Plant-based delivery systems for bioactive compounds: Mechanisms of release and functional food applications

The increasing awareness of the relationship between diet and health has driven a growing demand for functional foods enriched with bioactive compounds. These compounds, including polyphenols, carotenoids, vitamins, minerals, peptides, and unsaturated fatty acids, provide countless health benefits beyond basic nutrition, including antioxidant, anti-inflammatory, and antimicrobial properties. However, their direct use in food matrices is often limited due to challenges related to instability, poor solubility, and insufficient bioavailability. The past decade has witnessed extensive exploration of plant-based delivery systems as effective carriers for bioactive compounds due to their biocompatibility, biodegradability, low toxicity, and sustainable sourcing. Despite the enormous efforts and booming growth of scientific publications, our understanding of the precise release mechanisms of plant-based delivery systems within complex food matrices is limited. This review presents a unified and comprehensive description of plant-based delivery systems, dissecting their structural composition, formation mechanisms, and functional characteristics. We also explore how different plant-based carrier modalities, such as micro- and nanoparticles, emulsions, hydrogels, solid lipid nanoparticles (SLNs), nanostructured lipid carriers (NLCs), and vesicular systems, can be engineered to enhance the stability, solubility, and targeted release of bioactive substances. Additionally, this review comparatively examines the mechanisms underpinning controlled release, including diffusion, swelling, enzymatic degradation, and stimuli-responsive triggers. Lastly, we highlight key hurdles that hampered the practical implementation of plant-based delivery systems and propose some future directions to overcome them. The mechanistic insight of this paper is envisioned to enhance the health benefits of bioactive compounds and support sustainability in the food and healthcare industries.