Effect of Solvents on Bioactive Compounds and Antioxidant Activity of Padina Tetrastromatica and Gracilaria Tenuistipitata Seaweeds Collected From Bangladesh

Abstract Seaweeds are now recognized as a treasure of bioactive compounds. However, the seaweed of Bangladesh is still unexplored. So, this study was designed to explore the secondary metabolites and antioxidant activities of solvent extracts of Padina tetrastromatica and Gracilaria tenuistipitata. Phytochemical screening and Fourier transform infrared (FTIR) confirm the diverse type of bioactive compounds. Antioxidant activity of extracts were evaluated by 1, 1-diphenyl-2- picrylhydrazyl (DPPH), 2, 2-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), reducing power (RP), phosphomolybdenum and hydrogen peroxide assays. Here, methanolic extract of P. tetrastromatica showed the highest amount of total phenolic content (85.61 mg of GA/g), total flavonoid content (41.77 mg of quercetin/g), which showed as potent antioxidant properties confirmed by DPPH (77.07%), ABTS (77.65%), RP (53.24 mg AAE/g), phosphomolybdenum (31.58 mg AAE/g) and hydrogen peroxide (67.89%) assays followed by ethanol and water. This study concluded that bioactive compound and antioxidant activities are dose and solvent-dependent and seaweed type.