Anti-inflammatory activity of tannins from strawberries at gastric level

Background. Strawberries (Fragaria spp.) are commonly consumed berries, being eaten fresh, frozen and in different processed products. The nutritional quality of these fruits is correlated to the presence of several polyphenols, including tannins. In European diet strawberries represent the primary source of tannins, compounds which possess antioxidant and anti-inflammatory properties and are generally stable at gastric level. Several studies suggest the importance of polyphenols consumption to prevent/treat gastritis induced by Helicobacter pylori. This infection is characterized by the release of pro-inflammatory cytokines in the gastric mucosa, including IL-1β and TNFα, which in turn induce NF-κB activation in gastric epithelial cells causing the release of IL-8, a potent chemokine which promotes neutrophils infiltration. Aim. In the present work we investigated if tannins enriched extracts (TE) from common strawberries (Fragaria X ananassa Duch.) and wild strawberries (Fragaria vesca L.) could inhibit gastric inflammation. Methods. Fresh strawberries were homogenized in a solution of acetone/water (70/30 v/v) and TE were obtained using HPLC (Sephadex LH-20). TE were assayed to investigate the inhibition of NF- κB nuclear translocation and driven transcription; the effect on IL-8 transcription and release in gastric epithelial cell line (AGS) stimulated with TNFα and IL-1β. Digestion of TE was performed following the protocol adapted from RIVM (SOP 500). Results. Both TE from common and wild strawberries interfere with the metabolic cascade deriving from the activation and translocation of NF-κB, including IL-8 secretion (see table attached). The concentrations of TE necessary to halve IL-8 secretion were below 5 μg/ml for both strawberries. Agrimoniin, an ellagitannin isolated from these fruits, was responsible for the anti-inflammatory activity. The in vitro digestion decreased the activity of TE, but the extract still showed inhibition at very low concentrations. Conclusions. The anti-inflammatory activity exerted by tannins from strawberries occurs at extremely low concentrations, easy to reach at gastric level by the ingestion of a portion of strawberries. The outcome of this research suggests the possible use of strawberries as integration in dietary regimens designed to treat or prevent inflammatory gastric diseases.