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The antioxidant potential of bird cherry fruit of water, methanol, ethanol, and acetone extracts and their antioxidant efficiency against oxidation of PC liposomes using spectroscopic and chromatographic methods were investigated. The chromatographic methods quantified and specified the presence of phenolic and flavonoid compounds in the investigated extracts. The characteristic peaks in the UV spectrum at 275 nm and 370 nm confirmed the presence of phenols and flavonoids and their derivatives. Their presence was also confirmed by FTIR spectra, which revealed the presence of its functional groups. The total luminescence spectra with maxima at 314–318 nm, 325–355 nm, and 428–435 nm were ascribed to the presence of phenolic acids and tocopherols. The antioxidant properties of extracts and its inhibition properties against lipid peroxidation in PC liposomes were determined by fluorogenic probes DCF-H and C11-BODIPY581/591. The measured antioxidant properties against generated free radicals in aqueous and lipogenic phases revealed differences between extracts depending on their physicochemical properties with the greatest potential for acetone extract and sirup. The presented quantitative analysis indicated that cherry bird extracts possess significant amounts of phenolics and flavonoids, thus having the opportunity to be used as a natural antioxidant agent source with a large potential for application in pharmaceutical and food industries.

The interactions of G–quadruplexes of different topologies with highly fluorescent 9-methoxyluminarine ligand 9-MeLM were investigated by fluorescence and circular dichroism spectroscopy. The results showed that 9-methoxyluminarine was able to interact and did not destabilize any investigated molecular targets. The studied compound was selectively quenched by parallel c-MYC G-quadruplex DNA, whereas hybrid and antiparallel G4 topology caused only a negligible decrease in the fluorescence of the ligand. A high decrease of fluorescence of the ligand after binding with c-MYC G-quadruplex suggests that this molecule can be used as a selective probe for parallel G-quadruplexes.

Steady-state emission spectroscopy of 1-anilino-8- naphthalene sulfonate (ANS) and 1,6-diphenyl-1,3,5-hexatriene (DPH), fluorescence anisotropy, and DSC methods were used to characterize the interactions of the newly synthesized 1-carba-alpha-tocopherol (CT) with a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membrane. The DSC results showed significant perturbations in the DPPC structure for CT concentrations as low as 2 mol%. The main phase transition peak was broadened and shifted to lower temperatures in a concentration-dependent manner, and pretransition was abolished. Increasing CT concentrations induced the formation of new phases in the DPPC structure, leading to melting at lower temperatures and, finally, disruption of the ordered DPPC structure. Hydration and structural changes of the DPPC liposomes using ANS and DPH fluorescent probes, which are selectively located at different places in the bilayer, were studied. With the increased concentration of CT molecules in the DPPC liposomes, structural changes with the simultaneous formation of different phases of such mixture were observed. Temperature studies of such mixtures revealed a decrease in the temperature of the main phase transition and fluidization at decreasing temperatures related to increasing hydration in the bilayer. Contour plots obtained from concentration–temperature data with fluorescent probes allowed for identification of different phases, such as gel, ordered liquid, disordered liquid, and liquid crystalline phases. The CT molecule with a modified chromanol ring embedded in the bilayer led to H-bonding interactions, expelling water molecules from the interphase, thus introducing disorder and structural changes to the highly ordered gel phase.

The review focuses on the overview of electrochemical sensors based on molecularly imprinted polymers (MIPs) for the determination of uric acid. The importance of robust and precise determination of uric acid is highlighted, a short description of the principles of molecular imprinting technology is presented, and advantages over the others affinity-based analytical methods are discussed. The review is mainly concerned with the electro-analytical methods like cyclic voltammetry, electrochemical impedance spectroscopy, amperometry, etc. Moreover, there are some scattered notes to the other electrochemistry-related analytical methods, which are capable of providing additional information and to solve some challenges that are not achievable using standard electrochemical methods. The significance of these overviewed methods is highlighted. The overview of the research that is employing MIPs imprinted with uric acid is mainly targeted to address these topics: (i) type of polymers, which are used to design uric acid imprint structures; (ii) types of working electrodes and/or other parts of signal transducing systems applied for the registration of analytical signal; (iii) the description of the uric acid extraction procedures applied for the design of final MIP-structure; (iv) advantages and disadvantages of electrochemical methods and other signal transducing methods used for the registration of the analytical signal; (vi) overview of types of interfering molecules, which were analyzed to evaluate the selectivity; (vi) comparison of analytical characteristics such as linear range, limits of detection and quantification, reusability, reproducibility, repeatability, and stability. Some insights in future development of uric acid sensors are discussed in this review.

Recent studies show that alpha-tocopheryl succinate (TS) exhibits selective toxicity against cancer cells. In this study, we investigated the effect of TS&rsquo, s presence on the physico-chemical and structural properties of DPPC liposomes using fluorescence parameters (intensity, lifetime, and position of emission maximum) of 1-anilino-8-naphtalene sulphonate (ANS), differential scanning calorimetry (DSC) and zeta potential methods. Increasing the TS presence in the DPPC gel phase produced ANS fluorescence enhancement with a hypsochromic shift of the maximum. The zeta potential measurements show an increase in the negative surface charge and confirmed that this process is connected with the hydrophobic properties of dye, which becomes located deeper into the interphase region with a progressing membrane disorder. Temperature dependence studies showed that an increase in temperature increases the ANS fluorescence and shifts the ANS maximum emission from 464 to 475 nm indicating a shift from hydrophobic to a more aqueous environment. In the liquid crystalline phase, the quenching of ANS fluorescence occurs due to the increased accessibility of water to the ANS located in the glycerol region. The DSC results revealed that increasing the presence of TS led to the formation of multicomponent DSC traces, indicating the formation of intermediate structures during melting. The present results confirmed that TS embedded into the DPPC membrane led to its disruption due to destabilisation of its structure, which confirmed the measured biophysical parameters of the membrane.

α-Tocopherol oxalate (TO), a tocopherol ester derivative, was investigated for its effect on the structural changes of fully hydrated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes, as a function of concentration and temperature, by applying differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), and DPH fluorescence anisotropy methods. The DSC and DPH anisotropy data indicated that TO embedded into DPPC membrane lowered the enthalpy (ΔHm) and temperature (Tm) of the main phase transition as well its cooperativity. Fluidization of the membrane at a lowered temperature was accompanied by formation of mixed structures of tocopherol-enriched domains. SAXS studies showed the formation of various ordered structures in DPPC gel-phase during incorporation of TO into the bilayer, as evidenced by the existence of lamellar phases with repeat distances (d) of 6.13 and 6.87 nm, assigned to TO-enriched domains and a lamellar, liquid-ordered DPPC phase with d = 8.45 nm at increasing TO concentrations with lowering and broadening of the Bragg peaks, and diffuse scattering, characteristic of a fluid Lα phase, were observed. In DPPC fluid-phase, the increasing presence of TO at low concentrations resulted in the appearance of a liquid-ordered phase with repeat d = 6.9 nm coexistent with a lamellar structure with d = 9.2 nm, assigned to liquid-disordered structures. An increasing repeat distance observed with raising the TO amount in the DPPC bilayer evolved from an increasing interlamellar water layer of increasing thickness. Presence of TO facilitated penetration of water molecules into the acyl chain region which decreased van der Waals interactions in the bilayer. The DSC, SAXS, and fluorescence anisotropy data established that TO exhibited pronounced disruptive activity in DPPC membranes compared to α-tocopherol. The driving force of the observed action was attributed to electrostatic and dipole interactions of the acidic moiety with the polar head group of phospholipids in the interface region of the bilayer.

Our aim was to propose simple extraction process to obtain phospholipids along with yolk-derived vitamins and fats. Five extracts marked as ethanol/acetone, methanol-chloroform/acetone, hot ethanol, hexane, and cold ethanol were developed and compared. Extracts' compositions were analyzed in terms of phospholipid, polar and nonpolar fraction, cholesterol, carotenoids, and tocopherols content. Further, liposomes prepared from extracts were characterized. The highest extraction efficiency was achieved by a one-step hexane procedure. However, that sample, in contrast to the other four extracts, revealed distinctively lower permeability when used for liposomes membrane formation. Principal component analysis proved that major components contents were decisive for liposomes membranes permeability, whereas minor constituents' content controlled zeta potential and Z-average size.; Practical Application: Liposomes are nanocarriers widely used in pharmaceutical industry. Due to intravenous route of administration, they have to be produced from phospholipids of very fine purity. On the other hand, there is increasing interest in nanoencapsulation of labile, bioactive substances for manufacturing of health promoting food. Unfortunately, high-price pure phospholipids are prohibitive for food applications. The use of raw material obtained by simple extraction procedure instead of highly purified phospholipids could be an attractive alternative for food industry.; © 2018 Institute of Food Technologists®.

β-Cyclodextrin (βCD)-coated CdSe/ZnS quantum dots (QDs), provide a sensitive method for the determination of phenolic compounds. The current study aimed to explain the mechanisms involved in photoluminescence quenching of CdSe/ZnS QDs, during the determination of quercetin and gallic acid, and select derivatives thereof. Quercetin, quercetin glycosides, gallic acid and gallate esters, were investigated to understand how the glycoside moiety in glycosides and the hydrocarbon chain in esters, affect the interactions of the investigated polyphenols with βCD-coated QDs. The phenomenon of βCD-coated CdSe/ZnS photoluminescence quenching, is caused by the effective formation of host-guest inclusion complexes between polyphenols and βCD. The presence of the glycoside moiety in the quercetin molecule reduced the effectiveness of the complex formation, while, in contrast, the efficiency of complexation increased with increasing hydrocarbon chain length of the gallate ester molecule. QD photoluminescence quenching may be a consequence of the proximity between the interacting phenolic compounds with the QD surface, rather than βCDs peeling off from the QD surface, resulting in structural destabilization. From the thermodynamic parameters, it was concluded that the formation of the complexes is based both on the van der Waals interactions forces and hydrophobic interactions between guest and host molecules. Ionic interactions may also play an important role in the effectiveness of polyphenol-βCD inclusion complex formation. In order to obtain QDs with long-term stability, there is a need to increase the zeta potential value of the QD surface. Recognition of the above-described mechanisms, should enable the optimization of existing methods and the development of new applications of βCD-coated CdSe/ZnS QDs, such as determination of octyl gallate in foodstuffs.

α-Tocopherol (Toc) is known to degrade to the tocopheroxyl radicals (Toc) by exposure to UV light irradiation. In the present study, the stability of Toc ester derivatives exposed to UV light was investigated and compared with Toc in organic solution and in phospholipid vesicles. To follow the depletion of Toc and its esters the absorbance and fluorescence methods were applied whereas degradation products were detected using LC-MS method. The irradiation with UVB light of air-equilibrated solutions of di-α-Tocopheryl malonate (DTMO), α-Tocopheryl malonate (TMO) and α-Tocopheryl succinate (TS) strongly modifies their absorption and fluorescence spectra. Upon UVB irradiation, absorption band at 279/285nm becomes less pronounced indicating the photodegradation of esters. During irradiation, the fluorescence maximum of esters at 305nm shifts to 326nm, a maximum characteristic for Toc. Photorecovery of Toc from its esters derivatives was finally confirmed by LC-MS method. Among studied esters, only α-tocopheryl nicotinate (TN) did not undergo depletion and appeared resistant to UVB radiation. Kinetic studies indicated that photoinduced transformation occurs through the first order consecutive reaction chain mechanism. The photodissociation of Toc esters in the liposomes occurred with one order of magnitude slower than in organic solvents. Using MS/MS method it was found that final stable product of irradiation was α-tocopheryl quinone (TQ), an animal and plant metabolite of Toc.

Our aim was to propose simple extraction process to obtain phospholipids along with yolk-derived vitamins and fats. Five extracts marked as ethanol/acetone, methanol-chloroform/acetone, hot ethanol, hexane, and cold ethanol were developed and compared. Extracts' compositions were analyzed in terms of phospholipid, polar and nonpolar fraction, cholesterol, carotenoids, and tocopherols content. Further, liposomes prepared from extracts were characterized. The highest extraction efficiency was achieved by a one-step hexane procedure. However, that sample, in contrast to the other four extracts, revealed distinctively lower permeability when used for liposomes membrane formation. Principal component analysis proved that major components contents were decisive for liposomes membranes permeability, whereas minor constituents' content controlled zeta potential and Z-average size.Liposomes are nanocarriers widely used in pharmaceutical industry. Due to intravenous route of administration, they have to be produced from phospholipids of very fine purity. On the other hand, there is increasing interest in nanoencapsulation of labile, bioactive substances for manufacturing of health promoting food. Unfortunately, high-price pure phospholipids are prohibitive for food applications. The use of raw material obtained by simple extraction procedure instead of highly purified phospholipids could be an attractive alternative for food industry.

The physicochemical interactions between alpha-tocopherol and three phenolic acids, which constitute main phenolics in coffee brew: caffeic, chlorogenic and ferulic acid, in l-α-phosphatidylcholine liposome system were studied. Steady-state and fluorescence lifetime measurements were applied to elucidate location of investigated phenolic acids in liposomes, and the results have shown that ferulic acid is most embedded into membrane structure. Lipophilic studies have shown that at pH 7.4 the partition coefficients for all phenolic acids are similar. Antioxidant capacity measurements of studied antioxidants were taken using fluorescent probe BODIPY. The synergistic effect was observed in all tested antioxidant systems with the exception of sample consisting of chlorogenic acid (2.5 μM) and alpha-tocopherol (2.5 μM), where antagonistic effect was noted. Concentration of antioxidants was a significant factor in the observed phenomenon. The most effective antioxidant system against oxidation in liposomes was combination of alpha-tocopherol and ferulic acid. This phenomenon could be explained by interaction of ferulic acid with the interior of the phospholipids membrane.

Changes of the photoluminescent properties of QD in the presence of oxidized catechin (CQ) were investigated by absorption, steady-state fluorescence, fluorescence lifetime and dynamic light scattering measurements. Photoluminescence intensity and fluorescence lifetime was decreasing with increasing CQ concentration. Dynamic light scattering technique found the hydrodynamic diameter of QD suspension in water is in range of 45 nm, whereas in presence of CQ increased to mean values of 67 nm. Calculated from absorption peak position of excition band indicated on average QD size of 3.2 nm. Emission spectroscopy and time-resolved emission studies confirmed preservation of electronic band structure in QD–CQ aggregates. On basis of the presented results, the elucidated mechanism of QD fluorescence quenching is a result of the interaction between QD and CQ due to electron transfer and electrostatic attraction. The results of fluorescence quenching of water-soluble CdTe quantum dot (QD) capped with thiocarboxylic acid were used to implement a simple and fast method to determine the presence of native antioxidant quinones in aqueous solutions. Feasibility studies on this method carried out with oxidized catechin showed a linear relation between the QD emission and quencher concentration, in range from 1 up to 200 μM. The wide linear range of concentration dependence makes it possible to apply this method for the fast and sensitive detection of quinones in solutions.

This study describes in vitro digestion of lupin seed globulins by pancreatin, trypsin and chymotrypsin. Lupin seed globulins turned out to be almost totally susceptible to chymotrypsin digestion. When panceratin or trypsin were used for digestion of lupin seed globulins, γ-conglutin appeared to be resistant to proteolysis. Different fluorescence spectroscopic methods such as fluorescence anisotropy, fluorescence lifetimes and fluorescence quenching measurements were used for detailed characterisation of this phenomenon. A potential reason for γ-conglutin insensitivity to digestion may be related to the fact that lysine, as well as arginine, are positively charged at cell physiological pH. Simultaneously, flavonoids at this pH are partially ionised, which may lead to the occurrence of ionic interactions between these molecules at pH 7.5. The confirmation of this explanation may be the fact that γ-conglutin and vitexin form a static complex, which was observed using fluorescence quenching measurements.

Lupin seed globulin proteins form complexes with flavonoids, predominantly apigenin C-glycosides. Enzymes typical for the gastrointestinal tract were used to hydrolyze lupin seed globulins. Release of native flavonoids as a result of the proteolysis reaction was observed. Different analytical methods such as size exclusion chromatography, HPLC-MS, and fluorescence spectroscopy (steady-state fluorescence, fluorescence anisotropy, fluorescence lifetimes) were used for a detailed characterization of this phenomenon. Flavonoids liberated from lupin globulin proteins as a result of pancreatin-catalyzed digestion were bound by γ-conglutin resistant to this enzyme. Two possible mechanisms of this interaction may be suggested: hydrogen bonding between oligosaccharide chains of glycoproteins and the sugar moieties of the flavonoid glycosides or electrostatic attraction between positively charged γ-conglutin and flavonoids partially ionized at pH 7.5.

In this study we estimated how conjugation with a sugar moiety influences the spectral properties of tocopherol and relate the spectroscopic properties of glycosides to solvent properties such as viscosity and polarity. Spectroscopic properties (absorption, fluorescence, fluorescence anisotropy and fluorescence lifetime) of three dl-alpha-tocopheryl glycosides (dl-alpha-tocopheryl orthoacetate derivative and glycosides of dl-alpha-tocopherol model compounds: 2,2,5,7,8-pentamethyl-6-chromanol and Trolox) were studied in DMSO/water solution. In all investigated compounds dissolved in DMSO/water mixture the absorption and emission maxima were blue-shifted. The fluorescence lifetimes were longer compared with those obtained for the parent compounds, except for the Trolox glucoside, in which it was shorter. The observed effect is connected with an increase in the electronic energy in the ground state due to electron rearrangement in the chromanol system caused by interaction with the sugar moiety. The extent of the spectral shift is related to the sugar moiety substituted at the phenolic oxygen rather than to substitution at the 2a position in the chromanol ring. The fluorescent properties of dl-alpha-tocopheryl glucoside in organic solvents were measured. The Stokes shift was related to the orientational polarizability of the solvents. The study of viscosity suggested two different mechanisms explaining the results observed in a low- and high-viscosity environment. The results indicated the fundamental role of interactions between the chromophore and sugar moiety in a low-viscosity environment. The results obtained at high values of viscosity are discussed in terms of a frictional boundary solvent-solute interaction model.

Coffee brew is rich in chlorogenic and cinnamic acids, potent antioxidants. Its interaction with beta-cyclodextrin leads to formation of inclusion complexes which affect the physicochemical properties of the guest molecule. We investigated spectral changes in coffee-originated phenols, chlorogenic (CHA) and caffeic (CA) acids, due to complexation with beta-cyclodextrin (betaCD) in aqueous solutions and studied thermodynamic properties of the complexes formed. The spectroscopic data (absorption and fluorescence) were used for deducing the position of both phenols inside the beta-cyclodextrin cavity, as well as to calculate the binding constants of the complexes. The obtained data indicate the formation of a 1:1 complex between betaCD and CHA or CA. The temperature-dependence of the latter allowed the calculation of thermodynamic parameters (Δ H , Δ S and Δ G ) of the complexation. The negative values of all the thermodynamic parameters indicated that the formation of these inclusion complexes was an enthalpy-driven process in which a crucial role is played by weak van der Waals forces and hydrogen bonds. Molecular modelling confirmed experimental observations that, in aqueous phase, betaCD–CHA and –CA complexes are stable and energetically favourable, and additionally provided information regarding conformation and interaction between atoms forming the complexes. The experimental data were used to characterise the molecular mechanism of the complexation.