Wang et al. (2009) accounted that mechanisms of action of phlorotannin was also similar to fatty acids documented by Shannon and Abu-Ghannam (2016). Moreover, they added that phloroglucinol units of phlorotannin contains Phenolic aromatic rings and OH group that makes hydrogen bond with NH group of bacterial proteins that cause cell lysis. It was further evidenced by Wei et al. (2015) that phlorotannin extracted from S.thunbergii injured the cell membrane and cell wall of V.parahaemolyticus, leads to cytoplasm outflow and disassembly of cell inclusions. However, higher amount of phloroglucinol is required to destroy Gram-negative bacteria than the Gram-positive. This is due to the multifaceted structure of gram negative cell wall than the gram positive one (Kamei and Isnansetyo, 2003).