Tanaporn Monkhai. Selenium biotransformation and fractionation of bioactive Selenopeptide from Germinated Perilla (Perilla frutescens) seeds. Master's Degree(Food Science and Technology). Chiang Mai University. Library. : Chiang Mai University, 2569.
Selenium biotransformation and fractionation of bioactive Selenopeptide from Germinated Perilla (Perilla frutescens) seeds
Abstract:
Noncommunicable diseases (NCDs) are the leading causes of mortality worldwide, accounting for 70% of deaths in Thailand, with cardiovascular diseases and cancers as the major causes. While lifestyle changes can reduce disease risks, conventional drugs remain the central to NCDs management, but are often associated with adverse effects, including hypotension, kidney failure, and leukopenia from antihypertensive drugs or ACE inhibitors. In cancer therapy, chemotherapeutic and targeted drugs can cause nausea, bone marrow suppression, or immune-related complications. This has prompted growing interest in natural functional ingredients such as bioactive peptides. Perilla frutescens seeds, a local plants of northern Thailand, have been studied for their peptides with antioxidant, anti-inflammatory, and antihypertensive activities, highlighting their potential as a valuable source of bioactive peptides. Selenium (Se) is an essential micronutrient that supports antioxidant enzymes such as thioredoxin reductase (TrxR) and glutathione peroxidase (GPx), helping protect cells from oxidative stress. During germination, Se can also bind to amino acids to form Se-peptide with enhanced bioactivity. However, studies on Se-enriched perilla peptides remain limited. This study aimed to investigate Se biotransformation during perilla seed germination, evaluate enzymatic hydrolysis for Se-peptides production, and assess antioxidant, ACE-inhibitory, anti-inflammatory, and anticancer activities, along with identification of bioactive Se-peptides. Perilla seeds were germinated in sodium selenite solutions (0, 20, 40, 60, 80, and 100 ppm) and harvested when the root reached 2-3 cm in length. Protein, fat, and Se contents were analyzed to determine the optimal germination concentration, define as the treatment yielding the highest Se content. The seeds were defatted with petroleum ether (10 %w/v) and used for selenoprotein (Se-protein) extraction under alkaline conditions for 30, 60, and 90 min. The Se-protein was hydrolyzed using different enzymes (Alcalase, Flavourzyme, and combined enzymes). The enzyme treatment that produced the highest degree of hydrolysate and antioxidant activity was selected to produce selenopeptides (Se-peptides). These Se-peptides were further fractionated by membrane ultrafiltration at molecular weight cut-offs of 10, 5, and 3 kDa, resulting in four fractions (>10, 5-10, 3-5, <3 kDa). The antioxidants, ACE-inhibitory, anti-inflammatory and anticancer activities of the fractions were evaluated. The fraction exhibiting the strongest bioactivity was further purified by size-exclusion chromatography, and Se-peptides were analyzed for bioactivities. Finally, Se-peptide sequences were identified using LC-MS/MS. The results demonstrated that enriching perilla seeds with 80 ppm sodium selenite during germination effectively enhanced selenium accumulation without inducing toxicity. Se-peptides hydrolyzed with Alcalase for 5 hours achieved a 31.73% degree of hydrolysis and showed strong antioxidant activity (80.28% ABTS inhibition and 54.05% FRAP reducing power). Membrane ultrafiltration fractionation revealed that high-molecular-weight Se-peptides (>10 kDa) contained the highest selenium content (124.58 µg/g), along with the strongest antioxidant capacity (83.63% ABTS inhibition and 59.59% FRAP reducing power), and demonstrated notable ACE-inhibitory activity (80.19%) and slightly reduced the growth of human lung cancer A549 cells, reducing growth by 12.18%. Further purification using size-exclusion chromatography yielded Se-peptides that maintained bioactivity, with 66.30% ABTS inhibition, 54.93% FRAP reducing power), 83.87% ACE-inhibitory activity, and a 16.13% reduction in A549 cells growth. Finally, sequence identification by LC-MS/MS confirmed the bioactivity of perilla Se-peptides, with molecular weights ranging from 1 to 2 kDa and the presence of selenium-chelating amino acids, indicating successful incorporation of selenium into the peptide structures. This study demonstrates that Se-biotransformation in perilla seeds is an effective approach for producing bioactive Se-peptides with notable antioxidant, ACE-inhibitory, and anticancer properties. These findings highlight the potential of Se-peptides as innovative functional ingredients for food and health applications, offering a safer and more effective alternative for selenium supplementation.