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, izvirni znanstveni članek Opis: 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.
Ključne besede: ginger, supercritical fluid extraction, ultrasound-assisted extraction, antimicrobial activity
Objavljeno v DKUM: 09.05.2025; Ogledov: 0; Prenosov: 0
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2. Optimisation of the green process of industrial hemp - preparation and its extract characterisationTaja Žitek Makoter, Petra Kotnik, Teo Makoter, Vesna Postružnik, Željko Knez, Maša Knez Marevci, 2022, izvirni znanstveni članek Opis: Natural medicines and products are becoming increasingly important in the pharmaceutical
and food industries. The most important step in obtaining a natural remedy is the processing of
the natural material. This study offers the separation of the industrial hemp plant into fractions by
mechanical treatment, which has a significant impact on the selectivity of the obtained fractions. This
study also offers a solution to reduce waste by fractionating industrial hemp, focusing on the fraction
with the highest cannabinoid content (49.5% of CBD). The study confirmed the anticancer potential
of the extract, which prevents further division of WM-266-4 melanoma cells at a concentration of
10−3 mg/mL. However, application of the extract (c = 10−3 mg/mL) to normal human epidermal
melanocytes proved to be insignificant, as the metabolic activity of the cells was the same as in the
control cell group.
Ključne besede: supercritical fluid extraction, ultrasonic extraction, melanoma cells, extraction, WM-266-4
Objavljeno v DKUM: 09.05.2025; Ogledov: 0; Prenosov: 1
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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, izvirni znanstveni članek Opis: 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.
Ključne besede: antimicrobial activity, antioxidants, bioactive compounds, extraction, LC-MS/MS, phenolics, phytochemistry, pomegranate, Punica Granatum L., secondary metabolites
Objavljeno v DKUM: 24.03.2025; Ogledov: 0; Prenosov: 3
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4. Comparison of conventional and supercritical isolation methods from bee pollen and their effects on the concentrations of bioactive compoundsTaja Žitek Makoter, Vesna Postružnik, Anastasia Kyriakoudi, Elli Pantazi, Natasa Kalogiouri, Ioannis Mourtzinos, Željko Knez, Maša Knez Marevci, 2025, izvirni znanstveni članek Opis: The present work represents a profound investigation of material pretreatment, comparison of different isolation methods (conventional and supercritical), and characterization of phenolic compounds and amino acids from bee pollen. The determination of amino acids was carried out after developing a novel hydrophilic interaction chromatography combined with quadrupole time-of-flight tandem mass spectrometric method (HILIC-QTOF-MS/MS) with limits of detection over the range 1 mg/kg -5 mg/kg and recoveries over the range 87.6% - 97.1%. The optimal conditions for the isolation of amino acids are in the range of temperatures between 25°C to 55°C and at pressures between 300 bar and 350 bar. It can be concluded that the extraction temperature and the pressure affect antioxidant activity. The favored conditions are lower temperatures and higher pressures.
Ključne besede: bee pollen, in vitro antioxidant activity, HILIC-LC-QTOF-MS.MS, amino acids, WM-266-4 cells
Objavljeno v DKUM: 20.03.2025; Ogledov: 0; Prenosov: 2
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5. αP-x,y equilibrium data of the binary systems of 1-Butanol and 2-Butanol with argon at 313.15 K and 333.15 K – measurements and modelingDragana Borjan, Mariusz Nowak, Irena T. Žižović, Željko Knez, Maša Knez Marevci, 2024, izvirni znanstveni članek Ključne besede: high-pressure phase equilibrium Argon, 1-butanol, 2-butanol, Peng-Robinson equation of state, Boston-Mathias alpha function
Objavljeno v DKUM: 19.03.2025; Ogledov: 0; Prenosov: 2
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6. Ketoprofen-loaded PLGA-based bioactive coating prepared by supercritical foaming on a TiAl6V4 substrate for local drug delivery in orthopedic applicationsKatja Andrina Kravanja, Klodian Xhanari, Maša Knez Marevci, Uroš Maver, Matjaž Finšgar, 2024, izvirni znanstveni članek Opis: In this study, a novel biodegradable poly(lactic-co-glycolic) acid coating containing a model anti-inflammatory drug (ketoprofen) was prepared on TiAl6V4 substrate for use in orthopedic medicine by a two-step process combining drop casting and supercritical CO2-assisted foaming. The prepared coating was first investigated by surface analysis techniques using time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The combined results confirmed the loading of ketoprofen and its homogeneous spatial distribution in the coating. 3D profilometry revealed increased surface roughness of the coating compared to the bare TiAl6V4 substrate, which is favorable for cell adhesion. Furthermore, the electrochemical measurements (i.e., electrochemical impedance spectroscopy and potentiodynamic curve measurements) demonstrated that the coating application significantly mitigated corrosion compared to the bare TiAl6V4 substrate. In vitro drug release tests revealed extended drug release in simulated body fluids with zero-order release kinetics. Finally, the promising cell testing results using adipose-derived mesenchymal stem cells and osteoblasts confirmed the applicability of the coating for implants. Overall, the results of this study highlight the significant potential of the developed bioactive coating for future orthopedic applications.
Ključne besede: TiAlV, bioactive coating, implants, PLGA, supercritical foaming, ketoprofen
Objavljeno v DKUM: 14.03.2025; Ogledov: 0; Prenosov: 4
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7. Inovacijske tehnologije pridobivanja eteričnih olj in antioksidantov iz suhih listov rožmarina : magistrsko deloNina Kugl, 2025, magistrsko delo Opis: Namen magistrske naloge je bil pridobiti podatke o vplivu različnih tehnik obdelave suhih listov rožmarina na vsebnosti antioksidantov in na koncentracijo eteričnih olj (EO) v rožmarinu. Iskali smo metode, s katerimi lahko uspešno pridobivamo antioksidanta rožmarinsko kislino (RK) in karnozolno kislino (KK) ter EO iz mletih, suhih listov tunizijskega rožmarina. Preverili smo, kako uporabljene metode vplivajo na vsebnost antioksidantov in koncentracijo EO (γEO) v rožmarinu, tako da smo vsebnost antioksidantov in γEO v obdelanem rožmarinu primerjali z vsebnosti antioksidantov in γEO, pridobljenih iz rožmarina, ki ga nismo predhodno obdelali.
Primerjali smo tehnike mehanskega peletiranja, izpostavitve rožmarina v avtoklavu pri 70°C in različno visokih tlakih plinov N2 in CO2 ter mikrovalovno ekstrakcijo brez topil (SFME). Iz tako obdelanega rožmarina smo nato z hidrodestilacijo s Clevengerjevim aparatom destilirali EO, z acetonsko ekstrakcijo pa smo pridobili suhi praškast produkt z visoko vsebnostjo naravnih antioksidantov. Obdelane liste rožmarina in praškast ekstrakcijski produkt smo analizirali s tehnikama tekočinske kromatografije visoke ločljivosti z detektorjem UV-VIS in plinsko kromatografijo s plamensko ionizacijskim detektorjem.
Ugotovili smo, da smo s SFME najbolj znižali γEO v rožmarinu, kjer se po 10 min obdelavi koncentracija EO znižala za 80,52%. γEO v rožmarinu pa se je najmanj znižala pri mehanskem peletiranju. Najvišje vsebnosti antioksidantov RK in KK v rožmarinu smo določili v rožmarinu, ki je bil obdelan z mehanskim peletiranjem. V rožmarinu, obdelanem z mehanskim peletiranjem smo prav tako določili najvišje izkoristke ekstrakcije z acetonom.
Ključne besede: rožmarin, antioksidanti, eterična olja, SFME, peletiranje, hidrodestilacija, avtoklaviranje
Objavljeno v DKUM: 11.03.2025; Ogledov: 0; Prenosov: 8
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8. Izboljšanje stabilnosti fermentacijske brozge klavulanske kisline pred izolacijo z optimiranjem procesnih parametrov : magistrsko deloSimon Zadravec, 2025, magistrsko delo Opis: Bakterija Streptomyces clavuligerus med fermentacijskim procesom sintetizira klavulansko kislino (KK), ki učinkovito deluje kot inhibitor β-laktamaz in se uporablja v kombinaciji z antibiotiki za premagovanje bakterijske odpornosti. Nestabilnost KK med proizvodnim procesom predstavlja velik izziv, saj hitro razpada, kar zmanjšuje izkoristek in povečuje stroške proizvodnje. Namen te študije je izboljšati biosintezo KK z osredotočanjem na preučevanje vpliva procesnih parametrov na njeno stabilnost in produkcijo.
V magistrskem delu smo razvili kvantitativni spektrometrični model za merjenje koncentracij KK in glicerola. Razvit model omogoča hitro, učinkovito in robustno analizo teh dveh spojin med eksperimentalnimi poskusi, kar predstavlja izboljšanje v primerjavi s klasičnimi kromatografskimi tehnikami, saj pospeši pridobivanje rezultatov.
Model smo nato uporabili za spremljanje koncentracij KKin glicerola med eksperimentalnimi poskusi, v katerih smo spreminjali različne procesne parametre, kot so mešanje, zračenje, nadtlak, temperatura, redčenje ter kombinirali brozge iz različnih faz produkcijskega cikla S. clavuligerus. Poleg tega smo merili tudi koncentracijo raztopljenega kisika, viskoznost, pH in prisotnost nečistoče A, ki je razgradni produkt klavulanske kisline.
Rezultati so pokazali, da lahko pravilna nastavitev procesnih parametrov bistveno izboljša stabilnost in produktivnost klavulanske kisline. Povečanje zračenja in mešanja ter zvišanje tlaka je prineslo do 5 % izboljšanje izkoristka po 6 urah zadrževalnega časa ter 17 % izboljšanje izkoristka po 27 urah procesa, hkrati pa je koncentracija nečistoče A ostala stabilna, kar kaže na manjšo razgradnjo KK. Posamezno povečanje mešanja, zračenja ali tlaka ni dalo enako učinkovitih rezultatov, čeprav je prispevalo k zmanjšanju razgradnje KK od 11 % do 26 %. Ugotovitve prispevajo k optimizaciji industrijskega procesa proizvodnje KK, saj zmanjšujejo razgradnjo produkta in povečujejo izkoristek, kar vodi v bolj učinkovit proces in nižje stroške proizvodnje.
Ključne besede: klavulanska kislina, fermentacijski proces, stabilnost, optimizacija procesnih parametrov, spektrometrija
Objavljeno v DKUM: 28.02.2025; Ogledov: 0; Prenosov: 19
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9. Kromatografske metode za določevanje biooznačevalcev lipidne peroksidacije iz fizioloških vzorcev : magistrsko deloAmadeja Prša, 2025, magistrsko delo Opis: V magistrskem delu smo razvili in validirali kromatografske metode za določanje biomarkerjev lipidne peroksidacije v fizioloških vzorcih, s poudarkom na malondialdehidu (MDA), ki je ključni kazalec oksidativnega stresa. Uporabili smo tehnike plinske kromatografije z masno spektrometrijo (GC-MS) in tekočinske kromatografije z masno spektrometrijo (LC-MS/MS), ki omogočajo visoko občutljivost in selektivnost pri analizi kompleksnih bioloških vzorcev, kot je serum. Validacija metod je vključevala oceno linearnosti, ponovljivosti, točnosti in mej zaznave (LOD) za MDA in sorodne spojine. Poleg tega smo izvajali teste antioksidativne kapacitete, kot so DPPH, FRAP, CUPRAC, ORAC in TAC, da bi ocenili sposobnost seruma in drugih vzorcev pri nevtralizaciji prostih radikalov. Rezultati kažejo, da so razvite metode natančne, občutljive in primerne za analizo MDA v fizioloških vzorcih. Ugotovili smo, da koncentracije MDA korelirajo z intenzivnostjo oksidativnega stresa, kar potrjuje uporabnost teh biomarkerjev pri spremljanju patoloških stanj. Poleg tega smo pokazali, da ima serum pomembno antioksidativno kapaciteto, ki jo je mogoče učinkovito ovrednotiti z uporabo kombinacije različnih testov. Magistrsko delo prispeva k razvoju naprednih analitskih orodij za raziskave oksidativnega stresa, ki so ključnega pomena za razumevanje vpliva lipidne peroksidacije na zdravje in bolezni ter za razvoj novih terapevtskih strategij.
Ključne besede: Oksidativni stres, lipidna peroksidacija, malondialdehid, testi antioksidativnosti, kromatografske metode (GC-MS, LC-MS/MS).
Objavljeno v DKUM: 27.02.2025; Ogledov: 0; Prenosov: 24
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10. Optimization of the supercritical extraction and decarboxylation process of industrial hempTaja Žitek Makoter, Petra Kotnik, Teo Makoter, Željko Knez, Maša Knez Marevci, 2025, izvirni znanstveni članek Opis: Cannabinoids are the main active ingredients of Cannabis sativa L., obtained by a suitable extraction method and decarboxylation, in which the acid forms of the cannabinoids are converted into active forms. Supercritical CO2 extraction method and decarboxylation process were optimized for 7 cannabinoids (CBD, CBDA, THC, THCA, CBGA, CBN and CBC). The optimal extraction conditions for all cannabinoids were determined at a temperature of 60 °C and a pressure of 300 bar to 550 bar. At higher temperatures and reaction times, a significant depletion of neutral cannabinoids was observed. The optimal conditions of the decarboxylation process varied depending on the component. For the CBD component, which could be measured in the highest concentrations (560 mg/g), the optimal conditions were 140 °C and 10 min. The study can be an important model for predicting the behavior of cannabinoids under certain parameters.
Ključne besede: supercritical fluids, extraction, cannabinoids, decarboxilation, Cannabis sativa I
Objavljeno v DKUM: 08.01.2025; Ogledov: 0; Prenosov: 7
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