Structural and mechanistic analysis of semisynthetic α-mangostin derivatives with anticancer activity via topoisomerase II inhibition.

Eleven novel alkyl/arylalkyl substituted α-mangostin derivatives (M2-M12) were synthesized from isolated α-mangostin (M1) from the pericarp of Garcinia mangostana L. extract. Among all the compounds, M10 exhibited the most potent antiproliferative activity against MCF-7 cells, with an IC₅₀ of 8.39 ± 0.07 μM, comparable to the positive controls, camptothecin and etoposide. An apparent increase in the G₂/M cell population in MCF-7 cells after treatment with M10 indicated cell cycle arrest at the G₂/M phase. Additionally, M10 was identified as a selective topoisomerase II inhibitor with a DNA non-intercalating mechanism. Induced-fit docking, binding-site characterisation using SiteMap, and molecular dynamics (MD) simulations revealed the binding interactions and stability of compounds M1 and M10 within the ATP-binding region of topoisomerase II. Comparative analysis of alternative predicted binding sites further supported preferential accommodation of the α-mangostin derivatives within the canonical ATP-binding region. The differences in H-bond interactions and the presence of additional, unusual lipophilic contacts (P126, V127, L141, F142) suggested that M10 adopts an extended binding mode at the topoisomerase II binding site, contributing to its selective inhibition profile.