Physical treatments to induce the antibacterial and antioxidant activities of green algae Halimeda sp. from Seribu Islands, North Jakarta, Indonesia

Abstract

Seaweeds have ecological functions as primary producers in marine waters. Most of them have an important economic value as a producer of hydrocolloids (alginate, agar and carrageenan) that are used in various industries of food and pharmaceuticals. Secondary metabolites produced in seaweed are usually for self-defense from algae predators such as fish, echinodermata, crustaceans or mollusca. This study aimed to determine the antibacterial and antioxidant activities of green algae Halimeda gracilis and Halimeda macroloba, and to determine the effect of physical treatment to antibacterial and antioxidant activities. The yield of crude extract of H. gracilis obtained was about 18.55-23.94% while the extract of H. macroloba was just about 13.49-17.88%. Antibacterial activity of crude extract of H. gracilis was higher as compared to that of H. macroloba against both tested bacteria. Induction of bacteria (Vibrio harveyi and Stenotrophomonas maltophilia) on H. gracilis led to a reduction in the antibacterial activity against Escherichia coli. Induction of bacteria in H. gracilis did not show antibacterial activity against Staphylococcus aureus. Antibacterial activity of crude extracts of H. macroloba on cutting and bacterial induction treatments were higher in both test bacteria S. aureus and E. coli.