Marine microbial-derived cytotoxic alkaloids: a comprehensive review of structures, bioactivities, chemical syntheses, and biosynthetic advances (2000–2025)

The distinctive physicochemical conditions of marine habitats foster a diverse range of microbial resources. Microbially-derived alkaloidal metabolites, characterised by novel structures and potent bioactivities, have become increasingly important as sources of lead compounds for anticancer drug development. This review systematically classifies cytotoxic alkaloids obtained from marine microorganisms, outlines the structural traits of various alkaloid groups, evaluates their antiproliferative activity against various human cancer cell lines along with potential mechanisms, and summarises progress in chemical synthesis and biosynthetic investigations. Finally, it discusses the application prospects and existing challenges of these alkaloids in anticancer drug development, thus offering a data reference for exploring and utilising marine microbial-derived anticancer drug candidates.