Chemical Survey and Antifungal Efficacy of Sargassum muticum’s Alkaloids and Phenolic-Rich Fraction Against Airborne Toxigenic and Nosocomial Opportunistic Molds Isolates

The Atlantic coastline of El-Jadida, Morocco, is renowned for its plentiful algae, especially brown seaweed, which is rich in active compounds known for their antifungal properties. This valuable resource offers an exciting opportunity to tackle the numerous challenges posed by invasive fungal infections, allergies, mycotoxin-related food poisoning, and drug-resistant strains. Underscoring the urgent need to explore alternative, sustainable, and environmentally friendly antifungal agents derived from algae. This study aimed to evaluate the antifungal activity of total alkaloids and phenolic-rich fractions derived from seven species of Pheophyceae: Sargassum muticum , Sargassum vulgare , Bifurcaria bifurcata , Cystoseira tamariscifolia , Cystoseira humilis , Laminaria ochroleuca , and Fucus spiralis against four fungi: airborne toxigenic isolates of Aspergillus westerdijkiae and Chaetomium globosum as well as nosocomial opportunistic isolates of Aspergillus nidulans and Scopulariopsis brevicaulis . The study also aimed to identify the most effective alga and its specific active compounds through LC–MS and GC–MS analysis. The invasive Sargassum muticum was chosen as the most potent alga in inhibiting the growth of mycelium. For the first time, the alkaloids palmatine and jatrorrhizine, along with caulerpin, have been identified. The chloroform fraction revealed the prevalence of phenolic compounds including, phenolic acids, flavonoids, and phlorotannins. The lowest minimum inhibitory concentrations (MICs), with a maximum fungal load of 10 8 colony-forming unit (CFU), recorded ranged from 3.12 to 6.25 μg/mL by the phenolic-rich fraction against airborne toxigenic isolates, and from 100 to 200 μg/mL against nosocomial opportunistic isolates by the total alkaloids. In comparison, the positive control, ketoconazole, showed higher MICs and resistance against A. nidulans . The valorization of Sargassum muticum is proposed as a green strategy to preserve the ecological balance, combat antifungal resistance, and address public health challenges. Graphical Abstract