1. Inverse molecular docking elucidating the anticarcinogenic potential of the hop natural product xanthohumol and its metabolitesKatarina Kores, Zala Kolenc, Veronika Furlan, Urban Bren, 2022, original scientific article Abstract: Natural products from plants exert a promising potential to act as antioxidants, antimicrobials, anti-inflammatory, and anticarcinogenic agents. Xanthohumol, a natural compound from hops, is indeed known for its anticarcinogenic properties. Xanthohumol is converted into three metabolites: isoxanthohumol (non-enzymatically) as well as 8- and 6-prenylnaringenin (enzymatically). An inverse molecular docking approach was applied to xanthohumol and its three metabolites to discern their potential protein targets. The aim of our study was to disclose the potential protein
targets of xanthohumol and its metabolites in order to expound on the potential anticarcinogenic
mechanisms of xanthohumol based on the found target proteins. The investigated compounds were
docked into the predicted binding sites of all human protein structures from the Protein Data Bank,
and the best docking poses were examined. Top scoring human protein targets with successfully
docked compounds were identified, and their experimental connection with the anticarcinogenic
function or cancer was investigated. The obtained results were carefully checked against the existing
experimental findings from the scientific literature as well as further validated using retrospective
metrics. More than half of the human protein targets of xanthohumol with the highest docking scores
have already been connected with the anticarcinogenic function, and four of them (including two
important representatives of the matrix metalloproteinase family, MMP-2 and MMP-9) also have a
known experimental correlation with xanthohumol. Another important protein target is acyl-protein
thioesterase 2, to which xanthohumol, isoxanthohumol, and 6-prenylnaringenin were successfully
docked with the lowest docking scores. Moreover, the results for the metabolites show that their
most promising protein targets are connected with the anticarcinogenic function as well. We firmly
believe that our study can help to elucidate the anticarcinogenic mechanisms of xanthohumol and its
metabolites as after consumption, all four compounds can be simultaneously present in the organism.
Keywords: xanthohumol, metabolites, inverse molecular docking, anticarcinogenic effects
Published in DKUM: 10.04.2025; Views: 0; Downloads: 1
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2. Exploring antioxidative properties of xanthohumol and isoxanthohumol : an integrated experimental and computational approach with isoxanthohumol pKa determinationJelena Tošović, Zala Kolenc, Gregor Hostnik, Urban Bren, 2025, original scientific article Abstract: This study explores the antioxidative activities of xanthohumol (XN) and isoxanthohumol (IXN), prenylated flavonoids from Humulus lupulus (family Cannabaceae), utilizing the oxygen radical absorption capacity (ORAC) and ferric reducing antioxidant power (FRAP) assays along with computational Density Functional Theory methods. Experimentally, XN demonstrated significantly higher antioxidative capacities than IXN. Moreover, we determined IXN pKa values using the UV/Vis spectrophotometric method for the first time, facilitating its accurate computational modeling under physiological conditions. Through a thermodynamic approach, XN was found to efficiently scavenge HOO• and CH3O• radicals via Hydrogen Atom Transfer (HAT) and Radical Adduct Formation (RAF) mechanisms, while CH3OO• scavenging was feasible only through the HAT pathway. IXN exhibited its best antioxidative activity against CH3O• via both HAT and RAF mechanisms and could also scavenge HOO• through RAF. Both Single Electron Transfer (SET) and Sequential Proton Loss-Electron Transfer (SPLET) mechanisms were thermodynamically unfavorable for all radicals and both compounds.
Keywords: antioxidative activity, bio-active membranes, xanthohumol, isoxanthohumol, ORAC and FRAP assays, pKa determination, density functional theory, DFT
Published in DKUM: 31.01.2025; Views: 0; Downloads: 5
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4. Antimicrobial properties of different hop (Humulus lupulus) genotypesZala Kolenc, Tomaž Langerholc, Gregor Hostnik, Miha Ocvirk, Sara Štumpf Horvat, Maša Pintarič, Iztok Jože Košir, Andreja Čerenak, Alenka Garmut, Urban Bren, 2023, original scientific article Abstract: The antimicrobial activity of hop extracts obtained from different hop genotypes were investigated against Staphylococcus aureus and Lactobacillus acidophilus. In this study the pure xanthohumol, purified β-acids rich fraction, as well as α-acids with β-acids rich fraction were used to test antimicrobial activity against Staphylococcus aureus and Lactobacillus acidophilus; whereby, the antimicrobial activity of different hop extracts against Lactobacillus acidophilus was studied for the first time. Microbial susceptibility to purified hydroacetonic extracts from different hop varieties was investigated by the broth microdilution assay to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). The hop hydroacetonic extracts were more effective against Staphylococcus aureus than against Lactobacillus acidophilus. Strong inverse correlations of MIC and MBC values were obtained with xanthohumol, cohumulone, n+adhumulone, colupulone and n+adlupulone contents, suggesting that the identified chemical hop compounds are directly responsible for antimicrobial effects. Moreover, the effect of the growth medium strength on the MIC values of hop extracts against Staphylococcus aureus was systematically investigated for the first time. The current study also reveals the effect of different hop extracts on Staphylococcus aureus, which responds to their presence by lag phase extension and generation time prolongation.
Keywords: hop extract, xanthohumol, Staphylococcus aureus, Lactobacillus acidophilus, minimum inhibitory concentration, minimum bactericidal concentration
Published in DKUM: 09.05.2024; Views: 203; Downloads: 22
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6. Antioxidant activity of different hop (Humulus lupulus L.) genotypesZala 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: 271; Downloads: 19
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9. The Influence of Chestnut Extract and Its Components on Antibacterial Activity against Staphylococcus aureusSara Štumpf Horvat, 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: 363; Downloads: 74
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10. Uporaba vodnega curka kot prisilnega sredstva policije v izbranih državah Evropske unije in njegova uporaba v Sloveniji v času pandemijeSrečko Krope, Eva Kolenc, 2023, review article Abstract: Namen prispevka:
S primerjavo domače in tuje zakonodaje smo preučevali podobnosti in
razlike v načinih in pogojih uporabe vodnega curka kot prisilnega sredstva
policije v Sloveniji in izbranih državah Evropske unije (EU). Prav tako smo
ugotavljali, ali je v času pandemije koronavirusa v Sloveniji zaznati več primerov
uporabe vodnega topa kot v letih prej.
Metode:
Prispevek je kvalitativnega značaja, kjer smo v okviru pregleda znanstvene in
strokovne literature ter zakonodaje uporabili metodi deskripcije in kompilacije.
Pri tem smo opravili analizo preteklih letnih poročil policije s področja uporabe
prisilnih sredstev, s poudarkom na uporabi vodnega curka. Skozi primerjavo
domače in tuje zakonodaje o uporabi prisilnih sredstev policije smo uporabili
tudi metodi primerjave in sinteze, kjer smo postopek raziskovanja nadgradili z
združevanjem in sestavljanjem preprostih misli v smiselne zaključke.
Ugotovitve:
Rezultati kažejo, da je bilo pri izvajanju ukrepov za zajezitev virusa v
obdobju pandemije pri nas res zaznati več primerov uporabe vodnega curka
kot v obdobju prej. Ugotovitve kažejo tudi, da je zakonska ureditev uporabe
vodnega curka kot prisilnega sredstva policije med državami članicami EU
relativno podobna, z nekaj izjemami. Tako pri nas kot drugje je na tem področju
prostora za kar nekaj izboljšav, o katerih bo treba razmisliti v prihodnosti.
Praktična uporabnost:
Prispevek predstavlja preglednost ureditve prisilnega sredstva v državah
EU v primerjavi s Slovenijo. Kot je ugotovljeno, drugje pri pogojih uporabe niso
zelo natančni in puščajo odprte možnosti zlasti pri dodajanju plinskih sredstev
v vodni curek. Vse to pa nakazuje na nujnost po natančni opredelitvi uporabe
vodnega curka z raznimi dodatki pri njegovi uporabi. Izvirnost/pomembnost prispevka:
O uporabi vodnega curka ni bilo opravljenih veliko raziskav in se ji ni
posvečalo veliko pozornosti, vse dokler se to prisilno sredstvo ni začelo uporabljati
ob vzpostavljanju javnega reda in miru ob množičnih kršitvah.
Keywords: prisilna sredstva, vodni curek, množična kršitev
Published in DKUM: 15.01.2024; Views: 191; Downloads: 16
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