Study On Preparation Of Bioactive Peptides From Gonad Hydrolysates Of Jellyfish Rhopilema Esculentum Kishinouye

Sea food industrial by-product, gonad of jellyfish Rhopilema esculentum Kishinouye, was converted into bioactive peptides to upgrade its added value. The antioxidant activities and antihypertensive activities of prepared food-derived peptides were investigated, which aimed to find a substitute with low-cost and less harmful side effects in regulation of blood pressure mediate the oxidative balance.To obtain antioxidant peptides and antihypertensive peptides from jellyfish Rhopilema esculentum Kishinouye gonad protein hydrolysate(JGPH), we employed trypsin, papain, Alcalase and Neutrase for enzymatic hydrolysis, and the optimized conditions for hydrolysis were determined according to the preliminary result of degree of hydrolysis(DH). The prepared JGPH was evaluated for its potential to inhibit angiotensin-I-converting enzyme(ACE) and scavenge DPPH radicals using in vitro assays. Neutrase was choosed as the tool enzyme to obtain JGPH, The gonad of jellyfish Rhopilema esculentum Kishinouye was hydrolyzed by neutrase according to the optimized conditions(45℃, pH 7.0, substrate concentration 8%, enzyme/substrate ratio 2500 U/g substrate, and hydrolysis time 2h) to give JGPH, which exhibited potential DPPH radical scavenging activity and ACE-inhibitory activity(82.52% and 58.42%, respectively at the concentration of 2.0 mg/mL).Then JGPH was subjected to a series of purifications in order to fractionate the extracts for further evaluation of above activities. The hydrolysate was first ultrafiltrated using ultrafiltration membranes(molecular weight cut-offs of 1k and 3 kDa) to give three components JGPH-P1-3 which molecular weight distributions were >3 kDa, 1000-3 kDa, <1 kDa. Three components with different molecular weight distributions were obtained, among which the molecular below 1 kDa possessed the highest activity. From the JGPH-P3, Six fractions(P3A-F) were obtained using Sephadex G-25 column chromatography, followed by the collection of a higher bioactive fraction named P3D5, which was purified from P3 D using reverse-phase high-performance liquid chromatography(RP-HPLC). The antioxidant and ACEI property of P3D5 was assessed by electron spin resonance(ESR) and HPLC. we acquired six fractions named P3A-F and found the scavenging ability to DPPH and ACE-inhibitory activity of Fraction P3 F were comparatively higher(IC50= 0.38 mg/mL, 0.54 mg/mL, respectively), follewed by Fraction P3D(IC50=0.48 mg/mL, 0.96 mg/mL, respectively).P3D5 was a fraction isolated from D using RP-HPLC, and was analyzed by mass spectrography. The amino acid sequence of P3D5 was identified as Ser-Tyr, and then artificial synthesis.Its DPPH radical scavenging activity(IC50=22.7 μg/mL), hydroxyl radical scavenging activity(IC50=315.9 μg/mL), superoxide anion radical scavenging activity(IC50=122.5 μg/mL) and ACE-inhibitory activity(IC50=31.2 μg/mL) were investigated by using electron spin resonance measurement(ESR) and HPLC.