Chitosan and alginate, are non-toxic and biodegradable polymers used to enhance the stability of biotherapeutics by loading them into nanocarriers. In this study, the stone fish-derived low molecular weight peptide (Ala-Leu-Gly-Pro-Gln-Phe-Tyr), exhibited an in vitro ACE-inhibitory activity of 94.43 ± 2.05% and an IC50 of 0.012 ± 0.001 mM. The peptide was encapsulated via ionic gelation with alginate followed by polyelectrolyte complexation with chitosan. The resulting ACE-inhibitory peptide-loaded alginate-chitosan nanoparticles (ACE-I-ALG-CS NPs) were optimized to achieve small particle size (212.60 nm) and high encapsulation efficiency (EE, 74.48%). This was based on an optimum chitosan concentration (0.420%w/v), homogenization speed (6000 rpm), and homogenization time (30 min) using Box Behnken experimental design (BBED). Characterization of the ACE-I-ALG-CS NPs revealed a spherical, monodispersed morphology with high physicochemical stability during storage at 2 °C, 7 °C, and 12 °C for 12 weeks. Moreover, the in vivo study conducted on spontaneously hypertensive rats (SHRs) demonstrated a significantly higher (p < 0.05) systolic blood pressure (SBP)-lowering effect of the ACE-I-ALG-CS NPs compared to captopril and unencapsulated peptide. Hence, alginate and chitosan can be used as biocompatible coating materials to enhance the stability and in vivo anti-hypertensive effect of Ala-Leu-Gly-Pro-Gln-Phe-Tyr through encapsulation, thereby making it potentially valuable for various applications in pharmaceuticals and food industry.
We evaluated the acute (single-dose) and subacute (repeated-dose) oral toxicity of alcalase-hydrolyzed whey protein concentrate. Our acute study revealed no death or treatment-related complications, and the median lethal dose of whey protein concentrate hydrolysate was >2,500 mg/kg. In the subacute study, when the hydrolysate was fed at 3 different concentrations (200, 400, and 800 mg/kg), no groups showed toxicity changes compared with controls. Then, whey protein concentrate hydrolysate was orally administered to spontaneously hypertensive rats. Results revealed significant reductions in blood pressure in a dose-dependent manner, and dosing at 400 mg/kg led to significant blood pressure reduction (-47.8 mm Hg) compared with controls (blood pressure maintained) and the findings of previous work (-21 mm Hg). Eight peptides-RHPEYAVSVLLR, GGAPPAGRL, GPPLPRL, ELKPTPEGDL, VLSELPEP, DAQSAPLRVY, RDMPIQAF, and LEQVLPRD-were sequentially identified and characterized. Of the peptides, VLSELPEP and LEQVLPRD showed the most prominent in vitro angiotensin-I converting enzyme inhibition with half-maximal inhibitory concentrations of 0.049 and 0.043 mM, respectively. These findings establish strong evidence for the in vitro and in vivo potential of whey protein concentrate hydrolysate to act as a safe, natural functional food ingredient that exerts antihypertensive activity.