SMAD2 and pulmonary fibrosis: Baicalein, one of the flavones in Codium fragile, inhibited pulmonary fibrosis by reducing microRNA-21 levels, which play an important role in the pathogenesis of pulmonary fibrosis, and by suppressing the up-regulated expression levels of TGF-β1 and p-Smad-2/3 in bleomycin-treated rats [45].