Extracts of the seaweed Bifurcaria bifurcata display antifungal activity against human dermatophyte fungi

Abstract

Bifurcaria bifurcata is a seaweed of the Order Fucales (Ochrophyta, Phaeophyceae) that can be found all year round along the Portuguese Atlantic shore. Although it is considered edible in some countries, its biotechnological potential has not yet been assessed in detail and here we report its antimicrobial potential against human dermatophyte fungi. Three samples were harvested from Baleal Island (Peniche, Portugal) harvested in winter (BbPe); from Aguda Beach (Arcozelo, Vila Nova de Gaia, Portugal), harvested in autumn (BbAg) and a sample obtained by culturing the Aguda sample under laboratory conditions (BbLC). A broth macrodilution assay was applied to determine the MIC (minimum inhibitory concentration) and MLC (minimum lethal concentration) of the B. bifurcata extracts. Results show that the BbPe MeOH extracts were the most effective and had higher antifungal activity against all the tested dermatophyte strains than the BbLC and BaAg extracts [Epidermophyton floccosum FF9 (100–200 µg/mL MIC; 200 µg/mL MLC), Microsporum canis FF1 (400 µg/mL MIC; ≥400 µg/mL MLC), Trichophyton mentagrophytes FF7 (100 µg/mL MIC; >800 µg/mL MLC), M. gypseum CECT 2908 (800 µg/mL MIC; ≥800 µg/mL MLC), T. mentagrophytes var. interdigitale CECT 2958 (800 µg/mL MIC; ≥800 ug/mL MLC), T. rubrum CECT 2794 (200 µg/mL MIC; ≤400 µg/mL MLC)]. In fact, only E. floccosum FF9 was sensitive to BbAg and BbLC MeOH extracts. To our knowledge, this is the first report of antifungal activity of B. bifurcata against human dermatophyte fungi.