enzimska lipofilizacija vitamina C linolnom kiselinom - određivanje antioksidativnih i difuzionih svojstava L-askorbil-linolata

Lipophilic derivatives of vitamin C are additives with antioxidant properties, attractive for application in food, cosmetics and pharmaceutics. They could be synthesized in lipase-catalyzed processes by using various acyl donors. Hereby, we present application of linoleic acid, which is polyunsaturated fatty acid essential in human nutrition, for esterification of vitamin C catalyzed by immobilized enzyme preparation Novozym® 435 in acetone. Highest specific ester yield, 9.7 mmol/g of immobilized lipase, was accomplished with 0.15 M of vitamin C, 0.6 M of linoleic acid, 3 g/l of enzyme and 0.07% (v/v) of water, at 60°C. NMR analyses of purified product proved that synthesized molecule was identical to 6-O-ascorbyl linoleate. Capacity of ester for scavenging 2,2-diphenyl-1-picrylhydrazyl radicals was two times higher comparing to parent molecule, vitamin C. Its diffusion coefficient, determined using Franz cell and cellulose acetate membrane, was 40% higher than palmitate and 62% higher than oleate. Obtained results showed that L-ascorbyl linoleate could be successfully synthesized in biocatalyzed processes. Furthermore, it was demonstrated that it possess high potential for application in different lipophilic products due to its liposolubility, high antioxidant efficiency and good diffusion properties.Lipofilni derivati vitamina C su aditivi sa antioksidativnim dejstvom pogodni za primenu u prehrambenim, kozmetičkim i farmaceutskim proizvodima. Mogu biti sintetisani u procesima katalizovanim lipazama korišćenjem različitih acil-donora. U ovom radu, opisana je primena linolne kiseline, polinezasićene masne kiseline esencijalne u ljudskoj ishrani, u esterifikaciji vitamina C katalizovanoj imobilisanim enzimskim preparatom Novozym® 435 u acetonu. Najviši specifični prinos estra od 9,7 mmol/g imobilisane lipaze, ostvaren je sa 0,15 M vitamina C, 0,6 M linolne kiseline, 3 g/l enzima i 0,07 zapr. % vode, na 60°C. NMR analize prečišćenog proizvoda dokazale su da je sintetisani molekul identičan 6-O-askorbil-linolatu. Kapacitet estra za vezivanje 2,2- difenil-1-pikrilhidrazil radikala bio je dva puta viši u odnosu na sam vitamin C. Njegov koeficijent difuzije, određen korišćenjem Franz-ove ćelije i celuloza-acetatne membrane, bio je za 40% viši u odnosu na palmitat i za 62% u odnosu na oleat. Ostvareni rezultati pokazali su da L-askorbil-linolat može uspešno biti sintetisan u biokatalizovanom procesu. Pored toga, dokazano je da ovaj estar poseduje značajan potencijal za primenu u različitim lipofilnim proizvodima zbog svoje liposolubilnosti, snažnog antioksidativnog dejstva i pogodnih difuzionih karakteristika

Hydrogels based on poly(methacrylic acid) for controlled release of anti-inflammatory drugs

Everyday struggle of humanity with novel diseases and present once, urge researchers to find novel and improve existing therapies to enhance their efficiency and safety. One of the promising approaches to overcome these challenges is controlled release of drugs. Biomaterials based on poly(methacrylic acid) (PMAA) are excellent drug delivery systems because they can control release rate and released amount of drug. Also, due to their pH sensitivity the PMAA hydrogels can release drug at the site of action. Namely, these nontoxic and biocompatible hydrogels swell in the environment with pH value higher than pKa of PMAA (4.6) and release encapsulated drug during the process. In present study, PMAA hydrogels are synthetized under ambient conditions by simple, cost effective and eco-friendly synthesis. Novel initiation system based on hydrogen peroxide, potato peel peroxidase and vitamin C (VC) is used for the first time for free radical polymerization of PMAA hydrogel. In accordance with the principles of circular economy, peroxidase was isolated from potato peel waste by water extraction for 12 h at 4 ℃. Four PMAA hydrogels were prepared by using potato peel peroxidase with various enzyme activity (0.4; 0.8; 1.2 and 1.8 IU), whereas the amounts of H2O2 (30 mL) and VC (10 mg) have been kept constant. The composition of the PMAA hydrogels was confirmed by FTIR analysis, whereas their porous structure was revealed by SEM. The swelling of the PMAA hydrogels was monitored in two media: 0.1M HCl (as simulation of human stomach) and phosphate buffer with pH 7.4 (as simulation of human intestines). In order to encapsulate anti-inflammatory drug – dexamethasone into the PMAA hydrogels, the hydrogels were immersed into the dexamethasone aqueous solution (5 mg/ml) and left to swell to the equilibrium, after which they were dried at room temperature. Dexamethasone release from the PMAA hydrogels was monitored in the same environments as was the PMAA swelling. The results showed that around seven times higher amount of dexamethasone was released in the medium with pH 7.4 than in the medium with pH 1. Present study has showed that the PMAA hydrogels, prepared through green and eco-friendly method, have huge potential for encapsulation and controlled release of anti-inflammatory drugs and therefore, for the treatment of rheumatoid arthritis

Freeze vs. Spray Drying for Dry Wild Thyme (Thymus serpyllum L.) Extract Formulations: The Impact of Gelatin as a Coating Material

Freeze drying was compared with spray drying regarding feasibility to process wild thyme drugs in order to obtain dry formulations at laboratory scale starting from liquid extracts produced by different extraction methods: maceration and heat-, ultrasound-, and microwave-assisted extractions. Higher total powder yield (based on the dry weight prior to extraction) was achieved by freeze than spray drying and lower loss of total polyphenol content (TPC) and total flavonoid content (TFC) due to the drying process. Gelatin as a coating agent (5% w/w) provided better TPC recovery by 70% in case of lyophilization and higher total powder yield in case of spray drying by diminishing material deposition on the wall of the drying chamber. The resulting gelatin-free and gelatin-containing powders carried polyphenols in amount ~190 and 53-75 mg gallic acid equivalents GAE/g of powder, respectively. Microwave-assisted extract formulation was distinguished from the others by a higher content of polyphenols, proteins and sugars, higher bulk density and lower solubility. The type of the drying process mainly affected the position of the gelatin-derived -OH and amide bands in FTIR spectra. Spray-dried formulations compared to freeze-dried expressed higher thermal stability as confirmed by differential scanning calorimetry analysis and a higher diffusion coefficient; the last feature can be associated with the lower specific surface area of irregularly shaped freeze-dried particles (151-223 µm) compared to small microspheres (~8 µm) in spray-dried powder

THE EFFECT OF ENCAPSULATED AMOUNT OF CAFFEINE ON THE MECHANISM OF ITS RELEASE FROM HYDROGELS BASED ON POLY(METHACRYLIC ACID) AND CASEIN

Researchers are making everyday efforts to develop new drugs or improve present ones in order to enhance therapies of various diseases, especially serious ones like cancer. Drug delivery systems (DDS) are one of the solutions for safer and more efficient therapy. Hydrogels based on poly(methacrylic acid) (PMAA) are extensively investigated as DDS due to their nontoxicity, biocompatibility and pH sensitivity. Many chemotherapeutics are poorly watersoluble, so it is quite challenging to encapsulate them into highly hydrophilic PMAA. In our previous study we overcome this limitation by modifying PMAA with amphiphilic casein and demonstrated that poorly water-soluble model drug – caffeine can be successfully encapsulated and released in control manner from these samples (H hydrogels). In present study we go step forward and investigated how the change in the amount of encapsulated caffeine affect the mechanism of caffeine release from the H hydrogels in medium with pH of 6.8 (which simulates the environment in human intestines). Commonly used models for the analysis of kinetics of drug release from hydrogels: Ritger-Peppas, Higuchi and Kopcha model are employed for the analysis of the mechanism of caffeine release. Presented results indicate that it is possible to adjust the manner and mechanism of drug release by changing the amount of encapsulated drug, due to which the H hydrogels can adapt to the unique requirements of the therapy

Razmena čestica između pokretne i nepokretne zone u kontaktorima gas-pokretna čvrsta faza-pakovan sloj

In countercurrent gas - flowing solids - fixed bed contactors, a fraction of the flowing solids is in motion (dynamic holdup), while the other fraction is resting on the fixed bed elements. In this study it was experimentally proved that the stagnant zone should not be considered as a dead part of the column, but that there is a dynamic exchange between these two portions of flowing solids particles. Combining a mathematical model with tracer experiments, the rate of exchange was determined and it was shown that only a small part (ca. 20 %) of the stagnant region should be considered as a dead one.Kontaktori gas-pokretna čvrsta faza-pokovan sloj predstavljaju novi tip uređaja za separacione procese, prenos toplote i hemijske reaktore. U ovom tipu kontaktora gas struji na gore kroz pakovan sloj u koloni, dok sitne čestice pokretne čvrste faze struje na dole. Pokretnu čvrstu fazu karakterišu dinamički i statički sadržaj, jer se deo čestica nalazi u kretanju, dok drugi deo čestica miruje nataložen na elementima pakovanja. U ovom radu je pretpostavljeno i eksperimentalno dokazano da nataložene čestice na pakovanju ne predstavljaju neaktivni (mrtvi) deo pokretne čvrste faze, kao što se do sada pretpostavljalo, već postoji stalna razmena između pokretnih čestica u toku (dinamički sadržaj) i onih koje su nataložene (statički sadržaj). Primenom tehnike sa obeleženom supstancom pokazano je da samo mali deo nataloženih čestica na punjenju (oko 20 %) ne biva zamenjeno ni posle veoma dugog vremena i zaista predstavlja "mrtvu zonu". Kombinovanjem izvedenog matematičkog modela sa eksperimentalnim rezultatima određena je brzina razmene pokretnih i nepokretnih čestica

CONTROLLED RELEASE OF CAFFEINE FROM THREE DIMENSIONAL NETWORKS BASED ON POLY(METACRYLIC ACID) AND CASEIN - ANALYSIS OF THE EFFECT OF CAFFEINE CONCENTRATION ON RELEASE PROCESS

Everyday demands for safer and more efficient therapy for many diseases, especially serious ones such as various types of cancer, put various challenges in front of modern science. One of them lies in the fact that numerous anticancer drugs are poorly-water soluble and therefore their encap-sulation and controlled release are quite demanding processes. In the present study, we deepened our research of carrier based on hydrophilic poly(methacrylic acid) modified with amphiphilic ca-sein, in which poorly water-soluble model drug caffeine was encapsulated (PMAC-Caf hydrogels). It was investigated how neutralization degree of methacrylic acid (MAA) and amount of encapsulated caffeine affected swelling behavior of the PMAC-Caf hydrogels and caffeine release. Easy, one pot, simultaneous synthesis of the carrier and the encapsulation of caffeine is presented, obtaining thereby as prepared PMAC-Caf drug delivery system that could respond to the specific demands of the tar-geted delivery of the poorly water-soluble drug - protecting it in the environment which simulated human stomach and releasing it in the environment which simulated human intestines. Changing the synthesis parameters (neutralization degree of MAA and/or amount of encapsulated caffeine) we achieved controlled release of caffeine, indicating that the number of the required doses of the drug in the treatment and its side effects could be reduced. Results showed that the PMAC-Caf drug deliv-ery systems have huge potential for controlled release of poorly water-soluble drugs

Novel eco-friendly initiation system based on vitamin C for energy efficient synthesis of PMAA hydrogel used for delivery of phenolic compounds

This study reports successful free radical synthesis of pH-sensitive hydrogels based on poly(methacrylic acid) (PMAA) by using new green initiation system based on vitamin C and hydrogen peroxide (VC/H2O2). The application of proposed initiation system provides many advantages, above all cost effective and eco-friendly synthesis which can be carried out under ambient conditions. The obtained PMAA hydrogels are analyzed by various technics: Differential Scanning Calorimetry, Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy and by using single compression tests. In line with the intended application, PMAA hydrogels are further investigated in terms of their potential to be used for encapsulation and controlled release of active substances such as antioxidant phenolic compounds. To keep it green, the total phenolic compounds (TPC) were obtained from orange peels waste by applying ultrasonic-assisted extraction and deep eutectic solvent (DES) based on glycerol:urea:water. The TPC were successfully encapsulated into the PMAA hydrogels which were previously estimated to have the optimal mechanical and swelling properties with respect to the final application. The swelling behavior of the PMAA hydrogels and controlled release of the TPC were tested as a function of the various synthesis parameters in several media with different pH values. It was shown that TPC can be released in control manner in medium which simulates the environment in human intestines, finally resulting in enhanced bioavailability of TPC, reduced side effects and improved therapeutic effects

Novel eco-friendly initiation system based on vitamin C for energy efficient synthesis of PMAA hydrogel used for delivery of phenolic compounds

This study reports successful free radical synthesis of pH-sensitive hydrogels based on poly(methacrylic acid) (PMAA) by using new green initiation system based on vitamin C and hydrogen peroxide (VC/H2O2). The application of proposed initiation system provides many advantages, above all cost effective and eco-friendly synthesis which can be carried out under ambient conditions. The obtained PMAA hydrogels are analyzed by various technics: Differential Scanning Calorimetry, Fourier Transform Infrared spectroscopy, Scanning Electron Microscopy and by using single compression tests. In line with the intended application, PMAA hydrogels are further investigated in terms of their potential to be used for encapsulation and controlled release of active substances such as antioxidant phenolic compounds. To keep it green, the total phenolic compounds (TPC) were obtained from orange peels waste by applying ultrasonic-assisted extraction and deep eutectic solvent (DES) based on glycerol:urea:water. The TPC were successfully encapsulated into the PMAA hydrogels which were previously estimated to have the optimal mechanical and swelling properties with respect to the final application. The swelling behavior of the PMAA hydrogels and controlled release of the TPC were tested as a function of the various synthesis parameters in several media with different pH values. It was shown that TPC can be released in control manner in medium which simulates the environment in human intestines, finally resulting in enhanced bioavailability of TPC, reduced side effects and improved therapeutic effects

Polymer-Lipid Matrices based on Carboxymethyl Cellulose/Solagum and Liposomes for Controlled Release of Folic Acid

Liposome-encapsulated folic acid is incorporated into the films made from sodium carboxymethyl cellulose (CMC) (2 mas%) and a mixture of CMC and solagum (9:1 w/w) using the film-forming cast solution method. Histidine is used to increase solubility for folic acid in liposomes (1–5 mg mL−1), and propylene glycol is used as a film plasticizer (2.6 mas%). The obtained films (50–60 µm tick) containing 3.12–20.19 mg of folic acid per gram of film are envisaged to be used as patches for transdermal delivery of folic acid. Therefore, some physical, mechanical, release and structural attributes of the films are scrutinized. Folic acid gives yellow color to the films and contributes to stronger chemical bonds which result in improved strength of the film. Liposomes prolong the release of folic acid from films to 24 h without adverse effects on mechanical properties of the films, but degrade homogeneity of the films, which can be ascribed to its agglomeration within the film matrix as revealed by atomic force microscopy. According to the release at pH 5.5, the film formulation based on a blend of CMC and solagum containing 3 mg mL−1 liposome-encapsulated folic acid is recommended. Practical Application: Folic acid is effective in reducing oxidative stress levels in the skin and neutralizing the harmful free radicals and is also essential for various metabolic reactions in the body. However, the limited solubility of folic acid linked with its poor absorption in an organism, low storage stability, short half-life upon oral consumption, specific food preferences of some people, extensive liver metabolism, and pregnancy-induced vomiting point to a large potential in transdermal usage of folic acid. This has motivated us to design new multicomponent polymer-lipid systems as an alternative solution to overcome some of these drawbacks. The results obtained for these multicomponent films pointed to their potential for prolonged release of folic acid to 24 h, which can also be useful for scientists interested in encapsulating similar poorly soluble compounds in CMC patches. The finding can be also valuable information for pharmaceutical manufacturers and scientists worldwide