Formulation and mechanistic evaluation of Kaempferia galanga L. rhizome ethanolic extract as a natural broad-spectrum photoprotective agent: A preliminary study

Introduction: The increasing demand for natural photoprotective agents has driven the exploration of plant-derived bioactive compounds with ultraviolet (UV) absorbing and antioxidant properties. Objective: This study aimed to evaluate the antioxidant activity, total flavonoid and phenolic content, ethyl p-methoxycinnamate (EPMC) level, essential oil content, GC-MS profiling, and sunscreen potential of 70% ethanolic extract of Kaempferia galanga L. rhizome, followed by formulation into a topical sunscreen preparation. Methods: Antioxidant activity was determined using the DPPH radical scavenging assay, total flavonoid and phenolic content was measured by colorimetric method, EPMC content was analysed using thin-layer chromatography, essential oil content was determined by steam distillation, and chemical profiling was determined by GC-MS. Sun protection factor (SPF), percentage of erythema transmission (%TE), and percentage of pigmentation transmission (%TP) were evaluated spectrophotometrically. Results: The extract exhibited strong antioxidant activity with an IC₅₀ value of 26.40 3.43 ppm, while vitamin C showed an IC₅₀ of 7.89 0.45 ppm. Total flavonoid content was 3.26 0.28 mg quercetin equivalent (QE)/g extract and total phenolic content of the extract was 58.74 2.15 mg gallic acid equivalent (GAE) per gram of extract. EPMC level reached 22.43 3.45%, and essential oil content was 3.84 0.51%. The formulated sunscreen (5% extract) demonstrated an SPF of 40.04 (ultra-protection category), %TE of 0.98%, and %TP of 5.52%, indicating sun-blocking characteristics and broad-spectrum protection. Physicochemical evaluation revealed a pH of 5.21 0.32, a viscosity of 472.00 14.27 cP, and a particle size of 16.27 2.77 μm. Conclusion: These findings suggest that K. galanga rhizome extract possesses significant antioxidant and photoprotective properties and is a promising natural active ingredient for broad-spectrum sunscreen formulations.