Calliloboapins A-L, diterpenoids from the branches and leaves of Callicarpa loboapiculata and their biological activities.

Eleven new isopimarane diterpenoids and one new ent-pimarane diterpenoid, named calliloboapins A-L (1-12), were isolated from the branches and leaves of Callicarpa loboapiculata F. P. Metcalf. Their structures and absolute configurations were established by HRESIMS, UV, IR, 1D and 2D NMR spectroscopic analyses, single crystals X-ray diffraction and ECD calculations. Structurally, compound 1 possesses an unusual tricyclo [2.2.2.0] octane structure, and compound 2 is characterized by a cyclopentane ring B. Compound 3 contains an unprecedented ten-membered ring with an oxygen bridge connecting C-8 and C-9. The anti-inflammatory activities of all isolated compounds were evaluated by LPS-induced RAW264.7 cells. Compounds 1-12 inhibited the release of NO to varying degrees, and 3, 4, 8, 11 and 12 significantly suppressed the overexpression of inducible NO synthase. Moreover, liver X receptor alpha (LXRα) was predicted to be the probable target of isolates by Swiss Target Prediction tool, and compounds 2-4, 11 and 12 increased the protein expression of ATP-binding cassette transporter (ABCA1), showing potential antiatherogenic properties.