Aromatase (CYP19A1) Inhibitory Activity of Coltsfoot (Tussilago farfara L.) Phytochemicals: In Vitro and in Silico Evaluation

Abstract

Estrogen plays a critical role in the development and progression of hormone-sensitive breast cancer. Aromatase (CYP19A1), the key enzyme catalyzing the final step in estrogen biosynthesis, has emerged as a promising therapeutic target. Although third-generation synthetic aromatase inhibitors (AIs) are effective, their use is limited by serious side effects, highlighting the need for safer natural alternatives. In this study, we evaluated three major flavonoids from Tussilago farfara L., quercetin-3-rutinoside (1), quercetin-3-O-β-D-glucoside (2), and kaempferol-3-O-glucoside (3) for aromatase inhibitory potential. In vitro assays showed that compound 3 was the most potent (IC₅₀ = 3.46 µM), followed by compound 2 (3.79 µM) and compound 1 (3.81 µM), with activities comparable to potent dietary flavonoids and stronger than some reported natural analogues. Molecular docking supported these findings, showing favourable docking scores (-6.73 to -4.19) and binding energies (-60.3 to -43.7 kcal mol^-1), comparable to those of the standard inhibitor exemestane (IC₅₀ = 0.20 µM; -68.3 kcal mol^-1). However, the computational predictions did not fully replicate the experimental ranking, reflecting the limitations of docking methods. Overall, these results highlight the significance and therapeutic potential of T. farfara flavonoids as natural aromatase inhibitors.