Cytotoxic Acylphloroglucinol Derivatives from Callistemon salignus.

Callisalignenes G-I (1-3), three new meroterpenoids of β-triketone and monoterpene, along with two known analogues (4 and 5), were isolated from Callistemon salignus. Their structures and absolute configurations were unambiguously established by a combination of NMR and MS analysis and electronic circular dichroism (ECD) evidence. Callisalignenes H (2) and I (3) have a rare sec-butyl moiety at C-7. Meroterpenoids 1-3 exhibited cytotoxicity against HCT116 cells with IC50 values of 8.51 ± 1.8, 9.12 ± 0.3, and 16.33 ± 3.3 μM, respectively. Cytotoxic Acylphloroglucinol Derivatives from Callistemon salignus.