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Compounds, Volume 4, Issue 1 (March 2024) – 10 articles

Cover Story (view full-size image): Alternatives to petrochemical plastics are gaining commercial interest in various sectors, including biomedicine, the automotive industry, construction, agriculture, single-use items, and food packaging. Polylactic acid is a promising bioplastic with good mechanical properties and thermal processability. To increase biodegradability and reduce its costs, particulate or fibrous fillers can be incorporated into the polymer matrix. One promising composite filler is the potato peel, a highly available and low-economic byproduct. As the properties of composites are mainly influenced by the type, amount, and size of fillers, the effect of particle size on the thermal, mechanical, and barrier properties of the composite must be considered relative to potential food packaging applications. View this paper
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28 pages, 10778 KiB  
Review
Synthesis and Biological Activities of Some Metal Complexes of 2-Thiouracil and Its Derivatives: A Review
by Petja Emilova Marinova and Kristina Dimova Tamahkyarova
Compounds 2024, 4(1), 186-213; https://0-doi-org.brum.beds.ac.uk/10.3390/compounds4010010 - 27 Feb 2024
Cited by 1 | Viewed by 1186
Abstract
The thionamide antithyroid agents were discovered largely through observations carried out by various researchers in the 1940s that found that sulfhydryl-containing substances were goitrogenic in animals. Prof. Edwin B. Astwood started using these drugs to treat hyperthyroidism. In the current paper, we summarize [...] Read more.
The thionamide antithyroid agents were discovered largely through observations carried out by various researchers in the 1940s that found that sulfhydryl-containing substances were goitrogenic in animals. Prof. Edwin B. Astwood started using these drugs to treat hyperthyroidism. In the current paper, we summarize the development background of these agents and the coordination possibility of 2-thiouracil and its derivatives, as well as the biological activities of some of its complexes. Some of them are used as agents for the treatment of tuberculosis, and arthritis, others have bactericidal and fungicidal activity, the third cytotoxic properties, and could be used to treat various types of cancer. Full article
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4 pages, 1744 KiB  
Editorial
Milestones and New Challenges in Compounds
by Juan C. Mejuto
Compounds 2024, 4(1), 182-185; https://0-doi-org.brum.beds.ac.uk/10.3390/compounds4010009 - 21 Feb 2024
Viewed by 595
Abstract
Since 2021, we have been immersed in the challenge of publishing a journal that constitutes a form of communication of scientific achievements in the field of the synthesis and characterization of chemical compounds from a theoretical and experimental point of view [...] Full article
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10 pages, 1114 KiB  
Communication
Extraction of Rare Earth Elements from Chloride Solutions Using Mixtures of P507 and Cyanex 272
by Mikhail A. Afonin, Andrey V. Nechaev, Ilya A. Yakimenko and Vera V. Belova
Compounds 2024, 4(1), 172-181; https://0-doi-org.brum.beds.ac.uk/10.3390/compounds4010008 - 20 Feb 2024
Viewed by 645
Abstract
In this study, the extraction of rare earth elements (REEs) from chloride solutions after leaching REE carbonate concentrate with solutions of the mixtures of P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) and Cyanex 272 (bis(2,4,4-trimethylpentyl)phosphinic acid) (1:1) at various concentrations was experimentally studied. It was [...] Read more.
In this study, the extraction of rare earth elements (REEs) from chloride solutions after leaching REE carbonate concentrate with solutions of the mixtures of P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester) and Cyanex 272 (bis(2,4,4-trimethylpentyl)phosphinic acid) (1:1) at various concentrations was experimentally studied. It was shown that the distribution ratios of all REEs decrease with the increasing concentration of these metals in the initial solution, which is associated with the loading of the organic phase. The most significant improvement in the extraction is observed for the heavy group of rare earth elements. The extractability of REEs increases with the increasing atomic number of the element, as is typical for the extraction of these metals with acidic organophosphorus extractants. The data obtained show that the separation factors of adjacent rare earth elements decrease slightly with the increasing concentration of metals in the initial aqueous solution. Increasing the concentration of the extractant mixture does not have a significant effect on the values of the adjacent REE separation factors. The data obtained on the distribution ratios and separation factors made it possible to propose a flow sheet for the separation of rare earth elements with the production of Y, Ho, Tb and Dy. Full article
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31 pages, 13496 KiB  
Review
Recent Progress and Challenges in the Field of Metal–Organic Framework-Based Membranes for Gas Separation
by Shunsuke Tanaka, Kojiro Fuku, Naoki Ikenaga, Maha Sharaf and Keizo Nakagawa
Compounds 2024, 4(1), 141-171; https://0-doi-org.brum.beds.ac.uk/10.3390/compounds4010007 - 2 Feb 2024
Viewed by 1394
Abstract
Metal–organic frameworks (MOFs) represent the largest class of materials among crystalline porous materials ever developed, and have attracted attention as core materials for separation technology. Their extremely uniform pore aperture and nearly unlimited structural and chemical characteristics have attracted great interest and promise [...] Read more.
Metal–organic frameworks (MOFs) represent the largest class of materials among crystalline porous materials ever developed, and have attracted attention as core materials for separation technology. Their extremely uniform pore aperture and nearly unlimited structural and chemical characteristics have attracted great interest and promise for applying MOFs to adsorptive and membrane-based separations. This paper reviews the recent research into and development of MOF membranes for gas separation. Strategies for polycrystalline membranes and mixed-matrix membranes are discussed, with a focus on separation systems involving hydrocarbon separation, CO2 capture, and H2 purification. Challenges to and opportunities for the industrial deployment of MOF membranes are also discussed, providing guidance for the design and fabrication of future high-performance membranes. The contributions of the underlying mechanism to separation performance and adopted strategies and membrane-processing technologies for breaking the selectivity/permeability trade-off are discussed. Full article
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22 pages, 5007 KiB  
Article
Effect of Particle Size on the Physical Properties of PLA/Potato Peel Composites
by Katharina Miller, Corina L. Reichert, Myriam Loeffler and Markus Schmid
Compounds 2024, 4(1), 119-140; https://0-doi-org.brum.beds.ac.uk/10.3390/compounds4010006 - 1 Feb 2024
Viewed by 1190
Abstract
In recent years, agricultural by-product fillers have been investigated in composites to influence the physical properties of the packaging material, increase biodegradability, and reduce costs. In general, the properties of composites are mainly influenced by the type, amount, and size of fillers. The [...] Read more.
In recent years, agricultural by-product fillers have been investigated in composites to influence the physical properties of the packaging material, increase biodegradability, and reduce costs. In general, the properties of composites are mainly influenced by the type, amount, and size of fillers. The aim of this study was to characterize potato peel particles as a filler in a poly(lactic acid) (PLA) matrix and to determine the effect of particle size on the physical properties of the composite. Therefore, different fractions of potato peel powder (0–53 μm, 125–250 μm, and 315–500 μm) were incorporated into PLA matrix via compounding and injection-molding. Microscopic analysis of the injection-molded samples revealed that the average particle shape did not differ between the different fractions. Overall, increasing the particle size of potato peel particles resulted in increased stiffness and decreased ductility. The cold crystallization temperature and water vapor transmission rate of the composites were independent of particle size but increased upon the incorporation of potato peel particles. In conclusion, the effect of particle incorporation on packaging-related properties was higher than the effect of using different particle size fractions. This means that potato peel particles, regardless of their particle size distribution, are promising fillers for composites, with the potential to improve biodegradability, maintain some level of protection for the packaged product, and reduce the cost of the composites. Full article
(This article belongs to the Special Issue Polymeric Substrates Modification with Biobased Functional Compounds)
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13 pages, 8466 KiB  
Article
Designing and Manufacturing of Biocompatible Hydroxyapatite and Sodium Trisilicate Scaffolds by Ordinary Domestic Microwave Oven
by Giorgio Luciano, Maurizio Vignolo, Denise Galante, Cristina D’Arrigo, Franco Furlani, Monica Montesi and Silvia Panseri
Compounds 2024, 4(1), 106-118; https://0-doi-org.brum.beds.ac.uk/10.3390/compounds4010005 - 30 Jan 2024
Viewed by 772
Abstract
In this work, we present a versatile, rapid, and low-cost manufacturing technique to develop bioceramic scaffolds that could enhance bone tissue regeneration via microwave preparation using a domestic microwave oven. The scaffolds were prepared by combining hydroxyapatite and water glass (sodium trisilicate solution), [...] Read more.
In this work, we present a versatile, rapid, and low-cost manufacturing technique to develop bioceramic scaffolds that could enhance bone tissue regeneration via microwave preparation using a domestic microwave oven. The scaffolds were prepared by combining hydroxyapatite and water glass (sodium trisilicate solution), foamed by using a microwave oven, and then characterized by means of Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Analysis (EDX), mechanical properties, infrared spectroscopy (ATR-FTIR), and a density and stability test in water. Furthermore, in vitro tests were performed to verify the affinity of the scaffold for osteoclast cells. The morphology of the samples showed interconnected pores suitable for promoting tissue regeneration and vascularization, while specific mechanical properties were preserved. The physicochemical characterization and the in vitro tests presented promising results for bone regenerative applications. The scaffolds we obtained exhibited comparable properties to those fabricated using a laboratory microwave oven, including the ability to induce the formation of bone-like tissue in vitro. Full article
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35 pages, 1322 KiB  
Review
An Approach to 3D Printing Techniques, Polymer Materials, and Their Applications in the Production of Drug Delivery Systems
by Pedro H. N. Cardoso and Evando S. Araújo
Compounds 2024, 4(1), 71-105; https://0-doi-org.brum.beds.ac.uk/10.3390/compounds4010004 - 17 Jan 2024
Cited by 2 | Viewed by 1589
Abstract
Three-dimensional printing (3DP) technologies are characterized as a set of innovative manufacturing techniques that allow for the creation of complex and/or personalized three-dimensional physical objects on the work surface of a 3D printing machine (based on the computer-aided design (CAD) project designs of [...] Read more.
Three-dimensional printing (3DP) technologies are characterized as a set of innovative manufacturing techniques that allow for the creation of complex and/or personalized three-dimensional physical objects on the work surface of a 3D printing machine (based on the computer-aided design (CAD) project designs of these parts). Three-dimensional printing techniques are widely used in various areas of knowledge, such as education, engineering, and biomedicine. Polymeric materials are widely used for these applications, mainly due to their desirable workability during part manufacturing, compatibility with other chemical materials, the wide range of polymers with different physical and chemical characteristics, and the possibility for recycling. The development of polymeric drug delivery systems (DDSs) by 3D printing is currently an active field of research, both in academia and industry, given the potential of this technique for medical purposes. In this context, this work reviews potential polymers for the production of drug delivery systems via 3D printing techniques. The demonstrations of the main 3DP techniques used for drug delivery applications include their working principles and advantages and how the technologies develop the final product. In addition, potential synthetic and natural polymers that are currently used in 3DP drug delivery devices are presented and discussed based on recent scientific studies. Full article
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34 pages, 725 KiB  
Article
Chemical Compositions and Essential Fatty Acid Analysis of Selected Vegetable Oils and Fats
by Pawan Kumar Ojha, Darbin Kumar Poudel, Anil Rokaya, Salina Maharjan, Sunita Timsina, Ambika Poudel, Rakesh Satyal, Prabodh Satyal and William N. Setzer
Compounds 2024, 4(1), 37-70; https://0-doi-org.brum.beds.ac.uk/10.3390/compounds4010003 - 17 Jan 2024
Viewed by 3027
Abstract
The fatty acid (FA) compositions of thirty-nine vegetable oils and fats, including nangai nut, pili nut, shea butter, tamanu oil, baobab, sea buckthorn berry, Brazil nut, grape seed, black seed, evening primrose, passion fruit, milk thistle, sunflower, pumpkin seed, sesame, soybean, flax seed, [...] Read more.
The fatty acid (FA) compositions of thirty-nine vegetable oils and fats, including nangai nut, pili nut, shea butter, tamanu oil, baobab, sea buckthorn berry, Brazil nut, grape seed, black seed, evening primrose, passion fruit, milk thistle, sunflower, pumpkin seed, sesame, soybean, flax seed, kukui, red raspberry seed, walnut, chia seed, hemp seed, rosehip, almond, avocado, carrot seed, moringa, apricot kernel, camellia seed, macadamia, olive, marula, argan, castor, jojoba, pomegranate seed, medium-chain triglyceride (MCT) coconut, roasted coconut, canola, and mustard oil, were analyzed using gas chromatography–mass spectrometry (GC-MS). Vegetable oils and fats have different profiles in terms of their fatty acid composition, and their major constituents vary significantly. However, we categorized them into different classes based on the percentages of different fatty acids they contain. The saturated fatty acids, such as palmitic acid and stearic acid, and the unsaturated fatty acids, including oleic acid, linoleic acid, and linolenic acid, are the main categories. Among them, roasted coconut oil contained the greatest amount of saturated fatty acids followed by nangai nut (45.61%). Passion fruit oil contained the largest amount of linoleic acid (66.23%), while chia seed oil had the highest content of linolenic acid (58.25%). Oleic acid was exclusively present in camellia seed oil, constituting 78.57% of its composition. Notably, mustard oil had a significant presence of erucic acid (54.32%), while pomegranate seed oil exclusively contained punicic acid (74.77%). Jojoba oil primarily consisted of (Z)-11-eicosenoic acid (29.55%) and (Z)-docos-13-en-1-ol (27.96%). The major constituent in castor oil was ricinoleic acid (89.89%). Compared with other vegetable oils and fats, pili nut oil contained a significant amount of (E)-FA (20.62%), followed by sea buckthorn berry oil with a content of 9.60%. FA compositions from sources may be problematic in the human diet due to no labeling or the absence of essential components. Therefore, consumers must cast an eye over some essential components consumed in their dietary intake. Full article
(This article belongs to the Special Issue Feature Papers in Compounds (2022–2023))
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20 pages, 4000 KiB  
Article
Hydroxyhydroquinone and Quassinoids as Promising Compounds with Hypoglycemic Activity through Redox Balance
by Paulo R. dos Santos, Sidinéia Danetti, A. Joseph Rastegar, Wellington V. de Souza, Rafaele Frassini, Fernando J. Scariot, Sidnei Moura and Mariana Roesch-Ely
Compounds 2024, 4(1), 17-36; https://0-doi-org.brum.beds.ac.uk/10.3390/compounds4010002 - 3 Jan 2024
Viewed by 925
Abstract
In the present study, an insulin-resistant cell model (human hepatocellular carcinoma cell line: HepG2) was chosen to investigate the efficacy of two compound classes and their common molecular motif for glycemic control and insulin sensitization. The two compounds’ classes were flavonoid extracts from [...] Read more.
In the present study, an insulin-resistant cell model (human hepatocellular carcinoma cell line: HepG2) was chosen to investigate the efficacy of two compound classes and their common molecular motif for glycemic control and insulin sensitization. The two compounds’ classes were flavonoid extracts from Rourea cuspidata and quassinoid extracts from Picrasma crenata. The flavonoid-like hydroxyhydroquinone (HHQ) was synthesized. HepG2 cells were tested in a high-glucose environment (HepG2/IRM) by monitoring ROS activity, the concentration of adenosine triphosphate (ATP), and the measurement of mitochondrial membrane potential (MMP). The expression of forkhead box O1 (FOXO1) protein, which mediates gluconeogenesis and insulin resistance, was also investigated using indirect immunocytochemistry and Western blot techniques. A significant increase in glucose uptake and well-regulated ATP concentrations were observed in the treated cells. The downregulation of FOXO1 expression was seen in cells treated with HHQ and quassinoids in comparison to cells treated with flavonoids. This study provides a pharmacological basis for the application of HHQ, quassinoids from P. crenata, and flavonoids from R. cuspidata in the treatment of metabolic diseases such as type 2 diabetes mellitus. Full article
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16 pages, 2901 KiB  
Article
Bio-Based Tannin Foams: Comparing Their Physical and Thermal Response to Polyurethane Foams in Lightweight Sandwich Panels
by Marlon Bender Bueno Rodrigues, Ronan Côrrea, Pedro Henrique G. De Cademartori, Ana C. R. Ribeiro, Rodrigo Coldebella, Rafael A. Delucis, Nayara Lunkes and André L. Missio
Compounds 2024, 4(1), 1-16; https://0-doi-org.brum.beds.ac.uk/10.3390/compounds4010001 - 25 Dec 2023
Viewed by 1025
Abstract
Rigid polyurethane foams are the better-performing material for the most common insulation purposes, like sandwich panels. Nevertheless, they are highly flammable materials, release toxic gases, and are manufactured from fossil sources. As an alternative, tannin foams are bio-based materials that work as innovative [...] Read more.
Rigid polyurethane foams are the better-performing material for the most common insulation purposes, like sandwich panels. Nevertheless, they are highly flammable materials, release toxic gases, and are manufactured from fossil sources. As an alternative, tannin foams are bio-based materials that work as innovative alternatives thanks to their great fire resistance, as well as lower smoke and harmful gases emissions. In the present study, lab-made foams of both materials were compared through morphology, thermal and fire degradation, mechanical properties, and water affinity in order to fill the technological gap between them and their related sandwich panels. It was observed that tannin foams are still relatively inhomogeneous (since formaldehyde was not used) and present a high affinity for water but have higher thermal and fire resistance. The flat compression strength of the polyurethane sandwiches was greater than that of tannin sandwiches (3.61 and 3.09 MPa, respectively) thanks, mainly, to the crosslinking degree difference between the resins. Also, tannin foams presented a lower weight loss (−70.684% lower weight loss in flammability tests than polyurethane foams) and the ability to self-extinguish the flame. Therefore, sandwich panels with tannin foam cores could be successful materials in areas that require protection against fire, such as the building engineering and automotive industries. Full article
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