Seaweeds are notable in producing diverse kinds of polyphenolic compounds with direct relevance to cosmetic application. This investigation was done to assess the bioactive properties of a brown macroalga, Sargassum siliquosum J. Agardh. The alga has a total phenolic content of 30.34 ± 0.00 mg gallic acid equivalents (GAE) g-1. Relative antioxidant efficiency showed that S. siliquosum exerted potent DPPH (diphenyl-1, 2-picryl hydrazyl) scavenging activity and high ability of reducing copper ions in a dose-dependent manner with IC50 value of 0.19 mg GAE mL-1 and 18.50 μg GAE mL-1, respectively. Evaluation of antibacterial activities using microtiter plate dilution assay revealed that S. siliquosum showed strong activity against bacterial skin pathogen, Staphylococcus aureus (Minimum Inhibitory Concentration (MIC) = 125 μg mL-1 and Minimum Bactericidal Concentration (MBC) = 250 μg mL-1) and Staphylococcus epidermidis (MBC = 250 μg mL-1 and MBC = 500 μg mL-1). In vitro study of tyrosinase inhibition showed that S. siliquosum has greater inhibitory activity (IC50 of 65.0 μg GAE mL-1) as compared to that of the known skin-lightening ingredient, kojic acid with IC50 of 109.32 μg GAE mL-1. This study is useful for improved utilization of S. siliquosum extract as source of polyphenolic compounds important for the development of novel skin lightening ingredient for formulation cosmetic products.
Key words: antioxidant activity, Catanauan, cosmetics, lightening ingredient, polyphenols, Sargassum
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