Microalgae as multifunctional platforms for medicinal plant bioactives: Composite design, delivery behavior, and biological effects

Abstract

Medicinal plant bioactives exert diverse biological effects, but their application is constrained by poor solubility and stability, inefficient gastrointestinal delivery, and limited in vivo exposure. Microalgae are rich in proteins, pigments and other bioactive components. Beyond their intrinsic bioactivity, microalgae can be used in the form of intact cells, microalgal proteins, extracellular vesicles, and living photosynthetic systems, to bind, protect, release, and locally deliver plant bioactives, thereby providing multiple options for their incorporation and delivery. The composite application of microalgae with medicinal plant bioactives has progressed from simple combinations toward multilevel platforms with defined delivery functions. Focusing on the functional roles of different microalgal forms, this review summarizes strategies for constructing composites with medicinal plant bioactives, analyzes changes in cargo state, stability, release, local retention, bioaccessibility, and in vivo exposure following formation, and assesses how these changes relate to biological effects. Existing studies indicate that certain microalgal composite systems can improve the stability and delivery of bioactives, but comprehensive evidence extending from formulation-level improvements to pharmacokinetics, tissue distribution, and biological effects remains limited. Future research should improve structural characterization, clarify the contribution of individual components, strengthen standardization, and distinguish pharmacological synergy from delivery-mediated enhancement, thereby providing insights into the development and engineering application of these systems.