In Situ Thai Apis mellifera Propolis Film as Potential Protective Phytopharmaceuticals Against UVB-Induced HaCaT Keratinocyte Damage

Background/Objectives: Propolis is well recognized for its antioxidant, anti-inflammatory, and wound-healing properties, supporting its cutaneous application in phytopharmaceuticals for the management of ultraviolet B (UVB)-induced skin damage. However, the application of propolis is limited by its intense coloration, stickiness, and poor user convenience. In situ film-forming systems (FFS) represent a novel dosage form designed to overcome these challenges, although efficacy data for using FFS remains limited. Consequently, this study aimed to develop a propolis-based FFS and evaluate its efficacy in mitigating UVB-irradiated HaCaT keratinocytes. Methods: Apis mellifera propolis was macerated and analyzed for total phenolic content (TPC) and total flavonoid content (TFC), radical scavenging activity (DPPH assay), and nitric oxide scavenging capability. Bioactive compounds were identified using high-performance liquid chromatography analysis (HPLC). The propolis extract was formulated into FFS and investigated on UVB-damaged HaCaT keratinocytes. An MTT viability assay, propidium iodide flow cytometry for cell cycle analysis, and a scratch wound healing assay were used to evaluate the therapeutic effects of the FFS. Results: The 72 h macerated propolis extract contained high levels of TPC, TFC, and targeted phytochemicals. The propolis extract exhibited free radical scavenging and nitric oxide inhibitory activities. Seven formulations exhibited suitable performance, with formulation F7 (FFS-F7) demonstrating superior drying time and dose-dependent free radical scavenging. Notably, FFS-F7 (≥12.5 µg/mL) significantly enhanced HaCaT proliferation, mitigated UVB-induced cell cycle arrest, reduced cellular damage, and accelerated wound closure. Conclusions: This study successfully developed an FFS that not only overcomes these physical drawbacks but also preserves the biological activity of the extract. The significant protective and restorative effects against UVB-induced HaCaT damage demonstrate the therapeutic potential of Thai Apis mellifera propolis and establish the FFS as a versatile base with the potential for delivering other bioactive compounds.