Development and evaluation of an alginate-based cream formulation from Sargassum vulgare: Antimicrobial, antioxidant, and safety assessments

This study investigates the potential of alginate extracted from Sargassum vulgare as a multifunctional ingredient in cosmetic formulations, emphasizing its antimicrobial, antioxidant, and safety properties. Alginate was extracted and characterized, then incorporated into a topical cream formulation. The antimicrobial activity was evaluated using the microdilution method against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans. The minimum inhibitory concentration (MIC) values were determined as 0.31 mg/mL for S. aureus and Bacillus cereus, while P. aeruginosa exhibited the highest susceptibility with a minimal bactericidal concentration (MBC) of 0.63 mg/mL. The antioxidant potential of alginate was assessed through DPPH and iron chelating assays, yielding IC₅₀ values of 13.63 mg/mL and 0.26 mg/mL, respectively. The microbiological challenge test demonstrated that the alginate-based cream formulation significantly inhibited microbial growth, notably eliminating S. aureus by day 7 and E. coli by day 28. Cytotoxicity evaluations on L929 fibroblast cells confirmed the biocompatibility of the alginate-based cream, with a higher cell viability rate (56.22 % at 1 mg/mL) compared to the standard preservative-containing formulation (35.85 %). Molecular docking studies revealed that alginate interacts with Staphylococcus aureus Sortase A (1T2W) with a binding energy of −5.9 kcal/mol and an inhibition constant of 47.7 μM, suggesting a potential mechanism for its antibacterial effects. These findings support the application of alginate from S. vulgare in cosmetic formulations, providing a natural and sustainable alternative with antimicrobial, antioxidant, and protective properties.