Antimicrobial and antioxidant activities of the essential oil and various extracts of Salvia tomentosa Miller (Lamiaceae)

This study was designed to examine the in vitro antimicrobial and antioxidant activities of the essential oil and various extracts (prepared by using solvents of varying polarity) of Salvia tomentosa (Miller). The essential oil was particularly found to possess strong antimicrobial activity while other non-polar extracts and subfractions showed moderate activities while polar extracts remained almost inactive. GC and GC/MS analyses of the oil resulted in the identification of 44 compounds, representing 97.7% of the oil; β-pinene (39.7%), α-pinene (10.9%) and camphor (9.7%) were the main components. The samples were also subjected to screening for their possible antioxidant activity by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene-linoleic acid assays. In the first case, the free radical scavenging activity of aqueous methanol extract (MW) was superior to all other extracts (IC50=18.7 μg/ml). Polar extracts exhibited stronger activities than non-polar extracts. In the case of the linoleic acid system, oxidation of the linoleic acid was effectively inhibited by the polar subfraction of the MW extract, while the oil was less effective. The MW extract showed 90.6% inhibition, that is close to the synthetic antioxidant BHT.