Antioxidant, antimicrobial and analgesic activities of the invasive seagrass Halophila stipulacea leaf and stem extracts

Marine organisms, including marine plants, are important sources of new compounds endowed with interesting biological properties. The aim of this study was to evaluate the antioxidant, antibacterial and analgesic activities of the hexane, ethyl acetate and methanol extracts of seagrass Halophila stipulacea (Forssk.) Ascherson (Hydrocharitaceae) leaves and stems. Antioxidant activity was evaluated by through 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging ability and reducing power. Antimicrobial potential was assessed by the minimum inhibitory concentration (MIC) method. Analgesic activity was evaluated by the acetic acid method. Methanol and ethyl acetate extracts of H. stipulacea were found to have the highest phenolic content and showed higher antioxidant activity than hexane extracts. Stem extracts showed moderate antimicrobial activity against tested microorganisms (minimum inhibitory concentration range was 3.75-15 mg/mL). All tested extracts had a high analgesic activity in acetic acid-induced writhing assay, and their effects were comparable to the reference acetylsalicylate lysine drug (200 mg/kg, applied intraperitoneally). The methanol stem extracts had a higher analgesic effect than acetylsalicylate lysine used as a positive control, with a maximum inhibition of 84.06±5.47 % vs. 75.73±10.67 % for positive controls. In summary, the investigations indicate that H. stipulaceais a natural source of antioxidant, antimicrobial and analgesic activities.