Synergistic and antagonistic interactions of essential oils on the biological activities of the solvent extracts from three Salvia species

Abstract

The solvent extracts of aromatic plants contain both volatile (e.g. essential oils) and non-volatile compounds. The biological activities (antibacterial, anti-oxidant, antiplasmodial and anticancer) of the solvent extracts of three South African Salvia species (Salvia africana-caerulea, S. africana-lutea and S. lanceolata) were evaluated in the presence and absence of the essential oils. The solvent extract of S. africana-caerulea free of essential oil exhibited the best activity against Gram-positive bacteria (MIC value: 0.4 mg/mL), while the solvent extract containing essential oil of S. lanceolata was the most active against Gram-negative bacteria (MIC value: 2.0 mg/mL). No significant difference was obtained in the antiplasmodial activity of the solvent extract with or without the essential oils of S. africana-caerulea and S. lanceolata, while the activity of the solvent extract without essential oil was significantly higher than that of the solvent extract containing the essential oil in S. africanalutea (p < 0.05). The toxicity profile of all three species was significantly higher (p < 0.05) with the solvent extracts containing essential oils than when assessed in the absence of the essential oil.