Aqueous and enzyme-extracted phenolic compounds from brewers' spent grain (BSG): Assessment of their antioxidant potential

Brewers' spent grain (BSG) is a major coproduct of the brewing industry and a potential valuable source of protein, cell wall polysaccharides, lignin, lipid, and phenolic compounds. The aim of this study was to assess the antioxidant potential of phenolic extracts isolated from BSG using cell wall degrading enzymes, Depol 740L, Shearzyme and, Ultraflo Max. The phenolic extracts were prepared from black BSG (derived from barley grains roasted at 200°C) and pale BSG (derived from malted barley grains). The phenolic extracts protected against hydrogen peroxide (H₂O₂)-induced DNA single strand breaks in U937 cells as assessed using the comet assay. The extracts also protected against a H₂O₂ challenge in HepG2 cells, as assessed by measuring the cellular content of glutathione (GSH) and the activity of cellular antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT). Enzyme-extracted black and pale BSG phenolic extracts protected against oxidant-induced DNA damage and enhanced the cellular antioxidant activity in cells. Practical applications: Enzyme-extraction may be an effective alternative to conventional solvent extraction for the isolation of novel bioactive components, such as phenolics, from Brewers' spent grain. The BSG extracts may be used as a source of functional ingredients for the development of foods with potential benefits to human health.