ANTIBACTERIAL ACTIVITY OF THE EXUDATE OF SALVIA BUCHANANII HEDGE (LAMIACEAE)

A bioguided separation of the “exudate” mixture of the fresh aerial parts of Salvia buchananii Hedge (Hedge, 1963) was carried out. The exudate as well as several row fractions obtained during the purification process displayed a clear inhibitory activity on selected Gram positive multidrug resistant clinical strains, including Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus agalactiae, Enterococcus faecium and Enterococcus faecalis. The exudate showed MIC values (Clinical and Laboratory Standards Institute, 2010) ranging from 4 to 64 g/mL on the different Gram positive species, thus indicating a very interesting antibacterial activity. Two of the obtained row fractions displayed MIC values of 2 g/mL on Enterococcus faecium, and values ranging from 4 to 64 g/mL on the other Gram positive strains. The other row fractions showed MIC values ranging from 4 to 64 g/mL on the same bacterial species. Three new clerodane diterpenoids and eight known diterpenes have been isolated. The structures were established by extensive 1D, 2D NMR and HRESI-TOFMS spectroscopic methods. Four compounds displayed inhibitory activity on the two Enterococcal species examined. Interestingly, the inhibition provided by these compounds was independent of the resistance patterns of these pathogens to classic antibiotics. No action was reported on Gram-negative strains (Escherichia coli, Proteus mirabilis and Pseudomonas aeruginosae) nor on Candida albicans. These findings confirm the interesting antimicrobial activity of Salvia species and highlight the complex interactions among metabolites within the crude extract, that can give rise both to antagonism as well as synergism or indifference.