Angiotensin-converting enzyme inhibiting ability of ethanol extract, steviol glycoside and protein hydrolysate from stevia leaves
Efficient treatment of hypertension is vital. Inhibition of angiotensin-converting enzyme activity has been one of major bases of treating hypertension. Ethanol extract of stevia leaves, steviol glycoside (with 95% purity; a natural sweetener widely used in the food industry) isolated from the ethanol extract and stevia leaf protein hydrolysate inhibited 26.60%, 59.56% and 74.38% of angiotensin-converting enzyme activities, respectively. Their effect was dose-dependent, which should be beneficial for avoiding hypotension just by proper control of amount of their intake and superior to pharmaceutical drugs. Sensory test indicated that application of mixture of steviol glycoside and stevia protein hydrolysate to decaffeinated coffee or tea as well as formulated peanut protein drink was found to be well accepted and an animal test showed that they had significantly antihypertensive effect in spontaneously hypertensive rats. Steviol glycoside and stevia leaf protein hydrolysate should be good ingredient for making functional or healthy food products or beverages targeting the prevention or treatment of hypertension.