In vitro evaluation of the gastric anti-inflammatory activity of different grape varieties

In the past few years, several studies have shown that the Mediterranean diet is an important source of protective compounds that contribute to reduce risk factors for several chronic diseases. The Mediterranean diet traditionally includes a high consumption of vegetables and fruits, important source of phenolic compounds. In more detail, flavonoids and their metabolites, which belong to the most abundant phenolic fraction, are generally responsible for the antioxidant and radical scavenging activity. Some unfermented products from vine (Vitis vinifera L.), such as leaves and dried grapes, have been associated with a reduction of gastric inflammation, as shown by in vitro tests. On the other hands, the antioxidant and anti-inflammatory activity of fresh grapes has not been previously investigated. On this basis, the objectives of the research were: 1) the characterization of the phenolic pattern of some grape varieties using a High-Performance Liquid Chromatography (HPLC) coupled with electrospray ionization mass spectrometric (ESI-MS) method; 2) the in vitro evaluation of the associated antioxidant property; and 3) the anti-inflammatory properties at gastric level. The assessment of radical scavenging activity was performed by DPPH (1,1-diphenyl-2-picrylhydrazyl) spectrophotometric assay. As for the anti-inflammatory activity, grape extracts were assayed for their efficacy in inhibiting IL-8 release from human gastric epithelial cells (AGS) after their treatment with TNF-α. IL-8 levels were measured by Enzyme Linked Immunosorbent Assay (ELISA). The LC-MS analysis allowed a preliminary characterization of 16 grape samples including 7 white table grape varieties, 6 red table grape varieties and 3 red wine varieties for comparison, where 67 phenolic compounds were identified. The anti-inflammatory activity was tested on 2 grape samples, selected for their favorable phenolic profile and higher antioxidant activity (measured with the DPPH assay). The contribution of each part of the fruit (peel, pulp and seeds) to the biological activity has been also evaluated. The good correlation between the biological assays and the phenolic profile suggests that the active components of grapes could counteract the oxidative stress that occurs during the inflammatory process.