RIOFH - Repository of Institute of General and Physical Chemistry
Not a member yet
1118 research outputs found
Sort by
Rhamnolipid inspired lipopeptides effective in preventing adhesion and biofilm formation of Candida albicans
No full textRhamnolipids are biodegradable low toxic biosurfactants which exert antimicrobial and anti-biofilm properties. They have attracted much attention recently due to potential applications in areas of bioremediation, therapeutics, cosmetics and agriculture, however, the full potential of these versatile molecules is yet to be explored. Based on the facts that many naturally occurring lipopeptides are potent antimicrobials, our study aimed to explore the potential of replacing rhamnose in rhamnolipids with amino acids thus creating lipopeptides that would mimic or enhance properties of the parent molecule. This would allow not only for more economical and greener production but also, due to the availability of structurally different amino acids, facile manipulation of physico-chemical and biological properties. Our synthetic efforts produced a library of 43 lipopeptides revealing biologically more potent molecules. The structural changes significantly increased, in particular, anti-biofilm properties against Candida albicans, although surface activity of the parent molecule was almost completely abolished. Our findings show that the most active compounds are leucine derivatives of 3-hydroxy acids containing benzylic ester functionality. The SAR study demonstrated a further increase in activity with aliphatic chain elongation. The most promising lipopeptides 15, 23 and 36 at 12.5 mu g/mL concentration allowed only 14.3%, 5.1% and 11.2% of biofilm formation, respectively after 24 h. These compounds inhibit biofilm formation by preventing adhesion of C. albicans to abiotic and biotic surfaces
New herbal bitter liqueur with high antioxidant activity and lower sugar content: innovative approach to liqueurs formulations
No full textHerbal liqueurs are spirits with numerous functional properties, due to the presence of bioactive extractable compounds deriving from herbs. The aim of this study was to obtain new herbal bitter liqueur (HBL) on the basis of twelve selected bitter and aromatic plants extracts, with an optimal sensory profile for consumer acceptance. Also, the determination of optimal sugar content in HBL was done. Furthermore, antioxidant (AO) capacity and total phenolic content (TPC) of HBL was evaluated and compared to similar commercial herbal spirits. Among five tested formulations, assessed by 9-point hedonic scale, HBL with the ratio of bitter and aromatic plants 1:4 was the most acceptable. Ideal concentration of sugar in HBL, determined using a just-about-right scale, was found to be 80.32 g/l of sucrose, which is approximately 20% less than the minimum stipulated by European Union Regulation and several times lower than in the majority of commercial liqueurs. Obtained result indicates the possibility of sugar reduction in liqueurs, and suggests the need to carry out sensory analysis before production of these high-calorie beverages. Radical scavenging ability against DPPH and ABTS radicals, as well as ferric reducing antioxidant power and TPC of HBL were convincingly superior in comparison to similar commercial herbal alcoholic beverages. High correlation coefficients between TPC and other assays applied strongly support the significant role of the polyphenols in the total AO capacity of the HBL and other tested commercial herbal spirits. Headspace GC/MS revealed that the most abundant terpenes were menthone (3.75%), eucalyptol (3.42%) and menthol (3.10%), whereas methanol was present in a small amount (4.97 mg/l)
Unveiling the nonlinear optical response of Trictenotoma childreni longhorn beetle
No full textThe wings of some insect species are known to fluoresce under illumination by ultraviolet light. Their fluorescence properties are however, not comprehensively documented. In this article, the optical properties of one specific insect, the Trictenotoma childreni yellow longhorn beetle, were investigated using both linear and nonlinear optical (NLO) methods, including one- and two-photon fluorescence and second harmonic generation (SHG). These three distinct optical signals discovered in this beetle are attributed to the presence of fluorophores embedded within the scales covering their elytra. Experimental evidence collected in this study indicates that the fluorophores are non-centrosymmetric, a fundamental requirement for SHG. This study is the first reported optical behavior of this type in insects. We described how NLO techniques can complement other more convenient approaches to achieve a more comprehensive understanding of insect scales and integument properties
The effects of the osmotic dehydration parameters on reduction of selected microorganisms on chicken meat
No full textAnalysis of the influence of osmotic dehydration on reduction of selected microorganisms inoculated on dehydrating chicken meat, as a mean of assessing the microbiological safety of osmotic dehydration process, is conducted. Chicken meat cubes were inoculated with Esherichia coli, Listeria monocytogenes, and Salmonella spp. and subjected to the osmotic dehydration process with varied parameters of: process duration, osmotic solutions concentration, and type of solution. Samples of osmodehydrated chicken meat were analyzed by standard and modified ISO methods. The results pointed that the increase in time and concentration have led to the higher microbiological reduction, while the osmotic dehydration performed in sugar beet molasses exerted the higher reduction ratios compared to the process in aqueous osmotic solution. Calculated mathematical models of reduction ratios for selected microorganisms on chicken meat were statistically significant, indicating on satisfactory approximation of reduction ratios values within the applied parameters. Mathematical models, calculated in this investigation, which describe the effects of osmotic dehydration on reduction of selected microorganisms on chicken meat, allow better understanding and managing of product safety during the process of osmodehydration. Practical application
Thermal and Mechanical Behavior of Composite Mortars Containing Natural Sorptive Clays and Fly Ash
No full textMineral additives are extensively applied as cement replacement materials in both construction concrete and mortar. Fly ash is one of the most commonly utilized additives which improve Theological properties, as well as thermal and mechanical behavior of mortar, and as such it has been widely investigated. This industrial byproduct comprises heavy metals in its composition; therefore further research is needed to optimize its effective dosage. Moreover, certain sorptive clays, such as natural zeolite and bentonite, can prevent migration of toxic elements from fly ash by immobilizing them in their structure. Ten experimental mortars are prepared with Portland cement, river sand and addition of fly ash, zeolite and/or bentonite in accordance with chemometric experimental design rules. The aim of the study was to investigate the effect of mineral additives on thermal and mechanical performances of mortar. Thermal characteristics were monitored via dilatometric analysis and DTA method. Principal component analysis was used on the results of physico-mechanical testing (workability, bulk density, water absorption, shrinkage, compressive and flexural strength) to enable the divisions of the observed samples into groups in the factor space. The performance of Artificial Neural Network was compared with the experimental data in order to develop rapid and accurate method for prediction of mechanical parameters of mortar. The ANN model showed high overall prediction accuracy (r(2) = 0.989, during training cycle). The test results indicate that incorporation of the mineral additives gave cost effective mortars with sufficiently good properties. However, tools of analytical modeling highlighted mortar with zeolite and fly ash as the optimal composition regarding its mechanical performance
The influence of the extraction temperature on polyphenolic profiles and bioactivity of chamomile (Matricaria chamomilla L.) subcritical water extracts
No full textThe main goal of this research was to determine the relationship among chemical structure, bioactivity and temperature of chamomile during subcritical water extraction in isobaric conditions (45 bar) at seven different temperatures (65-210 degrees C). The influence of temperature on phenolic profiles was defined by UHPLC-HESI-MS/MS. The overall results indicate that the presence of conjugated double bonds, side chains, glucose moiety or ether moiety in molecules influence the efficiency of polyphenols' extraction in subcritical water. In terms of antioxidant activity, the extracts were the most active towards ABTS radicals (IC50 = 7.3-16.8 mu g/mL), whereby temperature of 150 degrees C was optimal. On the other hand, the extracts obtained at 115 degrees C showed highest cytotoxicity. Inhibition of alpha-amylase and alpha-glucosidase was the highest at 65 and 85 degrees C, i.e. 0.51 and 4.13 mmolAE/g, respectively. Activity against tyrosinase was the highest at 210 degrees C (17.92 mgKAE/g). The data showed that different non-phenolic compounds may also participate in bio-activities of the extracts
Copper leaching from chalcopyrite concentrate by sodium nitrate in sulphuric acid solution – chemometric approach
No full textHydrometallurgical processing of the copper concentrates is a promising alternative to the conventional pyrometallurgical production of copper due to significantly lower environmental impact, capital and operational costs. Development of the hydrometallurgical process for copper recovery from mineral concentrate requires extensive work in testing and optimization of operational parameters from laboratory to semi-industrial scale. Mathematical modelling of the copper leaching process can save human labour and time. Leaching of copper from chalcopyrite concentrate using sulphuric acid and sodium nitrate as an oxidant was tested, and the influence of temperature, particle size, stirring speed and concentrations of sulphuric acid and sodium nitrate were evaluated. Obtained results showed that increasing temperature and concentrations of sulphuric acid and sodium nitrate increase the leaching degree of copper, while increasing particle size and stirring speed reduce copper extraction. In this paper, second-order polynomial models (SOP) were applied to experimental data. Presented results show that mathematical models fit experimental data. The conclusion is that SOP models are a promising tool to be used for modelling leaching processes of metals
Preparation and characterization of poly(urethane-siloxane)/titanium-dioxide nanocomposites
No full textThis work is focused on preparation of poly(urethane-siloxane)/titanium-dioxide nanocomposites (PUSNs) with enhanced features. PUSNs were prepared by the in situ polymerization reaction using titanium-dioxide as a nano-filler in different amounts (1, 2, 3 and 5 wt.%) with respect to the poly(urethane-siloxane) (PUS) matrix. PUS copolymer was based on alpha,omega-dihydroxy-ethoxypropyl-poly(dimethylsiloxane), 4,4'-methylenediphenyldiisocyanate and 1,4-butanediole. In order to investigate the influence of TiO2 content on the structure, UV resistance, thermal properties, hydrophobicity and morphology of the prepared PUSNs, FTIR spectroscopy, UV-Vis diffuse-reflectance spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), contact angle measurements, surface free energy (SFE) analysis, water absorption, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were performed. The PUSNs showed excellent UV resistance, high hydrophobicity, low surface free energy and also higher thermal stability and rougher surface and cross-section relief structure as compared to the pure PUS copolymer. Based on the obtained results it can be concluded that prepared PUSNs could be potentially used as protective coatings
Free amino acid profiles of honey samples from Vojvodina (Republic of Serbia)
No full textAminokiselinski profil četiri vrste meda - dva monofloralna (bagremov i suncokretov med), polifloralnog (livadski med) i šumskog meda (medljikovac), sakupljenih sa teritorije Autonomne Pokrajine Vojvodine (Republika Srbija), određen je primenom jonoizmenjivačke hromatografije. Rezultati su ukazali da je prolin dominantna aminokiselina u svim ispitivanim uzorcima meda. Aminokiseline koje su, takođe, prisutne u značajnim količinama su glutaminska kiselina ˃ fenilalanin ˃ glicin serin u uzorcima bagremovog i livadskog meda, dok je suncokretov med odlikovalo prisustvo veće količine alanina u odnosu na serin. Uzorci šumskog meda sadržali su najviše prolina i odlikovao ih je najviši sadržaj ukupnih aminokiselina. Uzorci meda klasifikovani su na osnovu sadržaja aminokiselina primenom hemometrijskih metoda (klaster analiza (cluster analysis - CA) i analiza glavnih komponenti (principal component analysis - PCA)). Klaster analiza različitih vrsta meda ukazala je na mogućnost grupisanja nekih vrsta meda u odnosu na ostale. Primenom PCA uzorci različitih vrsta meda jasno su se izdvojili formirajući odgovarajuće grupe, te se, stoga, aminokiselinski profil uzoraka može iskoristiti kao indikator botaničke vrste meda.Amino acid profile of four honey types - two monofloral (acacia and sunflower), one polyfloral (meadow honey) and forest honey (honeydew honey) collected from the Autonomous Province of Vojvodina (Republic of Serbia) was determined using ion exchange chromatography. The results showed that proline was the dominant amino acid in all analyzed samples. Other amino acids present in substantial amounts were glutamic acid ˃ phenylalanine ˃ glycine ˃ serine in acacia and meadow honey samples, while sunflower was characterized by the presence of higher content of alanine compared to serine. Forest honey samples possessed the highest proline content and also the highest total amino acid content. Based on the amino acid contents, honey samples were classified using chemometric methods (cluster analysis (CA) and principal component analysis (PCA)). CA of different honey types could be applied to group honey types. According to the PCA, honey samples are clearly distinguished and form the specific groups. Therefore, amino acid profile could give an indication of honey botanical origin