Optimization of Hydrolysis Conditions for Production of Angiotensin-Converting Enzyme Inhibitory Peptides from Basa Fish Skin Using Response Surface Methodology

Effects of Balsa Fish Skin Gelatin, Lentinula edodes Mushrooms, Soy Protein Isolate, and Starch on the Sensory Quality and Characterization of Physicochemical and Antioxidant Properties of New Sausage

Sausages are loved by people for their unique texture, satisfying chewiness, and pleasant flavor. However, in the production of sausages, red meat and a large amount of fat are mainly used, and long-term consumption will increase the risk of diseases such as obesity, heart disease, hypertension, and cancer. Our previous studies have shown that the intake of red meat and fat can be reduced through the replacement of lean meat and fat in sausages by Lentinula edodes and Pleaurotus eryngii mushrooms, but this will lead to the deterioration of the gel of sausage products and seriously affect the sensory quality of sausages. In this study, the response surface method was used to optimize the amount of balsa fish skin gelatin, soy protein isolate, and starch added to, and the proportion of Lentinula edodes mushrooms replacing lean meat in, the new sausage, with Pleaurotus eryngii mushrooms replacing fat. The results show that Lentinula edodes mushrooms replaced 36.1% of the lean meat, and the addition of 0.96% balsa fish skin gelatin, 10.61% starch, and 9.94% soy protein isolate resulted in the highest sensory score and the sensory quality being the closest to that of traditional sausages. Compared with the control group, this novel sausage exhibits characteristics such as lower fat and saturated fatty acid content, reduced energy levels, and higher levels of amino acids (aspartic acid, glutamic acid, cysteine, methionine, and proline) and polyunsaturated fatty acids. The total phenolic content of the novel sausage is 12.52 times higher than that of the control. In comparison with the control group, the novel sausage demonstrates a 65.58% increase in DPPH radical scavenging activity and a 3.88-fold improvement in ABTS+ radical scavenging activity. These findings highlight the outstanding antioxidant performance of the novel sausage. This study provides new ideas for improving the sensory quality of new sausages, promoting the healthy development of the sausage industry, and promoting the high-value utilization of edible mushrooms.

ACE Inhibitory Activity and Molecular Docking of Gac Seed Protein Hydrolysate Purified by HILIC and RP-HPLC

Gac (Momordica cochinchinensis Spreng.) seed proteins (GSPs) hydrolysate was investigated for angiotensin I-converting enzyme (ACE) inhibitory activities. GSPs were hydrolyzed under simulated gastrointestinal digestion using a combination of enzymes, including pepsin, trypsin, and chymotrypsin. The screening of ACE inhibitory peptides from GSPs hydrolysate was performed using two sequential bioassay-guided fractionations, namely hydrophilic interaction liquid chromatography (HILIC) and reversed-phase high-performance liquid chromatography (RP-HPLC). Then, the peptides in the fraction with the highest ACE inhibitory activity were identified by LC-MS/MS. The flow-through (FT) fraction showed the most potent ACE inhibitory activity when HILIC fractionation was performed. This fraction was further separated using RP-HPLC, and the result indicated that fraction 8 (RP-F8) showed the highest ACE inhibitory activity. In the HILIC-FT/RP-F8 fraction, 14 peptides were identified using LC-MS/MS analysis coupled with de novo sequencing. These amino acid chains had not been recorded previously and their ACE inhibitory activities were analyzed in silico using the BIOPEP database. One fragment with the amino acid sequence of ALVY showed a significant ACE inhibitory activity (7.03 ± 0.09 µM). The Lineweaver-Burk plot indicated that ALVY is a competitive inhibitor. The inhibition mechanism of ALVY against ACE was further rationalized through the molecular docking simulation, which revealed that the ACE inhibitory activities of ALVY is due to interaction with the S1 (Ala354, Tyr523) and the S2 (His353, His513) pockets of ACE. Bibliographic survey allowed the identification of similarities between peptides reported as in gac fruit and other proteins. These results suggest that gac seed proteins hydrolysate can be used as a potential nutraceutical with inhibitory activity against ACE.

Mung Bean Protein Hydrolysates Protect Mouse Liver Cell Line Nctc-1469 Cell from Hydrogen Peroxide-Induced Cell Injury

Mung bean is nutritious and rich in protein (19.5%–33.1%). However, there are few studies on mung bean protein active peptides so the mung bean protein hydrolysates (MBPHs) were investigated for evaluating their ability to clear intracellular reactive oxygen species (ROS) and regulating the ability of antioxidant enzymes on NCTC-1469 cells. Results showed that MBPHs, MBPHs-I (molecular weight < 3 kDa), MBPHs-II (molecular weight between 3 and 10 kDa), and MBPHs-III (molecular weight > 10 kDa) could all improve the survival rate of cells compared with the model group. MBPHs, MBPHs-I, and MBPHs-II could significantly decrease the content of lactate dehydrogenase (LDH) and reduce the generation of malonaldehyde (MDA) at a concentration of 0.4 mg/mL. Regarding the intracellular ROS, the result showed that MBPHs-I significantly reduced the production of ROS (from 58.3% to 26.6%) and had a dose-dependent relationship. In addition, the amino acid analysis showed that MBPHs-I had a balanced amino acid composition. MBPHs-I is rich in lysine but was deficient in cereals. Therefore, the hydrophobic and aromatic amino acids in MBPHs-I were high, which could improve its antioxidant activity. According to the results, MBPHs-I was the best and most potent natural antioxidant and it can contribute to drug development and medical application.

Antihypertensive activity of fish protein hydrolysates and its peptides

The rising interest to utilize nutritionally exorbitant fish proteins has instigated research activities in fish waste utilization. The development of newer technologies to utilize fish waste has fostered use of bioactive value-added products for specific health benefits. Enzymatically obtained Fish Protein Hydrolysate (FPH) is a rich source of biologically active peptides possessing anti-oxidant, anticancer, antimicrobial and anti-hypertensive activity. Isolating natural remedies to combat alarming negative consequences of synthetic drugs has been the new trend in current research promoting identification of antihypertensive peptides from FPH. In this review, we aim to culminate data available to produce antihypertensive peptides from FPH, its composition and potential to be used as a therapeutic agent. These purified peptides are known to be rich in arginine, valine and leucine. Reports reveal peptides with low molecular weight (<1 kDa) and shorter chain length (<20 amino acids) exhibited higher antihypertensive activity. As these peptides have proven Angiotensin Converting Enzyme - I inhibitory activity in vitro and in vivo, their potential to be used as antihypertensive drugs is outrageous. However, current focus on research in the field of molecular docking is necessary to have improved understanding of interaction of the peptides with the enzyme.

Effect of combined ultrasonic and alkali pretreatment on enzymatic preparation of angiotensin converting enzyme (ACE) inhibitory peptides from native collagenous materials

The combined effect of ultrasonic and alkali pretreatment for the hydrolysis of native collagenous materials and release of ACE inhibitory peptides was investigated. The ultrasonic and alkali pretreatment of pig skin could accelerate the release of the ACE inhibitory peptides from the triple helix of collagen in early stages of hydrolysis. Furthermore, the pretreatment could also accelerate collapse of the triple helix and release more ACE inhibitory peptides during hydrolysis than collagen samples left untreated. Compared to untreated and alkali pretreated samples, the ultrasonic and alkali pretreatment could decrease the thermostability of pig skin significantly (P<0.05) because the ultrasonic and alkali pretreatment could weaken hydrogen bonds and break parts of covalent bonds in collagen, leading to damage of the triple helical structure in collagen. Therefore, the ultrasonic and alkali pretreatment could damage the triple helical structure of collagen in native collagenous materials and expose more inner sites for subsequent hydrolysis, and it could be a potential way to prepare ACE inhibitory peptides effectively from collagen-rich raw material.

Bioactive Peptides

The increased consumer awareness of the health promoting effects of functional foods and nutraceuticals is the driving force of the functional food and nutraceutical market. Bioactive peptides are known for their high tissue affinity, specificity and efficiency in promoting health. For this reason, the search for food-derived bioactive peptides has increased exponentially. Over the years, many potential bioactive peptides from food have been documented; yet, obstacles such as the need to establish optimal conditions for industrial scale production and the absence of well-designed clinical trials to provide robust evidence for proving health claims continue to exist. Other important factors such as the possibility of allergenicity, cytotoxicity and the stability of the peptides during gastrointestinal digestion would need to be addressed. This review discusses our current knowledge on the health effects of food-derived bioactive peptides, their processing methods and challenges in their development.