STUDIA CHEMIA - Issue no.2 / 2023 - Table of contents

This study presents the theoretical and practical aspects of the new technique, namely Mat Glass - Thin Layer Chromatography (MG-TLC) and application of invasion model. Our research is focused on the development and clarification of the phenomena that occur in thin layer separation technique: process flow, spreading on mat glass surface, impregnation of porous layers and the improvement of the quality of thin layer chromatographic separations by overlapping some mat glass plates, over the chromatographic plates. The experiments have confirmed the possibility that the movement of the invasive type displacement, which occurs on rough surface will influence favorably the chromatographic separation processes. Good results have been obtained in separation of the lipophilic dyes and the hydrophilic dyes by small adjustments, e.g., height of the free zone of porous layer h, or the roughness of glass plates. The results obtained demonstrate that this method can be successfully used in thin layer chromatography technique being easy to apply and inexpensive compared with other methods derived from chromatography.

Keywords: Capillarity, Invasive model, Mat Glass, Thin Layer Chromatography

Corrosion inhibitory effect of myricetin in alcoholic solutions has been studied by potentiodynamic polarization. Inhibitory efficiencies of 70%, 61%, 69% and 79% have been obtained for stainless steel, carbon steel, aluminum alloy, and aluminum, respectively. Adsorption Gibbs free energy, determined using Langmuir adsorption isotherms, has revealed that interactions between metal atoms and myricetin adsorbed molecules have chemical character. Moreover, quantum chemistry calculations have shown that myricetin, due to its molecular structure (O heteroatoms with lone pair electrons and π electrons from aromatic rings) has the ability to form an adsorption layer on the metal surface that inhibits the diffusion of molecules and ions participating in the global corrosion process.

Keywords: myricetin, corrosion inhibitor, potentiodynamic polarization, adsorption isotherm, food industry

Due to the ions in its structure, that have a variety of important roles in bone metabolism, forsterite (FS, Mg2SiO4) is a promising candidate for orthopedic and dental applications. This paper studies forsterite synthesized through two methods, namely sol-gel (FSsg) and precipitation (FSpp), based on a thermodynamic approach. Therefore, the precursor gel and precipitate were analyzed through thermal gravimetric (TG), differential thermal gravimetric (DTG) and differential scanning calorimetric (DSC) analysis. The FSsg and FSpp powders were characterized by X-ray powder diffraction (XRD) and atomic force microscopy (AFM). XRD reveals that the synthesized forsterite is of high crystallinity. As is evidenced by AFM, the average size of the nanoparticles is around 40 nm for FSsg and 30 nm for FSpp. The potential reaction mechanisms for the two synthesis routes were also established

Keywords: forsterite, sol-gel, precipitation method, synthesis mechanisms, thermodynamic approach

The catalytic performance of various biocatalysts obtained by the adsorption of lipase B from Candida antarctica (CaL-B) onto and into polyvinyl alcohol (PVA) and polylactic acid (PLA) nanofibers were tested in the kinetic resolution of racemic 1-benzo[b]thiophen-2-yl-ethanol by transesterification. Best performance regarding reaction velocity and selectivity was registered for CaL-B adsorbed onto PLA nanofibers. The high operational stability of this biocatalyst was confirmed in recycling experiments, after 5 cycles the biocatalyst maintained 86.6% of its initial activity. The optimal process parameters in continuous flow mode also were established.

Keywords: CaL-B, nanofibers, polyvinyl alcohol, polylactic acid, EKR

In this study, polylactic acid PLA was melt blended with bis(2-(2-butoxyethoxy)ethyl) adipate, tributyl citrate and/or sorbitan monooleate. The thermo-mechanical analysis of plasticized PLA highlighted an improvement in its behavior. Thus, the plasticization of PLA with the tested esters favored the lowering of its vitrification temperature and the bending resistance of the tested materials at room temperature varied in an area of interest for all the tested plasticizers. No significant difference was noted between the maximum flexural strengths and the elongation at deformation recorded at 25°C and those at 4°C for the three recipes. Also, the weight loss of PLA recipes in contact with water decreases in the presence of hydrophobic plasticizers.

Keywords: PLA, bioplasticizer, DSC analyses, vitrification temperature, flexural strength, water absorption

The aim of this study is to identify and test new natural photosensitizers used in antibacterial photodynamic therapy due to the antimicrobial and antioxidant effect they present. The experimental study was conducted on rats in which periodontal disease was induced. As treatment, photodynamic therapy was used in the presence of new developed natural photosensitizers based on oregano essential oil and curcumin extract. Malondialdehyde as well as low and oxidized glutathione levels were measured by spectrophotometry to assess oxidative stress in treated groups of rats. New photosensitizers were characterized by modern testing methods, using FTIR infrared spectroscopy, gas chromatography-mass spectrometry and UV-Vis analysis. The results obtained suggest that the prooxidant effect is mainly due to exposure to photodynamic therapy (irradiation) and leads to the antibacterial therapeutic effect that is maintained even when applying gels with antioxidant agents.

Keywords: Oxidative stress, essential oils, photodynamic therapy

The use of toothpastes is the best way to combat enamel loss and degradation. When they also contain hydroxyapatite nanoparticles, HAP NPs, the tooth enamel can be restored by remineralization. In this study, we developed two types of toothpastes, one with nano sized HAP, noted P1, and the other with nano multi-substituted hydroxyapatite (ms-HAP, HAP-Mg-Zn-Si), noted P2, which were used to treat the artificially demineralized teeth enamel surface. The remineralization efficacy of the two toothpastes was determined on artificially created enamel lesions by suspending healthy enamel slices in demineralizing solution, made of orthophosphoric acid of 37.5% for 90 s. For this purpose, six extracted third molars were collected and twenty-four enamel slices were cut and arbitrarily allocated to the four groups, namely n = 6 enamel slices for each group. One group served as untreated (natural) enamel control, and another group comprised demineralized enamel and two test groups, firstly demineralized, and then, they were treated with toothpastes P1 and P2, respectively, each of them for ten days, and finally were noted P1 and P2 enamel surfaces. The surface morphology and roughness of all enamel specimens were studied by atomic force microscopy (AFM) before and after applying the treatment with the toothpastes. The toothpastes effect was evidenced by the average diameter of ceramic nanoparticles deposited within the superficial smooth layer on enamel surface having, at the completion of 10 days treatment, a low surface roughness close to that of natural enamel. This in vitro comparative study demonstrated that both toothpastes P1 and P2 can promote surface enamel repair by remineralization and the formation of a protective hydroxyapatite coating layer on the enamel surface treated with these toothpastes.

Keywords: hydroxyapatite, multi-substituted hydroxyapatite, toothpastes, enamel remineralization, morphology, surface roughness, AFM

This study targets to prepare a metformin hydrochloride delivery system through the preparation and evaluation of 2-hydroxyl ethyl methacrylate (HEMA) based hydrogels. The current study explores the effect of photoinitiator (Irgacure 184, Irgacure 651), PEG-DA derivatives, 4-Acryloyl morpholine (4-AcM), and gelatine obtained by UV photopolymerization of HEMA hydrogels. Photopolymerization technique which was under UV irradiation was implemented at 365 nm and 300 s. Two different photoinitiators [2,2-Dimethoxy-2-phenyl-acetophenone (Irgacure 651)], [1-Hydroxycyclohexyl phenyl ketone (Irgacure 184)] were used to obtain the impact of photoinitiators on the metformin HCl release behavior of samples. In addition, PEG-DA Mn=258, PEG-DA Mn=700, 4-AcM, and gelatine were used to improve HEMA hydrogels. The prepared hydrogels have been characterized using Fourier transform infrared spectroscopy (FT-IR) and a digital microscope. The behaviors of hydrogels were specified by exploring swelling and release profiles in different medias. In-vitro metformin HCl release analyses have been done at pH 1.2, 6.8, and 7.4. UV-Vis spectrophotometer at 244 nm for releasing studies was used. The release results of hydrogels synthesized with Irgacure 651 demonstrated the majority quantity of the drug. Furthermore, the release amounts were higher in pH 1.2 than at mentioned pH medias before

Keywords: Photopolymerization, photoinitiators, hydrogels, release system, HEMA, metformin HCl

Majorana hortensis is widely distributed in the Mediterranean area with different medicinal potentials. In the current study, 1 mmol/L AgNO3 and 4% hydro-methanol leaf extract of M. hortensis at neutral pH (7.0) were successfully combined to create green Majorana hortensis – silver nanoparticles (MHE-AgNPs) after applying the reaction to sunlight for 30 minutes. MHE-AgNPs were characterized using atomic force microscope (AFM), high resolution-scanning electron microscope (HR-SEM) and energy-dispersive X-Ray (EDX). The size range of the MHE-AgNPs was between 50 and 95 nm, and they had a spherical form with smooth surface. With an IC50 of 36.39 μg/mL, MHE-AgNPs exhibited a 2,2′-diphenylpicrylhydrazyl (DPPH) scavenging ability in a concentration-dependent manner. The MTT colorimetric technique was used to determine the MHE-AgNPs cytotoxicity against A549 cell line. The green synthesis of MHE-AgNPs markedly improved the cytotoxic action of MHE-AgNPs against A549 cells. The multiparametric cytotoxicity assay using High-content Screening was employed. MHE-AgNPs was significantly reduced the cell viability, increased the membrane permeability, reduction in mitochondrial potential and stimulating the release of cytochrome c indicating the capability of MHE-AgNPs in killing A549 cells.

Keywords: Majorana hortensis, AgNPs, MTT Assay, Antioxidant, A549

Starting from commercially available 4-phenylbutanoic acids, a series of novel sulfamides were synthesized and investigated for their inhibition properties on the human carbonic anhydrase I and II (hCA I and II), acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes. SAR was also evaluated with molecular docking study. These new compounds were tested against hCA I and hCA II, BChE, and AChE. The majority of the synthetic compounds were more effective against AChE than tacrine, a common inhibitor. Additionally, tacrine was not the only synthetic substance that was more effective against BChE. The obtained results revealed that N,N-dimethyl-[3-(2,4-dimethoxyphenyl)propyl]sulfamide 25, with Ki of 94.22±42.37 nM against AChE and Ki of 230.91±46.22 nM against BChE, was the most potent compound against cholinesterase enzymes. These recently created substances were tested for their ability to inhibit hCA I and II isoforms. In comparison to the conventional inhibitor acetazolamide, the majority of produced sulfamide derivatives 25–29 also inhibited these investigated isoforms. In particular, sulfamide derivatives 25-29 with substituents N,N-dimethyl-[3-(3,5-dimethoxyphenyl)propyl]sulfamide 26 and N,N-dimethyl-[3-(3,4-dimethoxyphenyl)propyl]sulfamide 27 emerged as the most potent hCA inhibitors./p>

Keywords: Synthesis; 3-phenylbutylamine; sulfamide; biological effects; molecular docking

An experimental study based on the pulse-response technique was performed in a Sulzer packed-bed column in order to establish the residence time distribution for four different liquid flow rates, namely 200, 400, 600 and 800 L/h and five different gas flow rates of 0, 5, 10, 15, 20 m3/h. Depending on the phase flow rate, comparisons with the axial distribution and the N-tanks–in–series models rendered good similarities. Furthermore, the axial dispersion coefficient and its dependence on the superficial velocity of the liquid phase, for various gas flow rates and also, on the F factor of the gas phase, for various liquid flow rates, have been established.

Keywords: Sulzer column, axial dispersion, residence time distribution, dispersion model, cellular model

The present article presents the influence of some ingredients used for the preparation of homemade mayonnaise like thickening agents (potato versus cornstarch) and two types of oil (olive versus sunflower) on the viscosity and rheological behavior. The results show the increase of the viscosity when cornstarch or potato, and olive oil instead of sunflower oil are used for the preparation of the homemade mayonnaise. The rheological parameters, material constancy, K, and flow index, n, were determined by Power law model. They show the positive influence of thickening agents on stability of homemade mayonnaise, increasing the viscosities comparative to the sample without agents. The values of index flow, n between 0.3249 and 0.6482, lower than 1, confirms for all analyzed samples the shear-thinning (pseudoplastic) behavior (R2 > 0.99).

Keywords: cornstarch, potato, olive oil, sunflower oil, viscosity, shear-thinning

Although batteries containing heavy metals and toxic chemicals, including lead and cadmium, are supposed to be selectively collected, they still end up on municipal waste processing platforms. The separation of cadmium and lead ions is a problem that is circumscribed to the development of urban mining. This paper presents the recuperative separation of lead and cadmium ions by a composite membrane based on chitosan (Chi), sulfonated ethylene–propylene–diene terpolymer (sEPDM), and polypropylene hollow fiber (PPyHF). The performances of selected membranes are presented comparatively, both from the point of view of the morpho-structural characteristics, as well as of the performances in the target ion separation process, with recently reported results obtained with composite membranes based on chitosan.

Keywords: membranes, composite membranes, chitosan, sEPDM, hollow fiber, cadmium separation, lead separation.