An antibacterial ortho-quinone diterpenoid and its derivatives from Caryopteris mongolica.

Abstract To identify antibacterial components in traditional Mongolian medicinal plant Caryopteris mongolica , an ortho -quinone abietane caryopteron A ( 1 ) and three its derivatives caryopteron B–D ( 2 – 4 ) were isolated from the roots of the plant together with three known abietanes demethylcryptojaponol ( 5 ), 6α-hydroxydemethyl cryptojaponol ( 6 ), and 14-deoxycoleon U ( 7 ). The chemical structures of these abietane derivatives were elucidated on the basis of spectroscopic data. Compounds 1 – 4 had C-13 methylcyclopropane substructures, and 2 – 4 had a hexanedioic anhydride ring C instead of ortho -quinone in 1 . The stereochemistry of these compound was assumed from NOE spectra and ECD Cotton effects. Compounds 1 and 5 – 7 showed antibacterial activities against the Gram-positive bacteria Staphylococcus aureus , Staphylococcus epidermidis , Enterococcus faecalis , and Micrococcus luteus , being 1 the more potent.