Marine Macroalgae, a Source of Natural Inhibitors of Fungal Phytopathogens

Abstract

Fungal phytopathogens are a growing problem all over the world; their propagation causes significant crop losses, affecting the quality of fruits and vegetables, diminishing the availability of food, leading to the loss of billions of euros every year. To control fungal diseases, the use of synthetic chemical fungicides is widely applied; these substances are, however, environmentally damaging. Marine algae, one of the richest marine sources of compounds possessing a wide range of bioactivities, present an eco-friendly alternative in the search for diverse compounds with industrial applications. The synthesis of such bioactive compounds has been recognized as part of microalgal responsiveness to stress conditions, resulting in the production of polyphenols, polysaccharides, lipophilic compounds, and terpenoids, including halogenated compounds, already described as antimicrobial agents. Furthermore, many studies, in vitro or in planta, have demonstrated the inhibitory activity of these compounds with respect to fungal phytopathogens. This review aims to gather the maximum of information addressing macroalgae extracts with potential inhibition against fungal phytopathogens, including the best inhibitory results, while presenting some already reported mechanisms of action.

Keywords: algae phenols; antifungal activity; bioactive compounds; brown algae; crop losses; fungal membrane disruption; fungal resistance; lipophilic compounds; macroalgae metabolites; plant pathogens.

Figure 1

Fucosterol (C₂₉H₄₈O). Chemical structure obtained from PubChem database on 4 August 2021 (https://pubchem.ncbi.nlm.nih.gov/compound/5281328#section=2D-structure).

Figure 2

Ergosterol (C₂₈H₄₄O). Chemical structure obtained from PubChem database 4 August 2021 (https://pubchem.ncbi.nlm.nih.gov/compound/444679#section=2D-structure).

Figure 3

Schematic representation of a possible interaction of algae sterols in the fungal membrane.