Formosins A-F: Diterpenoids with Anti-microbial Activities from Excoecaria formosana

Three new halimane-type diterpenoids formosins A-C (1-3), and three clerodane-type diterpenoids formosins D-F (4-6), were isolated from the twigs of Excoecaria formosana. Their structures were assigned on the basis of spectroscopic data analysis. Compounds 1 and 4 showed moderate anti-microbial activities against Bacillus subtilis (MIC = 50 and 50 μg/mL, respectively). Compound 6 exhibited moderate anti-microbial activities against two strains of Helicobacter pylori (Hp-SS1 and ATCC 43504) with MIC values of 50 and 50 μg/mL, respectively.