Inhibition of TGF-β signaling by the fungal lactones (S)-curvularin, dehydrocurvularin, oxacyclododecindione and galiellalactone

► The fungal lactones antagonized TGF-β cellular effects. ► Oxacyclododecindione showed a highly potent inhibition of TGF-β signaling. ► All compounds inhibited DNA binding of the activated Smad transcription factors.