Inhibitory Potency of Amentoflavone and Bilobetin on the Binding of Androstenedione to Aromatase in HR+ Breast Cancer of Postmenopausal Women: An In Silico Approach

Department of Biology, Faculty of Mathematics and Natural Sciences, State University of Surabaya, Surabaya, 60231, Indonesia

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Abstract

Androstenedione (ASD) is a natural substrate of the aromatase enzyme in synthesizing estrone, a primary form of estrogen in postmenopausal women. Aromatase inhibition can be a promising strategy in treating hormone receptor-positive (HR+) breast cancer in post-menopausal women selectively. This study aimed to elucidate the binding mechanisms of two potential anticancer biflavonoids, amentoflavone and bilobetin, and their combination in inhibiting the binding of ASD to aromatase. This study used a molecular docking approach with Cuda HEX 8.0.0 software. 3D structure visualization and non-bond analysis were carried out by BIOVIA Discovery Studio 2020 Client. Amentoflavone bound outside the catalytic pocket and may sequester ASD into a non-productive complex, with a binding energy of -338.18 kcal/mol compared to ASD alone (-237.61 kcal/mol). Bilobetin directly engaged key ASD-binding residues (LYS440, MET444, TYR361, PHE430, TYR441) in aromatase with a binding energy of -334.16 kcal/mol, suggesting competitive or mixed-type inhibition. The amentoflavone-bilobetin complex further strengthened inhibitory potential, interacting with multiple ASD-binding residues with a binding energy of -410.90 kcal/mol, increasing steric interference. When pre-bound with this complex, ASD was displaced to alternative residues, preventing productive binding, with a binding energy of -403.08 kcal/mol. In conclusion, amentoflavone, bilobetin, and their combination can interfere with ASD binding to aromatase through distinct but complementary mechanisms, supported by their lower binding energies and steric effects. These findings suggest a potential strategy for aromatase inhibition in HR+ breast cancer, although experimental validation is required.