1. Kemijske lastnosti strupa Kranjske sivke in njegova uporaba v kozmetičnih produktih : diplomsko delo visokošolskega strokovnega študijskega programa I. stopnjeKlara Glušič, 2025, undergraduate thesis Abstract: Strup Kranjske sivke je manj raziskana surovina, ki postaja vedno popularna zaradi svojih lastnosti, katere so pomembne tako v kozmetiki kot v zdravstvu. Zato smo se v okviru te diplomske naloge odločili raziskati nekatere osnovnejše kemijske lastnosti čebeljega strupa, kot so vsebnost proteinov, antioksidativna aktivnost in protivnetna aktivnost. Pri tem smo primerjali pet vzorcev, ki so se razlikovali po času nabiranja, glede na obdobja paše čebel, in po mestu nabiranja strupa. Hkrati pa smo preverili obstojnost primera emulzije in hidrogela, ki vsebujeta raziskovano učinkovino.
Rezultati uporabljene Bradfordove metode so pokazali visoko vsebnost proteinov v vzorcih, ki je znašala približno 90 %.To je bilo pričakovano glede na sestavo, ki jo podajajo članki na temo strupa medonosnih čebel. Podobno temu so rezultati antioksidativne analize z DPPH radikalom in protivnetne aktivnosti, dokazane z metodo, ki uporablja jajčni albumin, pokazali pričakovane vrednosti glede na opise drugih avtorjev. Pri tem je test antioksidativne aktivnosti pokazal 50 % inhibicijo pri koncentraciji okoli 30 mg/mL, z odstopanjem dveh vzorcev, zaradi prisotnih nečistoč. Test protivnetne aktivnosti pa je pokazal od 30 do 45 % inhibicijo.
Keywords: Čebele, strup, kozmetika, lastnosti, kemija, proteini, antioksidativnost, protivnetnost, krema, hidrogel
Published in DKUM: 29.09.2025; Views: 0; Downloads: 20
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2. Izolacija maščobnih kislin iz lubeničnih semen (Citrullus lanatus, L.)Alja Polona Krasnič, 2025, undergraduate thesis Abstract: Diplomsko delo obravnava izolacijo maščobnih kislin iz semen lubenice (Citrullus lanatus, L.) z uporabo različnih ekstrakcijskih metod. Glavni cilj je bil raziskati vpliv izbire ekstrakcijske tehnike na izkoristek in sestavo pridobljenih maščobnih kislin, s poudarkom na vsebnosti linolne in oleinske kisline. V okviru eksperimentalnega dela so bili izvedeni postopki hladne in vroče maceracije, ultrazvočne ekstrakcije, Soxhlet ekstrakcije ter superkritične ekstrakcije s CO2 pri različnih tlakih in temperaturah.
Ekstrakti so bili podvrženi saponifikaciji, nato pa analizirani z metodo plinske kromatografije v povezavi z masno spektrometrijo (GC-MS). Rezultati so pokazali, da je linolna kislina najpogostejša sestavina vseh vzorcev, sledita ji oleinska in palmitinska kislina, medtem ko je bil delež stearinske kisline najmanjši. Najvišje vsebnosti maščobnih kislin so bile določene v ekstraktih, pridobljenih s Soxhletovo ekstrakcijo in superkritično ekstrakcijo pri višjih tlakih in temperaturah. Medtem so bili izkoristki ekstrakcij najvišji pri vroči maceraciji.
Na podlagi rezultatov lahko sklepamo, da ekstrakcijska metoda pomembno vpliva na količino izoliranih maščobnih kislin, manj pa na njihovo sestavo. Diplomsko delo poudarja potencial semen lubenice kot vir bioaktivnih lipidov in njihovo možno uporabo v prehranski, farmacevtski ter kozmetični industriji, hkrati pa prispeva k razvoju trajnostnih metod predelave živilskih stranskih produktov.
Keywords: ekstrakcija, kromatografija, saponifikacija, semena, superkritični fluidi
Published in DKUM: 12.09.2025; Views: 0; Downloads: 20
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3. Impact of storage conditions on stability of bioactive compounds and bioactivity of beetroot extract and encapsulatesVesna Postružnik, Slađana Stajčić, Dragana Borjan, Gordana ĆetkoviĆ, Željko Knez, Maša Knez Marevci, Jelena J. Vulić, 2025, original scientific article Abstract: Background: In this study, bioactive compounds (phenolics and betalains) extracted from beetroot were stabilized by encapsulation with maltodextrin and soy protein by the freeze drying method. Stability of bioactive compounds and bioactivities in a beetroot extract and encapsulates during 60 days of storage at 4 ◦C (without light) and at 25 ◦C (with and without light) were investigated. (2) Methods: Contents of bioactive compounds and bioactivity (antioxidant activity by DPPH, RP, and ABTS tests; anti-inflammatory and antihyperglycemic activity) were determined. Improvement in stability of bioactives’ content and bioactivity of prepared encapsulates in relation to the extract was observed after storage at room temperature under light conditions. (3) Results: Encapsulation with maltodextrin showed improvement in stability of all studied bioactive parameters, while an encapsulate with soy protein improved stability of bioactives and antioxidant activity compared to the extract. The encapsulated beetroot extract represents a promising food additive for functional foods due to their content of bioactive compounds and consequent bioactivities.
Keywords: isolation, phenolic copound, colorants, formulation, functional foods
Published in DKUM: 08.08.2025; Views: 0; Downloads: 10
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4. 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: 12
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5. 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, original scientific article Abstract: 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.
Keywords: supercritical fluid extraction, ultrasonic extraction, melanoma cells, extraction, WM-266-4
Published in DKUM: 09.05.2025; Views: 0; Downloads: 10
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6. 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: 14
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7. 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, original scientific article Abstract: 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.
Keywords: bee pollen, in vitro antioxidant activity, HILIC-LC-QTOF-MS.MS, amino acids, WM-266-4 cells
Published in DKUM: 20.03.2025; Views: 0; Downloads: 6
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8. Extraction of active compounds from mixtures of hemp (Cannabis sativa) with Pants of the Zingiberaceae familyVesna Postružnik, Taja Žitek Makoter, Darko Goričanec, Petra Kotnik, Željko Knez, Maša Knez Marevci, 2023, original scientific article Keywords: supercritical fluid extraction, ultrasound-assisted extraction, hemp, ginger, turmeric, cardamom
Published in DKUM: 08.05.2024; Views: 234; Downloads: 26
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9. 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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10. The extraction process, separation, and identification of curcuminoids from turmeric curcuma longaGal Slaček, Petra Kotnik, Azra Osmić, Vesna Postružnik, Željko Knez, Matjaž Finšgar, Maša Knez Marevci, 2023, original scientific article Abstract: Turmeric Curcuma longa is a well-known spice with various health benefits, attributed primarily to curcumin. Soxhlet extraction, cold maceration, ultrasound-assisted extraction (UAE), and supercritical fluid extraction were performed, and the content of total phenols, proanthocyanidins, and antioxidants was analysed by UV/VIS spectrophotometry. High-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was employed to identify and quantify the curcumin content. Supercritical extracts had the highest total phenolic content (538.95 mg GA/100 g material), while the Soxhlet extracts had the highest content of proanthocyanidins (4.77 mg PAC/100 g of material). Extracts obtained by UAE and supercritical extraction have the highest antioxidant potential. Antioxidant activity measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH center dot) was 64.27% and 1750.32 mg Trolox per g dry weight by 2,2-azinobis(3-ethylbenzothiazoline 6 sulphonic acid) (ABTS(+center dot)) for the extract obtained by supercritical extraction. The UAE resulted in the highest amount of curcumin (1.91 mg curcumin/g material). A kinetic study showed that extraction yield in supercritical extracts decreased with increasing temperature and that the content of isolated curcumin was inversely proportional to solvent-to-feed ratio (S/F). The present study has confirmed that turmeric is an excellent source of antioxidants, such as curcumin, that play an important role in reducing cellular stress by neutralising free radicals.
Keywords: turmeric, curcumin, total phenols, proanthocyanidins, antioxidants
Published in DKUM: 09.02.2024; Views: 361; Downloads: 60
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