Marine macroalgal metabolites in microbial modulation for next-generation microecological therapeutics

The marine environment harbours an extraordinary diversity of bioactive compounds, with seaweeds (marine macroalgae) emerging as prolific producers of secondary metabolites with potent antimicrobial and microbiota-modulating properties. Amid the escalating crisis of antimicrobial resistance (AMR) and increasing recognition of microbiome-related health disorders, seaweed-derived compounds offer a promising alternative to conventional therapeutics. This review explores the chemical diversity and therapeutic potential of secondary metabolites from brown, red, and green algae, including phlorotannins, sulfated polysaccharides, halogenated terpenoids, and peptides. The scope includes detailed discussions on their antimicrobial mechanisms, membrane disruption, enzyme inhibition, immune modulation and their role in microbiome modulation via prebiotic effects, probiotic synergy, and dysbiosis mitigation. The review also addresses recent advances in extraction technologies, nanocarrier delivery systems, and synthetic biology platforms that enhance the pharmacological utility of these bioactives. Despite substantial preclinical evidence, clinical translation is constrained by variability in metabolite composition, limited in vivo validation, and regulatory challenges. Future research directions emphasise standardised extraction protocols, omics-guided bioactivity mapping, microbiome-informed therapeutic design, and sustainable seaweed cultivation. Collectively, this review underscores the untapped potential of seaweed-derived secondary metabolites as next-generation therapeutics within microecological and microbiome-centred healthcare frameworks.