Thrombin inhibitory constituents from Duranta repens

The C-alkylated flavonoids 3,7,4'-trihydroxy-3'-(4-hydroxy-3-methylbutyl)-5 ,6-dimethoxyflavone (1), 3,7dihydroxy-3'-(4-hydroxy-3-methylbutyl)-5,6,4'-t rimethoxyflavone (2) and the trans-clerodane diterpenoids 6 beta hydroxy-15 ,16-epoxy-5 beta ,8 beta ,9 beta ,10 alpha -cleroda-3,13,(16),14-trien-oic acid (3) and the trans-clerodane diterpenoids 6 beta -hydroxy-15,16-epoxy 5 beta ,8 beta ,9 beta ,10 alpha -cleroda-3,13(16),14-trien-18-oic acid (4) were isolated from Duranta repens. Their structures and the relative config uration of 3 and 4 were determined by spectroscopic methods (H-1- and C-13- NMR, IR, and MS) and 2D-NMR experiments. The known flavonoid 5 is also repo rted for the first time from this species. The compounds 1, 3, and 5 showed significant enzyme-inhibitory activity against thrombin.