Antibacterial activity of constituents from Salvia buchananii Hedge (Lamiaceae)

The dichloromethane extract obtained from the aerial parts of Salvia buchananii Hedge was investigated for its antimicrobial properties following a bioassay-oriented fractionation approach. The extract displayed a clear inhibitory activity against several Gram-positive multidrug-resistant clinical strains including Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus agalactiae, Enterococcus faecium and Enterococcus faecalis. No activity was observed on Gram-negative strains and on Candida species. Phytochemical investigation of this extract led to the isolation of three new clerodane diterpenes (5, 6 and 8) and eight known clerodane diterpenes (1-4, 7, 9-11) as well as ursolic (UA) and oleanolic (OA) acids. Their structures were established by extensive 1D, 2D NMR and HR-MS spectroscopic methods. The mixture UA/OA manifested a broad and powerful activity on several Gram-positive species, while diterpenes 3, 6, 8 and 9 showed moderate inhibitory activity on the Enterococcus species.