Eucalypglobulusals A-J, Formyl-Phloroglucinol-Terpene Meroterpenoids from Eucalyptus globulus Fruits.

Ten new formyl-phloroglucinol-terpene meroterpenoids, eucalypglobulusals A-J (1-10), and ten known analogues were isolated from  Eucalyptus globulus fruits. The structures of 1-10 were determined by spectroscopic analysis, while their absolute configurations were established using calculated and experimental electronic circular dichroism (ECD) spectra. Eucalypglobulusal A was assigned as a new formyl-phloroglucinol-terpene meroterpenoid with a rearranged sesquiterpene skeleton, and an aldol condensation between C-3 and C-5 of the germacrene C moiety was proposed to be a key step in its putative biosynthetic pathway. Eucalypglobulusal F exhibited cytotoxicity against the human acute lymphoblastic cell line (CCRF-CEM) with an IC50 value of 3.3 μM, while eucalypglobulusal A, eucarobustol C, macrocarpal A, macrocarpal B, and macrocarpal D exhibited DNA topoisomerase I (Top1) inhibition. The compounds eucalypglobulusal A and macrocarpal A act as Top1 catalytic inhibitors and delay Top1 poison-mediated DNA double-strand damage.