Purpose: The main purpose of this study was to evaluate the phenolic compounds content and antimicrobial activity of Nori, Kombu, Wakame and Hijiki seaweed extracts.
Methods: The extracts were prepared with ethanol (60, 80 and 100%) at different times (2 and 7 days of extraction, at room temperature). Phenolics were quantified by the Folin - Ciocalteu method, and the antimicrobial activity was evaluated by the Minimum Inhibitory Concentration (MIC) against Escherichia coli (ATCC 25922), Salmonella Enteritidis (ATCC 13076), Staphylococcus aureus (ATCC 25923), Listeria monocytogenes (ATCC 7644) and Klebsiella pneumonia (ATCC 13883).
Results: For Wakame, the higher content of phenolics, 1.66 mg GA/g, were obtained by 2 days of extraction with 80% ethanol, while for Nori, Kombu and Hijiki (7.95, 0.54 and 6.04 mg GA/g, respectively) showed higher extraction with ethanol 60% as solvent, with two days of extraction. The ethanolic extracts of seaweed did not show antimicrobial activity against Escherichia coli, Salmonella Enteritidis and Staphylococcus aureus. With respect to Listeria monocytogenes and Klebsiella pneumoniae, it was observed that all ethanolic extracts to 100% showed inhibitory activity, regardless of the extraction time. May be evidenced the ethanolic extracts to 100% of Nori (7 days), Hijiki (2 days), Wakame (2 days) and Kombu (7 and 2 days), had the best performance, with MICs between 19.53 and 39.06 µg/ml for Klebsiella pneumoniae.
Significance: Based on the data, it can be said that several crude extracts of seaweed can be considered bioactives. There was no correlation between the concentration of phenolic compounds and the antimicrobial activity of the extracts.