Leaf extracts from Sicilian sumac (Rhus coriaria L.) show promising antioxidant and anti-inflammatory activities in gastrointestinal epithelial cells: A comparison with fruit extracts activity and role of digestion

Sumac ( Rhus coriaria L.) is reaching high attention as source of polyphenols and healthy properties. Most of the available studies were conducted on plant materials (fruit) from Middle East, in line with the geographical area of traditional use. Despite the wide consumption as spice or traditional medicine, the biological activity at gastrointestinal level is still poorly investigated. We previously suggested that fruit extracts from Iranian sumac may counteract H. pylori -related gastritis through anti-inflammatory mechanisms. Here, we investigated the antioxidant and anti-inflammatory effect of fruit and leaf from Sicilian sumac (Sicily, Italy) in gastric (GES-1) and intestinal (CaCo-2) cells, together with a chemical characterization of the phenolic profile. Extracts obtained by traditional methods, such as hot water infusion and hydroalcoholic maceration, were selected for polyphenolic content and stability evaluations after simulated gastrointestinal digestion. Fruit and leaf extracts both inhibited IL-8 and MCP-1 release in both models and reduced the level of ROS in CaCo-2 cells, but not in GES-1 cells. Since the hydroalcoholic leaf extract showed the most pronounced effects at the lowest concentrations among the extract, it was qualitatively characterized by its polyphenolic profile and quantified for its most abundant flavonoid, myricetin 3-rhamnoside, which accounts for approximately 13.66 mg/g of the extract, thus suggesting a potential role of this compound for the observed biological activities. The overall data suggest that traditional extracts from fruit and leaf of Sicilian sumac may counteract inflammation and oxidative stress related to gastrointestinal disorders, highlighting the interesting properties of leaf extracts, poorly investigated till now.