The physical and chemical properties of complexes of geniposide and heat-treated soybean protein isolate and effect on the bioavailability of geniposide.

Background: Geniposide (GE) exhibits diverse biological activities, but its poor stability and low bioavailability limit its applications. Combining GE with proteins can improve its stability. Heat-treated soybean protein isolate (HSPI) is widely used to transport bioactive substances due to its loading capacity. This study investigated the structural and functional changes in HSPI induced by its interaction with GE, as well as the resulting effects on GE's stability and bioavailability.

Results: Results showed that GE bonded to CN, CO and NH groups in HSPI via hydrogen bonding, altering the protein's secondary structure. The resulting GE-HSPI complexes exhibited superior foaming capacity, thermal stability, storage stability and ionic stability compared to free GE. In pharmacokinetic studies, animals fed with GE-HSPI complexes exhibited higher plasma GE concentration than those given GE solution alone. Ultimately, the oral bioavailability of GE in GE-HSPI complexes was around twofold higher than that of the GE solution, with GE and 80 °C-treated SPI complexes achieving the highest bioavailability (7.90%).

Conclusion: These findings highlight the potential use of GE-HSPI complexes as an effective strategy to enhance GE bioavailability. They also pave the way for further research into gardenia-derived applications in functional foods or pharmaceuticals. © 2025 Society of Chemical Industry.