Bioactive Compounds and Antibacterial Activity of Red Macroalgae (Kappaphycus alvarezii) from Aru Islands, Indonesia

Abstract

The red macroalga Kappaphycus alvarezii is a valuable marine resource widely cultivated in Indonesian waters. Beyond its economic importance as a source of carrageenan, this species contains a variety of bioactive secondary metabolites that can serve as natural antibacterial agents for fishery product preservation. This study aims to evaluate the antibacterial activity and phytochemical constituents of K. alvarezii collected from the waters of Aru Islands, Indonesia, using methanol and chloroform as extraction solvents. Extraction yields of methanol and chloroform extracts were 9.4% and 8.7%, respectively. Both extracts exhibited antibacterial activity against Staphylococcus aureus, with the methanol extract showing a higher inhibition zone (10.10±0.71 mm) than the chloroform extract (8.25±0.28 mm). However, neither extract was effective against Escherichia coli. Phytochemical analysis revealed the presence of alkaloids, flavonoids, and terpenoids in both extracts, while saponins were detected only in the methanol extract. These findings suggest that the methanol extract of K. alvarezii possesses higher antibacterial potency and could be developed as a natural preservative to enhance the shelf life and safety of fishery products. Further studies involving fractionation and GC–MS or LC–MS profiling are recommended to identify the active compounds responsible for the antibacterial effect.