Bioactivity of Ultrasound-Assisted Ethanolic Extract of Ulva lactuca: Antioxidant, Anti-Inflammatory, and Antibacterial Evaluation

Green seaweed contains many bioactive compounds, including phenols, saponins, flavonoids, and terpenoids. These compounds are considered to produce strong antioxidant activity, and it is hoped that they can provide health benefits and play a role in disease prevention. The aim of this study is to evaluate the antioxidant, anti-inflammatory, and antibacterial activities of Ulva lactuca ethanolic extract obtained using ultrasound-assisted extraction (UAE). Ulva lactuca powder was extracted using UAE with 96% ethanol at a 1:5 ratio in a closed container. The extract was then subjected to phytochemical screening for phenolic, flavonoid, alkaloid, saponin, tannin, and terpenoid compounds. Antioxidant activity was assessed using the DPPH, FRAP, and ABTS methods, with ascorbic acid as the standard. Anti-inflammatory activity was evaluated using the BSA method, with diclofenac sodium as the standard. Antibacterial activity was tested using the agar diffusion method against E. coli and S. aureus. The yield from ethanol extraction using the UAE method was 16.56%. Phytochemical screening showed that the extract contained phenols, flavonoids, alkaloids, saponins, and terpenoids, while tannins were absent. The IC50 values for antioxidant activity using DPPH, FRAP, and ABTS methods were 52.65 ± 0.46, 47.48 ± 0.52, and 41.17 ± 1.09µg/ mL, respectively. All extract results were significantly different compared to ascorbic acid as the standard. The anti-inflammatory activity of the extract (IC50 = 23.15 ± 1.61µg/ mL) was not significantly different from diclofenac sodium. Higher antibacterial activity against S. aureus indicates that the antibacterial compounds in Ulva lactuca are more effective against Gram-positive bacteria. The antibacterial activity against both S. aureus and E. coli was significantly different from K+ (amoxicillin), except for the 20% concentration extract, which did not significantly inhibit E. coli. In conclusion, extraction of Ulva lactuca using UAE can enhance its antioxidant, anti-inflammatory, and antibacterial activities.