Biomacromolecule-functionalized co-delivery systems for arbutin and coumaric acid: recent progress and challenges

Phenolic compounds such as arbutin and coumaric acid exhibit promising biological activities (e.g., antimelanogenic, antibacterial, antioxidant activities) in food, pharmaceutical, and cosmetic applications. However, their poor solubility, stability, and bioaccessibility limit practical use. The current review systematically summarizes the physicochemical properties, biological functions, application challenges and delivery systems of arbutin and coumaric acid, while highlighting the potential of water-in-oil-in-water (W/O/W) emulsions as efficient co-delivery systems. Special emphasis is placed on biomacromolecule-stabilized emulsions, which enhance emulsion stability through electrostatic interactions, steric hindrance, or gel network formation. For instance, gelatin, whey protein, starch, and chitosan-based systems have demonstrated improved resistance to pH, temperature, and enzymatic stress, while protein-polysaccharide complexes create robust interfacial architectures. We also discuss emerging trends, such as microencapsulation, microneedle delivery, and targeted release mechanisms, and identify gaps in current research, including the need for more sustainable biomacromolecules and precise control over release kinetics. Combining arbutin and coumaric acid represents a transformative approach to leverage their synergistic effects, offering new avenues for functional food and nutraceutical development.