In Vitro Antioxidant Properties of Hemp Seed (<Emphasis Type="Italic">Cannabis sativa</Emphasis> L.) Protein Hydrolysate Fractions

Simulated gastrointestinal hydrolysis of hemp seed proteins using pepsin and pancreatin followed by membrane ultrafiltration fractionation yielded fractions with peptide sizes of <1, 1–3, 3–5, and 5–10 kDa. Analysis of in vitro antioxidant properties showed that the hemp seed protein hydrolysate (HPH) exhibited a significantly weaker (p < 0.05) scavenging of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals when compared to the fractionated peptides. Metal chelation activity of the HPH was significantly greater (p < 0.05) than the activities of fractionated peptides. Fractionation of the HPH led to significant (p < 0.05) improvements in ferric reducing power, DPPH, and hydroxyl radical scavenging radical activities but decreased metal chelation capacity. Peptide fractions with longer chain lengths (3–5 and 5–10 kDa) had better metal chelation and ferric reducing power than the <1, and 1–3 kDa fractions. HPH and all the peptide fractions significantly inhibited (p < 0.05) linoleic acid oxidation when compared to the control. Glutathione (GSH) had significantly greater (p < 0.05) ferric reducing power, and scavenging of hydroxyl and DPPH radicals when compared to HPH and fractionated peptides. In contrast, HPH and peptide fractions >3 kDa had significantly higher (p < 0.05) metal chelation activity than GSH. The results show the potential use of HPH and peptide fractions of defined size for the treatment of oxidative stress-related diseases.