From crop to cure: Bioactive potential of pigmented rice and barley phenolics for allergy and gut health

Gastrointestinal disorders and allergic inflammation are global health challenges closely linked to oxidative stress and immune dysregulation. Pigmented cereal grains such as purple rice and purple barley are emerging as a novel dietary source of polyphenols with health benefits. The bioactivity of their polyphenols is critical to their effects in the body. However, the impact of gastrointestinal digestion on their bioactivity remains unclear.
This study investigated the effects of in vitro digestion on the ability of purple rice (PRx) and purple barley (PBx) phenolic extracts to alleviate oxidative stress-induced epithelial damage and allergic inflammation. Using a Caco-2 human intestinal cell model, we assessed cytoprotective effects against 1 mM hydrogen peroxide-induced cell death following pre-treatment with varying concentrations (50–500 μg/ml) of digested and undigested PRx and PBx extracts. Anti-allergic properties were evaluated using the RBL-2H3 basophilic model to mimic mast cell function, focusing on calcium ionophore-induced histamine and cytokine release.
Both digested and undigested extracts, significantly (p<0.001) reduced oxidative stress-induced cell death and Interleukin-8 (IL-8) secretion in Caco-2 cells, with PRx showing greater cytoprotective effects. In RBL-2H3 cells, significant (p<0.05) suppression of histamine release and pro-inflammatory cytokines was observed —including IL-2, IL-4, IL-13, MCP-1, IFN-γ, and TNF-α—particularly after 4 hours of treatment.
These findings demonstrate that digestion does not diminish the effects of purple rice and barley extracts to support intestinal barrier integrity and modulate allergic inflammation. This research supports the integration of pigmented, sustainably grown cereals into functional food strategies to improve gut and immune health.