The main goal of this systematic review on the flavonol class secondary metabolite quercetin is to evaluate and summarize the existing research on quercetin’s potential health benefits, therapeutic properties, and effectiveness in disease prevention and treatment. In addition to evaluating quercetin’s potential for drug development with fewer side effects and lower toxicity, this type of review attempts to collect scientific evidence addressing quercetin’s roles as an antioxidant, anti-inflammatory, antibacterial, and anticancer agent. In the first part, we analyze various flavonoid compounds, focusing on their chemical structure, classification, and natural sources. We highlight their most recent biological activities as reported in the literature. Among these compounds, we pay special attention to quercetin, detailing its chemical structure, physicochemical properties, and process of biosynthesis in plants. We also present natural sources of quercetin and emphasize its health benefits, such as its antioxidant and anti-inflammatory effects. Additionally, we discuss methods to enhance its bioavailability, analyzing the latest and most effective delivery systems based on quercetin.

Caffeic acid (CA), a phenolic acid, is a powerful antioxidant with proven effectiveness. CA instability gives it limited use, so encapsulation in polymeric nanomaterials has been used to solve the problem but also to obtain topical hydrogel formulas. Two different formulas of caffeic acid liposomes were incorporated into three different formulas of carbopol-based hydrogels. A Franz diffusion cell system was used to evaluate the release of CA from hydrogels. For the viscoelastic measurements of the hydrogels, the equilibrium flow test was used. The dynamic tests were examined at rest by three oscillating tests: the amplitude test, the frequency test and the flow and recovery test. These carbopol gels have a high elasticity at flow stress even at very low polymer concentrations. In the analysis of the texture, the increase of the polymer concentration from 0.5% to 1% determined a linear increase of the values of the textural parameters for hydrogels. The textural properties of 1% carbopol-based hydrogels were slightly affected by the addition of liposomal vesicle dispersion and the firmness and shear work increased with increasing carbomer concentration.

Liposomes represent a promising class of drug delivery systems that enhance the therapeutic efficacy and safety of various pharmaceutical agents. Also, they offer numerous advantages compared to traditional drug delivery methods, including targeted delivery to specific sites, controlled release, and fewer side effects. This review meticulously examines the methodologies employed in the preparation and characterization of liposomal formulations. With the rising incidence of adverse drug reactions, there is a pressing need for innovative delivery strategies that prioritize selectivity, specificity, and safety. Nanomedicine promises to revolutionize diagnostics and treatments, addressing current limitations and improving disease management, including cancer, which remains a major global health challenge. This paper aims to conduct a comprehensive study on the interest of biomedical research regarding nanotechnology and its implications for further applications.

Medical and pharmaceutical research has shown that liposomes are very efficient in transporting drugs to targets. In this study, we prepared six liposome formulas, three in which we entrapped caffeic acid (CA), and three with only phospholipids and without CA. Determination of entrapment efficiency (EE) showed that regardless of the phospholipids used, the percentage of CA entrapment was up to 76%. The characterization of the liposomes was performed using Dynamic Light Scattering (DLS), Atomic Force Microscopy (AFM), zeta potential and polydispersity and showed that about 75–99% of the liposomes had dimensions between 40 ± 0.55–500 ± 1.45 nm. The size and zeta potential of liposomes were influenced by the type of phospholipid used to obtain them. CA release from liposomes was performed using a six-cell Franz diffusion system, and it was observed that the release of entrapped CA occurs gradually, the highest amount occurring in the first eight hours (over 80%), after which the release is much reduced. Additionally, the time stability of the obtained liposomes was analysed using univariate and multivariate statistical analysis. Therefore, liposomes offer great potential in CA entrapment.

Background: Aristolochia clematitis L. (AC), a plant with diverse traditional uses, has gained increasing scientific interest due to its rich content of bioactive compounds such as flavonoids and polyphenols. However, its systemic use is limited by the presence of aristolochic acids, which are known for their nephrotoxic and carcinogenic potential. Methods: In this context, the present study investigates the therapeutic potential of A. clematitis extract by encapsulating it in liposomes with the aim of enhancing its topical efficacy. Results: The extract was characterized in terms of its flavonoid content (67.23 ± 0.33 mg QE/g DW (quercetin/dry plant material)) and polyphenols expressed as gallic acid equivalents (64.38 ± 0.16 mg GAE/g DW), as well as its antioxidant capacity using the reagents 1,1-diphenyl-2-picrylhydrazyl (DPPH − IC₅₀ = 0.1619 mg/mL extract) and diammonium 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS − IC₅₀ = 205.57 μg/mL extract). Four types of liposomes were synthesized (two loaded with extract and two empty), and their characterization was performed using Atomic Force Microscopy (AFM), Dynamic Light Scattering (DLS), Zeta Potential, polydispersity index, and in vitro release studies. Conclusions: The results demonstrated a high entrapment efficiency (over 82%), good stability over 30 days, and controlled release of flavonoids. Microbiological studies revealed relevant antimicrobial activity against Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, and Pseudomonas aeruginosa strains. The evaluation on HaCaT skin-derived cells (at 10–100 µg/mL) proved that the samples displayed good overall tolerability, slightly decreasing cell viability (the most statistically significant being associated with AC treatment) and showing no structural, nuclear, or mitochondrial morphological changes.

The objective of this study was to develop microspheres (Ms) from natural materials, chitosan (Ch) and sodium alginate (Na-Alg), that protect Ruta graveolens L. (RG) extract against temperature, pH, and the oxidative impact of degradation. The microspheres also masked the unpleasant taste by enclosing them in a biodegradable polymeric matrix. First, the total polyphenols, total flavonoid content, and antioxidant activity were quantified spectrophotometrically. Individual polyphenol contents were identified and quantified by high-performance liquid chromatography (HPLC) with UV detection. The RG extract was encapsulated in microspheres of chitosan–sodium alginate–Ruta graveolens L. extract (CARG-Ms) using two distinct procedures (method 1, in which the RG extract was added to the Ch solution and the Na-Alg solution was dripped into this mixture, and method 2, in which the RG extract was added to the Na-Alg solution and then dripped into the Ch solution) to determine which method was more advantageous. All microspheres were evaluated and characterized by confocal laser-scanning microscopy (CLSM), scanning electron microscopy (SEM), optical scanning, entrapping efficiency (EE%), swelling index (SWL%), and in vitro release (RGrel%), and all results underwent univariate and multivariate analysis using a regression model. Following these tests, it was observed that the extract had an appreciable flavonoid content of 37.98%, with antioxidant properties evidenced by the 54.25% inhibition of DPPH. Of the polyphenolic compounds identified in the extract by using the HPLC method, rutin was present in the highest amount, at 745.17 μg/mL. The microspheres prepared by method 2, which contained the highest concentration of chitosan, had several desirable properties, including a high degree of roughness, high entrapping efficiency (75%), a wrinkled appearance, a better in vitro release capacity, and a lower SWL%. On the other hand, CARG-Ms prepared by method 1, which contained a smaller concentration of Ch, had faster swelling and slower release of the extract due to the lower entrapping efficiency (35%). These results suggest that the concentration of wall material and the preparation method play important roles in the encapsulation process and final particle characteristics. According to the obtained results, after the multivariate statistical analysis, it can be observed that the microspheres prepared via method 2 of the complex coacervation process were the most efficient for encapsulating rue extract in microspheres, because the extract was protected against degradation from the gastrointestinal tract.