New Diterpenoids With Anti-Inflammatory Activity From Callicarpa rubella Collected in Vietnam

Callicarpa rubella is a notable folk medicinal plant of the genus Callicarpa. It is extensively ethnobotanically used for its traditional uses to cure rheumatism, inflammation, and pain in traditional Chinese medicinal systems.

This study aimed to isolate unreported diterpenoids with anti-inflammatory activities.

The planar structures of unreported compounds were characterized by interpreting 1D and 2D NMR spectra and HREIMS data. The absolute configurations were determined by comparing the experimental ECD spectra with calculated ECD ones. The potential anti-inflammatory activities of all isolated compounds were assessed by testing their in vitro inhibitory effects against superoxide anion generation and elastase release by human neutrophils in response to fMLP/CB.

Investigation of chemical constituents from the leaves and twigs of C. rubella leads to the isolation of four unreported diterpenoids (1-4) along with 17 known diterpenoids (5-21). The results showed compounds 1, 3, 5-7, 9, 12, 16, 18, and 20 have potent inhibition against FMLP/CB-induced superoxide anion generation with IC₅₀ values range from 1.37 ± 0.09 μM to 6.29 ± 1.14 μM, while compounds 3, 6, 7, 9, 12, 16, 18, and 20 showed potent inhibition of elastase release with IC₅₀ ranging from 1.47 ± 0.15 μM to 5.79 ± 1.16 μM.

The results obtained from the current study will enhance our understanding of diterpenoids from the Callicarpa genus and support the identification of unreported diterpenoids with potential anti-inflammatory agents.