Pectic polysaccharides from unripe and mature kiwifruit alleviate ulcerative colitis by modulating gut microbiota and restoring the intestinal barrier

Thinned unripe kiwifruit, a significant byproduct of commercial kiwifruit production, contains abundant pectic polysaccharides comparable to mature kiwifruit. Although acidic heteropolysaccharides from mature kiwifruit exhibit potent anti-inflammatory activity, the protective effects of unripe kiwifruit-derived pectic polysaccharides against ulcerative colitis (UC) remain unclear, ultimately limiting their potential utilizations. Therefore, to bridge this knowledge gap and facilitate their utilization, the chemical structures and anti-UC effects of two pectic polysaccharides, TKP (from unripe kiwifruit) and MKP (from mature kiwifruit), were systematically studied and compared. Results demonstrated that TKP and MKP share nearly identical primary chemical structures, predominantly comprising homogalacturonan (HG) and rhamnogalacturonan I (RG-I) domains. Particularly, TKP exhibited a longer side chain length (14.37 vs. 8.21) and higher RG-I content (73.62 mol% vs. 50.02 mol%) than MKP. Furthermore, both TKP and MKP significantly alleviated dextran sulfate sodium (DSS)-induced UC in mice. Notably, TKP exhibited superior effects to MKP in several aspects, such as enhanced butyrate production, more effective restoration of goblet cell populations, enhanced upregulation of tight junction protein ZO-1, and greater reduction in pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α). Both TKP and MKP effectively suppressed pathogenic bacteria (e.g., Escherichia-Shigella and Oscillibacter ) while promoted beneficial bacteria (e.g., Akkermansia and Bacteroides ). Notably, TKP significantly and selectively enhanced Paraprevotella growth, an effect not observed within MKP. These differential effects between TKP and MKP may be linked to their structural differences. Collectively, these findings provide valuable insights to develop TKP as a promising functional food or ingredient for preventing and ameliorating intestinal inflammatory disorders.