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

Comprehensive Summary (+/-)-Atrachinenins A-C (1-3), three meroterpenoids possessing novel C-27 skeletons, were isolated from the rhizomes of Atractylodes 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 calculation, and X-ray diffraction. A plausible biogenetic pathway was proposed. Compound 1 exhibited potential TGF-beta inhibitory activity at 25 mu mol/L. [GRAPHICS] .

Automated summary

Atrachinenins A-C (1-3), isolated from the rhizomes of Atractylodes chinensis, are meroterpenoids with novel C-27 skeletons. Atrachinenin A (1) features a unique cage-like skeleton, while atrachinenin B (2) has an additional peroxyl bridge ring, forming a complex cyclic ring system. Structural elucidation was done through various spectroscopic techniques and a plausible biosynthetic pathway was proposed. Atrachinenin A exhibited potential TGF-beta inhibitory activity at 25 μmol/L.