Synthesis, in vivo colon-targeted delivery effect and gut microbiota modulation of indole-acetylated starches derived from various native starch structures.

Indole-3-acetic acid (IAA) is a gut microbial metabolite of tryptophan that plays a crucial role in gut health. To maximize its bioactivity, colon-targeted delivery using acylated starch was developed. This study aims to investigate the interrelationships among the structural characteristics of starch and the biological functions of acylated starch in vivo. Three starches with distinct native structures (potato starch/POS, pea starch/PES and wheat starch/WHS), were acylated with IAA to produce POSIAA, PESIAA, and WHSIAA. All acylated starches showed substitution degrees of 0.31-0.36. The physicochemical properties of these acylated starches were thoroughly characterized. In vitro digestion demonstrated significant increases in resistant starch content for PESIAA and WHSIAA. In mice, acylated starches elevated IAA levels throughout the gastrointestinal tract, with maximal release in the colon. 16S rRNA sequencing revealed that acylated starches increased beneficial bacteria (Oscillospira and Parabacteroides) and reduced the Firmicutes/Bacteroidetes ratio, which are critical for maintaining intestinal homeostasis. Mice treated with PESIAA showed the highest gut microbiota community richness and diversity, as well as significantly improved colitis. These results provide insights into starch-based delivery systems that target metabolites to the colon, thereby regulating gut microbiota and promoting host health.