Di- and Sesqui-Terpenoids Isolated from the Pods of Sindora sumatrana and Their Potential to Inhibit Lipopolysaccharide-Induced Nitric Oxide Production

Activity-guided fractionation of the n-hexane and ${CHCl_3}-soluble$ fractions of Sindora sumatrana using a bioassay based on the inhibition of lipopolysaccharide (LPS)-induced nitric oxide (NO) production by inducible nitric oxide synthase (iNOS) in murine macrophage RAW 264.7 cells led to the isolation of the known compound, $(+)-7{\beta}-acetoxy-15,16-epoxy-3$, 13(16), 14-clero-datriene-18-oic acid (2) as an active constituent. In addition, a new trans-clerodane diterpenoid, (+)-2-oxokolavenic acid (1), together with six known compounds, (+)-3, 13-clerodadiene-16,15-olide-18-oic acid (3), $(+)-7{\beta}-acetoxy-3$,13-clerodadiene-16,15-olide-18-oic acid (4), $(+)-7{\beta}-acetoxy-16-hydroxy-3$,13-clerodadiene-16, 15-olide-18-oic acid (5), ${\beta}-caryophyllene$ oxide (6), $clovane-2{\beta},9{\beta}-diol (7),{\;}and{\;}caryolane-1,9{\beta}-diol$ (8) were isolated and found to be inactive. The structure of compound 1 was determined using physical and spectroscopic methods such as 1D and 2D-NMR experiments. The known compounds 2-8 were identified by the spectroscopic data and by comparison with the published values. Of eight isolates (1-8), only compound 2 exhibited an iNOS inhibitory activity with $IC_{50}$/ value of $51.6{\;}\mu\textrm{m}M$.