ABSTRACT. The objective of this work is to study the release of p-anisidine by the hydrolysis of synthesized Schiff bases N-vinylbenzylidene-p-anisidine (Im) as a monomer and its copolymers (Cp1, Cp2) with N,N-dimethylacrylamide (DMA). The hydrolysis behavior and kinetics are investigated in homogeneous media composed of ethanol/water (80% v/v) at 37 °C and at pH range of 4.0-10.0. The variation of the concentration over time is measured in thermostatically cells using UV-Vis spectroscopy. The results showed that the imine function hydrolysis obeyed to the first order for all compounds; the experimental kinetic constants are determined and the pH–rate diagram profile is established. It is noticed that the hydrolysis of imine function is extremely dependent on its carrier and the pH medium. KEY WORDS: p-Anisidine, Copolymer, Schiff base, Hydrolysis, pH–rate diagram, Controlled release Bull. Chem. Soc. Ethiop. 2023, 37(3), 745-755. DOI: https://dx.doi.org/10.4314/bcse.v37i3.16

The aim of the present study was the preparation of 2-aminobenzothiazole- loaded microspheres based on cellulose derivatives for controlled and prolonged release. Micro-encapsulation by the simple emulsion (O/W) solvent evaporation method was performed to prepare these formulations using two cellulose derivatives as matrices: ethyl cellulose (EC) and cellulose acetate butyrate (CAB). Optimization of the experimental parameters, such as the polymer/ solvent ratio, the matrix type, stirring speed and the number of blades, was performed to obtain a high encapsulation efficiency of the drug. The effect of the selected parameters on microsphere characteristics, as well as the release rate was investigated. SEM images show that the obtained microparticles were spherical in shape. The effective entrapment of 2-amino-benzothiazole (2-ABZT) in the microspheres was confirmed by FTIR spectroscopy and XRD diffraction analysis. The encapsulation efficiency was improved when the polymer concentration increased reaching 89 %. Microspheres in the size range of 61?278 ?m with EC and close to 113 ?m with CAB were obtained by varying the process conditions. The in vitro release kinetics of the cation of 2-ABZT were established at 37 ?C in simulated gastric medium pH 1.2 and the obtained data were analyzed according to the Fick law. The results showed that the surface morphology and encapsulation efficiency of the microspheres depended strongly on the polymer/solvent ratio and the release rate could be controlled by adjusting the process conditions.

New dosage forms able to control drug release in the gastro-intestinal media have been prepared and investigated in this paper. Two different type of medicinal agent bonding (MA), in our case Benzocaine (Bz), were chosen in order to examine drug release. i) MA attached to ethylenic monomer (m,p-vinylbenzaldehyde), condensation reaction. ii) The copolymer carrier (Cp) is obtained by copolymerizing this monomer. These two carriers were well characterized by microanalysis, FTIR, DSC (Tg) and GPC (Ip) and the two fraction α and β were calculated from elemental analyses of Cp. The results showed good polydispersity and low average molecular weight. MA linked to an organic product by the azomethine function (C=N), hydrolytically sensitive, allowed controlled release of Bz, from the monomer carrier and from the bending Schiff bases groups. Theoretical and experimental analyses of controlled release of Bz kinetics from monomer and copolymer carriers were conducted for the case of contact with synthetic gastro-intestinal fluids at various pH (1,2; 6,0 and 8,0) at 37°C. The process was found to be controlled by the nature of media (heterogeneous), which involved the preliminary hydrolysis, and the drug (Bz) diffusing out of structure of copolymer (Cp) to the external aqueous media. The results obtained on the rate of delivery showed a clear difference between pH = 1,2 and pH = 6,0 and 8,0 based on: i) The cation of p-aminoniumbenzoic acid (PABAH+) release at pH = 1,2 ii) Bz release at pH = 6,0 and 8,0

The grafting of drugs on macromolecular supports allows the modulation of the pharmaco-kinetics of the drug for a better spread its activities over time. For this, we were synthesized the procaine as monomer support. The imine was synthesized by radical copolymerization, in presence of AIBN, with 2-N-vinylpyrrolidone.The incorporation rates were determined by microanalysis. The procaine (pr) released by hydrolysis of the monomer Im and its copolymer Cp was followed by UV spectrometry in artificially reconstituted environments simulated as gastro-intestinal medium (pH=1.2; 6.0 and 8.0) in homogeneous medium hydroethanolic 33% (volume of ethanol) and heterogeneous medium by dispersing the copolymer (Cp) in aqueous pH. The results show that the hydrolysis of the imines' function unit is apparent order in a homogeneous medium, whereas it is largely controlled by the diffusion model according to the Fick's law heterogeneous medium. The comparison of these two studies showed a delayed effect substantially larger in the heterogeneous medium than in the homogeneous medium because the percentage of active ingredient (p.a) released is significantly lower in the homogeneous medium.

The present paper provides details of the preparation of polymeric tablets and microspheres based on piroxicam as a therapeutic active agent and the drug release study from these formulations. Tablets composed of ethylcellulose, Eudragit® or mixtures of Eudragit® and synthesised poly(oxepan-2-one) were prepared and tested. The effect of the matrix on the drug release at 37°C was studied. The drug-loaded microparticles were prepared using solvent evaporation microencapsulation. These systems were characterised by SEM and FTIR spectroscopy and the size and size distribution were also determined. The results demonstrated that the drug release could be modified by means of these formulations. Finally, piroxicam dissolution rate constants were calculated from Higuchi’s release model.

Four secondary amides have been prepared by the Schotten-Baumann reaction between model anilines (Pa1-4: p-XC6H4NH2: X1: H; X2:CH3; X3:COCH3; X4: CN) and methacryloyl chloride using aqueous THF/NaOH mixture at 0°C. MS1, MS2 and MS4 liquid monomers are obtained whereas MS3 is a solid monomer. Mass radical copolymerization of the different monomers (MS1-4) with N-vinyl-2-pyrrolidone yields to the corresponding four copolymers. All the monomers have been characterized by IR, 1H and 13C NMR. The (CP1-4) have been characterized by IR spectra, microanalysis, Tg ° and Mv. The kinetics of aniline delivery to give anilinium cations (PaH+)1-4 from solid MS3 and CP1-4 dispersed in water (pH= 1.2, 37°C) showed that aniline delivery from the different supports is controlled by a diffusion process and not the rate of amide hydrolysis. The amount (%) of free anilinium cations is inversely proportional to the molecular weight of polymeric supports. Accordingly, the monomer MS3 gave the largest amount of free anilinium cations (PaH+) 1-4

 The aim of the current study is to prepare controlled release formulations composed from 3-aminopyridine. This active molecule is modified by chemical grafting on monomer based on (m,p)-vinylbenzaldehyde and then copolymerized with dimethylacrylamide to get hydrosoluble systems. In these systems, the active agent is spaced out from copolymer chain by phenyl group. The obtained supports i.e. monomer and copolymers are characterized by FTIR, NMR (1H, 13C) and other techniques. The drug release from these formulations is studied and the values of release constants demonstrated that 3-aminopyridine release can be modified using these systems. Also, the effect of pH release media on the drug release is discussed.

2-Amino-thiazole reacts with methacryloyl or acryloyl chloride to give amides which are polymerized. Hydrolyses of polymers have been studied with and without enzymatic catalysis in a synthetic gastric liquid.