Investigation of Quercetin interaction behaviors with lipid bilayers: Toward understanding its antioxidative effect within biomembrane

Protective Effect of Field Horsetail Polyphenolic Extract on Erythrocytes and Their Membranes

Field horsetail (Equisetum arvense L.) is widely utilized in traditional medicine and is a rich source of bioactive compounds such as flavonoids, phenolic acids, and silica. This study investigates the protective effect of the polyphenolic extract from field horsetail (HLE) on erythrocytes and their cell membranes. The content of polyphenolic compounds in the extract was determined using the HPLC-DAD and Folin-Ciocalteu methods. The extract's hemolytic activity, toxicity, antioxidant activity, and its impact on the physical properties of erythrocytes and lipid membrane were investigated. The antioxidant properties were evaluated using erythrocytes and isolated erythrocyte membranes oxidized by UVC radiation and AAPH. The impact of the extract on the ordering and fluidity of erythrocyte and model lipid membranes was studied. Furthermore, the transmembrane potential, shape of erythrocytes and the dipole potential of the lipid membranes under the influence of HLE were evaluated. The results indicated that HLE extract exhibited no toxicity to erythrocytes and HMEC-1 cells. HLE components effectively protect erythrocytes and their membranes against oxidation. They interact with the outer, polar surface of the erythrocyte membrane and reduce both erythrocyte membrane potential and lipid membrane dipole potential. The HLE polyphenols decrease the concentration of free radicals at the surface of the membrane, where they are located, and serve as a protective barrier, preventing penetration into the membrane.

Structural modification of lipid membranes by polyphenols: A fluorescence spectroscopy study

The present study investigates the molecular mechanisms of polyphenol-lipid interactions and their impact on membrane properties. Using pyrene and DPH as reporter molecules, we examined the impact of quercetin, curcumin, gallic, and salicylic acids on membranes composed of phosphatidylcholine (PC) and its mixtures with phosphatidylglycerol (PG), cardiolipin (CL), and cholesterol (Chol). Quercetin was found to increase the lipid order without affecting the lipid bilayer free volume, indicating interactions near the membrane surface. In turn, curcumin exhibited more complex effects, reducing free volume in PC but increasing it in PG vesicles, reflecting its amphiphilic structure and variable penetration depth. Gallic and salicylic acids selectively increased free volume at the membrane core without influencing lipid order at the upper regions of lipid bilayer. The results obtained demonstrate that polyphenol structure and lipid composition dictate the resultant pattern of polyphenol-membranes interactions, which may have implications for drug delivery and nutraceutical design.

Impact of Pluronic F-127 on the Stability of Quercetin-Loaded Liposomes: Insights from DSC Preformulation Studies

The aim of the present study is to evaluate the stability of DMPC:Pluronic F-127 and DPPC:Pluronic F-127 liposomes, both with and without incorporated quercetin. Quercetin belongs to the class of flavonoids and has shown antioxidant, antiviral, anti-inflammatory, anti-cancer, and antimicrobial activities. Dynamic light scattering, electrophoretic light scattering, and differential scanning calorimetry (DSC) were utilized to investigate the cooperative behavior between liposomal components and its effect on stability. All formulations were stored at 4 °C and 25 °C and studied over 42 days. Furthermore, the interaction of the final formulations with serum proteins was assessed to evaluate the potential of Pluronic F-127 as a stabilizer in these liposomal nanosystems. This study highlights the impact of DSC in preformulation evaluations by correlating thermal behavior with quercetin incorporation and variations in size and the polydispersity index. According to the results, quercetin increased the fluidity and stability of liposomal nanosystems, while Pluronic F-127 was not sufficient for effective steric stabilization. Additionally, DSC thermograms revealed the integration of Pluronic F-127 into lipid membranes and showed phase separation in the DMPC nanosystem. In conclusion, the results indicate that the DPPC:Pluronic F-127:quercetin nanosystem exhibited the desired physicochemical and thermotropic properties for the effective delivery of quercetin for pharmaceutical purposes.

Comparing the Effects of Encapsulated and Non-Encapsulated Propolis Extracts on Model Lipid Membranes and Lactic Bacteria, with Emphasis on the Synergistic Effects of Its Various Compounds

Propolis is a resinous compound made by bees with well-known biological activity. However, comparisons between encapsulated and non-encapsulated propolis are lacking. Therefore, the antibacterial activity, effect on the phase transition of lipids, and inhibition of UV-induced lipid oxidation of the two forms of propolis were compared. The results showed that non-encapsulated propolis produces quicker effects, thus being better suited when more immediate effects are required (e.g., antibacterial activity). In order to gain an in-depth introspective on these effects, we further studied the synergistic effect of propolis compounds on the integrity of lipid membranes. The knowledge of component synergism is important for the understanding of effective propolis pathways and for the perspective of modes of action of synergism between different polyphenols in various extracts. Thus, five representative molecules, all previously isolated from propolis (chrysin, quercetin, trans-ferulic acid, caffeic acid, (-)-epigallocatechin-3-gallate) were mixed, and their synergistic effects on lipid bilayers were investigated, mainly using DSC. The results showed that some compounds (quercetin, chrysin) exhibit synergism, whereas others (caffeic acid, t-ferulic acid) do not show any such effects. The results also showed that the synergistic effects of mixtures composed from several different compounds are extremely complex to study, and that their prediction requires further modeling approaches.

Characterization of entrapment behavior of polyphenols in nanostructured lipid carriers and its effect on their antioxidative activity

Polyphenols are widely used as antioxidant agents to protect human health. Resveratrol, kaempferol, and quercetin have been reported to have potent antioxidant activity; however, these compounds have many problems related to their practical application, such as instability and insolubility. Thus, a nanostructured lipid carrier (NLC) was utilized as a drug delivery system (DDS) to overcome these limitations. This study investigated the particle stability, drug loading performance, and antioxidant activity of polyphenols-incorporated NLCs. The particle size and distribution were suitable for DDS applications, and all the samples demonstrated good stability after 2 months of storage. Based on Raman spectroscopy analysis, polyphenols were successfully encapsulated in NLCs. Quantitative high-performance liquid chromatography analysis indicated that NLCs could load resveratrol more than kaempferol and quercetin. In addition, NLCs have successfully improved all the antioxidant activity per unit concentration of polyphenol (specific antioxidant activity) compared to the free polyphenols. Quercetin-incorporated NLCs showed the highest specific antioxidant activity. This result is the opposite of entrapment efficiency and actual antioxidant activity, most likely influenced by the location of entrapped polyphenol molecules. As it was performed, NLCs are highly recommended to be applied as an antioxidant delivery system.

Ethosomes and Transethosomes as Cutaneous Delivery Systems for Quercetin: A Preliminary Study on Melanoma Cells

The present study is aimed to design ethosomes and transethosomes for topical administration of quercetin. To overcome quercetin low bioavailability, scarce solubility and poor permeability that hamper its pharmaceutical use, the drug was loaded in ethosomes and transethosomes based on different concentrations of phosphatidylcholine. Vesicle morphology was studied by cryogenic transmission electron microscopy, while size distribution and quercetin entrapment capacity were evaluated up to 3 months, respectively, by photon correlation spectroscopy and high-performance liquid chromatography. The antioxidant property was studied by photochemiluminescence test. Quercetin release and permeation was investigated in vitro, using Franz cells associated to different membranes. In vitro assays were conducted on human keratinocytes and melanoma cells to study the behavior of quercetin-loaded nano-vesicular forms with respect to cell migration and proliferation. The results evidenced that both phosphatidylcholine concentration and quercetin affected the vesicle size. Quercetin entrapment capacity, antioxidant activity and size stability were controlled using transethosomes produced by the highest amount of phosphatidylcholine. In vitro permeation studies revealed an enhancement of quercetin permeation in the case of transethosomes with respect to ethosomes. Notably, scratch wound and migration assays suggested the potential of quercetin loaded-transethosomes as adjuvant strategy for skin conditions.