ACE inhibitory and antioxidant activities of red scorpionfish (Scorpaena notata) protein hydrolysates

Fish protein hydrolysates with different degrees of hydrolysis were prepared from muscle and heads of red scorpionfish (Scorpaena notata) by treatment with different proteases (Flavourzyme, Trypsin from bovine pancreas and crude enzyme preparations from the intestines of red scorpionfish and from the fungus Penicillium digitatum). The antioxidant and the antihypertensive activities of the hydrolysates were tested. The antioxidant power was evaluated through DPPH free radical scavenging activity, reducing power and metal chelating activity. All hydrolysates showed different degrees of hydrolysis and varying degrees of antioxidant activity. The hydrolysates obtained by treatment with crude enzyme preparations exhibited the highest antioxidant activity. Further, red scorpionfish head protein hydrolysates obtained with fungal protease and with fish crude protease were found to strongly inhibit the angiotensin-I converting enzyme (IC50 of 0.489 and 0.901 mg/ml, respectively). These results suggested that hydrolysates of red scorpionfish obtained by treatment with crude enzyme preparations would be a beneficial ingredient for functional food or pharmaceuticals against hypertension.