Acylphloroglucinol Derivatives with a Tricyclo-[4.4.1.11,4] Dodecane Skeleton from Garcinia bracteata Fruits

Two novel polycyclic polyprenylated acylphloroglucinols (PPAPs), garcibractinones A (1) and B (2), as well as three known analogues doitunggarcinones A–B (3–4) and garcibracteatone (5) were isolated from Garcinia bracteata fruits. Their structures were elucidated by comprehensive spectroscopic methods and single crystal X-ray diffraction. Compounds 1 and 2 possess an unprecedented caged tricyclo-[4.4.1.11,4] dodecane skeleton, and their biosynthetic pathways are also proposed. Compounds 1–2 were tested for their inhibitory effects on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 macrophages.