Hydrogels are very attractive materials due to their multifunctional properties. Many natural polymers, such as polysaccharides, are used for the preparation of hydrogels. The most important and ...commonly used polysaccharide is alginate because of its biodegradability, biocompatibility, and non-toxicity. Since the properties of alginate hydrogel and its application depend on numerous factors, this study aimed to optimize the gel composition to enable the growth of inoculated cyanobacterial crusts for suppressing the desertification process. The influence of alginate concentration (0.1-2.9%, m/v) and CaCl
concentration (0.4-4.6%, m/v) on the water-retaining capacity was analyzed using the response surface methodology. According to the design matrix, 13 formulations of different compositions were prepared. The water-retaining capacity was defined as the system response maximized in optimization studies. The optimal composition of hydrogel with a water-retaining capacity of about 76% was obtained using 2.7% (m/v) alginate solution and 0.9% (m/v) CaCl
solution. Fourier transform infrared spectroscopy was used for the structural characterization of the prepared hydrogels, while the water content and swelling ratio of hydrogels were determined using gravimetric methods. It was concluded that alginate and CaCl
concentrations play the most important role regarding the gelation time, homogeneity, water content, and swelling ratio of the hydrogel.
This study aimed to improve the conventional procedure of alginate isolation from the brown seaweed (Laminaria digitata L.) biomass and investigate the possibility of further valorization of the ...ethanolic fraction representing the byproduct after the degreasing and depigmentation of biomass. The acid treatment of biomass supported by ultrasound was modeled and optimized regarding the alginate yield using a response surface methodology based on the Box–Behnken design. A treatment time of 30 min, a liquid-to-solid ratio of 30 mL/g, and a treatment temperature of 47 °C were proposed as optimal conditions under which the alginate yield related to the mass of dry biomass was 30.9%. The use of ultrasonic radiation significantly reduced the time required for the acid treatment of biomass by about 4 to 24 times compared to other available conventional procedures. The isolated alginate had an M/G ratio of 1.08, which indicates a greater presence of M-blocks in its structure and the possibility of forming a soft and elastic hydrogel with its use. The chemical composition of the ethanolic fraction including total antioxidant content (293 mg gallic acid equivalent/g dry weight), total flavonoid content (14.9 mg rutin equivalent/g dry weight), contents of macroelements (the highest content of sodium, 106.59 mg/g dry weight), and microelement content (the highest content of boron, 198.84 mg/g dry weight) was determined, and the identification of bioactive compounds was carried out. The results of ultra high-performance liquid chromatography–electrospray ionization–tandem mass spectrometry analysis confirmed the presence of 48 compounds, of which 41 compounds were identified as sugar alcohol, phenolic compounds, and lipids. According to the 2,2-diphenyl-1-picrylhydrazyl assay, the radical scavenging activity of the ethanolic fraction (the half-maximal inhibitory concentration of 42.84 ± 0.81 μg/mL) indicated its strong activity, which was almost the same as in the case of the positive control, synthetic antioxidant butylhydroxytoluene (the half-maximal inhibitory concentration of 36.61 ± 0.79 μg/mL). Gram-positive bacteria (Staphylococcus aureus, Enterococcus faecalis, and Bacillus cereus) were more sensitive to the ethanolic fraction compared to Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, and Shigella sonnei). The obtained results indicated the possibility of the further use of the ethanolic fraction as a fertilizer for plant growth in different species and antifouling agents, applicable in aquaculture.
: 8-hydroxyquinoline derivatives and their complexes with transition metals are the subject of many studies due to their anticancer, anti-inflammatory, anti-infective, and antidiabetic activities.
: ...Within this article, the authors review the synthesis and current applications of metal-8-hydroxyquinoline complexes in drug design with a critical overview of the latest advancements in the field.
: Metal-8-hydroxyquinoline complexes are especially interesting because of their simple synthesis procedures and possible applications in modern medicine. The complexation between transition metal ions and 8-hydroxyquinoline or its derivatives is achieved via their O and N atoms. The main problem with their application is lipophilicity. This particular property has an impact on their solubility, biological activity, transport through the cell membrane, construction of the complex with a receptor, and development of drugs. Furthermore, in the treatment of neurodegenerative diseases and brain cancers, the passage of the complexes through the blood-brain barrier can only be ensured through novel drug design.
This paper examines the life of Blessed Cardinal Alojzije V. Stepinac during three regimes that were very hostile towards the Catholic Church and its values. The paper discusses the values by which ...Blessed Stepinac lived and explains that his teachings correspond to the rules of conduct established by the German legal philosopher Gustav Radbruch. According to the latter, laws that contain no traces of humanity and are unbearably unjust should not be considered laws that must be followed. Cardinal Stepinac accepted the political realities of his times but denounced the evils present in each of the regimes under which he served as archbishop of Zagreb and shepherd of his flock. In doing so, he always underlined the values of equality, humanity and religious freedom.
Black locust flower extract contains various polyphenols and their glucosides contribute to the potential health benefits. After intake of these bioactive compounds and passage through the ...gastrointestinal tract, their degradation can occur and lead to a loss of biological activity. To overcome this problem, the bioactive compounds should be protected from environmental conditions. This study aimed to encapsulate the black flower extract in the microparticles based on biodegradable polysaccharides, alginate, and chitosan. In the extract, the total antioxidant content was found to be 3.18 ± 0.01 g gallic acid equivalent per 100 g of dry weight. Also, the presence of lipids (16), phenolics (27), organic acids (4), L-aspartic acid derivative, questinol, gibberellic acid, sterol, and saponins (2) was confirmed using the UHPLC-ESI-MS analysis. In vitro assays showed that the extract has weak anti-
-glucosidase activity and moderate antioxidant and cytotoxic activity against the HeLa cell line. The extrusion method with secondary air flow enabled the preparation of microparticles (about 270 μm) encapsulated with extract. An encapsulation efficiency of over 92% was achieved in the alginate and alginate-chitosan microparticles. The swelling study confirmed a lower permeability of alginate-chitosan microparticles compared with alginate microparticles. For both types of microparticles, the release profile of antioxidants in the simulated gastrointestinal fluids at 37 °C followed the Korsmeyer-Peppas model. A lower diffusion coefficient than 0.5 indicated the simple Fick diffusion of antioxidants. The alginate-chitosan microparticles enabled a more sustained release of antioxidants from extract compared to the alginate microparticles. The obtained results indicated an improvement in the antioxidant activity of bioactive compounds from the extract and their protection from degradation in the simulated gastric conditions via encapsulation in the polymer matrixes. Alginate-chitosan showed slightly slower cumulative antioxidant release from microparticles and better antioxidant activity of the extract compared to the alginate system. According to these results, alginate-chitosan microparticles are more suitable for further application in the encapsulation of black locust flower extract. Also, the proposed polymer matrix as a drug delivery system is safe for human use due to its biodegradability and non-toxicity.
This study aimed to develop a fast procedure for caffeine extraction from roasted coffee beans. The microwave-assisted extraction was carried out in the microwave oven with an operating frequency of ...2450 MHz. The response surface methodology based on a Box–Behnken design was used to model and optimize the extraction process. Among the analyzed extraction parameters (factors), the influence of extraction time (2–6 min), liquid-to-solid ratio (5–15 mL/g), and microwave power (336–595 W) were considered, while the yield of extracted caffeine was observed as the response of the system. Water was used as the solvent of choice for the extraction of caffeine. The optimum conditions were as follows: extraction time, 2 min; liquid-to-solid ratio, 15 mL/g; and microwave power, 500 W. In this optimized condition, the expected extraction yield of caffeine was 1.01 g/100 g dry weight (value confirmed by experimental assays). The total energy consumed of 1.7 kWh/100 g of purified caffeine indicated a more energy-efficient procedure by about 1200–15,000 times than the reported procedures. This study showed that caffeine can be quantitatively extracted from roasted coffee beans through a green approach and that the isolated caffeine has a high purity degree, which was confirmed by the UHPLC-ESI-MS/MS method. With this quality, isolated caffeine could be further used as an active ingredient in the food industry, while for pharmaceutical purposes, it must be further purified.
The design of two environmentally friendly protocols regarding ultrasound-assisted extraction (UAE) of valuable bioactive compounds from common centaury (Centaurium erythraea Rafn, Gentianaceae) ...aerial parts with aqueous mixtures of „green“ organic solvents (ethanol and propylene glycol) was conducted. In order to ensure the maximum total polyphenolic content (TPC), Box-Behnken experimental design (BBD) was used for both UAE/aqueous ethanol (UAE/aEtOH) and UAE/aqueous propylene glycol (UAE/aPPG) systems to optimize time, solvent concentration, liquid-to-solid ratio and temperature. The liquid-to-solid ratio had the highest effect on the TPC for tested extraction systems. For UAE/aEtOH system under the optimal conditions the predicted and experimentally obtained TPC were close (4.11 and 4.13 ± 0.04 g GAE/100 g d.w., respectively). The predicted and experimentally obtained TPC for UAE/aPPG system under the optimum conditions were 4.12 and 4.16 ± 0.04 g GAE/100 g d.w., respectively. According to UHPLC-DAD-MS/MS analysis, key bioactive components in both extracts were organic acids and derivates, flavanols, xanthones and secoiridoid glycosides. UAE/aPPG and UAE/aEtOH extracts contained 45 and 42 compounds, respectively. Since these extracts can be incorporated into different products as natural active ingredients, the extraction protocols are likely to ensure easy transfer to a large-scale production and further utilization in different industries, specifically ensuring cleaner production with reduced impact on the environment. Moreover, the usage of ethanol and its presence in the final industrial products has downsides: evaporation, flammability, irritation of different organs, discouraged use for some consumers due to preexisting medical conditions, interactions with various prescribed medicines, ethical reasons, etc. Thus, a much safer UAE/aPPG system, providing extract with more biologically functional phytochemicals and higher TPC at a lower temperature, is more recommended for eco-friendly future industrial use.
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•Two UAE methods for obtaining extracts from common centaury were compared.•Both environmentally friendly and cost effective methods were optimized.•45 and 42 compounds detected in aqueous propylene glycol and ethanolic extracts.•Aqueous propylene glycol extract had the highest TPC (4.16 g GAE/100 g d.w.).•The obtained extracts have potential industrial applications.
Objectives
An inclusion complex of biochanin A (BCA) with (2‐hydroxypropyl)‐β‐cyclodextrin (HP‐β‐CD) was prepared in the ethanol solution to improve its water solubility.
Methods
Using the FTIR, ...1H‐NMR, XRD, DSC and SEM methods, the structural characterization of the prepared complex was analysed.
Key findings
The phase‐solubility study has shown that the solubility of BCA was increased twofold in 42% (v/v) ethanol solution after complexation with HP‐β‐CD. The complex between BCA and HP‐β‐CD was prepared in the molar ratio of 1 : 1. The antibacterial activity of the inclusion complex was investigated against the various bacteria, fungus and yeast using the microdilution method. The minimal inhibitory concentration values for the analysed strain of bacteria were in the range of 0.84–1.69 mg/cm3, whereby the prepared inclusion complex exhibited less effect on the reduction of the number of Escherichia coli and Klebsiella pneumoniae species compared to pure BCA. The inclusion complex of BCA was significantly more active against Candida albicans than pure BCA. Biochanin A and its inclusion complex has not expressed the activity against Aspergillus niger.
Conclusions
Based on the obtained results, it can be concluded that the antimicrobial activity of BCA was remained unchanged after complexation.
Conventional extraction techniques require high consumption of available resources and thus are ineffective and expensive, especially at an industrial scale. The aim of the study was to optimize the ...ultrasound-assisted extraction of polyphenols from fresh wheatgrass (
Triticum aestivum
L.). The effects of different extraction techniques and solvents were investigated on the yield of extractive substances and antioxidant activity. The ultrasound-assisted extraction technique and ethanol gave the highest yield of extractive substances so that they were used in the optimization studies. The central composite design was employed to find the optimal levels of ethanol concentration, extraction temperature, and extraction time. The total phenolic content was varied in the range of 10.50–15.50 grams of gallic acid equivalents per 100 g of dry weight of plant material (g GAE 100 g
−1
dw). The optimal conditions for ultrasound-assisted extraction were: (1) 56% (v/v) ethanol, (2) temperature of 59 °C, and (3) extraction time of 28 min. The results of ANOVA indicated that the highest impact had the extraction temperature on the total phenolic content. The toxic solvents were not used in the developed extraction procedure. The consumption of energy and raw plant material is estimated to be lower by at least 10% compared to conventional techniques.
The paper was aimed at developing an ultrasound-assisted extraction of carotenoids from orange peel using olive oil as a solvent. A central composite design was used to define the optimal conditions ...for their extraction. Under the optimal conditions (extraction time of 35 min, extraction temperature of 42 ℃, and a liquid-to-solid ratio of 15 mL/g), the experimental and predicted values of carotenoid content were 1.85 and 1.83 mg/100 g dry weight, respectively. The agreement of these values indicated the adequacy of the proposed regression model. The extraction temperature only had a negative influence on carotenoid content. The impact of extraction parameters on the carotenoid content was decreased according to the following order: extraction time, liquid-to-solid ratio, and extraction temperature. Ca-alginate beads were prepared using the extrusion process to increase the stability and protect the antioxidant activity of olive oil enriched with carotenoids. The encapsulation efficiency and particle mean diameter were 89.5% and 0.78 mm, respectively. The presence of oil extract in Ca-alginate beads was confirmed by Fourier-transform infrared spectroscopy. The antioxidant activity of the oil enriched with carotenoids before and after encapsulation in the alginate beads was determined according to the DPPH assay.
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