(±)-Atrachinenins A-C,Three Pairs of Caged C27 Meroterpenoids from the Rhizomes of Atractylodes chinensis

(+)-Atrachinenins A-C(1-3),three meroterpenoids possessing novel C27 skeletons,were isolated from the rhizomes of At-ractylodes chinensis.(±)-Atrachinenin A(1)possesses an unprecedented cage-like skeleton with a fused 6/6/5/5 tetracyclic system(decahy-dro-1,5:4a,7-dimethanobenzo[7]annulene),which may be formed by the intermolecular cyclization of(±)-atrachinenin C(3).Compared to 1,(±)-atrachinenin B(2)features an additional unique five-membered peroxyl bridge ring to form a complex 6/6/5/5/5 cyclic ring system.Their structures and absolute configurations were elucidated by HRESIMS,NMR spectroscopic data,ECD calcula-tion,and X-ray diffraction.A plausible biogenetic pathway was proposed.Compound 1 exhibited potential TGF-6 inhibitory activity at 25 μmol/L.