Cyanidin-3-O-glucoside

Anthocyanins are important natural plant pigments with many physiological activities. However, because of their highly reactive nature, anthocyanins are unstable, a new approach was established in this study to encapsulate cyanidin 3-β-D-glucoside (C3G) into the inner cavity of recombinant H-2 of soybean seed apoferritin (rH-2) using high pressure processing (HPP) to improve its stability. At the optimal conditions (500 MPa/20 min, C3G/rH-2 mass ratio of 1 to 1), 15 C3G molecules could be encapsulated by per protein cage, which is comparable with pH shift method with stirring, and much higher than urea method. Moreover, the antioxidant capacity of C3G was improved by rH-2 and such interaction and encapsulation increased the stability of C3G at different temperatures and against metal ions. Multi-spectroscopy methods and molecular dynamics simulation revealed that HPP induced significant conformational changes in ferritin, disturbing the highly ordered α-helix structure and increasing the overall flexibility, which allowed the diffusion of C3G into the nanocage via emerging gaps. Furthermore, HPP encapsulation was applied in C3G enriched plant-based beverage and pudding, showing high retention of C3G. The findings of this study suggest that HPP encapsulation is a novel and green approach for in situ orderly encapsulation of heat-sensitive bioactive hydrophilic phytochemicals. Moreover, this approach has been successfully used for non-acylated anthocyanins stabilization in the real plant-based foods for the first time.

Since starch is a native biomaterial for anthocyanin delivery, its binding capacity plays a crucial role in its applications. In this study, four starch fractions derived form starch (granule, outer shell, blocklet, molecules including AM and AP) were separated and characterized. Following that, their interactions with cyanidin-3-O-glucoside (C3G) under different pH conditions (3, 5, and 7) were investigated. The structural characteristics of outer shell appeared to increase its binding capacity. It was found that outer shell exhibited the highest binding capacity to C3G at pH 3, resulting in enhanced oxidation, photolysis, and simulated in vitro digestion stability. To explain the highest binding capacity of outer shell, interactions between each starch biomaterial and C3G was revealed through microscopic morphology, ordered structure, and interaction force. It was observed that C3G disrupted the morphology and ordered structures of starch biomaterials through bridging interactions. Additionally, electrostatic interactions played a dominant role in the binding of outer shell/granule with C3G, while hydrogen bonds were primarily involved in the binding of blocklet/AM/AP with C3G. In summary, C3G exhibited strong electrostatic interactions with both the exterior and interior of the outer shell, owing to its large spatial structure, which contributed to the enhanced binding capacity and stability of C3G.