Phlorotannins from marine algae: Structural diversity, biological activities, and industrial applications

Phlorotannins, a unique group of marine secondary metabolites, have garnered increasing attention due to their structural complexity and multifaceted bioactivities. This article systematically summarizes recent advances in understanding these compounds, from their chemical diversity to industrial applications. First, the ecological roles and natural distribution of phlorotannins are introduced, highlighting their significance in marine ecosystems and traditional uses. Second, the structural classification and biosynthetic pathways of phlorotannins are discussed, with an emphasis on key enzymes and environmental factors influencing their production. Third, their bioactivities, including antioxidative, anti-inflammatory, antimicrobial, and anticancer effects, are critically evaluated, providing mechanistic insights into molecular targets. Fourth, challenges in bioavailability, stability, and potential toxicity are addressed, along with limitations in current delivery systems and metabolic studies. Finally, future directions are proposed, such as green extraction technologies and structure-activity relationship optimization. By integrating diverse insights, this work enhances phlorotannin research and practical uses in food, pharmaceuticals, and cosmetics.