Study of antioxidant and antibacterial activities of depolymerized fucoidans extracted from Sargassum tenerrimum

This work was performed to compare the effect of two water-extraction methods of fucoidan from Sargassum tenerrimum on their chemical composition, antioxidant capacity and antimicrobial activity after hydrothermal depolymerization. The number of extraction steps and ethanol concentration used for extraction were different between the two methods. Extraction yield of fucoidan obtained from the first method (DFM1) and the second method (DFM2) were 3.68 and 1.09%, respectively (P < 0.05). The IC50 value of DPPH radical scavenging activity for DFM1 was 1.93 times more than DFM2. The Fe+2 ions chelating activity were 78.3% for DFM1 and 89.4% for DFM2 at 10 mg/mL concentration. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration of DFM2 were lower compared to DFM1 for Enterococcus faecalis and Escherichia coli The DFM2 was more effective to decrease the MIC value of chloramphenicol on the gram negative strains than DFM1. Both of the fucoidans showed a synergistic effect in combination with chloramphenicol to inhibit the growth of Escherichia coli Based on the results of this study, depolymerized fucoidans can also be more considered as effective antibacterial agent with synergistic potential in combination with antibiotics to decrease the prescribed doses of antibiotic drugs in humans and animals.