Abstract
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.
Highlights
Momordica cochinchinensis Spreng. seeds have long been considered waste products in gac industry in Southeast Asian countries, such as Thailand, Laos, Myanmar, Cambodia, Vietnam, Malaysia, India, and Taiwan, where the fruit is widely grown [1]
The IC50 of angiotensin I-converting enzyme (ACE) inhibitory activitywas of neem (Azadirachta indica) seeds peptides hydrolysate determined using different concentrations to givewas a value of 70.0 ±increased
The results from this study clearly indicate that gac seed protein hydrolysates have rich
Summary
Momordica cochinchinensis Spreng. seeds have long been considered waste products in gac industry in Southeast Asian countries, such as Thailand, Laos, Myanmar, Cambodia, Vietnam, Malaysia, India, and Taiwan, where the fruit is widely grown [1]. In traditional Chinese medicine, gac seeds have been used as a treatment of certain diseases, such as diabetes, eye disorders, fluxes, liver spleen disorders, hemorrhoids, wounds, bruises, boils, sores, scrofula, tinea, swelling, and pus [2,3]. Bioactive peptides can prevent oxidation and microbial degradation in foods and can be used for the treatment of various medical conditions, increasing the quality of life [4]. Bioactive peptides are liberated during proteolytic digestion of proteins and during food processing (cooking, fermentation, and ripening) [5]. The enzymatic hydrolysis produces bioactive peptides more efficiently than microbial fermentation due to the short reaction time, ease of scalability, and predictability [6]. The bioactivity of peptides has been suggested to depend mainly on the amino acid composition, sequence, structure, and other factions, such as hydrophobicity, charge, or even the binding properties of peptides [7,8]
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