Kurarinone

Kurarinone was purchased from Sigma-Aldrich (St. Louis, MO, USA), kushenol A from BioBioPha (Kunming, China), and kushenol I and sophoraflavanone G from MedChemExpress (Monmouth Junction, NJ, USA). Antibodies against total Erk1/2 (T-Erk1/2; catalogue No. #9102), phospho-Erk1/2 (P-Erk1/2; #9101), total Akt (T-Akt; #4691), and phospho-Akt (P-Akt; #4060) were obtained from Cell Signaling Technology (Ipswich, MA, USA). Additionally, 17β-estradiol (E₂) and ICI 182,780 (ICI: an estrogen receptor antagonist) were purchased from Sigma-Aldrich (St. Louis, MO, USA), and we acquired dimethyl sulfoxide (DMSO) from FUJIFILM Wako Pure Chemical (Osaka, Japan). Human breast cancer MCF-7 cells were obtained from the Japanese Collection of Research Bioresources Cell Bank, and consistently cultured in an RPMI 1640 medium at 37 °C in 5% CO₂. RPMI 1640 (phenol red-free) and RPMI 1640, containing 10% (v/v) dextran-coated charcoal-treated FBS (DCC-FBS), were purchased from Gibco, Thermo Fisher Scientific (Waltham, MA, USA).

Flavonoids including kurarinone (Figure S1A) were isolated from S. flavescens and purified using the method described by Kwon et al. and Lee et al. [24 (link),25 (link)]. Purity was measured at 97.46% by ultra-performance liquid chromatography (UPLC) (Figure S1B). Commercial kurarinone and bleomycin (BLM) used for the in vivo experiment were purchased from Sigma-Aldrich-Merck (St Louis, MO, USA). Pirfenidone (PFD) was obtained from MedChem Express (Monmouth Junction, NJ, USA).