VALORIZATION OF CHESTNUT BY-PRODUCT FOR GASTROINTESTINAL HEALTH

Castanea sativa Mill. (C. sativa) processing and pruning generate several by-products, including leaves, burs, and shells (inner and outer teguments), which are considered an important source of high-value phytochemicals. Ellagitannins from C. sativa leaf extracts have been described to impair H. pylori viability and inflammation in gastric cells. Dietary polyphenols, including tannins, have been reported to interfere with key targets of inflammation, including the nuclear factor κB (NF-κB). A promising role as a further therapeutical target for gut disorders has been recently proposed for the regulatory subunit of hypoxia-inducible factor (HIF-1α), as a potential stabilizer of intestinal barrier integrity. Therefore, the main objective of this PhD work includes a qualitative and quantitative phytochemical characterization of several chestnut by-products (bud, spiny bur, wood, pericarp and episperm), together with the exploitation of scavenging capacity, anti-inflammatory properties in intestinal (CaCo-2) and gastric (AGS and GES-1) cells, and anti-H. pylori activities. Stability of the extracts was assessed by following gastric and gastrointestinal digestion. The chemical characterization confirmed the presence of bioactive polyphenols in the extracts, including ellagitannins. In CaCo-2 cells stimulated by an IL-1β-IFN-γ cocktail, nearly all chestnut by-products (50 µg/mL) inhibited the release of proinflammatory mediators (CXCL-10, IL-8, MCP-1, ICAM-1), along with the NF-κB-driven transcription, and induced the HRE-driven transcription. In AGS and GES-1 cells stimulated with TNFα (10 ng/mL) or infected with H. pylori, the external part of chestnut fruit exhibited the highest inhibition of IL-8 release among all by-products. According to H. pylori infection, nearly all extracts inhibited bacterial growth (MICs of 400 μg/mL) and chestnut shell extracts significantly reduced H. pylori adhesion at 100 μg/mL Despite the significant reduction in total polyphenol index and scavenging capacity of chestnut by-products after gastric and intestinal digestion, the activity of these extracts on anti-inflammatory parameters at gastric and intestinal level remained promising. By integrating phytochemical profiling with biological activity testing, this study seeks to provide a better understanding of the potential applications of chestnut by-products in developing sustainable, bioactive formulations. These findings may open the way for their use in functional foods, nutraceuticals, or therapeutic agents aimed at supporting gastrointestinal health while promoting environmental sustainability.