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  • Title: Peptide conjugates of 18β-glycyrrhetinic acid as potent inhibitors of α-glucosidase and AGEs-induced oxidation.
    Author: Khan SN, Shaheen F, Aleem U, Sheikh S, Tamfu AN, Ashraf S, Ul-Haq Z, Ullah S, Wahab AT, Choudhary MI, Jahan H.
    Journal: Eur J Pharm Sci; 2022 Jan 01; 168():106045. PubMed ID: 34666184.
    Abstract:
    18β-Glycyrrhetinic acid (18β-GA) is known for several biological activities, and has been the focus of extensive research for the development of therapeutic agents. In the current study, 18β-GA-peptide conjugates 2-11 were evaluated for their in vitro α-glucosidase inhibitory and antiglycation activities. Structure-activity relationship (SAR) established and molecular interactions of active bioconjugates with the enzyme's binding sites were predicted through molecular modeling approach. In tripeptide moiety of conjugates 2-11, peptide residue at position 1 was found to have a significant role on α-glucosidase inhibition. The most active 18β-GA-peptide conjugates 5 (18β-GA-Cys1-Tyr2-Gly3), and 8 (18β-GA-Pro1-Tyr2-Gly3) exhibited several-fold potent α-glucosidase inhibition (IC50 values 20-28 μM), as compared to standard drug acarbose (IC50 = 875.8 ± 2.10 µM). Kinetic studies of potent compounds, 4-8 revealed that conjugate 5 exhibits competitive-type of inhibition, while conjugates 6-8 showed a non-competitive type of inhibition. The simulation studies also supported the kinetic results that conjugate 5 (18β-GA-Cys1-Tyr2-Gly3) inhibits the α-glucosidase enzyme by blocking its substrate binding site. AGEs-induced NO inhibitors play an important role in controlling the inflammation associated with diabetes mellitus. The peptide conjugates 2-11 were also evaluated in vitro for AGEs-induced NO inhibition using RAW 264.7 macrophage cell line. Our data revealed that conjugates 7-10 were the more potent AGEs-induced NO inhibitors, comparable to standards rutin, and PDTC. The peptide conjugate 5 (a competitive inhibitor of α-glucosidase) also exhibited a strong inhibitory activity against AGEs-induced NO production. Furthermore, peptide conjugates 2-11 were found non-cytotoxic to mouse fibroblast NIH-3T3, and murine macrophages RAW 264.7 cell lines. In conclusion, our data demonstrates that besides possessing strong α-glucosidase inhibition, the newly synthesized peptide conjugates also alleviated the AGEs-induced NO production in RAW macrophages. Dual inhibition of α-glucosidase enzyme, and AGEs-induced NO production by 18β-GA-peptide conjugates qualify them for further research in anti-diabetic drug discovery.
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