Chemical composition and in vitro antioxidant and antibacterial activities of Sargassum vulgare C. Agardh from Lobo, Batangas, Philippines

Seaweeds are notable in producing diverse kinds of bioactive compounds with promising pharmacological properties. A study was conducted at the National Institute of Molecular Biology and Biotechnology (BIOTECH), University of the Philippines Los Baños [Philippines] from July to November 2018 to evaluate the proximate composition and potential antioxidant and antibacterial properties of a brown macroalga, Sargassum vulgare C. Agardh. Determination of the total phenolic compounds using Folin-Ciocalteu reagent showed that the dried algal biomass have a total phenolic content of 10.13 +- 0.166 mg GAE/g. Relative antioxidant efficiency showed that S. vulgare exerted potent radical scavenging activity in a concentration dependent manner with EC50 value of 37.2 +- 0.015 ug GAE. The tested algal extract exhibited radical scavenging activity that is dose-dependent and positively correlated to its phenolic content. On the other hand, proximate composition of the dried macroalga showed that S. vulgare contains high carbohydrate, ash and crude fiber content of 34.18+-0.32%, 27.09+-0.00%, and 22.59+-0.21 respectively. Methanolic extract of the macroalgal strain was subjected to microtiter plate dilution assay against a wide spectrum of pathogenic bacteria. S. vulgare showed pronounced activity against Staphylococcus aureus having MIC of 250 ug/ml. Aeromonas hydrophila, Bacillus cereus and Methicillin-resistant S. aureus were also moderately inhibited each having MIC of 500 ug/mL, 500 ug/mL, and 1000 ug/mL, respectively. Minimum bactericidal activity against S. aureus is higher than that of Bacillus cereus and Aeromonas hydrophila, having 500 ug/mL and 1000 ug/mL, respectively. On the other hand, Methicillin-resistant S. aureus exhibited MBC value of 1000ug/ml. This study showed the potential antioxidant and antibacterial activity of S. vulgare, which make it a suitable candidate for production of new bioactive compounds important for pharmacological and food industries.