Polyprenylated acylphloroglucinols from Garcinia species and structural revision of seven analogues

Our continuous study of the fruits of Garcinia xanthochymus and Garcinia subelliptica led to the isolation and structural characterization of six new polyprenylated acylphloroglucinols, xanthochymusones N and O (1 and 2), (-)-garciyunnanin L (3), and garsubelones C-E (4-6), together with two known analogues. Their structures were elucidated by interpretation of NMR and MS spectroscopic data. It was found that the Grossman-Jacobs rule is no longer applicable to determination of the C-7 configuration of compounds 1-3, as they possess a complex 6/6/6/6/6 fused ring system. The inhibitory activities of all the compounds against two human hepatocellular carcinoma cell lines Huh-7 and HepG2 were evaluated, and compound 1 exhibited moderate cytotoxic activities against HepG2 cells with IC₅₀ value 7.3 μM. Furthermore, the previous assignments of some polyprenylated acylphloroglucinols have been proved to be incorrect in this study, and analysis of NMR data enabled the structural revision of seven analogues: hyperselancins A and B, garcinielliptones F and G, garxanthochins A and B, and 13,14-didehydroxygarcicowin C. The revised structures of garcinielliptone F and garxanthochin A were shown to have the same structures of garsubelone B and xanthochymusone K, respectively, and the revised structures of other five compounds have not been reported.