Macromolecular behavior and structural characteristics of β-glucans from different species on their noncovalent interactions with avenanthramide-C

Avenanthramide-C (AVN) is a unique ingredient in oats with various bioactivities, but its low gastrointestinal stability limits its application. The AVN was encapsulated with curdlan (CD), oat (OG), and yeast (YG) β-glucans by alkali-neutralization (AN) in this study. Both CD and YG exhibited more ordered aggregation than OG based on Congo red result, possibly contributing to differences in their interaction with AVN. OG-AVN exhibited a higher binding degree (86.57%) than CD-AVN (71.61%) and YG-AVN (81.44%), indicating that the more AVN was retained, the higher solubility and antioxidant capacity of β-glucans-AVN complexes during in vitro digestion. Lower viscoelasticity of OG-AVN and YG-AVN than CD-AVN suggested that the different glycosidic bonds within linear backbone of OG or branches within the triple helix of YG perhaps weakened the tight entanglement, thus providing sufficient regions for AVN binding. Differences in hydrogen bonding structure among β-glucans contributed to their noncovalent interactions with AVN, supported by FTIR (O–H stretching band shift of β-glucans vs. AN-treated ones), XRD (lower relative crystallinity of AVN than complexes), and ITC (higher binding affinity of OG-AVN than YG-AVN and CD-AVN). AFM results supported the change in linear backbone from long to short, which promoted the AVN loading into OG. The binding regions might be located at the OH-7 of AVN with the H-3 of OG or YG, but not CD-AVN, as evidenced by NMR analyses. It demonstrated that the short chains of OG and the branches of YG potentially interacted more easily with AVN, while OG-AVN achieved even better performance.