The structural integrity, elasticity, and fluidity of lipid membranes are critical for cellular activities such as communication between cells, exocytosis, and endocytosis. Unsaturated lipids, the main components of biological membranes, are particularly susceptible to the oxidative attack of reactive oxygen species. The peroxidation of unsaturated lipids, in our case 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), induces the structural reorganization of the membrane. We have employed a multi-technique approach to analyze typical properties of lipid bilayers, i.e., roughness, thickness, elasticity, and fluidity. We compared the alteration of the membrane properties upon initiated lipid peroxidation and examined the ability of flavonols, namely quercetin (QUE), myricetin (MCE), and myricitrin (MCI) at different molar fractions, to inhibit this change. Using Mass Spectrometry (MS) and Fourier Transform Infrared Spectroscopy (FTIR), we identified various carbonyl products and examined the extent of the reaction. From Atomic Force Microscopy (AFM), Force Spectroscopy (FS), Small Angle X-Ray Scattering (SAXS), and Electron Paramagnetic Resonance (EPR) experiments, we concluded that the membranes with inserted flavonols exhibit resistance against the structural changes induced by the oxidative attack, which is a finding with multiple biological implications. Our approach reveals the interplay between the flavonol molecular structure and the crucial membrane properties under oxidative attack and provides insight into the pathophysiology of cellular oxidative injury.

Flavonoids, polyphenols with anti-oxidative activity have high potential as novel therapeutics for neurodegenerative disease, but their applicability is rendered by their poor water solubility and chemical instability under physiological conditions. In this study, this is overcome by delivering flavonoids to model cell membranes (unsaturated DOPC) using prepared and characterized biodegradable mesoporous silica nanoparticles, MSNs. Quercetin, myricetin and myricitrin have been investigated in order to determine the relationship between flavonoid structure and protective activity towards oxidative stress, i.e., lipid peroxidation induced by the addition of hydrogen peroxide and/or Cu²⁺ ions. Among investigated flavonoids, quercetin showed the most enhanced and prolonged protective anti-oxidative activity. The nanomechanical (Young modulus) measurement of the MSNs treated DOPC membranes during lipid peroxidation confirmed attenuated membrane damage. By applying a combination of experimental techniques (atomic force microscopy—AFM, force spectroscopy, electrophoretic light scattering—ES and dynamic light scattering—DLS), this work generated detailed knowledge about the effects of flavonoid loaded MSNs on the elasticity of model membranes, especially under oxidative stress conditions. Results from this study will pave the way towards the development of innovative and improved markers for oxidative stress-associated neurological disorders. In addition, the obtained could be extended to designing effective delivery systems of other high potential bioactive molecules with an aim to improve human health in general.

Satureja hortensis L. unifloral honey was characterized by pollen analysis, electrical conductivity, pH and extensively by chromatographic and spectroscopic techniques. UV / VIS spectro-scopy measurements revealed total phenol content of 682.1 mg GAE / kg by Folin-Ciocalteu assay, antiox-idant capacity by DPPH assay of 1.7 mmol TEAC / kg and by FRAP assay of 4.3 mmol Fe2+ / kg as well as CIE L*a*b*Cab*h°ab chromaticity coordinates. GC-MS after headspace solid-phase microextraction (HS-SPME) revealed hotrienol (22.8 %) along with other linalool derivatives, benzaldehyde (6.1 %), phenylacetaldehyde (4.9 %) and few norisoprenoids (safranal (7.6 %) as the major). Ultrasonic solvent ex-traction (USE) followed by GC-MS allowed identification of methyl syringate (54.7 %) as predominant compound along with other benzene derivatives. HPLC-DAD analysis determined tyrosine (382.0 mg kg−1), phenylalanine (140.4 mg kg−1) and methyl syringate (39.32 mg kg−1). Methyl syringate and hotrienol can be considered non-specific chemical markers of S. hortensis honey. FTIR-ATR spectral characteristics of S. hortensis honey in fingerprinting region were not significantly different from other honey types, but the integrated intensity of the region was smaller than in other unifloral honeys

Three refractive index mixing rules, Arago–Biot, Lorentz–Lorenz, and Newton, are generalized to complex refractive index and used to define infrared (IR) spectra of the corresponding ideal liquid mixtures. Using the measured optical constants n and k for acetonitrile-water mixtures (Bertie and Lan, 1997) the excess absorbances, A ^E = A ^obs − A ^ideal , are calculated. Relying upon the well-established properties of the acetonitrile–water mixtures, the interpretation of the excess absorbances is established that is essentially based on the understanding of a liquid as a set of oscillators. The set depends on the composition of the mixture and comprises oscillators as present in the pure components and oscillators perturbed by hydrogen bonding between unlike molecules. The main features of an excess spectrum can be established assuming chemical equilibria among various oscillators. The most informative parts of the spectrum of a yet unstudied binary system can well be observed and even qualitatively explained from the excess absorbance provided: first, a detailed vibrational study of the components has been done; and, second, it is well understood what actually is subtracted from A ^obs . As examples, the binary mixtures of ethynylbenzene and tetrachloroethylene and 2-ethynylpyridine and tetrachloroethylene are considered.

The actual cumulative mass of released quercetin from nanoparticles within the dialysis membrane was determined under the influence of external stationary and alternating magnetic fields. We have shown that the control of the release kinetics of quercetin from MNPs, i.e., the distribution of quercetin between the nanoparticles and the suspension within the membrane, can be tuned by the simple combination of stationary and alternating magnetic fields. Under non-sink conditions, the proportion of quercetin in the suspension inside the membrane is increased toward the nanoparticles, resulting in the increased release of quercetin. The results obtained could be applied to the release of insoluble flavonoids in aqueous suspensions in general.