Phytochemical Composition and Antibacterial Properties of Surface Extracts of Six Salvia Species

The chemistry and biological activity of cuticular waxes and the secondary metabolites produced in the indumentum of different plant organs has been attracting the interest of botanists. This work was aimed to investigate the chemistry and antibacterial activity of the surface extracts (SE) of different organs of six Salvia species. The cuticles and indumenta of the leaves, calyxes, and stems of Salvia atropatana Bunge., S. lachnocalyx Hedge., S. ceratophylla L., S. palaestina Benth., S. persepolitana Boiss., and S. hydrangea DC. ex Benth. were extracted with dichloromethane. The SEs were analyzed using gas chromatography-mass spectrometry (GC/MS). The antibacterial activity of each extract was assessed against Escherichia coli, Staphylococcus epidermidis, and Bacillus subtilis strains using the agar disc diffusion bioassay. The yields of extracts were in the range from 1.1- 2.3% w/w, while the detected compounds constituted 59.3-95.4% of the total extract composition. All species except S. persepolitana contained the sesquiterpenes, including β-caryophyllene (0.5-19.5%) and germacrene D (0.4-12.9%), while sclareol (2.1-75.6%) was the major labdane diterpenoid in the examined Salvia species excepting S. hydrangea. In addition to terpenoids, the analyzed SEs contained long-chain n-alkanes, fatty acids, alcohols, and aldehydes in the range from 4.8-78.5%. E. coli was the most susceptible microorganism to the tested extracts of S. persepolitana calyxes and stems (20 and 18 mm) and the S. lachnocalyx stems (17 mm), respectively. The antibacterial properties of the SEs of the plants suggested their protective role against pathogenic microorganisms, which can be attributed to their major phytochemicals such as sclareol and abienol.