The hydrophobic interaction for ellagic acid binding to soybean protein isolate: Multi-spectroscopy and molecular docking analysis

The need for value-added soy protein isolate (SPI) based food products that incorporate natural food components to boost nutritional content and make them more beneficial to human health significantly increased in recent years. To broaden the application of ellagic acid (EA) in SPI based food products, the interaction of SPI and EA was investigated. The fluorescence quenching of SPI by EA showed mainly static quenching and hydrophobic interaction played a dominant role in the combination of EA and SPI. Synchronous fluorescence suggested that EA reduced the polarity of SPI around Tyr and Trp residues, which were exposed to a more hydrophobic microenvironment. Meanwhile, circular dichroism showed that EA noticeably changed the secondary structure of SPI, which was mainly reflected in the increase of α-helix content and the decrease of β-sheet and β-turn content. Finally, the molecular docking simulation found that SPI could have 10 active sites binding to EA, and there were hydrogen bond interactions besides hydrophobic interactions. The knowledge provides insights into the interaction mechanism between SPI and EA, which is of vital importance for the development of new multifunctional plant derived protein products in the food system.