Fabrication of barley protein-apigenin covalent complexes for delivery of apigenin: improved bioavailability and neuroprotective activity.

Background: The application of apigenin (AP) with strong neuroprotective effects that can rapidly cross the blood-brain barrier, offering potential therapeutic effects for diverse neurological diseases, is limited by its poor water solubility and chemical instability. The barley protein (BP) covalence effect with AP will have the potential to overcome these obstacles. The present study investigated systematically the characterization and structure of BP-AP complexes. The performance of BP-AP complexes in digestion and cellular transport were evaluated using in vitro gastrointestinal digestion and Caco-2 cells. HO-induced damage cell model was provided a potential information for BP-AP complexes with respect to neuroprotective application.

Results: Apigenin demonstrated successful covalent binding to chromophoric groups (Tyr and Trp) in BP. The BP-AP covalent complexes (C-BA) were within the nanometric size range and exhibited high apigenin encapsulation efficiency (88.85%) with the highest apigenin solubility (9.428 μg mL), attributed to covalent binding facilitating BP's structure unfolding and irregularity. Additionally, C-BA demonstrated a superior release rate and transmembrane transport capacity over four times and two times higher than that of free apigenin, respectively. C-BA exhibited the superior nerve protective activity.

Conclusion: The present study has demonstrated that the covalent binding complex of BP and AP exhibits excellent properties, which confirms that BP may serve as an excellent carrier for apigenin delivery, expanding applications of AP in the food industry. © 2025 Society of Chemical Industry.