Antioxidant and free radical-scavenging activities of smooth hound (Mustelus mustelus) muscle protein hydrolysates obtained by gastrointestinal proteases

Amino acid composition and antioxidant properties of pea seed ( Pisum sativum L.) enzymatic protein hydrolysate fractions

The amino acid composition and antioxidant activities of peptide fractions obtained from HPLC separation of a pea protein hydrolysate (PPH) were studied. Thermolysin hydrolysis of pea protein isolate and ultrafiltration (3 kDa molecular weight cutoff membrane) yielded a PPH that was separated into five fractions (F1-F5) on a C(18) reverse phase HPLC column. The fractions that eluted later from the column (F3-F5) contained higher contents hydrophobic and aromatic amino acids when compared to fractions that eluted early or the original PPH. Fractions F3-F5 also exhibited the strongest radical scavenging and metal chelating activities; however, hydrophobic character did not seem to contribute to reducing power of the peptides. In comparison to glutathione, the peptide fractions had significantly higher (p < 0.05) ability to inhibit linoleic acid oxidation and chelate metals. In contrast, glutathione had significantly higher (p < 0.05) free radical scavenging properties than the peptide fractions.

Analysis of novel angiotensin I-converting enzyme inhibitory peptides from enzymatic hydrolysates of cuttlefish (Sepia officinalis) muscle proteins

The angiotensin I-converting enzyme (ACE) inhibitory activities of protein hydrolysates prepared from cuttlefish (Sepia officinalis) proteins by treatment with various bacterial proteases were investigated. The hydrolysate generated by the crude enzyme from Bacillus mojavensis A21 displayed the highest ACE inhibitory activity, and the higher inhibition activity (87.11 +/- 0.92% at 2 mg/mL) was obtained with hydrolysis degree of 16%. This hydrolysate was fractionated by size exclusion chromatography on a Sephadex G-25 into eight major fractions (P(1)-P(8)). Fraction P(6), which exhibited the highest ACE inhibitory activity, was then fractionated by reversed-phase high performance liquid chromatography (RP-HPLC). Eleven ACE inhibitory peptides were isolated, and their molecular masses and amino acids sequences were determined using ESI-MS and ESI-MS/MS, respectively. The structures of the most potent peptides were identified as Ala-His-Ser-Tyr, Gly-Asp-Ala-Pro, Ala-Gly-Ser-Pro and Asp-Phe-Gly. The first peptide displayed the highest ACE inhibitory activity with an IC(50) of 11.6 microM. The results of this study suggest that cuttlefish protein hydrolysates are a good source of ACE inhibitory peptides.