Inhibitory activity and mechanism of guavinoside B from guava fruits against α-glucosidase: Insights by spectroscopy and molecular docking analyses

Caseinate-coated zein nanoparticles as potential delivery vehicles for guavinoside B from guava: Molecular interactions and encapsulation properties

Guavinoside B (GUB) is a characteristic constituent from guava with strong antioxidant activity; however, its low water solubility limits its utilization. Herein, we investigated the interaction between GUB and zein, a prolamin with self-assembling property, using multiple spectroscopic methods and fabricated GUB-zein-NaCas nanoparticles (GUB-Z-N NPs) via the antisolvent coprecipitation approach. GUB caused fluorescence quenching to zein via the static quenching mechanism. Fourier-transform infrared spectroscopy and computational analysis revealed that GUB bound to zein via van der Waals interaction, hydrogen bond, and hydrophobic forces. The GUB-Z-N NPs were in the nanometric size range (< 200 nm) and exhibited promising encapsulation efficiency and redispersibility after freeze-drying. These particles remained stable for up to 31 days at 4 °C and great resistance to salt and pH variation, and displayed superior antioxidant activity to native GUB. The current study highlights the potential of zein-based nanoparticles as delivery vehicles for GUB in the food industry.

Comprehending the inhibition mechanism of indole-based bis-acylhydrazone compounds on α-glucosidase: Spectral and theoretical approaches

Indole-based bis-acylhydrazone compounds can inhibit the activity of α-glucosidase and control the concentration of blood glucose. In this paper, the characteristics of three indole-based bis-acylhydrazone compounds with different inhibitory activities of α-glucosidase as well as the interaction with α-glucosidase were studied by experiments and computational simulation techniques. Enzyme kinetic and spectral experiments showed that the indole-based bis-acylhydrazone compounds were able to inhibit enzyme activity through mixed inhibition dominated by competitive inhibition, and during the binding reaction, indole-based bis-acylhydrazone compounds can quench the intrinsic fluorescence of α-glucosidase through static quenching and an aggregation of the indole-based bis-acylhydrazone with α-glucosidase produces a stable complex with a molar ratio of 1:1, and the combination of indole-based bis-acylhydrazone compounds could lead to slight change in the conformation of α-glucosidase. The theoretical simulation demonstrated that the stability of the complex systems was positively correlated with the inhibitory activity of indole-based bis-acylhydrazone compounds, and the indole-based bis-acylhydrazone compounds occupied the active site in the multi-ligand system, resulting in a significant decrease in the binding ability of starch to active amino acids. These results suggested that indole-based bis-acylhydrazone compound was expected to be a new type of α-glucosidase inhibitor.

Rapid screening of the novel bioactive peptides with notable α-glucosidase inhibitory activity by UF-LC-MS/MS combined with three-AI-tool from black beans

This work aimed to propose a rapid method to screen the bioactive peptides with anti-α-glucosidase activity instead of traditional multiple laborious purification and identification procedures. 242 peptides binding to α-glycosidase were quickly screened and identified by bio-affinity ultrafiltration combined with LC-MS/MS from the double enzymatic hydrolysate of black beans. Top three peptides with notable anti-α-glucosidase activity, NNNPFKF, RADLPGVK and FLKEAFGV were further rapidly screened and ranked by the three artificial intelligence tools (three-AI-tool) BIOPEP database, PeptideRanker and molecular docking from the 242 peptides. Their IC50 values were in order as 4.20 ± 0.11 mg/mL, 2.83 ± 0.03 mg/mL, 1.32 ± 0.09 mg/mL, which was opposite to AI ranking, for the hydrophobicity index of the peptides was not included in the screening criteria. According to the kinetics, FT-IR, CD and ITC analyses, the binding of the three peptides to α-glucosidase is a spontaneous and irreversible endothermic reaction that results from hydrogen bonds and hydrophobic interactions, which mainly changes the α-helix structure of α-glucosidase. The peptide-activity can be evaluated vividly by AFM in vitro. In vivo, the screened FLKEAFGV and RADLPGVK can lower blood sugar levels as effectively as acarbose, they are expected to be an alternative to synthetic drugs for the treatment of Type 2 diabetes.