Polyphenol-Rich Fruit Beverage Extracts Reduce Cytokine Secretion in THP-1 Cells

Background/Objectives. Inflammation, comprising many complex and finely coordinated immunological processes, represents a vital protective mechanism of the human body. By regulating inflammatory processes, cytokines play a key role in the modulation of the immune system. Secondary plant compounds such as polyphenols influence cellular immunological processes which might contribute to ensuring a physiologically healthy immune status. Methods/Results. This study investigated eleven polyphenol-rich extracts from red fruit beverages in terms of potential inhibitory effects on pro-inflammatory cytokine secretion of leukemic monocyte THP-1 cells. Extracts originating from fruit juice (apple), fruit juice concentrate (red grape, black currant, pomegranate, elderberry, aronia), fruit juice puree (cranberry, blueberry) or fruit juice pulp (strawberry, sour cherry) were obtained by adsorption onto Amberlite® XAD-7 resin. The Folin–Ciocalteu assay showed a high content of phenolic compounds in the eleven extracts and HPLC-DAD-ESI-MSn analysis revealed that the extracts contained various anthocyanins in addition to copigments and polymers. Further screening using Lumit® Immunoassay showed that all tested extracts caused a reduction in pro-inflammatory cytokine secretion (interleukins (IL): IL-1β, IL-6, IL-8 and tumor necrosis factor TNF-α). The extracts from red grape and black currant were the most active ones. Conclusions. Overall, our results showed that polyphenol-rich fruit extracts can inhibit inflammatory processes in vitro. In vivo studies on the anti-inflammatory effect of fruit juice will be a promising approach to determine the fruit juice-dependent, health-promoting effects in humans.