Littordials A–E, novel formyl-phloroglucinol-β-caryophyllene meroterpenoids from the leaves of Psidium littorale

Five novel formyl-phloroglucinol-β-caryophyllene meroterpenoids, namely littordials A–E (1–5), were isolated from the leaves of Psidium littorale. Their structures were established by spectroscopic data and computational methods, and the structure of 1 was confirmed by X-ray crystallography. Littordials A–E feature unusual acyl phloroglucinol units, and 5 possesses a rare 6/7/9/4-fused tetracyclic ring system. Compounds 2, 3 and 5 exhibited cytotoxic activities on two cancer cell lines (MDA-MB-231 and B16) with IC50 values from 6.6 ± 1.5 to 9.2 ± 1.7 μM.