TCH) in the free state and as its metal complex, and as a hydrazone by chloramine-T (CAT) in aqueous HClO₄ medium, and by dichloramine-T (DCT) in 1:1 (v/v) water-methanol medium in the presence of HClO₄ have been studied. Rates of oxidation of TCH in the free state and in metal complex by CAT were determined. The rate law for the oxidation of TCH at high [H⁺ ] and for complex oxidations were identical to that for CAT oxidations. The conversion of TCH into its hydrazone changed the order in [H⁺] from a positive to a negative value, probably signalling the change of reaction site. The rate law for oxidation under these conditions was determined. Addition of the reduced product of the oxidants had no effect on the rate of oxidations. Variation in ionic strength of the medium had little positive effect, while decrease in dielectric constant of the medium decreased the rate in both the oxidations. Oxidation processes generally follow a Michaelis-Menten type of mechanism. Constants of the rate limiting steps have been calculated at different temperatures and these constants have been used to calculate the activation parameters from the Arrhenius plots. The proposed mechanisms are supported by investigations with HOC1 under identical reaction conditions. Metal complexation of the substrate decreased the reactivity, while conversion of TCH into its hydrazone changed the rate dependence on [H⁺].     

Oxidation Of Di-Peptides With Mn(III): Synthesis, Characterization And Mechanistic Study

Synthesis and characterization of the dipeptides(DP) namely Glycyl-Proline (Gly-Pro), Alanyl-Proline (Ala-Pro) and Valyl-Proline (Val-Pro), were made. Kinetics of oxidation of these DP by Mn(III) have been studied in the presence of sulfate ions in acidic medium at 26C. The reaction was followed spectrophotometrically at _max = 500 nm. A first order dependence of rate on both Mn(III) and DP was observed. The rate is independent of the concentration of reduction product, Mn(II) and hydrogen ions. Effects of varying dielectric constant of the medium and addition of anions such as sulfate, chloride and perchlorate were studied. Activation parameters have been evaluated using Arrhenius and Eyring plots. The oxidation products were isolated and characterized. A mechanism involving the reaction of DP with Mn(III) in the rate limiting step is suggested.     

N,N′-dichloro-p-nitrobenzenesulfonamide (dichloramine-N) as a new oxidimetric reagent: Synthesis and analytical application

A new oxidimetric reagent, dichloramine-N (N,N′-dichloro-p-nitrobenzenesulfonamide; DCN) has been synthesized and its structure elucidated from the spectral data and elemental analyses. The ultraviolet, infrared, nuclear magnetic resonance, and mass spectral data have been presented. Analytical applications of DCN as a potential redox titrant in the determination of diverse reductants such as ascorbic acid, methionine, sulfite, arsenite, glutathione, and indigocarmine have been described.