Abstract
Hot water was used to obtain Chlorella sorokiniana hot water extract (HWE). Subsequently, this byproduct was freeze-dried, hydrolysed at 50 °C using Protease N to obtain C. sorokiniana protein hydrolysates (PN-1), and then digested with a gastrointestinal enzyme (PN-1G). The inhibitory effects of the HWE and hydrolysates against angiotensin I-converting enzyme (ACE) were investigated. The soluble protein and peptide contents were 379.9 and 179.7 mg/g, respectively, for HWE and 574.8 and 332.8 mg/g, respectively, for PN-1. The IC50 values of the HWE, PN-1, and PN-1G on ACE were 1.070, 0.035, and 0.044 mg/mL, respectively. PN-1G was separated into seven fractions through size exclusion chromatography. The sixth fraction of the hydrolysate had a molecular weight between 270 and 340 Da, and the lowest IC50 value on ACE was 0.015 mg/mL. The amino acid sequences of the ACE-inhibitory peptides were Trp-Val, Val-Trp, Ile-Trp, and Leu-Trp, of which the IC50 values were 307.61, 0.58, 0.50, and 1.11 µΜ, respectively. Systolic blood pressure and diastolic blood pressure were reduced 20 and 21 mm Hg, respectively, in spontaneously hypertensive rats after 6 h of oral administration with a dose of 171.4 mg PN-1 powder/kg body weight.
Highlights
Hypertension has been identified as a cardiovascular risk factor and is often called a “silent killer” because people with hypertension can remain asymptomatic for years [1]
The results revealed that compared with hot water extract (HWE), hydrolysates subjected to protease hydrolysis had higher yields and higher soluble protein and peptide content
7 PN-2: hydrolysate from protease N hydrolysis at 2% for 5 h. These results show that use of PN-1 in the mass processing of plants can reduce the amount of enzymes used in this process, thereby lowering cost
Summary
Hypertension has been identified as a cardiovascular risk factor and is often called a “silent killer” because people with hypertension can remain asymptomatic for years [1]. The prevalence of hypertension has reached epidemic levels, affecting 15 to 20% of adults worldwide [2]. One therapeutic approach to treating hypertension is inhibition of angiotensin I-converting enzyme (ACE) using synthetic drugs. ACE plays a key physiological role in blood pressure regulation of the renin–angiotensin system. ACE inhibitors such as captopril and enalapril [3,4] have been used as antihypertensive drugs [5,6]. Such therapy can produce adverse effects, including coughing, loss of taste, angioedema, and skin rashes [7]. A trend has formed towards the development of natural ACE inhibitors
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