Isolation, Characterization, and Structure-Activity Relationship Analysis of Abietane Diterpenoids from Callicarpa bodinieri as Spleen Tyrosine Kinase Inhibitors

Species belonging to the genus Callicarpa are used traditionally in Chinese medicine for the treatment of inflammation, rheumatism, and pain. Investigation of the leaves and twigs of Callicarpa bodinieri resulted in the isolation of nine new abietane Diterpenoids, bodinieric acids A-I (1-9), along with six known compounds (10-15). The structures of 1-9 were elucidated on the basis of the interpretation of their HRESIMS and NMR data and by ECD calculations. To explore the potential therapeutic target of this plant for immune-mediated disease, the inhibitory activities of the isolates obtained were determined against 13 kinase enzymes. Eight compounds exhibited moderate inhibitory effects on spleen tyrosine kinase (Syk), and the IC₅₀ values of compounds 2 and 6 were 7.2 and 10.7 μM, respectively. In addition, a preliminary structure-activity relationship of this scaffold was analyzed with both molecular docking and a 3D-QSAR pharmacophore model.