STUDIA CHEMIA - Issue no.3 / 2024 - Table of contents

Three decavanadate (V10O28)6- containing compounds were used to test their catalytic activity in the sulfoxidation reaction of diphenyl sulfide using environmentally friendly conditions (low temperature, non-toxic solvent). The compounds of interest for our study, (NH4)2(H2en)2{V10O28}·4H2O, (H2en)3{V10O28}·6H2O and {Li2(H2O)10}(V10O28)(NH4)4, were evaluated, showing good activity in sulfoxidation reaction and leading to complete conversion of the sulfide even after three runs. The tetraammonium decaaqualithium decavanadate, with the formula {Li2(H2O)10}(V10O28)(NH4)4 was obtained through a modified literature method and its structure re-determined and investigated, giving similar results as previously described and confirming the structure of the used material.

Keywords: decavanadate derivatives, catalytic sulfoxidation, green and sustainable chemistry

The most efficient method to produce hydrogen is by electrolysis of water, and scientist’s current research is focused on developing inexpensive catalysts for this process. The article aims to study a carbon material (CM) obtained from shungite raw materials as electrocatalyst support in hydrogen evolution reaction (HER). The obtained activated CM has a multi-layered lamellar morphology with a specific surface area 356.40 m2/g. Electrocatalytical properties of the activated carbon material are the following: overpotential (η) at 10 mА/cm2 of 0.515 V vs. RHE with a Tafel slope of 172.5 mV/dec and good stability in acidic media. The obtained results show that activated CM from shungite raw material can be used as an electrocatalyst for obtaining hydrogen.

Keywords: hydrogen, carbon material, shungite, electrocatalyst, hydrogen evolution reaction

The pleiotropic effects of Lamium species are extensively utilized for treating urinary bladder injuries and infections and addressing blood hypertension or liver toxicities. Despite widespread Lamium consumption in animals and humans, its impact on brain biochemical parameters remains unexplored. In our study, we demonstrated the regenerative effect of L. album L. in a rat model of restraint stress, commonly employed to investigate neuropsychological stress. Following extract administration, there was a reduction in stress hormones (corticosterone, adrenaline), inflammation (TNFα), and oxidative stress. These neuroregenerative effects may be attributed to Lamium’s phytochemical composition, particularly its iridoids and luteolin content, which appear to mimic the action of glucagon-like peptide 1 (GLP-1). These findings suggest the potential use of L. album as a neuroregenerative adjuvant.

Keywords: iridoids, Lamium album, GLP1

Understanding biochemical mechanisms involved in acute myocardial infarction is crucial for future treatments. The current study analyzed the oxidative stress markers in patients with percutaneously treated acute ST-elevation myocardial infarction and correlated the findings to coronary anatomy and Syntax II score (SS-II). Blood samples were obtained before coronary re-perfusion, after one and 24 hours. The following markers of oxidative stress were determined: malondialdehyde (MDA), reduced glutathione to oxidized glutathione ratio (GSH/GSSG) and total antioxidant capacity (TAC). Thirty-seven consecutive patients were included. The patients were divided into groups according to the infarct-related artery: left anterior descending artery (LAD- group) vs non-LAD group, and according to the calculated SS-II, SS-II≤ 34 vs. SS-II>34. MDA concentration and GSH/GSSG ratio showed non-significant differences between LAD vs non-LAD groups at all time frames. Patients with LAD as the infarct-related artery had a significantly lower TAC 24 hours after re-perfusion: 30.22 ± 9.78 % inhibition in the LAD group vs. 35.7 ± 5.78 % inhibition in the non-LAD group, p=0.013. The oxidative stress markers were similar between patients regardless of the SS-II value, and neither the culprit vessel nor the SS-II significantly influenced the dynamics of oxidative stress markers.

Keywords: oxidative stress, myocardial infarction, Syntax Score

Cataract, the leading cause of blindness worldwide, is characterized by the presence of a cloudy area in the eye lens resulting in a loss of transparency. A number of mechanisms contribute to the longevity and transparency of the human lens, a reducing and oxygen deficient environment, the presence of UV-filters, and most importantly a unique supramolecular organization of its structural proteins, the α-, β- and γ-crystallins. With advancing age, progressively, or due to some mutations, this fragile equilibrium can be perturbed, causing γ-crystallin insolubilization, misfolding, fragmentation and aggregation. In this study, we performed a comparative molecular docking analysis of several experimentally investigated molecules of natural origin, that might protect γ-crystallins from destabilization and aggregation. Our specific protein targets are wild-type human γD-crystallin, and its mutant P23T γD-crystallin, associated with congenital cataract. Thirteen phytochemicals were investigated as potential inhibitors of γD-crystallin aggregation, and we compared their binding energies with those of lanosterol, an ingredient present in over-the-counter eye products, to prevent cataracts. We performed a detailed comparative molecular docking analysis and we found that the binding energies of lanosterol outcompete those of all the other investigated potential natural inhibitors.

Keywords: γ-crystallins, aggregation inhibitors, molecular docking

Knema elegans Warb. is an evergreen tree belonging to the Myristicaceae family, primarily native to Southeast Asia. This study examined the chemical composition and assessed the antioxidant and anti-acetylcholinesterase properties of the essential oil from the leaves of K. elegans in Vietnam. Gas chromatography/mass spectrometry analysis revealed the main compounds in the essential oil, including bicyclogermacrene (23.8%), germacrene D (17.1%), β-caryophyllene (15.4%), δ-cadinene (8.2%), and α-cadinol (7.9%). Antioxidant activity was assessed using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) methods, with half-maximum inhibitory concentration (IC50) values of 93.11 ± 1.95 μg/mL and 114.95 ± 2.41 μg/mL, respectively, indicating moderate antioxidant potential. Additionally, the essential oil exhibited significant anti-acetylcholinesterase effects, with an IC50 value of 87.44 ± 2.52 μg/mL. These findings highlight the biological significance of K. elegans essential oil and suggest avenues for further investigation, particularly in elucidating its mechanisms of action in antioxidant and anti-acetylcholinesterase activities. Notably, this research represents the first comprehensive exploration of the chemical composition, antioxidant activity, and acetylcholinesterase inhibition effects of K. elegans essential oil from its leaves.

Keywords: Knema elegans, sesquiterpenes, Myristicaceae, DPPH, ABTS, AChE

The study investigates the influence of various catalysts (Ni/TiO2, Co/TiO2, and Zeolite) on the hydrothermal liquefaction of microalgae and explores the effect of co-solvents (acetone, methanol, and toluene) on biocrude yield from different microalgae three species namely Nannochloropsis oculata, Chlorella vulgaris, and Spirulina maxima. Catalyst characterization using FE-SEM, XRD, and BET analysis revealed distinct properties. Under Co-TiO2, Nannochloropsis oculata and Chlorella vulgaris yield 56.21% and 57.6% biocrude at 5% loading; Spirulina maxima yields 45.3% at 2.5% loading. With Ni-TiO2, Nannochloropsis oculata yields 52.4% at 2.5% loading; Chlorella vulgaris yields 44.7% at 5%; Spirulina maxima yields 44% at 2.5% loading. Zeolite yields: Spirulina maxima and Chlorella vulgaris yield 53.8% and 52.1% at 2.5%; Nannochloropsis oculata yields 48.3% at 7.5% loading. Co-solvent addition significantly boosts biocrude yield; methanol and toluene yield 53.7% and 49.2% for Chlorella vulgaris and Spirulina maxima, respectively, while acetone yields 57.6% for Nannochloropsis oculata. Different solvents extract diverse functional groups such as alkanes, halides, aromatics, and aldehydes which has wide industrial applications.

Keywords: Biocrude, Catalysts, Co-Solvents, Hydrothermal Liquefaction, Microalgae

Acid tars, a waste unique to the oil processing industry, pose a significant toxicity risk. These by-products originate from refining certain petroleum fractions, such as oil and paraffin, and are commonly found in the waste streams of crude oil processing. In Romania, particularly in the post-war period, acid tars were predominantly managed through storage. Although advancements in catalytic processes have considerably reduced the generation of acid tars in the Romanian refining industry, an efficient treatment method is still required to address the existing acid tars lagoons. The present research refers to a case study carried out on a laboratory scale for the physico-chemical stabilization/encapsulation of acid tars from a lagoon belonging to a refinery in Prahova-Romania county. The experimental program aimed at formulating and applying optimal stabilization recipes for acid tar from the selected lagoon was conducted to reduce the total hydrocarbon and toxic metal content, in compliance with Order No. 95 of 12.02.2005 from Romanian legislation.The leaching data showed that the recipes that stabilize and encapsulate acid tar provide a good immobilization capacity for the five heavy metals (Pb, Cd, Cu, total Cr, Ni) and As, while their releases are dependent on the pH- and varies with the total hydrocarbon content of the treated tar. The laboratory study carried out and presented in this work, as well as the results obtained after performing the leaching test, allow the extrapolation and application of this stabilization - encapsulation procedure on a macro-in situ scale and the remediation of the lagoon where the acid tar was stored.

Keywords: refinery waste, acid tars, lagoon, encapsulation, stabilization, total petroleum hydrocarbons (TPH), heavy metals and As, leaching test

This paper presents a gravimetric method for the quantification of total organic carbon by ignition at 1100°C and carbonates by acid dissolution in rock samples containing coal. Two minerals (CM-1 and CM-2) and a sub-bituminous coal (SBC) were used in the study. The mineralogical characterization of the samples was performed by X-ray diffraction and scanning electron microscopy. This revealed the presence of calcite in samples CM-1 (20.4%) and CM-2 (74.7%), dolomite in CM-2 (0.7%), and graphite in sample SBC (42.6%). To eliminate carbonates, the samples were treated with 4 mol/L HCl, which allowed quantification. Results of the carbonate gravimetric quantification were compared with those obtained with a calcimeter. A significant difference was observed for the sample CM-2 (70.3% versus 63.4% by calcimetry, p-value = 0.0042). For the sample without carbonates, no differences were observed for loss on ignition without and with the acid treatment, so this is not necessary for this type of sample. A morphological study showed no significant surface change after acid treatment, but fracture of iron oxide particles was observed in CM-1 and CM-2 after heat treatment. In this study it was demonstrated that rock mineralogy is essential to correctly analyze organic and inorganic carbon content.

Keywords: total organic carbon, gravimetry, carbonates, coal, mineralogy

The esterification reactions, which lead to esters with a big diversity of uses across numerous industries, is one of the most important reactions in organic synthesis. Within these esterification reactions, a variety of strategies have been used to improve conversion, reaction rate, and equilibrium. This paper investigated the effects of the audio frequency electric fields on the esterification reactions of acetic acid with C4-C8 branched aliphatic alcohols. The aim of these studies was to synthesize a few acetic acid esters in an environmentally and friendly manner utilizing a new method. The only raw materials used were acetic acid, C4–C8 branched aliphatic alcohols and an audio frequency electric field acting as an accelerator. In order to determine the efficacy of the suggested approach, these esters were also synthesized without applying the audio frequency electric field. Analysis using gas chromatography technique revealed that the audio frequency electric field significantly increased esterification yields. The highest yields of ester were obtained for 2-octyl acetate, exhibiting a notable increase in comparison to the synthesis that did not employ the application of an audio frequency electric field as an enhancer of the reaction rate. The proposed new method, as well as the employing of raw materials of natural origin, allows the production of esters in an environmentally friendly manner and with reduced costs. These esters can be used without any restrictions in a variety of industries, including food, pharmaceuticals, and cosmetics.

Keywords: audio frequency electric field, esterification reactions, natural esters, food and pharmaceutical industry, green method

The technological progress and consumerism trend stimulate electric and electronic equipment replacing, inducing the generation of huge amounts of wastes, many of them containing dangerous (but valuable) waste printed circuit boards (WPCBs). A promising technology for their recycling is based on the electrochemically regenerable Br-/Br2 leaching system, for which the raw materials can be produced and recycled by electrochemical ways. In this context, the present work presents our research concerning the feasibility to produce by electrodialysis, on-site, HBr and KOH, which are required for the electro-hydrometallurgical recovery of metals from WPCBs. For this purpose, a four-compartment filter-press electrochemical reactor, divided by two cation and one anion exchange membranes, was used. The obtained results demonstrate that the proposed process can produce, at a current density of 4 kA/m2, target solutions with concentrations over the required value (of 0.5 M), with average current efficiencies over 73% and 82%, and average specific energy consumptions around 40 and 25 kWh/kg for HBr and KOH, respectively. Moreover, several preliminary measurements performed simultaneously with the electrodialysis tests revealed that, by acquiring rigorous temperature data, the concentrations of the target solutions can be easily and rapidly evaluated and monitored on-line using simple electrochemical sensors for pH and conductivity, but more accurate and exhaustive calibration data is required.

Keywords: WPCBs recycling, on-site KOH and HBr electrosynthesis, electrodialysis, filter-press electrochemical reactor, electrochemical concen-trations monitoring

Various food supplements provide antioxidant benefits by neutralizing free radicals, thus preventing diseases associated with oxidative stress. The antioxidant properties of pure icariside II (ICS), icariside II whey protein concentrate complex (ICS-WPC), and surfactant-based icariside II whey protein complexes (S-ICS-WPC) were evaluated. The assessment was conducted using the Briggs-Rauscher oscillating system and the 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radical scavenging assay, with the latter providing a quantitative analysis of antioxidant capacity. The complexation procedure successfully increased the antioxidant activity of ICS. Additionally, the inclusion of various surfactants such as Tween 80 and lecithin in the ICS-WPC complex led to further significant advancements.

Keywords: icariside II, antioxidant activity, whey protein complexes, Briggs-Rauscher oscillating reaction, DPPH· radical scavenging

Plant extracts are becoming an increasingly important trend in phytocosmetic preparations, replacing chemical synthesis products and ensuring the quality of products in line with consumer requirements. Using propanediol as an extraction solvent, this paper characterizes Acmella oleracea extracts obtained by traditional or combined extraction methods. The evaluation of their antioxidant activity and their content of polyphenols and flavonoids served as a basis for their physico-chemical characterization. Based on the best extract of Acmella oleracea, an emulsion was prepared and its stability and homogeneity were preliminary evaluated.

Keywords: Acmella oleracea, antioxidant activity, oxidative stress, propanediol, vegetal extract

The essential oil of Salvia officinalis L. (sage) exhibits versatile biological properties. The high sensitivity of sage essential oil (SEO) to environmental conditions and limited processability represent important hurdles in its use, which, however, can be overcome by microencapsulation. The objective of the current study was to encapsulate sage essential oil into core-shell type microcapsules by complex coacervation technology and to transform it into solid form by freeze-drying. Arabic gum (GA) and three different type A gelatin (G) grades were used to investigate the effect of the gel strength on microcapsule characteristics. The formation of essential oil containing microcapsules during complex coacervation was assessed by optical microscopy while SEM imaging was used to determine the morphology of the freeze-dried forms. Characterization of microcapsules was completed with FT-IR spectroscopy. Encapsulation efficiency was determined by UV-VIS spectrophotometry and the composition of essential oil by GC-MS technique. Results revealed that by the application of selected microencapsulation technology and freeze-drying method high encapsulation efficiency values could be achieved, the gel strength of gelatin has a decisive role in microcapsule particle size and the composition of essential oil is well preserved following the technological process.

Keywords: microencapsulation, complex coacervation, essential oil, Salvia officinalis L.