Angiotensin I-Converting Enzyme (ACE) Inhibitory Peptide Isolated from Biodiesel Byproducts of Marine Microalgae, Nannochloropsis Oculata

To utilize biodiesel byproduct massively discarded from the lipid extraction step of marine alga Nannochloropsis oculata and investigate its biomedical and nutraceutical benefits, we examined an angiotensin I converting enzyme (ACE-I) inhibitory activity of various enzymatic hydrolysates derived from biodiesel byproducts of N. oculata. Among the enzymatic hydrolysates prepared using various commercial enzymes such as Alcalase, Neutrase, Flavourzyme, PTN, and Protamex, the biodegradable hydrolysate produced by Alcalase showed the highest ACE-I inhibitory activity (IC50 = 0.126 mg ml(-1)). Using consecutive purification by liquid chromatographic techniques with a Hiprep 16/10 DEAE FF anion exchange and an octadecylsilane (ODS) YMC-Pack Pro 018 reversed phase column, an ACE-I inhibitory peptide from N. oculata (NAIP) was purified and identified to be a pentameric peptide (LVTVM, 561.0 Da) by the tandem MS analysis. Lineweaver-Burk plots illustrate that the purified peptide, NAIP play a role as a non-competitive inhibitor against ACE-I. MTT assay showed no cytotoxicity on human embryonic lung fibroblasts cell line (MRC-5). Hence, this study suggests that the ACE-inhibitory peptide derived from biodiesel byproducts of N. oculata could be applied in nutraceutical and pharmaceutical applications as potential candidates.