New clerodane diterpenoids from Salvia buchananii Hedge

The antimicrobial activity of the surface exudate obtained by rinsing the aerial parts of S. buchananii Hedge (Lamiaceae) [1] with CH2Cl2 was preliminary evaluated by testing 10 μl of 2-fold dilutions (ranging from 1000 mg/L to 64 mg/L) on selected multi-drug-resistant Gram-positive strains, appropriately seeded on agar plates [2]. A clear halo of inhibition was observed on Staphylococcus epidermidis, Staphylococcus aureus (minimum active concentrations for both strains 125 mg/L) and, particularly, on Enterococcus faecium and Enterococcus faecalis (minimum active concentrations for both strains 64 mg/L). The exudate, subjected to repeated column chromatography on Sephadex LH-20 and silica gel and to semi-preparative RP-HPLC, yielded two new clerodane diterpenoids (1 and 2), identified by IR and NMR analysis, including TOCSY, COSY, HSQC, HMBC and ROESY experiments, and ESI-TRAP-MS and HR-MS analysis.