Antibacterials and modulators of bacterial resistance from the immature cones of Chamaecyparis lawsoniana

Several anti-staphylococcal diterpenes were isolated from the immature cones of the conifer Chamaecyparis lawsoniana. The most active, ferruginol, caused an 80-fold potentiation of oxacillin activity against EMRSA-15, with more modest potentiation of antibiotic activity against effluxing clinical isolates of Staphylococcus aureus. The results of an efflux inhibition assay suggest that ferruginol is a weak efflux pump inhibitor.