Extraction And Characterization of Bioactive Peptides Derived from the Hydrolysates of Total Soluble Proteins of Pistachio Nuts (Pistacia vera L.)

Abstract

This study explored the potential of pistachio nut (Pistacia vera L.) total soluble proteins to release bioactive peptides exhibiting angiotensin-converting enzyme (ACE) inhibition, antioxidative, and antibacterial activities. The total soluble proteins were extracted from the ground, defatted nut using 0.010 M phosphate buffered saline, pH 6.8. The extracted proteins were hydrolyzed at different time intervals using trypsin and chymotrypsin. Hydrolysates of the total soluble proteins at 24 h digestion time exhibited the highest ACE-inhibition activity of 76.67 ± 0.10% and 70.83 ± 0.00% for chymotrypsin and trypsin digestion, respectively. The 24 h enzymatic hydrolysates were further fractionated in RP-HPLC using a C18 Vydac column. The C1 fraction from the 24 h chymotryptic hydrolysates and T2 from the 24 h tryptic hydrolysates exhibited the highest ACE-inhibition activities with an IC50 value of 147.7 ± 0.8 and 148.7 ± 0.6 μg/mL, respectively. The 24 h chymotryptic and tryptic hydrolysates also exhibited a DPPH radical scavenging activity of 83.7 ± 1.1% (EC50 = 356.5 ± 1.0 μg/mL) and 80.4 ± 0.2% (EC50 = 402.7 ± 1.1 μg/mL), respectively. The hydroxyl radical scavenging activities of the 24 h chymotryptic and tryptic hydrolysates were found to be 22.8 ± 1.0 and 16.6 ± 3.7%, respectively. However, the 24 h tryptic and chymotryptic hydrolysates did not exhibit any antibacterial activity against the gram-negative Escherichia coli and gram-positive Staphylococcus aureus. Therefore, the total soluble proteins of pistachio nuts were found to contain peptides exhibiting ACE-inhibition and antioxidative activities upon hydrolysis with trypsin and chymotrypsin.