Glycation with uronic acid-type reducing sugar enhances the anti-inflammatory activity of fish myofibrillar protein via the Maillard reaction

[Display omitted] •Fish myofibrillar protein (Mf) was glycated by the Maillard reaction.•Glycation with uronic acid enhanced the anti-inflammatory activity of Mf.•Glycation with neutral sugar had no effect on the anti-inflammatory activity.•The enhancement could be related to the number of carboxyl group introduced to Mf.•Alginate oligosaccharide is an excellent functional modified sugar for Mf. The role of carboxyl group in uronic acid in enhancing the anti-inflammatory activity of fish myofibrillar protein (Mf) was investigated, when lyophilized Mf was reacted with various reducing sugars at 60 °C and 35% relative humidity through the Maillard reaction. After pepsin and trypsin digestion, the anti-inflammatory activity was evaluated by measuring the secretions of tumor necrosis factor-α, interleukin-6, interleukin-1β, and nitric oxide in lipopolysaccharide-stimulated RAW 264.7 macrophage. The anti-inflammatory activity of Mf was not affected by glycation with glucose or galactose, whereas strongly enhanced by glycation with uronic acid-type reducing sugars: glucuronic acid, galacturonic acid, and alginate oligosaccharide. These results indicate that the presence of carboxyl group in reducing sugar is important for enhancing the anti-inflammatory activity of Mf. This study also shows that the enhanced effect could depend upon the number of carboxyl group in bound reducing sugar.