Development and optimization of HPLC method for determination substances in dried lemon extract

Hesperidin, eriocitrin, rutin ter kavna in klorogena kislina so antimikrobne snovi, ki jih najdemo v limoni in njenem suhem ekstraktu. Zaradi njihovih pozitivnih učinkov, predvsem na zdravje ljudi, se vse bolj pogosto uporabljajo v raznih prehrambenih dodatkih. V magistrskem delu smo razvili in optimizirali HPLC metodo, s katero identificiramo in kvantificiramo te antimikrobne snovi v suhem ekstraktu limone. Za ločevanje spojin smo uporabili gradientno elucijo, kjer smo 0,4 % ocetni kislini postopoma dodajali vse več organske faze (metanola) pri pretoku 0,8 ml/min. Komponente v ekstraktu smo identificirali s primerjavo UV spektrov in retenzijskih časov referenčnih substanc, vsebnost komponent pa smo določili na podlagi umeritvene krivulje. Pokazali smo linearnost metode za določevanje klorogene kisline, eriocitrina in hesperidina v območju 2,5–300 g/ml, kavne kisline v območju 1,0–300 g/ml in rutina v koncentracijskem območju 5,0–300 g/ml. Določili smo mejo zaznave (LOD), ki za vse komponente znaša 1,0 g/ml ter mejo določljivosti (LOQ), ki je 2,5 g/ml za hesperidin, eriocitrin in klorogeno kislino, 1,0 g/ml za kavno kislino ter 5,0 g/ml za rutin. Rezultati kažejo, da je metoda natančna za določevanje vseh komponent, medtem ko je točna za določevanje hesperidina in kavne kisline. Z optimizirano metodo smo določili vsebnost posameznih antimikrobnih komponent v različnih vzorcih ekstrakta limone. Vse komponente smo zaznali v liofiliziranem suhem ekstraktu limone, v katerem sta prevladovala hesperidin (7,09 mg/g ekstrakta) in eriocitrin (3,81 mg/g ekstrakta). Visoke vsebnosti hesperidina smo zaznali tudi v liofiliziranem ekstraktu limete, kjer je ta vrednost znašala 9,74 mg/g ekstrakta. Ostale komponente so bile v teh in ostalih vzorcih zaznane v manjših količinah, nekje od 0,15 do 2,5 mg komponente/g ekstrakta.Hesperidin, eriocitrin, rutin, caffeic acid and chlorogenic acid are antimicrobial substances found in lemon and its dry extracts. Due to their positive effects, especially on human health, they are increasingly used in various dietary supplements. Development and optimization of the HPLC method was needed in order to identify and quantify these antimicrobial substances in dried lemon extracts. In order to separate the compounds, gradient elution was used, in which an increasing amount of organic phase (methanol) was gradually added to 0.4% acetic acid at a flow rate of 0.8 ml/min. The components in the extract were identified by comparing the retention times, and the component content was determined based on the calibration curve. We showed the linearity of the method for the determination of chlorogenic acid, eriocitrin and hesperidin in the range from 2.5 to 300 μg/ml, caffeic acid in the range from 1 to 300 μg/ml and rutin in the concentration range from 5 to 300 mg/ml. The limit of detection (LOD) value was 1m μg/ml for all components and the limit of quantification (LOQ) values were 2.5 μg /ml for hesperidin, eriocitrin and chlorogenic acid, 1 μg /ml for caffeic acid and 5 μg /ml for rutin. The results showed that the method is precise for the determination of all components, while it is accurate for the determination of hesperidin and caffeic acid. The final method was used to determine the content of individual antimicrobial components in the samples. All components were detected in lyophilized dried lemon extract, in which hesperidin (7.09 mg/g extract) and eriocitrin (3.81 mg/g extract) predominated. High levels of hesperidin were also detected in the lyophilized lime extract, where this value was 9.74 mg/g of extract. Other components were also detected in samples, in which quantities were somewhere between 0.15 and 2.5 mg of component/g of extract

Hybrid Polylactic-Acid–Pectin Aerogels: Synthesis, Structural Properties, and Drug Release

Wound-dressing materials often include other materials stimulating wound healing. This research describes the first formulation of biodegradable hybrid aerogels composed of polylactic acid and pectin. The prepared hybrid material showed a highly porous structure with a surface area of 166 ± 22.6 m2·g−1. The addition of polylactic acid may have decreased the surface area of the pure pectin aerogel, but it improved the stability of the material in simulated body fluid (SBF). The pure pectin aerogel showed a high swelling and degradation ratio after 3 h. The addition of the polylactic acid prolonged its stability in the simulated body fluid from 24 h to more than one week, depending on the amount of polylactic acid. Biodegradable aerogels were loaded with indomethacin and diclofenac sodium as model drugs. The entrapment efficiencies were 63.4% and 62.6% for indomethacin and diclofenac sodium, respectively. Dissolution of both drugs was prolonged up to 2 days. Finally, sodium percarbonate and calcium peroxide were incorporated into the bioaerogels as chemical oxygen sources, to evaluate oxygen generation for potential wound healing applications

Simple, One-Pot Method for Preparing Transparent Ethyl Cellulose Films with Good Mechanical Properties

In this research, ethyl cellulose films were prepared by a simple, easy, controlled one-pot method using either ethanol or ethyl lactate as solvents, the films being formed at 6 °C. Titanium dioxide nanoparticles were incorporated to improve the oxygen transmission and water vapour transmission rates of the obtained films. This method used no plasticizers, and flexible materials with good mechanical properties were obtained. The resulting solvent-free and transparent ethyl cellulose films exhibited good mechanical properties and unique free-shapable properties. The obtained materials had similar properties to those reported in the literature, where plasticizers were incorporated into ethyl cellulose films with an elastic modulus of 528 MPa. Contact angles showed the hydrophobic nature of all the prepared materials, with contact angles between 80 and 108°. Micrographs showed the smooth surfaces of the prepared samples and porous intersections with honeycomb-like structures. The oxygen and water vapor transmission rates were the lowest for the ethyl cellulose films prepared in ethyl lactate, these being 615 cm3·m−2·day−1 and 7.8 gm−2·day−1, respectively, showing that the films have promise for food packaging applications

Fouling of nanofiltration membranes based on polyelectrolyte multilayers: The effect of a zwitterionic final layer

In this work, we investigate the effect of membrane surface chemistry on fouling in surface water treatment for polyelectrolyte multilayer based nanofiltration (NF) membranes. The polyelectrolyte multilayer approach allows us to prepare three membranes with the same active separation layer, apart from a difference in surface chemistry: nearly uncharged crosslinked Poly(allylamine hydrochloride) (PAH), strongly negative poly(sodium 4-styrene sulfonate) PSS and zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine-co-acrylic acid) (PMPC-co-AA). Initially, we study foulant adsorption for the three different surfaces (on model interfaces), to demonstrate how a different surface chemistry of the top layer affects the subsequent adsorption of five different model foulants (Humic Acids, Alginates, Silica Nanoparticles, negatively and positively charged Proteins). Subsequently, we study fouling of the same model foulants on our polyelectrolyte multilayer based hollow fiber NF membranes with identical surface chemistry to the model surfaces. Our results show that nearly uncharged crosslinked PAH surface generally fouls more than strongly negatively charged PSS surface. While negative BSA adsorbs better on PSS, probably due to charge regulation. Overall, fouling was mainly driven by electrostatic and acid-base interactions, which led, for both PAH and PSS terminated membranes, to flux decline and changes in selectivity. In contrast, we demonstrate through filtration experiments carried out with synthetic and real surface water, that the bio-inspired zwitterionic phosphatidylcholine surface chemistry exhibits excellent fouling resistance and thus stable performance during filtration

Hydrogeochemistry of submarine springs in Izola, Slovenia

Not far from the coast of Izola, Slovenia, are twelve funnel-shaped depressions on the seabed containing springs of warm, sulphurous water. These submarine depressions with springs are divided into three groups: from east to west, Izola, Bele skale, and Ronek. Water with similar thermal and sulphuric properties also occurs in the terrestrial spring in Izola. Some of these submarine springs (M03 - Izola, M05 - Bele skale and M10, M11 - Ronek) and the terrestrial spring (K04) were sampled for hydrogeochemical study. Three sampling campaigns took place in June and July 2020, October 2020, and April 2021. In addition, samples of seawater (SW01, SW02, SW03), groundwater from a well (VK01) and local non-sulphuric springs (K01, K02, K03) were taken for comparison. The submarine spring water was sampled using 100-ml syringes. In April 2021, an 8-litre Niskin water sampler (OceanTest Equipment, Inc.) was used in addition to the syringes. Samples collected in April 2021 using two different methods are labeled with an additional letter: /B for syringes and /N for Niskin. In-situ physicochemical parameters - pH, temperature, electrical conductivity, oxidation-reduction potential, and dissolved oxygen - were measured in the samples from the seawater and the submarine springs using a digital Multi 3430 meter (WTW GmbH, Weilheim, Germany) as soon as they were brought aboard the boat. Measurements of the terrestrial waters were performed on site using the same digital meter. A total of 26 water samples were collected for further analysis. All water samples were collected in HDPE bottles, except those for isotopic composition of dissolved inorganic carbon, which was sampled directly to Labco glass ampoules after 0.45 µm pore-sized membrane filtration. The samples were then chemically treated where required and stored in a refrigerator until analysis. The samples were then prepared for further laboratory analysis: geochemical composition (cations, anions), isotopic composition of oxygen (δ¹⁸O) and hydrogen (δ²H), total alkalinity (TA), isotopic composition of dissolved inorganic carbon (δ¹³CDIC), tritium activity (³H), isotopic ratio of strontium (⁸⁷Sr/⁸⁶Sr), and isotopic composition of sulphur (δ³⁴Sₛ₀₄ ‰) and oxygen (δ¹⁸Oₛ₀₄ ‰) in sulphate. This database contains information on the sampling dates and basic characteristics of the sampling sites, as well as the results from field measurements and laboratory analyses