Prunus leaf extracts are rich in phenolic and flavonoid compounds like rutin, and they are known for their antioxidant potential. This study compares the bioactivity and stability of leaf extracts from Prunus domestica L. (EL), Prunus salicina Lindl. (JL), and Prunus cerasifera Ehrh. (CL) and evaluates the dermal safety of a cream containing the extract with the most favorable in vitro properties for potential cosmetic use. Ethanolic extracts were assessed for total phenolic and condensed tannin contents, as well as antioxidants, using DPPH assay and lipid peroxidation inhibitory activities. The CL extract exhibited moderate total phenolic content, the highest condensed tannin content, and strong antioxidant (IC₅₀ = 22.1 ± 3.1 µg/mL) and anti-lipid peroxidation (62.3 ± 1.0%) activities. Based on these results, CL was incorporated into a cream formulation (CCL), which was then evaluated for physicochemical properties, antioxidant retention, and in vitro skin permeation using Franz diffusion cells. The formulation remained physically stable under ambient conditions and retained antioxidant activity above 74.5% under thermal cycling conditions. Rutin from the CCL formulation was retained within the Strat-M™ membrane (4.0 ± 1.1%), which was 5.7-fold higher than that of the control (0.7 ± 0.6%) over 8 h; however, it was not detected in the receptor chamber under these in vitro conditions. A semi-open patch test conducted on 26 healthy volunteers under double-blind conditions revealed no signs of irritation, confirming the formulation’s dermal safety. Overall, the findings support the feasibility of using P. cerasifera extract as a stable antioxidant component in topical skincare formulations.

Natural polymer-based nanoparticles have emerged as promising stabilizers for Pickering emulsions, offering biocompatibility, environmental sustainability, and improved protection of active compounds. This study developed chitosan/gum arabic (CH/GA) nanoparticles as solid stabilizers for quercetin-loaded Pickering emulsions to enhance the stability and antioxidant bioactivity of quercetin (QE), a plant-derived flavonoid known for its potent radical-scavenging activity but limited by oxidative degradation. A systematic formulation strategy was employed to evaluate the effects of CH/GA concentration (0.5–2.0% w/v), oil type (olive, soybean, sunflower, and coconut), and oil volume fraction (ϕ = 0.5–0.7) on emulsion stability. The formulation containing 1.5% CH/GA and olive oil at ϕ = 0.6 exhibited optimal physical and interfacial stability. Quercetin (0.1% w/w) was incorporated into the optimized emulsions and characterized for long-term stability, particle size, droplet morphology, rheology, antioxidant activity (DPPH), cytocompatibility, and intracellular reactive oxygen species (ROS) protection using HaCaT keratinocytes. The olive oil-based formulation (D1-QE) exhibited greater viscosity retention and antioxidant stability than its soybean-based counterpart (E2-QE) under both room temperature (RT) and accelerated heating–cooling (H/C) storage conditions. Confocal microscopy confirmed the accumulation of CH/GA nanoparticles at the oil–water interface, forming a dense interfacial barrier and enhancing emulsion stability. HPLC analysis showed that D1-QE retained 92.8 ± 0.5% of QE at RT and 82.8 ± 1.5% under H/C conditions after 30 days. Antioxidant activity was largely preserved, with only 4.7 ± 1.7% and 14.9 ± 4.8% loss of DPPH radical scavenging activity at RT and H/C, respectively. Cytotoxicity testing in HaCaT keratinocytes confirmed that the emulsions were non-toxic at 1 mg/mL QE and effectively reduced H₂O₂-induced oxidative stress, decreasing intracellular ROS levels by 75.16%. These results highlight the potential of CH/GA-stabilized Pickering emulsions as a polymer-based delivery system for maintaining the stability and functional antioxidant activity of QE in bioactive formulations.