Antibacterial properties of a glycolipid-rich extract and active principle from Nunavik collections of the macroalgae Fucus evanescens C. Agardh (Fucaceae)

This study investigated the antibacterial activity of glycolipid-rich extracts of the brown macroalga Fucus evanescens in cell culture. Accessions were collected on the Arctic coast of Ungava Bay, Nunavik, Quebec. The crude ethyl acetate extract of these accessions showed strong antibacterial activity (≥4 log(10) cfu) against Hemophilus influenzae , Legionella pneumophila , Propionibacterium acnes (ATCC and clinical isolate), and Streptococcus pyogenes at 100?μg/mL. This algal extract inhibited by 3 log(10) Clostridium difficile and methicillin-resistant Staphylococcus aureus , whereas Bacillus cereus , Escherichia coli , Klebsiella pneumoniae , and Pseudomonas aeruginosa were not significantly affected. Further investigations of the activity of a glycolipid-rich fraction, extracted with dichloromethane, against Propionibacterium acnes showed an MIC(100) of 50?μg/mL, with an inhibition of more than 99% at only 7.8?μg/mL. The main active compound, a β-d-galactosyl O-linked glycolipid, was synthesized for the bioassay and showed an MIC(100) of 50?μg/mL but lost its activity more quickly with only 50% of inhibition at 12.5?μg/mL. Therefore, the semipurified F. evanescens extract could be a good choice for future research into the development of alternative treatments for acne therapy.