Angiotensin-converting enzyme (ACE) inhibitory effects of hazelnut protein hydrolysate prepared using pepsin

Abstract

Objective/ Purpose: The aim of this study is to find out the effect of protein isolate and pepsin hydrolysates of hazelnut protein on Angiotensin-Converting Enzyme (ACE) inhibition. Material and Methods: Unshelled hazelnuts (Corylus avellana L.) was firstly grinded and defatted by petroleum ether. Alkaline extraction and isoelectric precipitation method was used in order to obtain protein isolate. Neutralized protein suspension was freeze dried before analysis and stored at -18°C. Pepsin hydrolysis was conducted at pH 2 with 1:20 (w:w) enzyme/substrate ratio at 37°C for 60 min. Hydrolysis was stopped by heating samples to 85°C for enzyme inactivation and hydrolysates were analyzed for ACE inhibitory effect. 100 µL of 2 mM HHL, 20 µL of hydrolysate and 20 µL of 2 mU of ACE were incubated in 37°C for 60 min. Reaction was terminated by adding 85 µl of 1 M HCl. Shimadzu HPLC system with C18 column and DAD was used for ACE inhibition analysis. Results and Discussion: Hazelnut protein isolate and peptides have over 95% ACE inhibition. On the other hand, IC50 values of samples taken at 0, 30 and 60 minutes of pepsin hydrolysis were 1.29 mg protein/ml, 0.25 mg protein/mL and 0.22 mg protein/mL, respectively. Conclusion: Results shows that hazelnut protein isolate and peptides have reasonable ACE inhibition properties. Pepsin hydrolysates of hazelnut isolates gives almost 6 times more anti-hypertensive activity than hazelnut protein isolate.