Phytochemicals, antioxidant and antibacterial activity of crude extract of Sargassum polycystum collected from Bangladesh

Abstract

Marine seaweed species have been extensively studied in recent decades due to their potential biological activities, such as antioxidant and antibacterial characteristics. This study investigates the phytochemicals, total phenolic content (TPC), total flavonoid content (TFC), antioxidant, and antibacterial properties of Sargassum polycystum extracts collected from Bangladesh and crude extracts were prepared using methanol, ethanol, and water as extraction solvents. Phytochemical analysis revealed the presence of terpenoids, saponins, phlobatannins, and cardiac glycosides. Fourier-transform infrared spectroscopy (FT-IR) identified functional groups, including phenols, carboxylic acids, ketones, ethers, aromatics, alkanes, and ethers. The methanol extract exhibited the highest TPC (95.34 ± 1.21 mg of GAE/g) and TFC (51.48 ± 0.92 mg of QE/g). Methanol extracts displayed superior antioxidant activity in the Phosphomolybdenum assay (1.96 ± 0.08), DPPH assay (81.33 ± 5.60%, IC50 = 1.17 mg/mL), ABTS assay (71.65 ± 4.10%, IC50 = 2.54 mg/mL), and Nitric oxide scavenging assay (67.64 ± 4.10%, IC50 = 3.81 mg/mL). Ethanol extract demonstrated the highest antibacterial activity against Escherichia coli (16.50 ± 0.13 mm), while the methanol extract excelled against Salmonella typhimurium (14.6 ± 0.18 mm) at 7 mg/mL dosage. A positive correlation was found among TPC, TFC, and different antioxidant assays.