Optimization study for the production of an opioid-like preparation from bovine casein by mild acidic hydrolysis

Several bioactive peptides (phosphopeptides, opioid peptides and immunopeptides) derived from milk proteins have been shown to exert beneficial effects. however only a few biologically active peptides from natural sources have found applications to date. In order to quantitatively produce opioid-like bioactive fragments from major milk proteins, the efficacy of a gastric-like digestive process to release casein-derived peptides that induce a myorelaxant effect, was investigated. Whole bovine casein was incubated with pepsin at low pH. The release of bioactive material occurred over time and correlated with the acidity rather than with the enzymatic activity. The acidic hydrolysate was tested for its opioid potencies in several conventional bioassay systems. It exhibited a naloxone-reversible inhibitory effect of the electrically evoked contractions of GPI, MVD and RVID. This opioid-like effect was estimated by the determination of the "apparent" IC50 values, and the antinociceptive efficacy confirmed ill vitro. (C) 2003 Elsevier Ltd. All rights reserved.