1. Identification and content of astaxanthin and its esters from microalgae Haematococcus pluvialis by HPLC-DAD and LC-QTOF-MS after extraction with various solventsBiljana Todorović, Jaša Veno Grujić, Andreja Urbanek Krajnc, Roman Kranvogl, Jana Ambrožič-Dolinšek, 2021, original scientific article Abstract: Haematococcus pluvialis, a unicellular green microalga that produces a secondary metabolite under stress conditions, bears one of the most potent antioxidants, namely xanthophyll astaxanthin. The aim of our study was to determine the content of astaxanthin and its esterified forms using three different solvents—methyl tert-butyl ether (MTBE), hexane isopropanol (HEX -IPA) and acetone (ACE)—and to identify them by using high performance liquid chromatography coupled with diode array detection and the quadrupole time-of-flight mass spectrometry (HPLC-DAD and LC-QTOF-MS) technique. We identified eleven astaxanthin monoesters, which accounted for 78.8% of the total astaxanthin pool, six astaxanthin diesters (20.5% of total), while free astaxanthin represented the smallest fraction (0.7%). Astaxanthin monoesters (C16:2, C16:1, C16:0), which were the major bioactive compounds in the H. pluvialis samples studied, ranged from 10.2 to 11.8 mg g−1 DW. Astaxanthin diesters (C18:4/C18:3, C18:1/C18:3) were detected in the range between 2.3 and 2.6 mg g−1 DW. All three solvents were found to be effective for extraction, but MTBE and hexane-isopropanol extracted the greatest amount of free bioactive astaxanthin. Furthermore, MTBE extracted more low-chain astaxanthin monoesters (C16), and hexane-isopropanol extracted more long-chain monoesters (C18 and above) and more diesters. We can conclude that MTBE is the solvent of choice for the extraction of monoesters and hexane-isopropanol for diesters.
Keywords: astaxanthin diesters, astaxanthin monoesters, carotenoids, Hematococcus pluvialis, astaxanthin diesters, solvent extraction
Published in DKUM: 22.11.2024; Views: 0; Downloads: 6
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2. Sustainable All-Cellulose Biocomposites from Renewable Biomass Resources Fabricated in a Water-Based Processing System by the Vacuum-Filtration-Assisted Impregnation MethodÖzkan Yapar, Petteri Piltonen, Ajra Hadela, Aleksandra Lobnik, 2024, original scientific article Keywords: all-cellulose composites, NaOH/urea/water solvent system, full dissolution of cellulose, dissolving pulp, regenerated cellulose
Published in DKUM: 16.07.2024; Views: 125; Downloads: 26
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3. Optimizacija postopka ekstrakcije učinkovin iz arnike arnica montana in formulacija produktov : master's thesisÁlvaro Pequeno Alonso, 2022, master's thesis Abstract: Arnica Montana je obetaven vir bioaktivnih spojin, predvsem fenolov, ki zaradi svoje antioksidativne aktivnosti izkazujejo koristi za zdravje ljudi. Da bi dosegli stopnjo farmacevtske uporabe, je treba cvetove Arnice Montana predelati v izdelek, ki je primeren za preživetje. V ta namen so bile izvedene različne ekstrakcijske tehnike z različnimi topili: hladna maceracija, ultrazvok, Soxhlet in superkritični CO2; uporabljena topila so bila etanol, metanol in mešanica etanola in vode 95:5 (v:v). Analiza, ki je vključevala ultravijolično/vidno spektrometrijo, je bila opravljena za merjenje antioksidativne aktivnosti in celotne vsebnosti fenolov v ekstraktih. Končno je bil organogel oblikovan z uporabo izvlečka, olja konoplje in voska riževih otrobov ter testiran glede njegove stabilnosti. V okviru tega dela je bil prvič formuliran organogel z visoko stabilnostjo, saj do sedaj v znanstveni literaturi ni bilo podatkov o tovrstni formulaciji. Za določitev njegovih reoloških lastnosti in topnosti v različnih topilih pri različnih temperaturnih pogojih bodo potrebne dodatne študije.
Keywords: Arnica Montana, organogels, solvent extraction, phenolic compounds, isolation, formulation
Published in DKUM: 13.07.2022; Views: 584; Downloads: 40
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4. Including solvent-mediated interactions into the Poisson-Boltzmann theoryKlemen Bohinc, 2012, doctoral dissertation Abstract: Electrostatic interactions are omnipresent in colloidal and biological systems; for example they take place in aqueous solutions that contain mobile salt ions. Water plays a crucial role for the energetics of such systems. The ordering of water molecules changes the polarization and thus contributes to the electrostatic properties of the system. In particular, structural correlations between solvent molecules give rise to an inhomogeneous and non-local dielectric response that contributes to the energetics and the stability of biomacromolecules.
This work is concerned with including solvent structures into mean-field electrostatics. It consists of three related subjects.
In the first part we introduce a solvent model of interacting Langevin dipoles and incorporate that model into the Poisson-Boltzmann (PB) theory for an aqueous solution of monovalent ions in contact with a charged surface. The interplay between the electric double layer and the orientational ordering of solvent molecules determines the spatial decay of the solvent polarization. We showed that our model can result in a sign inversion of the electrostatic potential at a charged surface.
The second part applies the PB model for a solvent of interacting Langevin dipoles to a mixed anionic/zwitterionic lipid layer. In the model the headgroups have ability to polarize the water in the headgroup region. The result is a positive electrostatic potential everywhere in the system.
In the last part we introduce the Poisson-Helmholtz-Boltzmann theory, which adds to the electrostatic interaction potential between two ions an additional Yukawa potential. The latter accounts for solute-mediated ion-ion interactions. We demonstrate that these interactions can give rise to ion specific effects. One of the possible applications of the theory is related to the Hofmeister series. The presented analysis focuses on two systems. The first is the system of two charged surfaces embedded in a solution of only counterions, whereas the second system is one single charged surface in contact with a symmetric 1:1 electrolyte solution.
Keywords: Biomacromolecules, Solvent structure, Langevin dipoles, Electrostatics, Poisson and Helmholtz equations, Boundary-value problems, Yukawa potential
Published in DKUM: 19.09.2012; Views: 2566; Downloads: 181
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5. Comparison of the esterification of fructose and palmitic acid in organic solvent and supercritical carbon dioxideSaša Šabeder, Maja Leitgeb, Željko Knez, 2005, original scientific article Abstract: Sugar fatty acid esters are nonionic surfactants, which are used for personal care products, cosmetic applications, and as emulsifiers for food. In recent years, enzymatic synthesis of sugar fatty acid esters is attracting keen attention as a new manufacturing method for future application. Reaction parameters of lipase-catalyzed synthesis of fructose fatty acid esters in organic solvent were optimized in a batch reactor at atmospheric pressure. Optimum conditions for reaction performed in organic solvent at atmospheric pressure were 10% (wžw of substrates) of lipase from Candida antarctica B, 12.14% (wžw of reaction mixture) of molecular sieves at 60 C, and stirring rate of 600 rpm. Esterification of fructose and palmitic acid was performed insupercritical carbon dioxide with and without addition of cosolvent (organicsolvent) at 60 C. Effect of pressure on enzyme activity was studied.
Keywords: chemical processing, high pressure technology, supercritical CO2, esterification, organic solvent, lipase catalysed synthesis, fructose fatty esters, Candida antarctica B, enzyme activity
Published in DKUM: 01.06.2012; Views: 2400; Downloads: 189
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6. Enzymatic synthesis of sugar fatty acid esters in organic solvent and in supercritical carbon dioxide and their antimicrobial activityMaja Leitgeb, Saša Šabeder, Željko Knez, 2008, original scientific article Abstract: Lipase-catalyzed synthesis of different sugar fatty acid esters was performed in high yields in 2-methyl-2-butanol at atmospheric pressure and in supercritical carbon dioxide (SC CO2) at 10 MPa. Influence of molecular sievesconcentration on conversion in SC CO2 was studied. Growth inhibitory effect of commercial sucrose fatty acid esters and enzymatically synthesized sucrose and fructose fatty acid esters on Gram-positive and Gram-negative micro-organisms, as well as on yeast was tested. Sucrose laurate inhibited the growth of Bacillus cereus food poisoning bacteria at a concentration of 9.375 mg/ml.
Keywords: biocatalysis, lipase, sugar fatty acid ester, organic solvent, cupercritical CO2, antimicrobial activity
Published in DKUM: 31.05.2012; Views: 2326; Downloads: 110
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7. Isolation of chlorophylls from stinging nettle (Urtica dioica L.)Maša Hojnik Niderl, Mojca Škerget, Željko Knez, 2007, original scientific article Abstract: This study was aimed to assess the feasibility of extracting chlorophylls fromstinging nettle (Urtica dioica L.) by solvent extraction. In preliminary, the investigation concerned three parts of raw material (leaves, stalk and whole plant), different preservation techniques (blanching and drying) and different storage temperatures of preserved material ( |20 C for blanched and 4 C for dried sample). Extracts were analysed for chlorophyll A and chlorophyll B, respectively, by means of HPLC method. Afterwards, optimizationof single-step conventional extraction was carried out by examining the influence of the following process parameters on the extraction yield and isolation efficiency of chlorophylls: type of organic solvent, content of water in ethanol/water mixtures, ratio solvent/material, temperature, time of extraction and pH of the extraction mixture. Furthermore,to improve the yield and/or the selectivity of the extraction, multi-step conventional extraction experiments as well as other solid ]liquid extraction techniques (soxhlet and ultra-sound assisted) were performed and compared. c 2007 Elsevier B.V. All rights reserved.
Keywords: chemical processing, extraction, nettle, isolation of chlorophyll, chlorophyll content, solvent extraction
Published in DKUM: 31.05.2012; Views: 2872; Downloads: 118
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