Polycyclic polyprenylated acylphloroglucinol derivatives from Hypericum scabrum

Three new polycyclic polyprenylated acylphloroglucinol derivatives (PPAPs), hyperibrins E–G (1–3), along with seven known compounds were identified from the air-dried aerial parts of Hypericum scabrum. Their structures were determined by NMR spectroscopic methods, both experimental and calculated electronic circular dichroism (ECD) spectra and comparison with known compounds. Compound 1 was derived from an analogue of compound 2 by cyclization, while a retro-Claisen reaction transformed another analogue of compound 2 into compound 3. Compounds 3, 4, 5, and 10 showed obvious hepatoprotective activities against paracetamol-induced HepG2 cell damage.