Chemoenzymatic and Protecting-Group-Free Synthesis of 1,4-Substituted 1,2,3-Triazole-α-d-glucosides with Potent Inhibitory Activity toward Lysosomal α-Glucosidase

Flavone-1,2,3-triazole derivatives as potential α-glucosidase inhibitors: Synthesis, enzyme inhibition, kinetic analysis and molecular docking study

α-Glucosidase inhibitors are considered prime therapeutics in the management of type-2 diabetes and are preferred due to their localized action ushered by limited side effects. In this regard, nineteen new flavone-1,2,3-triazole derivatives have been designed and synthesized via utilizing an efficient click reaction protocol, and screened for the inhibition of the α-glucosidase enzyme. The reaction conditions were mild, good yielding and required easy work up. All the synthesized flavone-triazole derivatives were found more active against the yeast α-glucosidase with IC₅₀ values ranging from 24.37 ± 0.55-168.44 ± 0.77 μ M as compared to standard inhibitor acarbose (IC₅₀ = 844.81 ± 0.53 μM). The derivatives with 2,5‑dichloro 9k (IC₅₀ = 24.37 ± 0.55 μM) and 4‑chloro 9d (IC₅₀ = 24.77 ± 0.30 μM) substituent bearing an amide linkage were the most active. In the kinetic study of most active derivatives 9k and 9d, they were found to be mixed and uncompetitive inhibitors, respectively. In molecular docking studies, blind docking of the most active compounds was accomplished to find the interactions between the compounds and α-glucosidase that further confirms the mixed or uncompetitive nature of the inhibitors.

Systematic Functional and Computational Analysis of Glucose-Binding Residues in Glycoside Hydrolase Family GH116

Glycoside hydrolases (GH) bind tightly to the sugar moiety at the glycosidic bond being hydrolyzed to stabilize its transition state conformation. We endeavored to assess the importance of glucose-binding residues in GH family 116 (GH116) β-glucosidases, which include human β-glucosylceramidase 2 (GBA2), by mutagenesis followed by kinetic characterization, X-ray crystallography, and ONIOM calculations on Thermoanaerobacterium xylanolyticum TxGH116, the structural model for GH116 enzymes. Mutations of residues that bind at the glucose C3OH and C4OH caused 27–196-fold increases in KM for p-nitrophenyl-β-D-glucoside, and significant decreases in the kcat, up to 5000-fold. At the C6OH binding residues, mutations of E777 decreased the kcat/KM by over 60,000-fold, while R786 mutants increased both the KM (40-fold) and kcat (2–4-fold). The crystal structures of R786A and R786K suggested a larger entrance to the active site could facilitate their faster rates. ONIOM binding energy calculations identified D452, H507, E777, and R786, along with the catalytic residues E441 and D593, as strong electrostatic contributors to glucose binding with predicted interaction energies > 15 kcal mol−1, consistent with the effects of the D452, H507, E777 and R786 mutations on enzyme kinetics. The relative importance of GH116 active site residues in substrate binding and catalysis identified in this work improves the prospects for the design of inhibitors for GBA2 and the engineering of GH116 enzymes for hydrolytic and synthetic applications.

Recent Advances in Bioactive Flavonoid Hybrids Linked by 1,2,3-Triazole Ring Obtained by Click Chemistry

As a result of the biological activities of natural flavonoids, several synthetic strategies aiming to obtain analogues with improved potency and/or pharmacokinetic profile have been developed. Since the triazole ring has been associated with several biological activities and metabolic stability, hybridization with a 1,2,3-triazole ring has been increasingly reported over the last years. The feasible synthesis through copper (I) catalyzed azide-alkyne cycloaddition (CuAAC) has allowed the accomplishment of several hybrids. Since 2017, almost 700 flavonoid hybrids conjugated with 1,2,3-triazole, including chalcones, flavones, flavanones and flavonols, among others, with antitumor, antimicrobial, antidiabetic, neuroprotective, anti-inflammatory, antioxidant, and antifouling activity have been reported. This review compiles the biological activities recently described for these hybrids, highlighting the mechanism of action and structure-activity relationship (SAR) studies.