Oxadiazole-based Inhibitors Targeting Carbohydrate-Hydrolyzing Enzymes in Type 2 Diabetes Mellitus: Synthetic Strategies, Structure- Activity Relationships, and Translational Perspectives.

Type 2 diabetes mellitus (T2DM) is a multifactorial metabolic disorder characterized by insulin resistance, progressive β-cell dysfunction, and chronic hyperglycemia, leading to microvascular and macrovascular complications. Among current therapeutic strategies, inhibition of intestinal carbohydrate-hydrolyzing enzymes, namely α-amylase and α-glucosidase, represents an established approach for controlling postprandial glucose excursions. However, clinically used inhibitors such as acarbose, miglitol, and voglibose are associated with gastrointestinal intolerance, limited selectivity, and variable efficacy, highlighting the need for improved therapeutic agents. In this context, 1,3,4-oxadiazole-based scaffolds have emerged as promising pharmacophores in antidiabetic drug design. The 1,3,4-oxadiazole ring acts as a bioisostere of amide and ester functionalities, conferring favorable physicochemical properties including enhanced metabolic stability, lipophilicity, and hydrogen-bonding capability. Structure-activity relationship (SAR) studies reported between 2015 and 2025 demonstrate that substituent effects-particularly phenolic hydroxyl groups, halogenation patterns, and extended aromatic systems-play a critical role in optimizing enzyme inhibition through hydrogen bonding, hydrophobic interactions, and π-π stacking within catalytic sites. While several oxadiazole-based hybrids incorporating privileged scaffolds such as benzimidazole, coumarin, and thiazolidinedione have been explored, evidence supporting modulation of additional targets including protein tyrosine phosphatase 1B (PTP1B), aldose reductase (ALR2), and inflammatory pathways such as the NLRP3 inflammasome remains limited and primarily derived from in vitro or computational studies. Computational approaches, including molecular docking, 3D-QSAR, and molecular dynamics simulations, have supported the rational optimization of oxadiazole derivatives, although their predictive limitations should be acknowledged. Despite encouraging preclinical findings, clinical translation remains constrained by insufficient pharmacokinetic, toxicological, and long-term efficacy data. Future research should prioritize systematic ADMET evaluation, standardized biological validation, and mechanistic expansion beyond carbohydrase inhibition to enable the development of clinically viable oxadiazole-based antidiabetic agents.