Aldose reductase inhibitory activity, molecular docking,ADMET, and density functional theory investigation of flavonoids isolated from Euphorbia pulcherrima Willd Ex Koltz

Diabetes mellitus is a chronic metabolic disease associated with severe complications includingdiabetes cataracts which results from accumulating sorbitol in tissues due to aldose reductaeoveractivity. Approaches that would selectively modulate AR to prevent sorbitol accumulation have become one of the basic strategies for managing diabetes-linked complications.This study examines the two flavonoids derived from E. pulcherrima, 5,7,8,3′,4′-pentahydroxy-3- methoxyflavone (1), and kaempferol-3-β-D glucopyranosyl (2), and their potential to suppress AR activity. Compounds exhibited potent inhibitory effects with IC₅₀ values of 0.97 ± 0.53 μM and 0.92 ± 0.48 μM, respectively. These results are close to the SC-13,153 standard inhibitor, d-saccharic acid 1,4-lactone, with an IC₅₀ equal to 0.88 ± 0.34 μM. In silico molecular docking examined these flavonoids' interaction with AR more strongly (compound 2: -10.248 kcal/mol and compound 1: -9.629 kcal/mol) and showed that such complexation was stable at the enzyme's active site. The interaction analysisindicated that compound 1and compound 2 specifically bind through polar hydrogen bonding and hydrophobic interactions. In addition to docking, DFT calculations revealed compound 1 had a lower energy gap (3.02 eV) compared to compound 2 (3.84 eV), suggesting higher reactivity and stability for enzyme inhibition. The molecular electrostatic potential (MESP) surface mapping indicated well-distributed charge regions, favoring electrophilic and nucleophilic interactions.The molecular dynamics (MD) simulations investigation revealed the RMSD value (<2.5Å), suitable fluctuation in RMSF, and compactness of protein in ROG analysis for compound 1. Moreover, the MMGBSA analysis showedhigher binding free energy for compound 1 (-38.458 kcal/mol), highlighting the potential inhibitory efficiency of the compound.Therefore, E. pulcherrima flavonoids can be an effective natural AR inhibitor with a therapeutic application for treating hyperglycemia-connected complications. These compounds might be even more effective and less toxic than synthetic AR inhibitors, opening a new way for plant-based diabetes treatment.