Computational screening of Alternaria metabolites as potential DPP-4 inhibitors: ADMET, molecular docking, molecular dynamics, and network pharmacology analysis.

Type 2 diabetes (T2D) remains a major global health challenge, underscoring the need for safer and more effective therapeutic agents. Although fungi are rich sources of structurally diverse bioactive metabolites, the antidiabetic potential of the genus Alternaria remains poorly explored. Here, we investigated 278 Alternaria-derived metabolites as potential inhibitors of dipeptidyl peptidase-4 (DPP-4), a clinically validated target involved in glucose homeostasis through incretin regulation. An integrated computational pipeline combining ADMET profiling, molecular docking, 300 ns molecular dynamics simulations, MM-PBSA binding free-energy calculations, principal component analysis (PCA) and free energy landscape (FEL) mapping, clustering, and network pharmacology was employed to identify and characterize lead compounds. Among the screened metabolites, Anthrininone B (AntB) emerged as the most promising candidate, showing binding behaviour comparable to, and slightly more favourable than, the reference inhibitor Linagliptin (Lin). AntB exhibited the most favourable mean MM-PBSA binding free energy (- 26.77 ± 8.20 kcal/mol), stable conformational convergence, a compact free-energy landscape, and representative clustered conformations consistent with persistent binding. Mechanistically, AntB transitioned from the S2 extensive tunnel into a deeply seated catalytic pose, forming stable interactions with Glu206, Tyr662/Tyr666, and Ser630, while maintaining overall protein stability. Network pharmacology further suggested that AntB may modulate multiple T2D-relevant pathways, including insulin resistance, inflammation, oxidative stress, and β-cell preservation. Collectively, these findings identify Alternaria metabolites, particularly AntB, as promising scaffolds for antidiabetic drug discovery and warrant further experimental validation.