Ultrasonic, DFT and FT-IR studies on hydrogen bonding interactions in aqueous solutions of diethylene glycol

Selection of bionic Co-former improves the dissolution of Neohesperidin via Co-amorphous solid dispersion with Naringin

The co-amorphous solid dispersion (c-ASD) is a useful method to enhance water solubility of poorly soluble drugs. The objective of this study was to improve the dissolution of Neohesperidin (NE) via binary c-ASD which, to the best of our knowledge, has not yet been reported. Since NE and Naringin (NA) co-exist abundantly in Chinese herbal medicine Fructus Aurantii Immaturus, it was hypothesised that NA served as a co-former of NE-NA c-ASD to improve the dissolution profile of NE. Hence, NA was selected to prepare c-ASD with NE at a weight ratio of 4:10, 10:10, 10:4 by lyophilisation. They were characterised according to thermal properties, molecular interactions, dissolution properties and physical stability. We found that the 10:10 ratio was the most potent in enhancing the dissolution behaviour of NE; whereby NE and NA are highly synchronous in pair-wise solvation process. A molecular mixture was achieved through the intermolecular H-bond and pi-pi stacking force formed between NE and NA and was stable for 7 -months. We concluded that the NE-NA co-amorphous binary system is a promising strategy to improve the dissolution behaviour and stabilise the amorphous state of NE. Bionic co-former selection may be an innovative and effective way to accurately determine the appropriate co-former of poorly water soluble substances.

Study of Thermodynamic and Acoustic Properties of Niacin in Aqueous Hexylene Glycol and Propylene Glycol at Different Temperatures

The densities and speed of sound for liquid mixtures containing vitamin B₃ (niacin) at 0.01, 0.03, and 0.05 mol·kg^-1 concentrations in aqueous propylene glycol and hexylene glycol at the variation of temperatures from 293.15 to 308.15 K have been measured using an Anton Paar DSA 5000 M. From volumetric experimental data, apparent molar volume (V _ϕ), partial molar volume (V _ϕ ⁰), and partial molar volume of transfer (ΔV _ϕ ⁰) are calculated along with the apparent molar isentropic compression (K _ϕ, S ), partial molar isentropic compression (K _ϕ, S ⁰), and partial molar isentropic compression of transfer (ΔK _ϕ ⁰) using experimental acoustic data. The positive volumetric data (i.e., apparent molar volume and partial molar volume) indicates strong solute-solvent interactions inside the mixture. Along with these values, the empirical constants a, b, and c with the pair and triplet coefficients (V _AB, V _ABB, K _AB, K _ABB) are also calculated.

Hydrophobics of C n TAB in an aqueous DMSO-BSA nanoemulsion for the monodispersion of flavonoids

Herein, philicphobic interactions between flavonoids (quercetin, apigenin, and naringenin) and bovine serum albumin (BSA) were analyzed using physicochemical properties obtained at T = 298.15, 303.15, 308.15 K and 0.1 MPa, from 0.01 to 0.10 mol kg-1 of alkyl trimethyl ammonium bromide (C n TAB : DTAB, C n = 12; TDTAB, C n = 14; HDTAB, C n = 16). The flavonoids with cationic surfactants strongly interacted with BSA, as illustrated by the physicochemical parameters (PCPs), refractive index (n D), Walden product, pH, electrostatic potential and molar conductance (Λ m). Viscosity (η), density (ρ), η D, sound velocity (u) and specific conductance (k) data were used to calculate the relative viscosity (η r), viscous relaxation time (τ), Walden product, entropy (ΔS), enthalpy (ΔH), Gibbs free energy (ΔG), heat capacity (Δq) limiting dielectric constant (ε ∞), speed of light (C), acoustic impedance (Z) and molar refraction (R). These PCPs have quantitatively predicted the hydrophilic and hydrophobic (philicphobic) interactions developed are on increasing the alkyl chain (AC) of C n TAB. These interactions assist a monodispersion of the flavonoids, and a similar mechanism could equally be applicable to monodisperse the antioxidants in the aqueous nanoemulsions. Their philicphobic stoichiometry weakened the cohesive forces (CF) when the shear stress was increased, and enhanced surface activities were achieved that facilitated the flavonoids to interact with BSA due to intermolecular forces (IMF) to develop a stable nanoemulsion; Upon increasing the C n TAB concentrations, the n D value increases since the polarizability increases with stronger shear stress due to van der Waal forces and electrostatic interactions to achieve better flavonoid-BSA linkages.

Quantitative structure-activity relationship analysis of substituted arylazo pyridone dyes in photocatalytic system: Experimental and theoretical study

A series of arylazo pyridone dyes was synthesized by changing the type of the substituent group in the diazo moiety, ranging from strong electron-donating to strong electron-withdrawing groups. The structural and electronic properties of the investigated dyes was calculated at the M062X/6-31+G(d,p) level of theory. The observed good linear correlations between atomic charges and Hammett σp constants provided a basis to discuss the transmission of electronic substituent effects through a dye framework. The reactivity of synthesized dyes was tested through their decolorization efficiency in TiO2 photocatalytic system (Degussa P-25). Quantitative structure-activity relationship analysis revealed a strong correlation between reactivity of investigated dyes and Hammett substituent constants. The reaction was facilitated by electron-withdrawing groups, and retarded by electron-donating ones. Quantum mechanical calculations was used in order to describe the mechanism of the photocatalytic oxidation reactions of investigated dyes and interpret their reactivities within the framework of the Density Functional Theory (DFT). According to DFT based reactivity descriptors, i.e. Fukui functions and local softness, the active site moves from azo nitrogen atom linked to benzene ring to pyridone carbon atom linked to azo bond, going from dyes with electron-donating groups to dyes with electron-withdrawing groups.