Angiotensin-I-Converting Enzyme Inhibitory Activity of Protein Hydrolysates Generated from the Macroalga Laminaria digitata (Hudson) JV Lamouroux 1813

Abstract

Seaweeds have a long history of use as both food and medicine, especially in Asian cultures. Moreover, there is growing interest in the use of seaweed ingredients and bioactive compounds in pharmaceutical and nutraceutical products. One ailment that seaweed bioactive compounds may impact is hypertension caused by the enzyme Angiotensin Converting Enzyme 1 (ACE-1; EC 3.4.15.1), found within the Renin-Angiotensin Aldosterone System (RAAS), which causes vasoconstriction of blood vessels, including veins and arteries. The aim of this paper is to generate bioactive peptide containing protein hydrolysates from the brown seaweed Laminaria digitata (Hudson) JV Lamouroux 1813. Proteins were extracted from this seaweed by disrupting the seaweed cell wall using a combination of carbohydrases and proteolytic enzymes. Bioactive peptide containing permeates were generated from L. digitata protein hydrolysates, and both hydrolysates and permeates were screened for their ability to inhibit the enzyme ACE-1. The protein content of the permeate fractions was found to be 23.87% compared to the untreated seaweed, which contained 15.08% protein using LECO analysis. Hydrolysis and filtration resulted in a “white” protein powder, and the protein content of this powder increased by 9% compared to the whole seaweed. The total amino acid (TAA) content of the L. digitata protein permeate was 53.65 g/100 g of the sample, and contains over 32% essential amino acids (EAA). Furthermore, the L. digitata permeate was found to inhibit the ACE-1 enzyme by 75% when compared to the commercial drug Captopril© when assayed at a concentration of 1 mg/mL. The inhibition of ACE-1 (the IC50 value) of 590 µg/mL for the L. digitata permeate compares well with Captopril©, which had 100% inhibition of ACE-1, with an IC50 value of 500 µg/mL. This study indicates that there is potential to develop protein powders with ACE-1 inhibitory bioactivities from the brown seaweed L. digitata using enzymatic hydrolysis as a cell disruption and protein extraction/hydrolysate generation procedure.

Advanced Processing of Giant Kelp (Macrocystis pyrifera) for Protein Extraction and Generation of Hydrolysates with Anti-Hypertensive and Antioxidant Activities In Vitro and the Thermal/Ionic Stability of These Compounds

“…As for the conditionally essential amino acids, there was no substantial difference in their content between F5, F4, F3, and F2, but all these fractions had higher levels of these amino acids compared to F1 and the full hydrolysate. In a study conducted by Purcell et al [ 47 ], it was reported that the sum of conditionally essential amino acids obtained from Laminaria digitata decreased from 2.7 g/100 g DW to 1.5 g/100 g DW after passing through an ultrafiltration unit with the molecular weight cut off 3 kDa. This depletion of some amino acids could be due to the inability of some peptides containing them to have a molecular weight higher than the filter cut-off [ 44 ].…”

Identification of Bioactive Peptides from Nannochloropsis oculata Using a Combination of Enzymatic Treatment, in Silico Analysis and Chemical Synthesis

“…The ACE-1 inhibitory activity of the 3-kDa permeate fraction generated from Nannochloropsis sp. protein treated with xylanase was determined using the ACE-1 inhibition colorimetric method as described previously [ 38 ]. The permeate fraction inhibited ACE-1 by 96.6% when assayed at a concentration of 1 mg/mL compared to the positive control Captopril ® which inhibited ACE-1 by 99.3% when tested at a concentration of 0.5 mg/mL.…”

Identification of Bioactive Peptides from a Laminaria digitata Protein Hydrolysate Using In Silico and In Vitro Methods to Identify Angiotensin-1-Converting Enzyme (ACE-1) Inhibitory Peptides

“…The ACE-1 IC 50 value for IGNNPAKGGLF was 174.4 µg/mL (0.161 µM) ACE-1. Peptide YIGNNPAKGGLF had an IC 50 value of 133.1 µg/mL (0.11 µM) compared to Captopril© with a documented ACE-1 IC 50 value of 500 µg/mL (2.3 µM) [ 8 ]. Previous studies on marine cryptides, used Captopril© as a positive control with IC 50 values of (1.79–15.1 nM) for ACE-1, and another drug Losartan was used as a negative control for ACE-II inhibition, and had IC 50 values of (17.13–146 μM) [ 49 ].…”

“…Protein extraction and peptide enrichment using molecular weight cut-off (MWCO) filtration was performed prior to MS characterisation in accordance with the method outlined in [ 8 ].…”

“…Recently, we utilized enzymatic hydrolysis combining the enzymes Viscozyme ® and Alcalase ® as a method to extract protein from the brown seaweed Laminaria digitata [ 8 ]. Hydrolysis is a well-known strategy for the generation of bioactive peptides.…”