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1.
Vpliv kovin na protibakterijsko učinkovitost taninov
Miha Fermišek, 2024, master's thesis

Abstract: Tanini so sekundarni metaboliti višjih rastlin. Pri rasti in razvoju rastlin ne sodelujejo, pač pa je njihova glavna naloga varovanje rastlin pred rastlinojedci in drugimi napadalci iz okolja. Po svoji strukturi in lastnostih so si zelo različni, kar jim omogoča tvorbo koordinacijskih spojin z raznimi kovinskimi ioni, kompleksacijo s proteini, obenem pa kažejo tudi dobre protimikrobne lastnosti. Ravno zaradi slednjih se danes vse pogosteje uporabljajo kot potencialne protimikrobne učinkovine. Eksperimentalno delo je zajemalo karakterizacijo izbranega seva Escherichia coli, čemur je sledilo določanje minimalne inhibitorne koncentracije (MIC) čistih taninov (veskalagin, kastalagin, veskalin, kastalin in galna kislina) ter vodnega kostanjevega ekstrakta Farmatan. Nato smo preučevanim taninom in ekstraktu dodali še kovinske ione različnih koncentracij in spremljali njihov vpliv na vrednost MIC. V obeh postopkih smo določili vrednosti MIC z metodama turbidimetrije in dodajanjem jodonitrotetrazolijevega klorida (INT barvilo). Na začetku smo okarakterizirali izbran sev E. coli tako, da smo izrisali umeritveno in rastno krivuljo. Z umeritveno krivuljo smo določili enačbo premice, katero smo uporabili v vseh nadaljnjih korakih dela. Rastno krivuljo pa smo izrisali ob pripravi primerne redčine bakterijske kulture. Za to smo morali pomerjati optično gostoto (OD) skozi daljši čas (3 dni). Čiste tanine in kostanjev ekstrakt smo pripravili v različnih koncentracijah in določili vrednosti MIC posameznih učinkovin potrebne za zaviranje rasti E. coli. Dobljene vrednosti MIC po metodi turbidimetrije so bile za veskalagin: 0,112 ± 0,074 g/L; kastalagin: 0,217 ± 0,093 g/L; veskalin: 0,145 ± 0,034 g/L; kastalin: 0,078 ± 0,022 g/L; galna kislina: 4,200 ± 0,748 g/L; in Farmatan: 0,794 ± 0,213 g/L. Z dodatkom INT barvila, pa so bile za veskalagin: 0,138 ± 0,070 g/L; kastalagin: 0,171 ± 0,019 g/L; veskalin: 0,145 ± 0,034 g/L; kastalin: 0,078 ± 0,022 g/L; galna kislina: 4,333 ± 0,745 g/L; in Farmatan 0,481 ± 0,030 g/L. V nadaljevanju smo uporabljenim taninom in ekstraktu dodali različne koncentracije kovinskih ionov Fe(II), Fe(III), Cu(II), Mn(II), Zn(II) in Ni(II) in z enakima metodama spremljali vpliv na MIC vrednosti. Iz dobljenih rezultatov je bilo razvidno, da so se vrednosti MIC večine vzorcev ob dodatku kovinskih ionov dvignile. To nakazuje na interakcije med kovinskimi ioni ter tanini, saj pride do nastanka koordinacijskih spojin, kar vpliva na protibakterijsko aktivnost taninov.
Keywords: tanini, hidrolizirajoči tanini, protibakterijske lastnosti, kovinski ioni, minimalna inhibitorna koncentracija, Escherichia coli
Published in DKUM: 18.04.2024; Views: 15; Downloads: 0
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2.
The effect of microwaves on protein structure: molecular dynamics approach
Matic Broz, Chris Oostenbrink, Urban Bren, 2024, original scientific article

Published in DKUM: 12.04.2024; Views: 44; Downloads: 4
.pdf Full text (2,76 MB)

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Antioxidant activity of different hop (Humulus lupulus L.) genotypes
Zala Kolenc, Tamara Hribernik, Tomaž Langerholc, Maša Pintarič, Maja Prevolnik Povše, Urban Bren, 2023, original scientific article

Abstract: The antioxidant activity (AA) of hop extracts obtained from different hop genotypes (n = 14) was studied. For comparison, the purified β-acids-rich fraction and α-acids-with-β-acids-rich fraction were also used to test the antioxidative potential. The AA of purified hydroacetonic hop extracts was investigated using the Ferric Reducing Ability of Plasma (FRAP), Oxygen Radical Absorption Capacity (ORAC) and Intracellular Antioxidant (IA) methods. The FRAP values in different hop genotypes ranged between 63.5 and 101.6 μmol Trolox equivalent (TE)/g dry weight (DW), the ORAC values ranged between 1069 and 1910 μmol TE/g DW and IA potential values ranged between 52.7 and 118.0 mmol TE/g DW. Significant differences in AA between hop genotypes were observed with all three methods. AAs were determined using three different methods, which did not highly correlate with each other. We also did not find significant correlations between AA and different chemical components, which applies both to AA determined using individual methods as well as the total AA. Based on this fact, we assume that the synergistic or antagonistic effects between hop compounds have a more pronounced effect on AA than the presence and quantity of individual hop compounds.
Keywords: hop, antioxidant activity, FRAP, ORAC, intracellular antioxidative potential, genotypes
Published in DKUM: 20.03.2024; Views: 116; Downloads: 4
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5.
Helichrysum italicum : From Extraction, Distillation, and Encapsulation Techniques to Beneficial Health Effects
Veronika Furlan, Urban Bren, 2023, review article

Abstract: Helichrysum italicum (family Asteraceae), due to its various beneficial health effects, represents an important plant in the traditional medicine of Mediterranean countries. Currently, there is a renewed interest in this medicinal plant, especially in investigations involving the isolation and identification of its bioactive compounds from extracts and essential oils, as well as in experimental validation of their pharmacological activities. In this paper, we review the current knowledge on the beneficial health effects of Helichrysum italicum extracts, essential oils, and their major bioactive polyphenolic compounds, ranging from antioxidative, anti-inflammatory, and anticarcinogenic activities to their antiviral, antimicrobial, insecticidal, and antiparasitic effects. This review also provides an overview of the most promising extraction and distillation techniques for obtaining high-quality extracts and essential oils from Helichrysum italicum, as well as methods for determining their antioxidative, antimicrobial, anti-inflammatory, and anticarcinogenic activities. Finally, new ideas for in silico studies of molecular mechanisms of bioactive polyphenols from Helichrysum italicum, together with novel suggestions for their improved bioavailability through diverse encapsulation techniques, are introduced.
Keywords: Helichrysum italicum, polyphenolic compounds, biological effects, extraction methods, distillation methods, encapsulation methods
Published in DKUM: 15.03.2024; Views: 124; Downloads: 6
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6.
Monocarbonyl Curcumin Analogues as Potent Inhibitors against Human Glutathione Transferase P1-1
Panagiota Pantiora, Veronika Furlan, Dimitris Matiadis, Barbara Mavroidi, Fereniki Perperopoulou, Anastassios C. Papageorgiou, Marina Sagnou, Urban Bren, Maria Pelecanou, Nikolaos E. Labrou, 2023, original scientific article

Abstract: The isoenzyme of human glutathione transferase P1-1 (hGSTP1-1) is involved in multi-drug resistance (MDR) mechanisms in numerous cancer cell lines. In the present study, the inhibition potency of two curcuminoids and eleven monocarbonyl curcumin analogues against hGSTP1-1 was investigated. Demethoxycurcumin (Curcumin II) and three of the monocarbonyl curcumin analogues exhibited the highest inhibitory activity towards hGSTP1-1 with IC50 values ranging between 5.45 1.08 and 37.72 1.02 M. Kinetic inhibition studies of the most potent inhibitors demonstrated that they function as non-competitive/mixed-type inhibitors. These compounds were also evaluated for their toxicity against the prostate cancer cells DU-145. Interestingly, the strongest hGSTP1-1 inhibitor, (DM96), exhibited the highest cytotoxicity with an IC50 of 8.60 1.07 M, while the IC50 values of the rest of the compounds ranged between 44.59–48.52 M. Structural analysis employing molecular docking, molecular dynamics (MD) simulations, and binding-free-energy calculations was performed to study the four most potent curcumin analogues as hGSTP1-1 inhibitors. According to the obtained computational results, DM96 exhibited the lowest binding free energy, which is in agreement with the experimental data. All studied curcumin analogues were found to form hydrophobic interactions with the residue Gln52, as well as hydrogen bonds with the nearby residues Gln65 and Asn67. Additional hydrophobic interactions with the residues Phe9 and Val36 as well as – stacking interaction with Phe9 contributed to the superior inhibitory activity of DM96. The van derWaals component through shape complementarity was found to play the most important role in DM96-inhibitory activity. Overall, our results revealed that the monocarbonyl curcumin derivative DM96 acts as a strong hGSTP1-1 inhibitor, exerts high prostate cancer cell cytotoxicity, and may, therefore, be exploited for the suppression and chemosensitization of cancer cells. This study provides new insights into the development of safe and effective GST-targeted cancer chemosensitizers.
Keywords: curcuminoids, curcumin analogues, human glutathione transferase P1-1 (hGSTP1-1), glutathione transferase, enzyme inhibition, multi-drug resistance
Published in DKUM: 12.03.2024; Views: 102; Downloads: 9
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7.
The Influence of Chestnut Extract and Its Components on Antibacterial Activity against Staphylococcus aureus
Sara Štumpf, Gregor Hostnik, Tomaž Langerholc, Maša Pintarič, Zala Kolenc, Urban Bren, 2023, original scientific article

Abstract: Increasing antimicrobial resistance has caused a great interest in natural products as alternatives or potentiators of antibiotics. The objective of this study was to isolate individual tannins from crude chestnut extract as well as to determine the influence of both crude extracts (tannic acid extract, chestnut extract) and individual pure tannins (gallic acid, vescalin, vescalagin, castalin, castalagin) on the growth of Gram-positive Staphylococcus aureus bacteria. Their antibacterial activity was monitored by measuring the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) as well as the duration of the lag phase, growth rate and generation time. The effect of growth medium strength on the MIC of different tannins was also investigated. Bacterial growth was followed spectrophotometrically, and MIC values were determined by the microdilution method. The MIC values of various isolated compounds allowed us to determine the bioactive compounds and their contribution to antimicrobial activity. It was found that MIC values increase with increasing growth medium strength and that the lag phase lengthens with increasing tannin concentrations, while the growth rates decrease. Comparing the results of the two studies, the antimicrobial activity of tannins against S. aureus was not as pronounced as in the case of E. coli, which may indicate that a different mechanism of action is responsible for the antimicrobial effects of tannins on Gram-positive than on Gram-negative bacteria, or that a different mechanism is more pronounced.
Keywords: tannins, antibacterial activity, MIC, MBC, Staphylococcus aureus, lag phase, generation time
Published in DKUM: 20.02.2024; Views: 153; Downloads: 9
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8.
Nanomaterials and their recent applications in impedimetric biosensing
Zala Štukovnik, Regina Fuchs-Godec, Urban Bren, 2023, review article

Abstract: Impedimetric biosensors measure changes in the electrical impedance due to a biochemical process, typically the binding of a biomolecule to a bioreceptor on the sensor surface. Nanomaterials can be employed to modify the biosensor's surface to increase the surface area available for biorecognition events, thereby improving the sensitivity and detection limits of the biosensor. Various nanomaterials, such as carbon nanotubes, carbon nanofibers, quantum dots, metal nanoparticles, and graphene oxide nanoparticles, have been investigated for impedimetric biosensors. These nanomaterials have yielded promising results in improving sensitivity, selectivity, and overall biosensor performance. Hence, they offer a wide range of possibilities for developing advanced biosensing platforms that can be employed in various fields, including healthcare, environmental monitoring, and food safety. This review focuses on the recent developments in nanoparticle-functionalized electrochemical-impedimetric biosensors.
Keywords: impedimetric biosensor, electrochemical impedance spectroscopy, nanomaterials, metal nanoparticles, carbon nanofibers, carbon nanotubes, graphene oxide, quantum dots
Published in DKUM: 12.02.2024; Views: 5953; Downloads: 10
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Design of Tetra-Peptide Ligands of Antibody Fc Regions Using In Silico Combinatorial Library Screening
Marko Jukič, Sebastjan Kralj, Anja Kolarič, Urban Bren, 2023, original scientific article

Abstract: Abstract Peptides, or short chains of amino-acid residues, are becoming increasingly important as active ingredients of drugs and as crucial probes and/or tools in medical, biotechnological, and pharmaceutical research. Situated at the interface between small molecules and larger macromolecular systems, they pose a difficult challenge for computational methods. We report an in silico peptide library generation and prioritization workflow using CmDock for identifying tetrapeptide ligands that bind to Fc regions of antibodies that is analogous to known in vitro recombinant peptide libraries’ display and expression systems. The results of our in silico study are in accordance with existing scientific literature on in vitro peptides that bind to antibody Fc regions. In addition, we postulate an evolving in silico library design workflow that will help circumvent the combinatorial problem of in vitro comprehensive peptide libraries by focusing on peptide subunits that exhibit favorable interaction profiles in initial in silico peptide generation and testing.
Keywords: peptide design, in silico combinatorial library, peptide combinatorial library, peptide library design, high-throughput virtual screening, peptide molecular docking, antibody purification, peptide drug design, recombinant peptide libraries
Published in DKUM: 01.12.2023; Views: 190; Downloads: 11
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