In vitro anti-inflammatory activity of tannins-enriched extracts from Fragaria spp

Gastritis is an inflammation of gastric mucosa that is caused for 90% of cases by the presence of the bacterium Helicobacter pylori (H. pylori). During H. pylori infection macrophages produce pro- inflammatory cytokines, including TNFand IL-1, which determinate the activation of NF-B factor in epithelial gastric cells. Strawberry is one of the most commonly consumed fruits and its high amount of polyphenols, including anthocyanosides and tannins, has increased interest towards this fruit; gastric effects of strawberry have been documented by some in vitro and in vivo studies but these effects were related to anthocyanosides, while the contribution of tannins from strawberry against gastric inflammation was not evalueted. The aim of this work was to evaluate the effect of tannins- enriched extracts of two species of Fragaria (Fragaria X Ananassa and Fragaria Vesca) in an in vitro model of gastric inflammation. Tannins-enriched extracts were prepared from Fragaria spp., strawberries were collected at maturity and the extraction of polyphenols was carried out with a mixture acetone/water (70/30 v/v); anthocyanosides were removed using a chromatography Sephadex LH-20 obtaining extracts enriched in tannins. The extracts were assayed on human gastric epithelial cells (AGS) stimulated with TNFα and IL-1β (both 10 ng/mL). NF-κB driven transcription and IL-8 promoter activity were evaluated by transient transfection assays in AGS cells with report plasmids, while NF-κB nuclear translocation and IL-8 secretion were performed by an ELISA assay, after 1 and 6 hours treatment respectively. Both Fragaria extracts and agrimoniin, which is the most abundant ellagitannins present in the extracts, were able to inhibit NF-B driven-transcription and NF-B nuclear translocation in concentration-dependent way; IC50 of Fragaria X ananassa and Fragaria vesca extracts on TNFα-induced NF-κB nuclear translocation were 0.25 and 1.01 μg/ml, respectively; the extracts and agrimoniin were also active on IL-8 promoter activity and secretion; this chemokine is strictly involved in gastric inflammation and its expression is regulated by NF-B transcription factor. IC50 of Fragaria X ananassa and Fragaria vesca extracts on TNFα-induced IL-8 release were 0.09 and 0.29 μg/ml, respectively. These results suggest that tannins from strawberry could exert a beneficial effect on gastric inflammation and agrimoniin explains, at least in part, the biological effects observed with the extracts.