Multi-tiered in silico evaluation identifies Sarsasapogenin as a promising ERα-targeted phytochemical against breast cancer.

Abstract

Sarsasapogenin, a spirostanol sapogenin with reported activity against ERα-positive breast cancer cells, has no defined molecular target, and its metabolic fate has not been considered in computational studies of this compound class. Network pharmacology, biotransformation profiling, and multi-level molecular modeling were combined to address both questions. Of 108 targets shared between Sarsasapogenin and breast cancer, ERα gave the most favorable docking energy among ten hub proteins (-10.46 kcal/mol), against -8.73 kcal/mol for the reference modulator Bazedoxifene. BioTransformer predicted 16 metabolites, of which five phase-I derivatives retaining the spirostanol scaffold bound ERα within a narrow window (-10.01 to -10.30 kcal/mol). The representative metabolite BTM00010, a 6-hydroxylated derivative, retained affinity at -10.30 kcal/mol and formed a hydrogen bond to Val533 that is absent from the parent pose. Over 100 ns of simulation, all three complexes reached comparable plateaus in RMSD (0.20-0.30 nm) and radius of gyration (1.68-1.80 nm), and MMGBSA ranked them in the same order as docking (-47.30, -21.48, and -11.83 kcal/mol). Post-dynamics analysis showed lower collective-motion amplitude for the metabolite complex than for the parent, and a correlated-motion network closer to the parent than to the reference modulator. Predicted phase-I hydroxylation, therefore, does not abolish ERα engagement, which argues for evaluating biotransformation products alongside the parent compound in computational screening of plant sapogenins.