Binding of proanthocyanidins to soybean (Glycine max) seed ferritin inhibiting protein degradation by protease in vitro

Biofortification with phytoferritin is considered as a promising approach to the eradication of iron deficiency anemia. However, phytoferritin is not stable enough to be against degradation by protease(s) in the gastrointestinal tract, thereby leading to its low bioaccessibility. Fortunately, binding of proanthocyanidins (PAs) to protein offers the opportunity to prevent phytoferritin from degradation by the protease(s). To test this idea, the interaction of PAs from grape seeds with soybean seed ferritin (SSF) was studied using a combination of fluorescence, CD spectra, stopped-flow light scattering (SLS), and dynamic light scattering (DLS). Results showed that PAs can indeed bind to SSF in a dose-dependent manner. Consequently, such binding can significantly inhibit the degradation of SSF by the protease(s) in simulated gastric fluid (SGF) at pH 4.0 when the mass ratio of PAs to SSF is more than 1:1. Similarly, the stability of SSF in simulated intestinal fluid (SIF) was also increased upon treatment with PAs. These findings raise the possibility that the bioaccessibility of phytoferritin to the gastrointestinal tract was improved in the presence of proanthocyanidins.