Inhibition zone steadily increased as the polarity of the solvent used for extraction increase and later decreased, forming a bell shape. This suggests that the active later decreased, forming a bell shape. This suggests that the active compound is neither highly polar nor least polar. This explains why extract obtained using ethyl-acetate (a highly polar solvent), although having the highest polyphenol content, did not cause more zone of inhibition. This result agrees with the work of Bystrom,
Lewis, Brown, Rodriguez, and obendori (2008) which showed that 70% acetone extract with highest polyphenol contents but without causing highest inhibition zone against the microbes testd. The significance of various phenolic compound found in seaweed have been linked with defensive mechanism in marine water. Halogenated phenol compounds are unique to marine metabolites such as Bromohenol, arising from tendency of phenol undergoing conversion through electrophilic bromination. These groups of compounds are found on the cell wall of seaweed and have natural tendency of preventing cells from microbial attack ( Gupta & Abu-Ghannam.2011).