Abstract
In recent years, angiotensin-converting enzyme (ACE) inhibitory peptide has become a research hotspot because of its essential role in maintaining human blood pressure balance. In this study, two novel ACE inhibitory peptides of Val-Glu-Arg-Gly-Arg-Arg-lle-Thr-Ser-Val (Valine-Glutamate-Arginine-Glycine-Arginine-Arginine-Isoleucine-Threonine-Serine-Valine, VERGRRITSV) and Phe-Val-Ile-Glu-Pro-Asn-Ile-Thr-Pro-Ala (Phenylalanine-Valine-Isoleucine-Glutamate-Proline-Asparagine-Isoleucine-Threonine-Proline-Alanine, FVIEPNITPA) were isolated and purified from defatted walnut meal hydrolysates through a series of preparation processes including ultrafiltration, Sephadex G-15 gel chromatography, and reverse high performance liquid chromatography (RP-HPLC). Both peptides showed high ACE inhibitory activities. The molecular docking study revealed that VERGRRITSV and FVIEPNITPA were primarily attributed to the formation of strong hydrogen bonds with the active pockets of ACE. The binding free energies of VERGRRITSV and FVIEPNITPA with ACE were −14.99 and −14.69 kcal/mol, respectively. Moreover, these ACE inhibitory peptides showed good stability against gastrointestinal enzymes digestion and common food processing conditions (e.g., temperature and pH, sugar, and salt treatments). Furthermore, animal experiment results indicated that the administration of VERGRRITSV or FVIEPNITPA exhibited antihypertensive effects in spontaneously hypertensive rats. Our results demonstrated that walnut could be a potential source of bioactive peptides with ACE inhibitory activity.
Highlights
Walnut (Juglans regia L.) is known as one of the world’s famous “four dried fruits”together with almonds, cashews, and hazelnuts
Of 19 fractions, A3 (MW < 3 kDa) showed the highest Angiotensin–converting enzyme (ACE) inhibitory activity (62.25% ±61.54%), which was significantly higher than the glutelin-1 hydrolysate before ultrafiltration separation (50.91% ± 2.65%, p < 0.01)
These findings demonstrated that the walnut glutelin-1 ACE inhibitory peptide could inhibit the ACE activity and over-activated RASS, thereby reducing the production of AngII, preventing the excessive secretion of ALD, slowing the reabsorption of sodium by the kidneys, and lowering blood pressure (BP) levels of spontaneously hypertensive rat (SHR)
Summary
Walnut (Juglans regia L.) is known as one of the world’s famous “four dried fruits”. together with almonds, cashews, and hazelnuts. Walnut meal and related products have limited market acceptance due to their bitter and astringent taste, so most are processed and used as fertilizers, or even directly discarded as waste This processing method wastes high-quality protein resources and pollutes the natural environment [2]. Very few reports have focused on the mechanism, the effects of lowering blood pressure in rats, the stability of the simulated gastrointestinal (GI) environment, and typical food processing conditions. We evaluated the antihypertensive effects of walnut glutelin-1 ACE inhibitory peptides in vivo using a spontaneously hypertensive rat (SHR) model. We have investigated the stability of walnut glutelin-1 ACE inhibitory peptides under different food processing conditions and simulated GI digestion environments. The outcomes of this study can improve the deep processing and comprehensive utilization of walnuts and provide theoretical and technical references for the research and development of walnut antihypertensive peptides
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