Antioxidant activities of acetone extract of Sargassum polycystum from different parts of Thallus

Abstract

Brown alga Sargassum polycystum in Indonesian waters is relatively abundant, and several studies show that brown alga has more antioxidant activity than red and green algae. Analysis of active compounds in the alga is generally carried out as a whole of macroalga thallus. This research was carried out to study the effect of thallus parts, namely basal, middle, and apical, on the antioxidant activity and fucoxanthin content in acetone extract of S. polycystum. The results determined the best part of the thallus as a producer of antioxidant compounds. The extraction was performed by an ultrasonic-assisted method using 90% acetone. The basal part contained the highest fucoxanthin of 1.00±0.025 mg/kg, while the most increased antioxidant activity was in the apical part of 65.78±5.31 μg/mL for the antioxidant activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) method, 383.19±8.81 μmol ascorbic acid/g for the antioxidant activity of the cupric reducing antioxidant capacity (CUPRAC) method, and 964.75±3.91 μmol Fe2+/g for the antioxidant activity of the ferric reducing antioxidant power (FRAP) method. This study shows antioxidant activity had a negative correlation with the fucoxanthin content. It is concluded that fucoxanthin was not the major contributor to an antioxidant activity acetone extract of S. polycystum thallus.