Antimicrobial and Antioxidant Activities of Some Selected Seaweeds Species from the Western Coast of the Northern Egyptian Red Sea

The present investigation was carried out to evaluate the antimicrobial and antioxidant activities of four seaweed species gathered from the western coast of the northern Egyptian Red Sea using two different solvents: dichloromethane/ methanol (1:1 v/v) and ethyl acetate. These species are Turbinaria ornata, Padina pavonica (Phaeophyta), Actinotrichia fragilis (Rhodophyta) and Ulva lactuca (Chlorophyta). The antimicrobial activity of the crude extracts was assessed in vitro against three microorganisms: Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Staphylococcus aureus) and the yeast Candida albicans by the disc diffusion method. Both extracts of T. ornata and P. povonica showed a wide spectrum of antibacterial activity, however, the fungal entity Candida albicans was not inhibited in any way by any of the examined seaweed extracts. The efficacy of both solvents was discussed. The antioxidant activity was detected using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. The highest activity was recorded in the dichloromethane/ methanol extract of the brown seaweed T. ornata. On the other hand, the lowest activity was recorded in the ethyl acetate extract of the green seaweed Ulva lactuca. These findings revealed the potential of the Red Sea brown seaweeds as a promising candidate to act as antibacterial and antioxidant agent in medical applications. Further work is required to identify and separate the exact active compounds responsible for the biological activity.