Antimicrobial phenolic abietane diterpene from Lycopus europaeus L. (Lamiaceae)

A new acetylated highly oxygenated abietane-type diterpenoid named euroabienol was isolated in pure state from Lycopus europaeus L. (Lamiaceae) fruits and its structure elucidated through both extensive spectral and chemical means. The presence of a phenolic C ring with a rare substitution pattern in euroabienol and its high relative amount in the fruits (1%, based on the weight of the fruits) urged us to try to establish its possible biological role. Thus, it was screened for its in vitro antimicrobial activity against fifteen strains of bacteria and six fungal strains. Euroabienol showed a broad spectrum of activity and probably is a first line defense plant metabolite against pathogen attack. This is the first report on the occurrence of abietanes in the genus Lycopus.