Cytoprotective properties of Castanea sativa (Mill.) by-products in human gastric cells and role of in vitro digestion

Background. Castanea sativa (Mill.) or sweet chestnut (Fam. Fagaceae) is a plant widely spread worldwide, with Italy among leading European producer [1]. Chestnut industry produces substantial by-products by processing and trimming, however, evidence highlighted that these materials are source of bioactive compounds, mostly tannins and flavonoids, endowed with promising antimicrobial, antioxidant and anti-inflammatory properties [1,2]. Particularly, promising results have been displayed in cell models of gastritis and in Helicobacter pylori infection [2,3]. Damage by H. pylori is induced by oxidative stress, DNA damage and cell degeneration [4]. Moreover, infiltration of immune cells and release of pro-inflammatory factors, like TNFα, are pivotal in the onset of inflammation [3]. In line with this evidence, we investigated the protective properties of diverse extracts from C. sativa byproducts towards TNFα-induced inflammation and oxidative stress in human gastric epithelial cells. Methodologies. Aqueous and hydroalcoholic extracts from barks, fruit shells and burs of C. sativa were characterized for the content of polyphenols, tannins and flavonoids by spectrophotometric methods [5]. The extracts and their in-vitro digested were tested at non-toxic concentrations for their protective properties towards oxidative and inflammatory damage induced by tert-butyl hydroperoxide (tBOOH) and TNFα in gastric adenocarcinoma AGS and noncancerous GES-1 cells. The ability of the samples to restore cell viability, intracellular ROS levels, LDH release and cell regeneration abilities (wound healing assay) was assessed [6]. Nrf2, a transcription factor pivotal in antioxidant defence, and phosphorylated H2AX histone, sign of a genotoxic injury, were investigated by immunofluorescence [6,7]. Results. The results highlighted fruit shell extracts as the richest in polyphenols and tannins, while higher flavonoids levels were found in barks and burs. After 6 h co-treatment with tBOOH or TNFα, all the extracts restored cell viability, albeit slightly, and lowered intracellular ROS levels to basal values. After digestion, the observed bioactivities were not affected. Improvement in the wound healing abilities and a modulation of Nrf2 pathway were observed too. Conclusions. Altogether the obtained results suggest that chestnuts by-products may represent a strategy towards inflammation and oxidative stress, typical of gastritis, and may promote environmental sustainability and circular economy. However, further studies are needed to clarify the phytochemicals, the underlying mechanisms and to confirm this power in vivo. References [1] Braga et al. Nat Prod Res 2015, 29(1), 1–18. [2] Sangiovanni et al. Pharmacol Res 2018, 134, 145–155. [3] Piazza et al. Nutrients 2023, 15(6), 1504. [4] Han et al. Front Microbiol 2022, 13, 811258. [5] Di Sotto et al. Molecules 2019, 24:3103. [6] Di Sotto et al. Biomedicines 2022,10,2257. [7] Di Giacomo et al. Antioxidants 2023, 12(9), 1771.