Marine Macroalgae in Topical Formulations: Bioactive Compounds, Variability, Analytical Challenges and Skin Benefits.

Marine macroalgae, classified into three major groups, brown (Phaeophyceae), red (Rhodophyta), and green (Chlorophyta), represent a source of structurally diverse compounds relevant for topical applications. This narrative review of the peer-reviewed literature and regulatory databases targets macroalgae-derived active ingredients in cosmetic formulations and in wound-healing applications. It outlines major compound classes (polyphenols, sulfated polysaccharides, carotenoids, fatty acids, and peptides), along with their documented biological effects on skin (antioxidant, anti-inflammatory, moisturizing, photoprotective, and anti-aging activity) and regulatory/safety aspects with formulation strategies. This review also addresses the variability in compound concentrations resulting from species, environmental conditions, and seasonal factors, which impacts reproducibility and standardization. Common extraction techniques like solvent extraction, ultrasound-assisted extraction, supercritical fluid extraction, and enzyme-assisted methods are described in relation to compound class and yield. Analytical methods used for the identification and quantification of these compounds, including HPLC, GC-MS, and FTIR, are then summarized. Additionally, recent in vitro and in vivo studies evaluating the bioactivity and safety of macroalgae-derived ingredients are discussed. This review compiles relevant evidence to inform formulation strategies and ingredient evaluation in the context of marine-based topical products.