1. Synergistic effect of supercritical and ultrasound-assisted ginger (Zingiber officinale Roscoe) extractsTaja Žitek Makoter, Nika Kučuk, Vesna Postružnik, Maja Leitgeb, Željko Knez, Mateja Primožič, Maša Knez Marevci, 2022, original scientific article Abstract: Proper processing of natural material is crucial to obtain an extract with high content of
biologically active components. Dried, grinded ginger roots were extracted by ultrasonic method
and supercritical extraction with CO2
. The aim of the study was to determine if a mixture of the two
types of extracts attained by different methods and solvents exhibits better bioavailability than each
extract itself. Therefore, both extracts were analytically evaluated and then mixed in a ratio of 1:1.
The supercritical extract (SCG extract) and the mixed extract (mixG extract) had high antioxidant
activity (78% and 73%) and total phenols (827 mg/g ext. and 1455 mg/g ext.), which is also consistent
with the levels of gingerol (303 mg/g ext. and 271 g/g ext.) and shogaol (111 mg/g ext. and 100 g/g
ext.) in the extracts. In comparison to both pure extracts higher levels of total phenols were found
in the extract mixG. This could be the reason for the significant inhibition of melanoma cells and
antimicrobial potential (against Staphylococcus aureus, Escherichia coli, and Candida albicans). The
combination of the extracts resulted in a significant increase in the inhibition of selected microbial
and melanoma cells WM-266-4 compared to the control. Cell viability decreased below 60% when
mixG extract was applied. Antimicrobial activity has been confirmed.
Keywords: ginger, supercritical fluid extraction, ultrasound-assisted extraction, antimicrobial activity
Published in DKUM: 09.05.2025; Views: 0; Downloads: 0
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2. Extraction of bioactive metabolites from Achillea millefolium L. with choline chloride based natural deep eutectic solvents: a study of the antioxidant and antimicrobial activityMilena Ivanović, Dragana Grujić, Janez Cerar, Maša Islamčević Razboršek, Ljiljana Topalić-Trivunović, Aleksandar Savić, Drago Kočar, Mitja Kolar, 2022, original scientific article Abstract: In this study, the extraction efficiency of natural deep eutectic solvents (NADES) based on choline chloride as a hydrogen bond acceptor (HBA) and five different hydrogen bond donors (HBD; lactic acid, 1,4-butanediol, 1,2-propanediol, fructose and urea) was evaluated for the first time for the isolation of valuable bioactive compounds from Achillea millefolium L. The phytochemical profiles of NADES extracts obtained after ultrasound-assisted extraction were evaluated both spectrophotometrically (total phenolic content (TPC) and antioxidant assays) and chromatographically (UHPLC-MS and HPLC-UV). The results were compared with those obtained with 80% ethanol, 80% methanol, and water. The highest TPC value was found in the lactic acid-based NADES (ChCl-LA), which correlated with the highest antioxidant activity determined by the FRAP analysis. On the other hand, the highest antiradical potential against ABTS$^{+•}$ was determined for urea-based NADES. Phenolic acids (chlorogenic acid and dicaffeoylquinic acid isomers), flavones (luteolin and apigenin), and their corresponding glucosides were determined as the dominant individual phenolic compounds in all extracts. The antibacterial and antifungal properties of the extracts obtained against four bacterial cultures and two yeasts were evaluated using two methods: the agar dilution method to obtain the minimum inhibitory concentration (MIC) and the minimum bactericidal or fungicidal concentration (MBC or MFC), and the disc diffusion method. ChCl-LA had the lowest MIC and MBC/MFC with respect to all microorganisms, with an MIC ranging from 0.05 mg mL$^{−1}$ to 0.8 mg mL$^{−1}$, while the water extract had the weakest inhibitory activity with MIC and MBC/MFC higher than 3.2 mg mL$^{−1}$.
Keywords: viskoznost, fenoli, antioksidanti, natural deep eutectic solvents (NADES), density and viscosity, yarrow, phenolic compounds, antioxidant activity, antimicrobial activity
Published in DKUM: 09.04.2025; Views: 0; Downloads: 3
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3. Supercritical fluid and conventional extractions of high value-added compounds from pomegranate peels waste: production, quantification and antimicrobial activity of bioactive constituentsKaja Kupnik, Maja Leitgeb, Mateja Primožič, Vesna Postružnik, Petra Kotnik, Nika Kučuk, Željko Knez, Maša Knez Marevci, 2022, original scientific article Abstract: This study is focused on different extractions (Cold Maceration (CM), Ultrasonic Extraction
(UE), Soxhlet Extraction (SE) and Supercritical Fluid Extraction (SFE)) of bioactive compounds from
pomegranate (Punica Granatum L.) fruit peels using methanol, ethanol, and acetone as solvents in
conventional extractions and changing operating pressure (10, 15, 20, 25 MPa) in SFE, respectively.
The extraction yields, total phenols (TP) and proanthocyanidins (PAC) contents, and antioxidant
activity of different extracts are revealed. TP and PAC recovered by extracts ranged from 24.22 to
42.92 mg gallic acid equivalents (GAE)/g and 2.01 to 5.82 mg PAC/g, respectively. The antioxidant
activity of extracts ranged from 84.70% to 94.35%. The phenolic compound identification and
quantification in selective extracts was done using the LC-MS/MS method. The contents of different
flavonoids and phenolic acids have been determined. SFE extract, obtained at 20 MPa, contained
the highest content (11,561.84 µg/g) of analyzed total polyphenols, with predominant ellagic acid
(7492.53 µg/g). For the first time, Microbial Growth Inhibition Rates (MGIRs) were determined at
five different concentrations of pomegranate SFE extract against seven microorganisms. Minimal
Inhibitory Concentration (MIC90) was determined as 2.7 mg/mL of SFE pomegranate peel extract in
the case of five different Gram-negative and Gram-positive bacteria.
Keywords: antimicrobial activity, antioxidants, bioactive compounds, extraction, LC-MS/MS, phenolics, phytochemistry, pomegranate, Punica Granatum L., secondary metabolites
Published in DKUM: 24.03.2025; Views: 0; Downloads: 3
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4. Nanodelci hitozana kot potencialni protimikrobni premazZdenka Peršin Fratnik, Uroš Maver, Metod Kolar, Olivera Šauperl, Lidija Fras Zemljič, Boštjan Vihar, 2024, original scientific article Abstract: Namen študije je bil ugotoviti protimikrobno učinkovitost hitozanskih nanodelcev v primerjavi s hitozansko raztopino in sled temu njihovo učinkovito rabo na medicinskih tekstilnih materialih.
Keywords: chitosan, nanoparticles, antimicrobial activity, coatings, medical textile materials
Published in DKUM: 07.01.2025; Views: 0; Downloads: 24
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5. Antimicrobial activity of amino-modified cellulose nanofibrils decorated with silver nanoparticlesVesna Lazić, Jovan Nedeljković, Vanja Kokol, 2024, original scientific article Abstract: Silver nanoparticles (Ag NPs) conjugated with amino-functionalized cellulose nanofibrils (NH2−CNFs) were in situ-prepared by reducing silver ions with free amino groups from NH2−CNFs. The spectroscopy and transmission electron microscopy measurements confirmed the presence of non-agglomerated nanometer-in-size Ag NPs within micrometer-large NH2−CNFs of high (20 wt.-%) content. Although the consumption of amino groups during the formation of Ag NPs lowers the ζ-potential and surface charge of prepared inorganic–organic hybrids (from +31.3 to +19.9 mV and from 2.4 to 1.0 mmol/g at pH 7, respectively), their values are sufficiently positive to ensure electrostatic interaction with negatively charged cell walls of pathogens in acidic and slightly (up to pH ~8.5) alkaline solutions. The antimicrobial activity of hybrid microparticles against various pathogens (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans) is comparable with pristine NH2−CNFs. However, a long-timescale use of hybrids ensures the slow and controlled release of Ag+ ions to surrounding media (less than 1.0 wt.-% for one month).
Keywords: amino-modified cellulose nanofibrils, silver nanoparticles, hybrid microparticles, zeta-potential, antimicrobial activity
Published in DKUM: 09.12.2024; Views: 0; Downloads: 6
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6. Enzymatic, Antioxidant, and Antimicrobial Activities of Bioactive Compounds from Avocado (Persea americana L.) SeedsKaja Kupnik, Mateja Primožič, Vanja Kokol, Željko Knez, Maja Leitgeb, 2023, original scientific article Keywords: avocado seed, Persea Americana, HPLC, phenolic compounds, enzymatic activity, phytochemistry, antioxidant, antimicrobial activity
Published in DKUM: 10.04.2024; Views: 351; Downloads: 345
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7. Arnica Montana L. supercritical extraction optimization for antibiotic and anticancer activityTaja Žitek Makoter, Vesna Postružnik, Željko Knez, Andrej Golle, Barbara Dariš, Maša Knez Marevci, 2022, original scientific article Keywords: mountain arnica, natural extract, gactive ingredients, antimicrobial activity, anticarcinogenic activity
Published in DKUM: 05.04.2024; Views: 169; Downloads: 5
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8. Extending the protection ability and life cycle of medical masks through the washing processJulija Volmajer Valh, Tanja Pušić, Mirjana Čurlin, Ana Knežević, 2023, original scientific article Abstract: The reuse of decontaminated disposable medical face masks can contribute to reducing the environmental burden of discarded masks. This research is focused on the effect of household and laboratory washing at 50 °C on the quality and functionality of the nonwoven structure of polypropylene medical masks by varying the washing procedure, bath composition, disinfectant agent, and number of washing cycles as a basis for reusability. The barrier properties of the medical mask were analyzed before and after the first and fifth washing cycle indirectly by measuring the contact angle of the liquid droplets with the front and back surface of the mask, further by measuring air permeability and determining antimicrobial resistance. Additional analysis included FTIR, pH of the material surface and aqueous extract, as well as the determination of residual substances—surfactants—in the aqueous extract of washed versus unwashed medical masks, while their aesthetic aspect was examined by measuring their spectral characteristics. The results showed that household washing had a stronger impact on the change of some functional properties, primarily air permeability, than laboratory washing. The addition of the disinfectant agent, didecyldimethylammonium chloride, contributes to the protective ability and supports the idea that washing of medical masks under controlled conditions can preserve barrier properties and enable reusability.
Keywords: medical masks, washing, detergent, didecyldimethylammonium chloride, air permeability, antimicrobial activity, residuals
Published in DKUM: 15.03.2024; Views: 333; Downloads: 31
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9. Functionalisation of silicone by drug-embedded chitosan nanoparticles for potential applications in otorhinolaryngologyUrban Ajdnik, Lidija Fras Zemljič, Matej Bračič, Uroš Maver, Olivija Plohl, Janez Rebol, 2019, original scientific article Keywords: silicone, tympanostomy tube, chitosan, nanoparticles, drug delivery, antimicrobial activity
Published in DKUM: 22.03.2019; Views: 1460; Downloads: 6 |
10. Effect of peptides' binding on the antimicrobial activity and biocompatibility of protein-based substrates Maja Kaisersberger Vincek, 2017, doctoral dissertation Abstract: This work reveals the effect of coupling approach (chemical by using carbodiimide chemistry and grafting-to vs. grafting-from synthesis routes, and enzymatic by using transglutaminase) of a hydrophilic ε-poly-L-lysine (εPL) and an amphiphilic oligo-acyl-lysyl (OAK) derivative (K-7α12-OH) to wool fibers and gelatine (GEL) macromolecules, respectively, and substrates antibacterial activity against Gram-negative E. coli and Gram-positive S. aureus bacteria after 1–24 h of exposure, as well as their cytotoxicity. Different spectroscopic (ultraviolet-visible, infrared, fluorescence and electron paramagnetic resonance) and separation techniques (size-exclusion chromatography and capillary zone electrophoresis) as well as zeta potential and potentiometric titration analysis, were performed to confirm the covalent coupling of εPL/OAK, and to determine the amount and orientation of its immobilisation.
The highest and kinetically the fastest level of bacterial reduction was achieved with wool/GEL functionalised with εPL/OAK by chemical grafting-to approach. This effect correlated with both the highest grafting yield and conformationally the highly-flexible (brush-like) orientation linkage of εPL/OAK, implicating on the highest amount of accessible amino groups interacting with bacterial membrane. However, OAK`s amphipathic structure, the cationic charge and the hydrophobic moieties, resulted to relatively high reduction of S. aureus for grafting-from and the enzymatic coupling approaches using OAK-functionalised GEL.
The εPL/OAK-functionalised GEL did not induce toxicity in human osteoblast cells, even at ~25-fold higher concentration than bacterial minimum inhibitory (MIC) concentration of εPL/OAK, supporting their potential usage in biomedical applications.
It was also shown that non-ionic surfactant adsorbs strongly onto the wool surface during the process of washing, thereby blocking the functional sites of immobilized εPL and decreases its antibacterial efficiency.
Keywords: wool, gelatine, antimicrobial peptides, ε-poly-L-lysine, oligo-acyl-lysyl, grafting chemistry, grafting approach, peptide orientation, antibacterial activity, cytotoxicity
Published in DKUM: 17.08.2017; Views: 1931; Downloads: 180
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